ASTM D4057 standard practice for manual sampling of petroleum and petroleum products
9. Sampling Requirements, Considerations, and Procedures
9.1 General - This section provides requirements, recommendations and procedures for sampling preparation, sampling, and sample handling. More than one sampling method may provide satisfactory samples. A summary of the manual sampling procedures and their applications is presented in Table 3.

9.2 Sampling Requirements and Considerations:
9.2.1 Sample Request - The sampling process is often initiated with a sample request. The request should provide adequate details and information necessary to establish the sample procedure, device, container, sample quantity, and sample handling. To assess sampling requirements, the following information should be established:
(1) Requestor contact information;
(2) Date of request and required timeline;
(3) Batch/job/vessel/voyage number;
(4) Product description - Applicable safety data sheet (MSDS) and Department of Transportation (DOT) information should be provided or available;
(5) Product location, tank or vessel number(s), and volume(s);
(6) Test name(s) and method(s), and;
(7) Special handling requests or precautions, such as splitting of samples, additional retention requirements, or suspected product stratification. In some cases, a test method may require a special container, a minimum amount of sample, or a special sample handling procedure. At times, multiple test methods may have conflicting requirements, such as volatility testing and homogenizing for S & W. In these instances, it may be necessary to obtain separate samples for each test.

9.2.2 Equipment and Sample Container Preparation - Use only sampling equipment and containers that are resistant to solvent action by the product handled. Inspect all sampling equipment, including container, caps, lids, and stoppers to ensure that they are clean and dry. Any residual material left in a sampling device or sample container may contaminate the sample. It is recommended to rinse the sample container and equipment with the product to be sampled before drawing samples.

9.2.3 Sample Transfers and Handling Requirements:
9.2.3.1 The number of transfers from the primary container to intermediate sample containers and the testing apparatus should be minimized to maintain the product integrity and representation. Common areas of concern related to transfers include loss of light ends, water, and heavy component disparities and possible residue contamination. Some of the tests affected might include, but are not limited to, flash point, vapor pressure (RVP), density, S & W, product clarity, ash, trace metals, and micro-separometer (MSEP).

9.2.3.2 Each time a sample is transferred, including to the test apparatus, the sample should be completely mixed to ensure it is homogenized, unless the specific test method allows or specifies otherwise. The transfer should be completed during the period that the sample remains homogenous. There may be specific practices that allow or specify the sample being placed directly into the test apparatus, such as from the thief via petcock into the centrifuge tube for small crude gathering tanks. Refer to API MPMS Chapter 18.1.

9.2.4 Requirements for Mixing and Compositing Individual Samples:
9.2.4.1 When compositing samples (e.g. a multiple compartment composite sample for a marine vessel or a tank composite sample for a shore tank), each primary sample should be thoroughly mixed before pouring off into the intermediate composite container. Based on the product, and as described in the applicable test methods, adequate mixing may be obtained by shaking (manual or mechanical) or through the use of a power mixer, also known as a homogenizer. Higher viscosity products, such as residual fuel oil, and IFO 380 bunker fuel, and most crude oils should be homogenized before pouring into the composite sample, and into the test apparatus. Manual and mechanical shaking of higher viscosity products, such as residual fuel oil, IFO 380 bunker fuel and most crude oils, may not impart sufficient energy to create and maintain a homogeneous representative sample. The specific mixing or homogenizing method should be recorded. Refer to Practice D5854 (API MPMS Chapter 8.3). There may be job-specific instructions to retain a portion of each individual sample.

9.2.4.2 With the intent that the final composite sample be representative of the combined parcels, compartments or components represented in the field, make the blend proportional to the quantities of each parcel, compartment, or component. The type of composite sample should be clearly marked on the sample tag and the analytical report, for example, "Vessel Volumetric Composite" or "Shore Tank Volumetric Composite".

9.2.5 Container Outage (Ullage) - Because of potential liquid thermal expansion, do not fill sample containers more than 70 to 85 % of the containers capacity, allowing room for expansion based on the temperature of the liquid at the time of filling and the probable maximum temperature to which the container may be subjected. If required by the test method, the sample ullage may be greater than 85 %, but in no case shall it be completely full. In these cases, take special handling precautions to consider the hazards associated with product thermal expansion. For safe fill of high-pressure cylinders, refer to maximum fill density and 9.30.

9.2.6 Standpipes:
9.2.6.1 Shore tanks, particularly floating-roof tanks, and vessel compartments are often fitted with standpipes. Often these standpipes are unslotted and sometimes poorly or inadequately slotted preventing the standpipes from being flushed out adequately during filling or tank circulation. Samples shall not be obtained from solid or unslotted standpipes, since it is unlikely that the samples will be representative of the tank or vessel compartment contents. Sampling through poorly or inadequately slotted standpipes may also result in unrepresentative samples. Additionally, in the case of both shore tanks and marine vessels, samples obtained from all standpipes may become contaminated from the presence of rust, foreign matter, moisture (condensation), and residue from prior products remaining on the standpipes. See Fig. 24.

9.2.6.2 In all cases, when possible, obtain samples directly from the tank or vessel compartment rather than through a standpipe. If sampling is performed through a slotted or perforated standpipe, it shall have either two rows of slots or two rows of holes (that is, perforations) located on the opposite sides of the pipe, perpendicular to the shell wall, that starts at the lower end of the pipe and continue to above the maximum liquid level. Typical sizes of the slots are 2.5 cm (1 in.) in width and 25 cm (10 in.) in length. The typical diameter of the perforation is 5 cm (2 in.). The maximum spacing between perforations or slots if not overlapping shall be 30 cm (12 in.).

Non-homogeneous (Stratified) Product
9.2.7 A tank, marine vessel compartment, or batch may not be homogenous for many reasons, some of which may include:
9.2.7.1 Water in Petroleum - The concentration of dispersed water in the oil is generally higher near the bottom of a tank or pipeline. A running or all-level sample, or a composite sample of the upper, middle, and lower samples, may not be representative of the concentration of the dispersed water present. The interface between oil and free water may be difficult to locate, especially in the presence of emulsions, layers, or water-bearing sediments. The free water level may vary across the tank bottom surface. Additionally, the bottom may be covered by pools of free water or water/oil emulsion impounded by layers of sediments or wax.

9.2.7.2 Layers of varying density or viscosity, for example, residual fuels with blend components such as light cycle oil. This will often lead to non-homogenous test results of other properties such as ash, metals, pour point or S & W.

9.2.7.3 Layers of varying volatility and light components impact properties such as vapor pressure, distillation, or flash point. Examples include distillate mixed in gasoline, gasoline mixed in distillate, kerosene in diesel fuel oil, crude oil blended into residual fuel oil or varying components such as naphtha and reformate blended into gasoline.

9.2.7.4 Liquids coexisting in a tank with solid or semi-solid materials typically referred to as "bottoms", for example, crude oil and heavy fuel oils.

9.2.8 Depending on the extent of stratification, it can be very difficult to obtain a representative manual sample. Spot samples, such as upper, middle and lower (UML), or top, middle and bottom (TMB) are recommended to establish the extent of stratification. Running or all-levels samples will contain all product layers in the vertical column from the sample point, although the rate of fill will be variable based on the depth of the product. Even with care, it may not be possible to exactly reproduce a manual sample from a non-homogeneous or stratified tank.

9.2.9 Spot samples may be taken to assess the level of stratification of a particular property within a shore tank or marine vessel compartment. The determination as to what constitutes stratification should be based on agreement of interested parties. In addition, the test method precision, or laboratory site precision may be considered as aids in determining if the analytical results differ significantly enough to indicate stratification. Refer to Practice D6299 and Guide E882. As agreed between interested parties, either individual spot sample test results can be averaged, a volumetric composite sample can be prepared and tested, or an alternate sample or sample location may be agreed upon.

9.2.10 If available, a validated automatic flow proportional pipeline sampler is preferred for non-homogenous products. An automatic sampler equipped with a mixing device immediately upstream of the sampler is particularly well suited to ensure mixing and water dispersion for heavy products and crude oils.

9.2.11 If an auto in-line sampler satisfying Practice D4177 (API MPMS Chapter 8.2) is not available, and manual samples are the only available option, the interested parties should consider agreeing upon the following:
9.2.11.1 Additional Sampling and Testing - To assess the level of stratification, draw spot samples, such as top, upper, middle, lower, and suction levels and test them individually for API gravity or density, viscosity, S & W, vapor pressure (RVP), Flash Point, or any other property of interest. Based on the differences of these properties relative to the test method precision, the extent of stratification can be determined. If the tank is considered to be non-homogeneous for the properties tested, additional spot samples may be taken at equidistant levels, and all the individual test results mathematically averaged. If the tank is determined to be homogenous individual samples obtained, such as those referenced above, should be representative. See 9.2.9.

9.2.11.2 Sample Downstream of Stratification - If available for consideration and agreeable by interested parties, the product may be sampled following the transfer (for example, marine vessel load or discharge or tank transfer). The product in the receiving tanks or compartments may be mixed adequately as a result of the transfer. Sampling and testing of properties of interest should be performed on the product to ensure it has been thoroughly mixed and homogeneous.

9.3 Marine Cargoes:
9.3.1 Interested parties should agree upon sampling instructions and requirements prior to any transfer, including what sample(s) will be considered the custody transfer sample. Considering terminal, vessel and regulatory requirements, the following is an example of typical manual samples that might be obtained for certain marine movements:
9.3.1.1 Running or all-levels samples from the shore tank before a vessel load and before and after a vessel discharge. Additional samples, such as spot samples, obtained based on specific requests from interested parties.

9.3.1.2 Running or all-levels samples from each vessel compartment after a load and before a discharge. Additional samples, such as spot samples, obtained based on a specific request from interested parties. Marine vessel samples may be taken either through open hatches or via vapor control valves (VCVs).

9.3.1.3 Manual samples may be obtained from the shore pipeline, or vessel manifold, typically at the start of the transfer as specifically requested by interested parties.

9.3.2 Deck Composites - Periodically field "deck composite samples" are requested. A deck composite is typically made by compositing a portion of each sample obtained from all vessel compartments containing a particular product or crude oil grade. The samples are not normally homogenized before compositing and are typically not volumetrically composited based on the quantity in each vessel compartment. It is for these reasons that deck composite samples are typically not considered representative of the product sampled. The sample label shall clearly read "deck composite sample". Deck composite samples are not recommended for volatility testing, such as Vapor Pressure, as described in the applicable test methods.

9.3.3 Sampling High Pressure Products on Marine Vessels - High pressure sampling procedures will likely be affected by the type and design of the marine vessel. Marine vessels transporting high pressure cargoes are generally classified into five groups: fully pressurized, semi-pressurized (semi-refrigerated), ethylene, fully refrigerated, and LNG. A special consideration is that barges are generally fully pressurized and are not fitted with cargo pumps, but are instead unloaded with vapor displacement from a shore compressor. It may be necessary to sample the gas phase in addition to the liquid phase, such as when the cargo tank had contained inert gas or a different cargo, or when the possibility of contamination exists. For some cargoes, the previous cargo vapors, the inert gas or other contaminants in even small concentrations can adversely affect the new cargo. The cargo sample may be used for composition, density or specification limits. Refer to API MPMS 17.10.2.

9.4 Sample Labeling:
9.4.1 The label or sample tag shall satisfy applicable regulatory, company, and custody transfer requirements. Use waterproof and oil-proof ink or a pencil hard enough to dent the tag. Soft pencils and ordinary ink markers are subject to obliteration from moisture, oil smearing, and handling. Label or tag the container immediately after a sample is obtained. See Fig. 25.

9.4.2 Many sample containers require special shipping packaging before they can be transported from the point of collection. All employees handling and shipping samples shall be familiar with applicable requirements and regulations.

9.4.3 The following information is typical on a label:
(1) Unique job identification (ID)
(2) Date and time sample was taken
(3) Product name/description
(4) Facility
(5) Tank/vessel/pipeline identifier or description
(6) Type of sample
(7) Before or after: load/discharge/transfer - sample only
(8) Name of individual who obtained the sample
(9) Applicable hazard communication information
(10) Special conditions such as rain or snow while sampling

9.4.4 Sampling Report and Chain of Custody - In addition to the sample label/tag, a sample report and chain of custody report are often required describing the samples taken. At any point when samples are handed over to another responsible party, whether the laboratory technician or someone transporting the samples, it is recommended that the transfer of samples be documented, for example, on a chain-of-custody form. Refer to Guide D4840.

9.4.5 Samples for Volatility Testing - It is recommended that samples used for volatility testing not be transferred into an intermediate sample container. If the sample is transferred from the primary sample container, it should be transferred to the intermediate sample container without delay. Keep the container closed except when the container is being filled. After delivery to the laboratory, these samples should be cooled before the containers are opened. Refer to Practice D5842 (API MPMS Chapter 8.4).

9.4.6 Sample Storage and Disposal - Samples should be stored in such a manner as to enable quick retrieval and kept safe and secure to prevent theft, tampering, weathering, or degradation from light, heat, cold, and any other conditions. Sample containers should have adequate caps to prevent loss of light ends. Store and dispose of samples in such a way to ensure compliance with company policy and regulatory requirements.

Sampling Methods and Procedures
9.5 Running and All-Levels Sampling:
9.5.1 Obtain a running sample by lowering an open sampling device to the bottom of the outlet suction level, but always above the free water, and returning it to the top of the product at a uniform rate such that the sampling device is between 70 and 85 % full when withdrawn from the product. If required by the test method, the sampler may be greater than 85 % full when withdrawn but in no case shall it be completely full. In these cases, take special handling precautions to consider the hazards associated with product thermal expansion.

9.5.2 Obtain an all-levels sample by lowering the closed sampling device to the bottom of the outlet suction level, but always above the free water, then opening the sampler and raising it at a uniform rate such that it is between 70 and 85 % full when withdrawn from the product. Alternatively, all levels samples may be taken with samplers designed for filling as they pass downward through the product. If required by the test method, the sampler may be greater than 85 % full when withdrawn but in no case shall it be completely full. In these cases, take special handling precautions to consider the hazards associated with product thermal expansion.

9.5.3 The running and all-levels methods have the advantage of sampling the full column of liquid as compared to spot samples that individually represent a single spot in the vertical column. However, running and all-levels samples may not necessarily be representative because the tank volume may not be proportional to the depth and the rate of filling is proportional to the square root of the depth of immersion.

9.5.4 Running and All-levels Sampling Procedure - The running and all-levels sample procedure is as follows:
(1) Inspect the sample container, typically a bottle or beaker, for cleanliness and use only clean, dry equipment.
(2) Place the container in a sampling cage or attach the weighted line to the bottle.
(3) Based on the height and viscosity of product, a restricted flow cap, a notched cork, or a restricted opening may be used to ensure the container emerges between 70 and 85 % filled. Refer to Table 4 for recommended opening sizes.
(4) For a running sample, lower the sampling device at a uniform rate to the bottom of the outlet suction level, while staying above the free water level, and without hesitation, raise it such that the sampling device is between 70 and 85 % full when withdrawn from the liquid.
(5) For an all-levels sample, lower the closed sampling device to bottom of the outlet suction, while staying above the free water level. Pull out the stopper with a sharp jerk of the sample line and raise it at a uniform rate such that it is between 70 and 85 % full when withdrawn from the liquid. Alternatively, all-levels samples may be taken with samplers designed for filling as they pass downward through the product.
(6) Verify that the volume of sample is 70 to 85 % full. If not, discard the sample and repeat the sampling procedure, adjusting the restriction and or the sampling rate. Also, if the sample device opening enters the free water zone of any tank or vessel compartment, discard the sample and repeat the running or all-levels sampling procedure staying above the free water.
(7) If sample will remain in the primary container, remove the sample from the cage, wipe the outside, cap tightly, and clearly label.
(8) If sample is to be transferred from the primary sample container, empty the contents into an intermediate sample container, using a clean funnel if necessary, cap tightly, and clearly label. Take precautions to protect the integrity of the sample while transferring during inclement weather.

9.6 Spot Sampling:
9.6.1 A spot sample is one taken at a specific location in a tank or from a flowing stream in a pipe at a specific time. It is recommended to use spot samples, such as upper, middle, and lower (UML) or top, middle, and bottom (TMB) to determine the extent of stratification, or to determine the quality of product at a specific location, in the vertical column being sampled. Compositing of spot samples should be performed only when the tank is known to be well mixed and homogenous or it is established that the spot samples are representative of the extent and levels of stratification in the entire tank or vessel compartment. Caution should be exercised when compositing spot samples since they represent product from only those respective points in the tank or vessel compartment and may not represent levels of significant stratification at any other point in the tank or marine vessel compartment, for example, S & W in crude oil.

9.6.2 Spot Sampling Procedure:
(1) Inspect the sampling device (typically a bottle or beaker) for cleanliness and use only clean, dry equipment.
(2) Determine the liquid level in the tank.
(3) Prepare the sampling device, for example place the container in a sample cage, or attach the weighted line to the bottle.
(4) Insert the stopper in the sample device.
(5) Lower the sampling assembly to the required location. When samples are required at more than one level, obtain the samples beginning at the top and working downwards to minimize disturbance to the product in the vertical column being sampled. See Table 5.
(6) At the required location, pull out the stopper with a sharp jerk of the sample line.
(7) Allow sufficient time for the sampling device to fill completely at the specific location.
(8) Withdraw the sampling device.
(9) Verify the sampling device is completely full. If it is not full, empty the sampling device and repeat the sampling procedure.
(10) If sample will remain in the primary sample container, remove it from the cage, discard approximately 20 % of the sample, wipe the outside, cap tightly, and clearly label.
(11) If the sample is to be transferred from the primary sample container, the intermediate container should be filled between 70 and 85 %, using a clean funnel if necessary, cap tightly, and clearly label. Take precautions to protect the integrity of the sample while transferring during inclement weather.

9.6.3 Core (Thief) Sampling Procedure:
(1) Inspect the sampler (thief), graduated cylinder (if used), and sample container for cleanliness and use only clean, dry equipment.
(2) Determine the liquid level in the tank.
(3) Check the sampler (thief) for proper operation.
(4) Open the bottom closure and set the tripping mechanism, if applicable.
(5) Lower the sampler to the required location. See Table 5.
(6) At the required location, close the bottom closure on the thief with a sharp jerk of the line. Alternatively, the type of core sampler may automatically close/seal when raised.
(7) Withdraw the sampler.
(8) If only a middle sample is required, pour the complete sample into the sample container. If samples are required at more than one location, measure out a specified amount of sample with the graduated cylinder and pour it in the sample container. The amount of sample measured will depend on the size of the thief and the tests to be performed but should be consistent for the samples taken at different levels.
(9) Discard the remainder of the sample from the sampler as required.
(10) Repeat sampling procedure to obtain a sample(s) at the other sample location(s) as required.
(11) Ensure that the sample is capped tightly and clearly labeled.

9.7 Bottom Sampling:
9.7.1 Bottom samples may be necessary for a variety of reasons including: determination of free water, S & W and non-merchantable material for custody transfer or tank cleaning, concerns with tank bottoms affecting the quality of the product if a tank will be stripped or emptied during a transfer, and sampling for possible microbial activity.

9.7.2 Bottom sampling essentially allows samples to be obtained anywhere from the bottom of the tank to a height of 300 mm (1 ft) in the shore tank, marine vessel compartment, or container. Bottom sampling can be performed with the open core (thief) sampler, dead bottom sampler, and the bottom water and ROB/OBQ sampler/scraper. Since the term "bottom sample" has a variety of meanings, the exact sampling location (for example, dead bottom, and 75 mm (3 in.) from the bottom) should be recorded on both the sample tag/label and on any analytical report.

9.7.3 Dead Bottom Sampling Procedure - The optimal point for lowering the sampler and the level for obtaining a bottom sample are dependent on the specific purpose for the sample and should be established before sampling commences. For shore tanks, the facility owner should provide information related to the tank floor configuration (for example, flat, cone down, crown up, sump), the location and type of datum plate, and the location and accessibility of the sump and water draw.
(1) Lower the clean dry dead bottom sampler slowly until it touches the bottom of the tank or vessel compartment floor.
(2) On impact with the tank floor, the sample will begin to fill from the bottom, simultaneously displacing air through the top valve. Allow time for the sampling device to fill. Extension rods can be placed on the nipple of the bottom valve allowing product to be sampled from varying bottom levels.
(3) For "open" core-type devices, gently raise the sample apparatus 5 to 10 cm and then lower it until it strikes the bottom trapping the sample in the sampling device.
(4) After obtaining the sample, remove from the tank or vessel, and transfer the contents to a suitable intermediate container.
(5) Ensure that the sample is capped tightly and clearly labeled.

9.7.4 Bottom Water and ROB/OBQ Sampler/Scraper Procedure:
(1) Lower the clean, dry sampler until it touches the bottom of the tank or vessel compartment floor.
(2) If sampling water under the product, the sampler fills with product at first, hits the bottom, and falls over. The design will allow the sampler to tip over on the tank or vessel compartment floor. Product rises to the top with free water displacing the product in the sampler. Allow time for the sampling device to fill with water.
(3) If sampling small volumes or residual material, lower the sampler until it hits the bottom and falls over. Allow time for the sampling device to fill. For semi-liquid or high-viscosity material residue, the sampler may need to be moved on the tank floor to accumulate product clinging to the sampler.
(4) After obtaining the sample, remove from the tank or vessel, and transfer the contents to a suitable intermediate container.
(5) Cap the sample tightly and clearly label.

9.7.5 Tank Tap Sampling - In the case of storage tanks, there may be one or more taps. A tap sample is considered a spot sample and it may be combined with other samples to form a composite.

9.7.6 Tank Tap Sampling Procedure:
(1) Inspect the sample container(s) and graduated cylinder (if used) for cleanliness.
(2) Determine the liquid level in the tank.
(3) Flush the sample tap and piping until they have been completely purged. (Warning - Open the taps with care when sampling under pressure. Make no attempt to clear a blocked connection by forcing a rod or any other tool through an opened valve.)
(4) Collect the samples as set forth in Table 6. If a delivery tube is used, ensure the end of the delivery tube is maintained below the liquid level during the withdrawal of the sample to minimize splashing and potential loss of light ends.
(5) If the sample was collected in a graduated cylinder, deposit the sample in the sample container.
(6) Disconnect the delivery tube and cooler, if used.
(7) Ensure that the sample is capped tightly and clearly labeled.

9.7.7 If the contents of a tank fail to reach the upper or middle sample connections on a tank equipped with three connections, take the samples for the tank as given in Table 6.

9.8 Tanks Other Than Upright Cylindrical:
9.8.1 Horizontal Tanks with Circular or Elliptical Cross Section - Except as noted, take samples as spot samples from the levels indicated in Table 1. By mutual agreement, a single spot sample at the location corresponding to 50 % of the contained volume may be considered sufficient. Alternatively, it may be acceptable to use one of the other methods.

9.8.2 Tanks with Other Geometrical Shapes - Take spot samples from spherical, spheroid, and irregular shape tanks. Determine the actual levels at which the samples are to be taken to allow for the volume distribution over the height of the tank.

Sampling Using Closed and Restricted Equipment
9.9 General - While recognizing open sampling as the preferred method to obtain the most representative samples, safety and environmental regulations may prohibit the opening of the tank or vessel compartment hatches allowing the release of inert gas or hydrocarbons vapors. The requirement to use restricted or closed equipment is typically based on the availability of an inert gas system, safety and environmental regulations, the hazardous nature of the product, and vessel owner or facility policy. As a result, sampling shall be performed through vapor control valves (VCVs) using either "closed" system sampling equipment with no vapor release, or "restricted" system sampling equipment with limited vapor release. Personnel sampling on board a marine vessel should be accompanied by a designated ship's representative.

9.10 Vapor Control Valves (VCVs) - The installation of VCVs should be in accordance with the requirements of the ship's classification society and the appropriate regulatory authorities. The type and size of the VCVs should be determined beforehand so that proper equipment and fittings can be available. The type and size of the VCV available for sampling can vary depending on the vessel's trade and products handled and can often have a significant impact on the ability to obtain timely samples. A 100-mm (4 in.) VCV is the recommended standard size. This standard size will allow access for various types of samplers and related fittings. Smaller VCVs can severely limit the type of sampling equipment to be used, increase the amount of time to obtain samples, and possibly the quality of the samples. See Fig. 26.

9.11 Restricted Sampling Equipment - Portable sampling units (PSUs) designed to obtain samples under restricted conditions operate via the VCVs fitted to the vessel normally using a simple tape system. See Fig. 3 and Fig. 4. Samplers (sample containers) of various types can be placed inside the extension tube, lowered to the desired level in the tank, and then retrieved. The VCV can then be closed and the sampler removed with a limited loss of vapor.

9.12 Closed Sampling Equipment - Closed system equipment is designed to be completely gas tight during sampling to prevent release of vapor to the atmosphere. See Fig. 27. The tape housing is hermetically sealed and the design should allow sample transfer to intermediate (transportation) sample container with minimal vapor loss. Typically, the same VCV used for gauging is also used for sampling. Additional options include:
(1) Use of multiple, sealed primary samplers to avoid sample transfer;
(2) Vapors held up within the housing to be displaced back to the tank or to an absorbent canister; or
(3) Purge the system with inert gas.

Sampler Types for Closed and Restricted Sampling
9.13 General - Closed and restricted sampling equipment can be used to perform several different types of sampling operations similar to those that are performed using open manual sampling, for example, running, all-levels, spot, bottom, and dead bottom samples. Samplers (sample containers) of various types can be placed inside the extension tube, lowered to the desired level in the tank, and then retrieved. This is achieved by using different designs of samplers with the PSU.

9.14 Running and All-Levels Samplers - Running samplers are equipped with a fixed or adjustable restricted flow opening at the top of the sampler designed to limit the flow into the sampler thereby allowing the sampler to be lowered to the tank bottom and raised to the surface without filling completely. Obtain the sample continuously, at a steady rate, as the sampler moves down through the product column and back up to the surface. All-levels samplers only collect the sample in one direction. For both running and all-levels samples, the sample container shall be between 70 and 85 % full when sampling is completed. If the sample container is full, it cannot be determined at which point the sampler completely filled in the tank or compartment, and the sample cannot be considered a representative running sample. Many closed and restricted sampling systems do not permit the visual verification of the primary sample container to confirm that running or all-level samples have been taken properly, containing between 70 and 85 %. See Fig. 4 and Fig. 28.

9.15 Spot Sampler - Use spot samplers to take samples at designated tank levels such as top, upper, middle, lower, or bottom. These samplers shall be manually opened to fill when they have been lowered to the required level and are primarily used to determine if a tank or vessel compartment is stratified.

9.16 Dead Bottom Sampler - Use the dead bottom sampler to collect a sample directly from the tank or compartment floor, to assess free water and sediment. This sampler, which may be equipped with extension rods for varying heights, is tripped open when it reaches the tank bottom and fills from the bottom.

9.17 Zone Sampler - Most zone samplers, also known as core samplers, operate on the basis of an open-ended tube with a free-floating ball valve at the bottom. When the sampler is introduced into the tank, liquid flows through the tube while it descends through the liquid. When the sampler is stopped, the ball valve closes and the sampler retains the column of product equivalent to the height of the sampler, from that level in the tank or compartment. The quality of the sample is largely dependent on the integrity of ball floating during descent and the seal of the ball valve as the sampler is retrieved, both of which can be affected by the product being sampled.

Closed and Restricted Sample Integrity
9.18 Closed and Restricted Sampling Equipment Cleanliness - To avoid contamination, properly clean samplers, fittings, and related equipment before use and between grades. This may or may not require partial disassembly of the unit. The traditional method of rinsing the primary sampling container with the product to be sampled may not be permitted under certain closed or restricted sampling conditions. However, if this method is used, care should be given to the handling, containment, and safe disposal of such rinse liquids. Fixed sampling equipment, standpipes, Vapor Control Valves (VCVs), and other fittings may contain residue from prior products, grease, rust, or scale, and may have been used for introducing additives to the tank either for the current or previous cargo, all of which has the potential to contaminate samples.

9.19 Sample Transfer - When performing restricted or closed sampling, it is normally not possible to retain the sample in the primary sampling container. The sample is typically required to be transferred from the sampling device into an intermediate sample container. This transfer process may affect the integrity of the samples obtained in the following ways:
(1) Light ends may be lost from the sample which may affect test results, including but not limited to, vapor pressure (RVP, TVP), flash point, density, assay, distillation, and hydrogen sulfide (H2S);
(2) Clingage may take place in the primary sampling container likely resulting in a non-representative transfer to the intermediate sample container; and
(3) Potential contamination from the intermediate container and inclement weather.

9.19.1 Stratification and Nature of Product - Sampling stratified and high-pour or high viscosity products can be further complicated using closed or restricted sampling equipment. For example, on high-pour point or high-viscosity products the weight of the sampler may be insufficient to penetrate readily through the liquid or may even become "stuck" in the extension tube housing, particularly while experiencing colder ambient temperatures. In these instances, the operator may think that the sampler has reached the desired depth when in fact the tape has merely stopped running with the sampler suspended at some undetermined level. Under these circumstances, and considering the limitations of closed and restricted samplers particularly with non-homogeneous product, alternate samples should be agreed upon between interested parties. For example, additional or alternate shore tank samples or spot line samples obtained during the transfer should be considered. Under these circumstances, all relevant samples and analytical results should be considered and agreed upon by all interested parties.

Manual Pipeline Sampling
9.20 Manual pipeline sampling is applicable to liquids in pipelines, filling lines, and transfer lines. All manual pipeline samples are considered spot samples, only representative of the product in the line at that particular point in the pipeline batch or parcel. The reasons manual pipeline samples are taken can vary significantly. One manual pipeline sample might be needed at the beginning of a product pipeline or marine vessel transfer to assure a clear and bright product of the right kind. Another sample might assist with the monitoring and measuring of a pipeline change of product (COP) between pipeline batches. Yet another might assist quality control and measurement with online instrumentation calibration. These instruments include density, flash point, vapor pressure (RVP), haze, dye, octane and sulfur analyzers as well as product interface detectors.

9.21 For custody transfer, continuous automatic sampling is generally preferred. Refer to Practice D4177 (API MPMS Chapter 8.2). In the event of automatic sampler failure, or if samples cannot be obtained from a marine vessel or shore tanks, manual spot line samples may be necessary. As agreed by interested parties, take manual samples as necessary during the transfer to obtain samples as representative as possible. The degree of product homogeneity, total transfer time, and testing requirements are just some factors to be considered when establishing the number, size and frequency of samples to be taken.

9.22 Manual Pipeline Sampling Procedure - The contents of flowing pipelines are often under considerable pressure and, as such, have some inherent additional hazards associated. A pressure gauge near the sample point is recommended.
(1) Adjust the valve or plug cock from the sampling probe so that a steady stream is drawn from the probe.
(2) After thoroughly flushing the sample probe and line, divert the sample stream to the sample container continuously or intermittently to provide a quantity of sample that will be of sufficient size for analysis. For volatility testing, samples should be obtained by filling from near the bottom of the container to minimize any risk of the evaporative loss of light ends, and a sample cooler may be used if appropriate. Refer to Practice D5842 (API MPMS Chapter 8.4).
(3) If samples are required over a complete batch for custody transfer, the size of the samples and the intervals between each sample should be based on flow rate, and on testing and sample retention requirements, as agreed by all interested parties. The time, and the amount of product transferred, should be recorded to correspond with each sample taken.
(4) Upon completion, the samples may be composited in one container or maintained separately and tested as agreed by all interested parties. Individual test results may be arithmetically averaged adjusting for variations in flow rate during the agreed upon time period.
(5) Tightly cap and clearly label all samples.

9.23 Pipeline Sampling of High Vapor Pressure Liquids - High pressure fixed volume cylinders and high pressure FPCs shall be filled in accordance with the procedures detailed in 9.30.

9.24 Rail Tank Cars - For tank cars, if open sampling is acceptable, use the procedures described for sampling horizontal cylindrical tanks. If restricted or closed system sampling is required, use one of the procedures described for sampling tanks fitted with vapor control valves.

9.25 Road Vehicle Tanks - For road vehicle tanks, if open sampling is acceptable, use the procedures described for sampling horizontal cylindrical. If restricted or closed system sampling is required, use one of the procedures described for sampling tanks fitted with vapor control valves. If the product is known to be homogenous, another common practice is to sample from a bleeder valve on the truck.

9.26 Dispenser (Nozzle) Sampling - This procedure is applicable for sampling light fuels from retail-type dispensers. Fit a nozzle extension to allow fuel to be dispensed to the bottom of the sample device without splashing. See Fig. 23. When the nozzle is fitted with a vapor recovery system, a spacer will be needed to hold back the nozzle sleeve. Fill the sample device slowly, through the nozzle extension, until between 70 and 85 % full. Remove the nozzle and extension and close or cap the container immediately. If the sample is to be analyzed for vapor pressure, refer to Practice D5842 (API MPMS Chapter 8.4).

9.27 Dipper/Ladle Sampling - Dipper sampling is applicable for sampling liquids and semi-liquids where a free or open discharge stream exists, as in small filling and transfer pipelines used for filling barrels, packages, and cans. The dipper device should have a capacity suitable for the amount of sample to be collected and shall be protected from dust and dirt when not being used.

9.27.1 Dipper/Ladle Sampling Procedure:
(1) Ensure the dipper is clean and free of dust and dirt.
(2) Insert the dipper in the free-flowing stream so that a sample is collected from the full cross section of the stream.
(3) Take samples at time intervals chosen so that a complete sample proportional to the pumped quantity is collected.
(4) Transfer samples into the intermediate container as soon as they are collected.
(5) Keep the container closed except when transferring samples into it. As soon as portions of the sample have been collected, close the container and clearly label it.
(6) The gross amount collected should be approximately 0.1 %, but not more than 150 L of the total quantity being sampled.

Sampling Package Lots (Cans, Drums, Barrels, or Boxes)
9.28 Take samples from a sufficient number of the individual packages to prepare a composite sample that is intended to represent the entire lot or shipment. Alternatively, samples may be tested separately. Select at random the individual packages to be sampled. The number of random packages will depend upon several practical considerations, such as:
(1) Tightness of the product specifications;
(2) Sources and type of the material and whether or not more than one production batch may be represented in the load; and
(3) Previous experience with similar shipments, particularly with respect to the uniformity of quality from package to package.

9.28.1 In most cases, the number specified in Table 7 will be satisfactory. If agreed between interested parties, a more statistically rigorous determination may be used.

9.28.2 Sampling Barrels, Drums, and Cans - Obtain samples from the number of containers per shipment as mutually agreed. In the case of expensive solvents, which are typically purchased in small quantities, it is recommended that each container be sampled. Withdraw a portion from each container to be sampled using the tube sampling procedure or bottle sampling procedure possibly using smaller bottles. Prepare a composite sample large enough to accommodate testing, retesting, splitting, and sample retention requirements. The composite should contain portions from each container sampled of the same batch and container size.

9.28.3 Tube Sampling:
(1) The tube sampling procedure is applicable for sampling liquids of 13.8 kPa (2 psig) vapor pressure (RVP) or less and semi-liquids in drums, barrels, and cans.

(2) Use a glass or metal tube, designed so that it will reach to within about 3 mm (1/8 in.) of the bottom of the container. Capacity of the tube can vary from 500 mL (1 Pt) to 1 L (1 qt). A metal tube suitable for sampling 189 L (50 gal) drums is shown in Fig. 21. Two rings soldered to opposite sides of the tube at the upper end are convenient for holding it by slipping two fingers through the rings, thus leaving the thumb free to close the opening. Use clean, dry cans or glass bottles for sample containers.

(3) Typically, the sample is obtained from the top while stood upright. If the drum has a side bung, place the drum or barrel on its side with the bung up. If detection of water, rust, or other insoluble contaminants is desired, let the barrel or drum remain in this position long enough to permit the contaminants to settle. Remove the bung and place it beside the bung hole with the product side up. Close the upper end of the clean, dry sampling tube with the thumb and lower the tube into the product to a depth of about 30 cm (12 in.). Remove the thumb, allowing product to flow into the tube. Again, close the upper end with the thumb and withdraw the tube. Rinse the tube with the product by holding it nearly horizontal and turning it so that the product comes in contact with the part of the inside surface that will be immersed when the sample is taken. Avoid handling any part of the tube that will be immersed in the product during the sampling operation. Allow the tube to drain. Insert the tube into the product again, holding the thumb against the upper end. If an all-levels sample is desired, insert the tube with the upper end open at a rate that permits the liquid level in the tube to remain at the same level as the liquid in the drum. Place the thumb on the top of the tube, withdraw the tube quickly, and transfer the contents to the sample container. Do not allow the hands to come in contact with any part of the sample. Close the sample container; replace and tighten the bung in the drum or barrel. Clearly label the sample container and deliver it to the laboratory.

(4) Obtain samples from cans of 18.9 L (5 gal) capacity or larger in the same manner as for drums and barrels using a tube of proportionately smaller dimensions. For cans of less than an 18.9 L (5 gal) capacity, use the entire contents as the sample, selecting cans at random as indicated in Table 7 or in accordance with the agreement between the purchaser and the seller.

Solid and Semi-Solid Sampling
9.29 Boring Sampling - The boring sample procedure is applicable for sampling waxes and soft solids in barrels, cases, bags, and cakes when they cannot be melted and sampled as liquids. Layering of product may require special sampling as agreed upon by interested parties. The auger should be of sufficient length to pass through the material to be sampled. Refer to Section 6 for a description of the auger.

9.29.1 Boring Sampling Procedure - Remove the heads or covers of barrels or cases. Open bags and wrappings of cakes. Remove any dirt, sticks, string, or other foreign substances from the surface of the material. Bore three test holes through the body of the material, one at the center and the other two halfway between the center and the edge of the package on the right and left sides. If any foreign matter is removed from the interior of the material during the boring operation, include it as part of the borings. Put the three sets of borings in individual sample containers and clearly label.

9.29.2 Grab Sampling:
(1) The grab sampling procedure is applicable for sampling all lumpy or granulated solids in bins, bunkers, freight cars, barrels, bags, boxes, and conveyors. It is particularly applicable for the collection of green petroleum coke samples from railroad cars and the preparation of such samples for laboratory analysis. Refer to Practice D346 when other methods of shipping or handling are used. Petroleum coke may be sampled while being loaded into railroad cars from piles or after being loaded into railroad cars from coking drums.

(2) Use a polyethylene pail of approximately 9.5-L (2.5-gal) capacity as the sample container. Use a stainless steel or aluminum No. 2 size scoop to fill the container.

(3) Grab Sampling Procedure - Lumpy and granulated solids are usually heterogeneous and difficult to sample accurately. It is preferable to take samples during the unloading of cars or during transit; obtain a number of portions at frequent and regular intervals and combine them.

(4) When sampling from railroad cars, use one of these procedures (5 or 6) below:

(5) Being loaded from a pile - Take a full scoop of sample at each of the five sampling points shown in Fig. 29 and deposit in a polyethylene pail. Each sample should be equidistant from the sides of the railroad car. Cover the sample and deliver to the laboratory.

(6) After direct loading from coking drums - At any five of the sample points shown in Fig. 30, take a full scoop of coke from about 30 cm (12 in.) below the surface and deposit it in a polyethylene pail. Cover the sample, clearly label, and deliver to the laboratory.

(7) When sampling from conveyors, take one scoop for each 7 to 9 tonnes (7 to 9 long tons) of coke transported. These samples may be handled separately or composited after all samples representing the lot have been taken.

(8) When sampling from bags, barrels, or boxes, obtain portions from a number of packages selected at random as shown in Table 7, or in accordance with the agreement between interested parties. In most cases, the number specified in Table 7 will be satisfactory. If agreed between interested parties, a more statistically rigorous determination may be used.

(9) Carefully mix the grab sample and reduce it in size to a convenient laboratory sample by the quartering procedure described in Practice D346. Perform the quartering operation on a hard, clean surface free from cracks and protected from rain, snow, wind, and sun. Avoid contamination with cinders, sand, chips from the floor, or any other material. Protect the sample from loss or gain of moisture or dust. Mix and spread the sample in a circular layer and divide it into quadrants. Combine two opposite quadrants to form a reduced sample. If this sample is still too large for laboratory purposes, repeat the quartering operation. In this manner, the sample will finally be reduced to what is intended to be a representative, suitable size for laboratory purposes. Clearly label and deliver the sample to the laboratory in a suitable container.

9.30 Spot Sampling of Liquids Using Cylinders:
9.30.1 Sampling Practices and Procedures - The following are provided as practices and procedures for obtaining liquid spot samples from pipelines, shore storage tanks, marine vessel tanks, rail cars and trucks using fixed volume and FPCs. Refer to Fig. 11 for a typical high pressure sampling system. It is recognized that other practices and procedures or use of alternate equipment, piping, valves, and tubing arrangements, may produce acceptable samples. Regardless of the process and procedures employed, the following shall be observed:
(1) The contents of all lines and components, from the sample probe to the inlet valve of the sample cylinder, are purged and representative of the product being sampled, prior to filling the sample cylinder;

(2) The sample shall remain in a liquid state at all times;

(3) All components that come in contact with the sample shall be compatible with the product being sampled;

(4) Strictly observe safe fill and safety precautions;

(5) Extreme care, good judgment, and sampling experience are necessary to obtain representative samples and to maintain sample integrity for the tests being performed; and

(6) Because of the potential hazards associated with high pressure cylinder sampling, sampling should be performed by, or under the supervision of, persons familiar with the necessary safety precautions. Refer to 6.9. Also refer to Practice D1265 and GPA S 2174 for obtaining samples in fixed volume cylinders.

9.31 Sampling Related Purging and Venting - Vapors vented during purging and sampling shall be controlled to ensure compliance with applicable safety and environmental regulations. The cylinder may be partially filled and then emptied prior to collection of the sample as an alternative to venting hydrocarbon to flush lines.

9.32 Sample Homogeneity - When it has been established that the product being sampled is homogeneous, either as determined by the nature of the product or through mixing or circulation, a liquid sample may be taken from any part of the system.

9.32.1 Slip Tubes and Fixed Sample Lines - Marine vessel cargo tanks and shore tanks, for example spheres and bullets, may be equipped with one or more slip tubes, or one or more sample lines having a fixed depth into the tank. The slip tube or sample line shall be equipped with a probe outlet valve and connections, impervious to the product being sampled, which permit the safe flushing of the probe and line contents, and the accumulation of sample in the cylinder. By design, the depth of the slip tube can be adjusted to ensure a liquid sample is obtained. Samples taken through fixed sample lines will provide either vapor or liquid at that level. In addition, the depth of the fixed sample lines should be recorded since it may be significant if the product being sampled is not homogenous. If the product is not homogenous, fixed sample lines should not be used for obtaining representative samples. An alternate sampling method, as agreed upon by interested parties, should be established, such as additional spot samples, a flow-proportional composite sampler, or an alternate sample point.

9.33 Line Sampling - Thorough purging of sample lines, pumps, and connections is necessary to avoid contamination of the sample. Sample loops should preferably be installed around pumps, valves, or other sources of pressure drop to minimize atmospheric emissions from purging of sample lines. Sampling pumps or other means of controlling pressures higher than the vapor pressure of the sample may be acceptable, and may be used to flush both the lines or the cylinder dead volume, or both, if any, prior to sample collection. See Fig. 31.

9.33.1 Sample Probe - The use of a sample probe in a flowing line is recommended. The sample probe should be located on the side or top of a line, extending into the center third of the flowing stream. Sample points should not be installed on the bottom of a line, unless provisions are made to flush any accumulated debris from the sample point immediately prior to sampling.

9.33.2 Circulating for Line Sampling - Due to the nature of the product and sample points available on shore or marine vessel tanks, it might be necessary or desirable to sample the product as it is being circulated through the pipeline or vessel cargo line. In these instances, it is recommended that the product be circulated for a minimum of 15 min before obtaining samples. The sample point shall be located in the flowing stream, or sample loop, and not located in a dead leg, or otherwise out of the main flow of the product.

9.34 Sample Storage and Disposal - Samples should be stored in such a manner as to enable quick retrieval and to prevent theft, tampering, weathering, or degradation from light, heat, cold, and any other conditions. In addition to the cylinder valves, caps or threaded plugs may be considered as an additional assurance to prevent loss of samples. Store and dispose samples in such a way to ensure compliance with company policy and regulatory requirements.

9.35 Other Liquid Sample Cylinders - Refer to the listed practices, methods, or manufacturer's instructions, or a combination thereof, for the following tests:
(1) Copper Strip Corrosion Cylinder - Test Method D1838;
(2) Vapor Pressure Cylinder - Test Method D1267;
(3) Pressure Hydrometer - Test Method D1657;
(4) Pressure Hydrometer Test Method for Density or Relative Density - API MPMS Chapter 9.2;
(5) Pressure Pycnometer - API MPMS 14.6.

Sampling into Fixed Volume Sample Cylinders
9.36 General - The liquid is sampled at the observed product pressure, and maintained at or above this observed pressure during transportation and subsequent sub-sampling. It is essential to create an ullage volume, typically of approximately 20 %, within the fixed volume sample cylinder immediately after taking the sample to prevent any unsafe increase in sample pressure due to thermal expansion.

9.37 Selection and Leak Testing of the Fixed Volume Sample Cylinder - The working (sample) volume of a fixed volume sample cylinder is typically 20 % less than the nominal volume to allow for the necessary ullage space. Select a fixed volume sample cylinder with the required capacity and a rated working pressure that exceeds the pipeline pressure. Verify that the pressure test certification for the fixed volume sample cylinder, and if so equipped verify the bursting (rupture) disk, is current. Ensure the fixed volume sample cylinder is clean and dry. Pressurize the fixed volume sample cylinder with inert gas to at least 100 kPa (14.5 psig) more than the anticipated pipeline pressure, and test for leaks. If a valve or fitting is found to leak, replace it and re-test, or use another fixed volume sample cylinder.

9.37.1 Purging the Sample Line:
(1) Confirm that all valves are initially closed.
(2) If the fixed volume sample cylinder has an internal outage tube fitted, determine which fixed volume sample cylinder valve is connected to the tube and connect this valve to the sample point control valve. If the fixed volume sample cylinder has a second valve, connect that valve to a closed drain or other safe disposal route. (Warning - Ensure the fixed volume sample cylinder is properly grounded before any sampling commences.)
(3) Purge the sample line by displacing at least 150 % of the line's volume (from the sample probe in the pipeline to the sample point) to the vent immediately before the sample point valve.
(4) Close the vent valve.

9.37.2 Purging a One-Valve Fixed Volume Sample Cylinder:
(1) Open the one valve fixed volume sample cylinder inlet valve to partly fill the fixed volume sample cylinder.
(2) Close the sample point control valve, and open the line vent valve to purge the fixed volume sample cylinder.
(3) Close the vent valve and repeat the partial filling and venting process at least twice more to purge the fixed volume sample cylinder.

9.37.3 Purging a Two-Valve Fixed Volume Sample Cylinder:
(1) For a two-valve fixed volume sample cylinder, open the fixed volume sample cylinder inlet valve to fill the fixed volume sample cylinder partly.
(2) Slowly open the fixed volume sample cylinder outlet valve to its vent.
(3) Close the sample point control valve, and allow part of the fixed volume sample cylinder contents to escape to vent through the fixed volume sample cylinder outlet valve.
(4) Close the fixed volume sample cylinder vent valve and open the sample line vent valve to allow further venting.
(5) Close the sample line vent valve and repeat the partial filling and venting process at least twice more to purge the fixed volume sample cylinder.

9.37.4 Filling the Fixed Volume Sample Cylinder:
(1) On completion of the purging operation, open the sample point control valve to fill the fixed volume sample cylinder;
(2) Close the fixed volume sample cylinder inlet valve;
(3) Close the sample point control valve;
(4) Open the sample line vent valve to safely depressurize the sample line;
(5) Disconnect the fixed volume sample cylinder.

9.37.5 Providing a Safe Ullage Space within a Fixed Volume Sample Cylinder Using an Internal Outage Tube:
(1) Position the fixed volume sample cylinder upright with the sample inlet valve (and internal outage tube) at the top. (Warning - Electrostatic safety considerations may mean that it is advisable to fit the fixed volume sample cylinder with an earth (grounding) connection before proceeding to the next partial venting step.)

(2) Slowly open the fixed volume sample cylinder inlet valve slightly until liquid is observed to escape. Allow the excess liquid to escape, but, as soon as it is observed that the escaping liquid material changes to vapor quickly, close the valve. If no liquid escapes initially then the fixed volume sample cylinder was not filled sufficiently, and the sample should be discarded and the sampling procedure repeated.

9.37.6 Providing a Safe Ullage Space within a Fixed Volume Sample Cylinder Using a Weighing Procedure:
(1) Weigh the filled fixed volume sample cylinder and deduct the tare weight to determine the total weight of sample that has been taken. Calculate the weight of sample that represents a 20 % ullage, and vent this amount by slowly opening the fixed volume sample cylinder inlet valve slightly. (Warning - Electrostatic safety considerations may mean that it is advisable to fit the fixed volume sample cylinder with an earth (grounding) connection before conducting the venting operation.)

(2) Close the fixed volume sample cylinder inlet valve and re-weigh the fixed volume sample cylinder to verify that a safe ullage space has been created. Repeat the partial venting operation if the gross weight still exceeds the tare weight plus 80 % of the original sample weight. (Warning - If the fixed volume sample cylinder weighing cannot be performed at the sampling location, it is important to ensure that a small quantity of the liquid phase sample is vented immediately to prevent excessive pressure build-up as a result of sample expansion due to any subsequent increase in temperature. The full weighing and ullaging procedure should then take place as soon as possible after transportation to a suitable location where the facilities are available.)

9.37.7 Fixed Volume Sample Cylinder Sample Handling:
(1) Upon completion of sampling, the fixed volume sample cylinder should be checked for leaks, for example with a proprietary leak detecting fluid, soapy water, or by immersing in water. If any leaks are detected, discard the sample and repair or replace the fixed volume sample cylinder then repeat the sampling procedure.

(2) Clearly label or tag the fixed volume sample cylinder and prepare it for transportation by packing in a suitable container, as required by the appropriate transportation regulations.

(3) Transport the fixed volume sample cylinder to the laboratory/test location without delay. Where intermediate storage is necessary, the sample should be protected from temperature extremes.

Sampling into Single Floating Piston Cylinders (FPCs)
9.38 General - The liquid is sampled at the observed product pressure, and during transportation and subsequent sub-sampling the liquid is maintained at a pressure close to the observed pressure (or higher) at which the sample was obtained. The sample is accumulated against one side of the floating piston by carefully reducing the pressure of an inert gas buffer on the opposite side of the piston. If the liquid is refrigerated, the effect of low temperatures on the cylinder piston seals, and extraordinary product volumetric expansion within the FPC should be considered. Refer to 6.9.4. See Fig. 8, Fig. 9, and Fig. 10.

9.39 Selection and Leak Testing of the Single Floating Piston Cylinder (FPC) - Select an FPC with the required capacity and a rated working pressure which exceeds the pipeline pressure and meets all applicable transportation requirements, rules, and regulations. Refer to 6.9. Confirm that all components, including the piston seal elastomer are compatible with the liquid, and capable of operating effectively at the anticipated temperature. Ensure the FPC is clean and dry. Refer to 6.9.6. Pressurize both sides of the single floating-piston variable volume sample cylinder with inert gas to at least 100 kPa (14.5 psig) more than the anticipated pressure, and test for leaks. Test the FPC piston seals for leakage by pressurizing each side in turn to the same pressure while the other side is open to atmosphere. If a valve, fitting or seal is found to leak, replace it and re-test, or use another FPC.

9.40 Pre-Charging the Single Floating Piston Cylinder (FPC):
(1) Open the sample inlet valve.
(2) Connect the inert gas pre-charge valve to a supply of the appropriate inert gas. The preferred pre-charge gas is one that is not normally present in the sample (such as, helium, nitrogen, or argon) or one that will not be detected should it leak into the sample. Refer to Practice D3700 for guidance on inert gas usage, and refer to the relevant test methods.
(3) Open the inert gas pre-charge valve slowly, and pressurize to at least 100 kPa (14.5 psig) above the pipeline pressure, or that recommended by the single floating-piston variable volume sample cylinder manufacturer, so that the piston is fully displaced against the sample inlet end plate.
(4) Close all valves.
(5) Depressurize the line safely.
(6) Disconnect the inert gas supply.
(7) Transport the pre-charged FPC to the sample point within its transportation case.

9.41 Purging the Sample Lines and Single Floating Piston
Cylinder (FPC):
(1) Connect the pre-charged FPC sample inlet valve to the sample point, either directly or using minimal tubing.

(2) With the FPC inlet valve closed, open the sample point control valve.

(3) Open the FPC purge (exhaust) valve to flush out sample line upstream of the FPC inlet valve. The flow should be fast enough to flush any debris from the line, but short enough duration to minimize venting. If the FPC does not have a purge (exhaust) valve, the line from the sample line control valve to the sample point should be similarly flushed our before connecting the FPC to be filled. In either case, the purge/vent line should be piped to a flare line or elsewhere in the process to minimize emissions to the atmosphere.

(4) Close the FPC purge valve.

9.42 Filling the Single Floating Piston Cylinder (FPC):
(1) Verify that the pressure in the pre-charge chamber of the FPC is higher than the pressure at the sample point.

(2) Open the FPC inlet valve. Provided the pre-charge chamber is at a higher pressure than the line, the piston should not move before the inert gas is vented. If the piston does move before the gas is vented, reject, and use another FPC, increasing the pressure as appropriate. (Warning - Do not attempt to fill a single FPC when there is little or no pressure on the pre-charge side of the cylinder, because the piston and attached indicator rod can move with extreme speed and force.)

(3) Slowly vent the inert gas from the balance chamber through the FPC inert gas pre-charge valve. When the pressure at the balance side approaches the pressure at the sample point, sample will begin to flow into the FPC, pushing the floating piston back. (Warning - Vent the inert gas slowly when approaching the sample pressure. Rapid venting can result in excessive vaporization, or cause the piston to move abruptly, or both.)

(4) Monitor the piston position indicator, stopping at the desired fill level (or fill density), not to exceed 80 % at 15°C (59°F). The pressure difference between the sample and the inert pre-charge sides of the piston should not exceed 100 kPa (14.5 psig) at any time during sampling to ensure that the sample does not drop below its bubble point and allow gas breakout to occur. (Warning - When filling a single FPC
below about -5°C, the maximum fill density shall be reduced below 80 % to account for the additional thermal expansion (based on the product being sampled), and satisfy regulatory requirements for increased outage or reduced fill density.)

(5) Close the FPC inert gas pre-charge valve.

(6) Close the FPC inlet valve.

(7) Close the sample line control valve.

(8) Before disconnecting the FPC, depressurize the sample line preferably to a flare line or elsewhere in the process to minimize emissions to the atmosphere.

(9) Disconnect the FPC. At the end of sampling, the sample in the FPC should be at the same pressure as the sample point, which may not be appropriate for subsequent use in the laboratory. It is good laboratory practice to adjust the pressure in the FPC to a suitable pressure prior to analysis. Refer to Practice D3700 for guidance, and refer to the relevant test methods.

(10) Clearly label or tag the FPC and prepare it for transportation by packing in a suitable container, as required by the relevant transportation regulations.

(11) Transport to the laboratory/test location without delay. Where interim storage is necessary, the sample should be protected from extremes of temperature.

9.43 Sampling into Double-Piston (Variable Volume) Cylinders:
9.43.1 General - The liquid is sampled at the observed product pressure, and during transportation and subsequent sub-sampling the liquid is maintained at a pressure close to the observed pressure (or higher) at which the sample was obtained. Sample is accumulated against only one of the floating pistons by carefully reducing the pressure of the inert gas buffer on the opposite side of that piston. The inert gas pressure on the second piston is kept significantly greater than the pipeline pressure throughout the sample accumulation stage to ensure that the DPC is not overfilled. Refer to Fig. 32 for an example of a DPC.

9.43.2 Selection and Leak Testing of the Double Piston Cylinder (DPC) - The working sample volume of a DPC is only about 50 % of the total volume. Select a DPC with the required capacity and a rated working pressure which exceeds the pipeline pressure and meets all applicable transportation requirements, rules, and regulations. Refer to 6.9.2 and 6.9.3. Confirm that all components, including the piston seal elastomer are compatible with the liquid, and capable of operating effectively at the anticipated temperature. Ensure the DPC is clean and dry. See 6.9.6.1. Leak test all components, and if a valve, fitting or seal is found to leak, replace it and re-test, or use another DPC.

9.44 Pre-Charging the Double Piston Cylinder (DPC):
(1) Open the sample inlet valve.

(2) Connect both inert gas pre-charge inlet valves to a supply of the appropriate inert gas. The preferred pre-charge gas is one that is not normally present in the sample (such as, helium, nitrogen, or argon) or one that will not be detected should it leak into the sample. Refer to Practice D3700 for guidance on inert gas usage, and refer to the relevant test methods.

(3) Open the inert gas pre-charge inlet valves slowly, and pressurize to at least 500 kPa (72.5 psig) above the pipeline pressure, or that recommended by the floating-piston variable volume sample cylinder manufacturer, so that both pistons are fully displaced against the central sample inlet/baffle plate.

(4) Close all valves.

(5) Depressurize the line safely.

(6) Disconnect the inert gas supply.

(7) Transport the pre-charged DPC to the sample point within its transportation case.

9.45 Purging the Sample Lines and the Double Piston Cylinder (DPC):
(1) Connect the pre-charged DPC inlet valve to the sample point, either directly or using minimal tubing.

(2) Connect the sample outlet port/septum adapter valve to a closed drain or other safe disposal route.

(3) Open the DPC outlet port valve fully and partially open the DPC inlet valve (typically one-quarter turn).

(4) Carefully open the pipeline sample point control valve to thoroughly flush the sample line and DPC dead volume.

(5) Connect the pre-charged DPC inlet valve to the sampling point. Connect the sample outlet port/septum adapter valve to a closed drain or other safe disposal route.

(6) Control the rate of liquid flow through the DPC by carefully opening the inlet valve and the sample point valve further until the dead volume has been thoroughly flushed.

9.46 Filling the Double Piston Cylinder (DPC):
(1) Close the DPC outlet port valve fully on completion of the flushing operation. Neither piston should move at this stage due to the buffer gas pressure being higher than the pipeline pressure.

(2) Slowly open one (but not both) of the inert gas end valves to gradually reduce the inert gas pressure on one side of the DPC. The reduction in the inert gas pressure will allow sample to accumulate into the working side of the DPC, as a result of the pressure differential between the pipeline and the inert gas buffer.

(3) The inert gas valve is to be carefully adjusted to ensure that the corresponding sample inlet flow rate is properly controlled. The pressure difference between the pipeline and the working inert gas buffer should not exceed 100 kPa (14.5 psig) at any time during the sample accumulation period.

(4) Close the valves when the piston position indicator shows that the double DPC has been filled to approximately 90 % of the filled side of the DPC (that is, about 45 % of the nominal total capacity).

(5) Before disconnecting the DPC, depressurize the sample line preferably to a flare line or elsewhere in the process to minimize emissions to the atmosphere.

(6) Finally, and as necessary, connect the working inert gas inlet valve to an inert gas supply and increase the inert gas pressure to at least 100 kPa (14.5 psig) above the pipeline pressure. Refer to Practice D3700 for guidance on inert gas usage, and refer to the relevant test methods. It is not necessary to equalize the pressure between both inert gas buffers, but this may be done provided that the resulting final inert gas pressure is maintained above the pipeline pressure.

(7) Disconnect the DPC.

(8) Clearly label or tag the DPC and prepare it for transportation by packing in a suitable container, as required by the appropriate transportation regulations.

(9) Transport to the laboratory/test location without delay. Where intermediate storage is necessary, the sample should be protected from extremes of temperature.

9.47 Sub-Sampling and Mixing - Before sub-sampling the primary sample for analysis, it may be homogenized by forcing the total sample quantity repeatedly through fine-bore transverse holes in the central baffle plate. This is achieved by alternately reducing the pressure of one inert gas buffer relative to the other (while maintaining the sample pressure above its bubble point). Alternate methods of mixing may also be acceptable based on product, equipment and experience. The efficiency of this multi-phase sample homogenization may be verified by controlled injection/recovery tests. Consequently, these DPCs are recommended for taking time-synchronized spot samples that are used for the calibration and verification of automatic pipeline water content analyzers operating on high pressure pipelines, including unstabilized crude oil and condensate production, and being used in fiscal or allocation accounting applications.