ASTM D4057 standard practice for manual sampling of petroleum and petroleum products
10. Special Instructions for Specific Products
10.1 This section provides specific additional equipment, container, sampling and sample handling guidance for the referenced products. It is meant to supplement, and be used in conjunction with, the guidance provided in the other sections. In addition, reference the test methods to determine if any special sampling and sample handling is required. Refer to Appendix X1 listing sample handling guidance for common crude oil tests.

Crude Oil
10.2 Properties - By its very nature, crude oil is typically non-homogenous, containing some percentage of sediment and water. It also typically contains volatile light ends, and finally crude oil will often exhibit high pour point and high viscosity properties, due to its asphaltenes and paraffin wax content. Each of these properties presents unique challenges with regard to obtaining representative samples from the field, and maintaining the integrity of the sample representation to the analytical apparatus.

10.2.1 Crude Oil Sediment and Water Component - Stratification - The water and sediment component of the crude oil will tend to naturally separate and stratify in shore tanks, marine vessel compartments and in flowing pipelines. The concentration of dispersed water and sediment in the oil is normally higher near the bottom of a shore tank, marine vessel compartment or pipeline. A running or all-level sample, or a composite of spot samples, for example upper, middle and lower samples, may not provide a sample representative of the concentration of the dispersed water and sediment present. Because of this stratification tendency, the representativeness of a manual sample may vary greatly based on many factors such as, but not limited to: the timing of obtaining manual samples following a transfer or tank mixing; velocity of the transfer rate, or capability of mixers; piping and inlet configurations; mixing elements in the transfer line; density of the crude oil relative to water; temperature and viscosity of the crude oil; use of additives; etc. In addition, the oil, water and sediment interfaces are often difficult to identify and quantify, especially in the presence of emulsions. Finally, the free water, sediment and emulsion levels can vary across the bottom of the shore tank, marine vessel compartment or pipeline.

10.2.2 Volatile Light Ends - Volatile light ends may be lost in manual sampling operations, particularly if the product is transferred from the primary sample container, potentially affecting vapor pressure, distillation, density, and possibly other volatility related properties. Transferring crude oil samples from the primary sample container to an intermediate container is a common and required practice using certain closed and restricted sampling systems.

10.2.3 High Pour Point and High Viscosity Crude Oil - If not maintained at a sufficiently high temperature, wax deposition on the walls of the shore tank, the marine vessel compartment, and the pipeline may occur likely leading to unrepresentative samples. Exercise great care, particularly with regard to heating and homogenizing, to ensure the sample remains representative during all handling stages from the primary sample container to the test apparatus. Refer to Practice D5854 (API MPMS Chapter 8.3).

Obtaining Crude Oil Samples
10.2.4 Plastic Containers - Plastic containers are generally not recommended for sampling crude oil primarily due to, but not limited to, the inability to retain volatile light-end components, and inability to heat high pour or high viscosity crude oils without deformation.

10.2.5 Shore Tank and Marine Vessel Compartment Manual Sampling:
10.2.5.1 Common Methods - The following methods are common for sampling crude oil shore tanks and marine vessel compartments:
(1) Running or all-levels sampling,
(2) Spot sampling - typically upper, middle, and lower (UML) or top, middle, and bottom (TMB),
(3) Dead bottom sampling, with or without extension rods.

10.2.5.2 Crude Oil Stratification - Spot samples may be taken to assess the level of stratification of a particular property within a shore tank or marine vessel compartment. The use of composite samples based on spot samples, such as upper, middle and lower (UML), is not recommended for S & W determination as the heaviest S & W is often located below the lower sample; therefore, the use of running or all level samples is recommended.

10.2.5.3 Closed System Crude Oil Sampling Issues - Closed and restricted manual sampling provides additional challenges in obtaining representative samples of crude oil containing water and sediment, including: (1) product residue on the primary sampler; (2) incompatible fittings; (3) inert gas pressure while sampling; (4) difficult and cumbersome using closed system equipment through vapor control valves; (5) size restrictions of primary sampler; (6) inability to see product being sampled; and (7) limited visibility of the sample volume obtained. During cold weather, high pour crude oils are very difficult to sample due to the wax build-up on deck equipment. Volatile light-end components may be lost in manual closed or restricted sampling operations, particularly with equipment that requires product to be transferred from the primary sample container. It is for many of these reasons that open tank and marine vessel compartment sampling is the preferred method to obtain the most representative manual samples.

10.2.5.4 Sampling Small Crude Oil Lease Tanks - Small crude oil lease tanks of less than 159 m3 (1000 barrels) used for custody transfer related to truck or pipeline gathering systems often require an assessment of crude oil quality be made onsite prior to beginning the custody transfer. The API MPMS Chapter 18.1 provides custody transfer guidelines for sampling, gauging, obtaining temperatures, and determining crude quality from small tanks to a tank truck.

10.2.6 Obtaining Large Sample Volumes of Crude Oil - If large-volume samples are required which may not, because of volatility or other considerations, be obtained by the bulking of smaller quantities, mix the tank contents thoroughly by the means available (for example, circulation, tank side mixer). Confirm homogeneity by tests on samples taken at different levels as agreed by interested parties. Fill the sample container using a sample inlet designed to fill from near the bottom of the container, with the sample taken from tank-side taps, or from a sample point on the tank circulation system.

10.2.7 Obtaining Spot Line Samples of High Pour Point Crude Oils from Shore Tanks or Pipelines - If the crude oil being sampled has a high pour point, it may be necessary to insulate the sample line thermally or to provide means of heating the sampling connections in order to prevent solidification.

10.2.8 Obtaining Spot Line Samples of Crude Oil for Volatility Measurement from Shore Tanks or Pipelines - If testing for volatility properties, fill the sample container using a sample inlet designed to fill from near the bottom of the container to minimize the loss of light ends. Cooling of the sample container and the use of a cooler for sample transportation may also be considered. Also refer to Practice D5842 (API MPMS Chapter 8.4).

10.2.9 Obtaining Spot Line Samples of Low Pressure Crude Oil from Shore Tanks or Pipelines - Fill fixed volume sample container after thoroughly flushing the sample probe and line. Empty low pressure variable volume sample container (for example, collapsible flexible containers, bladders or diaphragm containers) prior to use. Where appropriate, the container may be evacuated. The container shall be filled directly after thoroughly flushing the sample probe and sample line.

10.2.10 Obtaining Spot Pipeline Samples of High Vapor Pressure Crude Oil - Refer to 9.30. (Warning - Use of low pressure variable volume containers (for example, collapsible flexible containers, bladders or diaphragm containers), or low pressure fixed volume containers (for example, bottles or cans) for sampling high vapor pressure pipeline liquids are not recommended. If such containers are used, phase separation may occur as the pressure is reduced and light ends may be lost. Manufacturers' guidelines and limitations are to be strictly followed regarding the pressure limitations, and handling, of the variable volume container.)

10.2.11 Obtaining Spot Samples of Crude Oil Production Flowing Pipelines:
10.2.11.1 The following procedure should be used for atmospheric crude oil sampling from crude oil production and process systems for performance monitoring and quality analysis.
(1) Prior to sampling, prepare all sampling equipment in compliance with applicable safety procedures and facility specific requirements.

(2) Ground the sample can to a suitable and designated bonding point. In addition, in order to earth any static charge on their person, the individual obtaining the sample shall touch some part of the structure, at least 1 m (3 ft) from any sample point immediately before carrying out the sampling operation. (Warning - Plastic containers are not to be used for sampling and subsequent homogenization due to the risk of static build-up. When connecting earth leads to the sample cans, ensure metal to metal contact is not compromised by painted surfaces or coatings. To ensure metal to metal contact clean a small area of paint away from the rim of the can and manipulate the earth lead clip back and forth on connecting surface to make sure direct contact is achieved. Alternatively use a purpose designed grounding lead and static earthing clamp. Some devices are fitted with tungsten carbide teeth to cut through paint and provide visual indication that a resistance of 10 ohms or less is present and do not have the potential to accumulate sufficient energy to create a spark.)

(3) Flush the sample point and associated upstream piping into a grounded metal container until the sample line has been thoroughly purged of crude oil, and any residual water or deposition products.

(4) Fill the metal sample can such that it is between 70 and 85 % full in order to provide ullage space for subsequent homogenization, and to allow for possible crude oil thermal expansion.

(5) Cap and immediately label the sample container in preparation for transportation or delivery for testing or retention.

Handling of Crude Oil Samples
10.3 General - The handling of samples shall be based on individual and composite testing requirements, anticipated retesting, retain and sharing of samples. This practice is written with the understanding that any unique or special sample handling instructions will be provided in the relevant test method.

10.3.1 Sequence of Test Methods - When performing several tests on a sample of crude oil it is very important to ensure that the sequence of testing is evaluated to minimize altering the properties of the remaining sample to be tested or retained. If crude oil samples are to be tested for vapor pressure, H2S, or any other test in which retention of light ends is critical, sub samples for these test methods should be taken first before any other sample handling procedures are performed, as provided in the specific test methods. For some tests, such as vapor pressure and some H2S test methods, the primary sample container is typically used to provide the sample directly into the analytical instrument. If the test methods have conflicting requirements, separate samples may be necessary for testing directly from each individual primary sample container, as described or required in the test method.

10.3.2 Crude Oil Sample Transportation - The sample is to be transported to the test laboratory in the original sample container, without transfer or compositing (bulking), in order to maintain the integrity of the sample. If the sample needs to be transferred, it shall be performed following the recommendations as provided in Practice D5854 (API MPMS Chapter 8.3). Many test methods specify time constraints and limitations on how soon a sample is to be tested following the time the samples were obtained. In these instances, the samples shall be transported to the testing location in a safe and timely manner to maintain the integrity of the sample, and sample container, or stored in an appropriate cool, dark, dry location. If the sample is to be tested for volatility measurement, refer to Practice D5842 (API MPMS Chapter 8.4) and the related test methods.

10.3.3 Heating of Crude Oil Samples - Crude oils stored at temperatures below their cloud point will show wax deposition on the walls of the sample containers. The wax coming out of the solution will be, preferentially, the wax with the high melting point. It is this type of wax that has the most pronounced influence on the crude oil pour point and, at the same time, is the most difficult to redissolve or disperse in the crude oil. In order to achieve complete solubility of the wax, heat crude oil samples to a temperature above the cloud point. Since this value is seldom known, heating the sample to a temperature of 20°C above the expected pour point will usually satisfy the cloud point requirement, although exceptions do occur. The vast majority of crude oils show a significant vapor pressure even at ambient temperatures. Crude production is usually stabilized at a vapor pressure of 50 kPa (Test Method D323, RVP at 37.8°C) or below. However, occasionally, high vapor pressure crudes (80 kPa) are produced and marketed. Before testing, never subject a crude oil sample to a temperature higher than 60°C or to a temperature above the bubble point (vapor pressure 100 kPa). As a rule of thumb, the vapor pressure doubles for every 20°C increase in temperature.

Crude Oil Mixing and Homogeneity
10.4 General - The proper means and effectiveness of mixing in order to achieve homogeneity depend on the physical properties (for example, viscosity, temperature, volatility, density, water and sediment) of the crude oil and the capacity, shape, and type of container in which the crude oil arrives at the laboratory. It is virtually impossible to anticipate every possibility and achieve optimum results under all circumstances. Refer to Practice D5854 (API MPMS Chapter 8.3) and the test method for specific guidance.

10.4.1 Cans, 1 to 15 L - (1 qt to 4 gal) Store the container at a temperature 20°C (36°F) above the expected pour point preferably in a water bath kept at the appropriate temperature. Alternatively, store the container in an explosion-proof oven, bearing in mind that local surface temperatures might be much higher than the oven temperature reading indicates. The time required to dissolve the wax will depend on the type of wax and the size of the container. For a 1-L (1-qt) tin, 2 h has been found to be adequate. For larger tins, longer times will be required. Although it is strongly recommended that the containers are closed when heated, after approximately 30 min, it is advised to slowly release the excess pressure before continuing the heating. Mixing can be accomplished by a mechanical shaker or by vigorous manual shaking. Although the use of (high speed) mixers or similar devices might be effective, it will require that the container be open for some time, during which the escape of light ends can be excessive, and hence, this procedure is not recommended. (Warning - (1) Exercise care when opening the container as significant vapor pressure will have built up. Opening the container may induce foaming with resultant spillage of sample and possible injury to personnel. (2) During this operation significant amounts of highly flammable vapors might escape. Vent in a safe area. Samples used for custody transfer shall be homogenized and composited following the guidance as provided in Practice D5854 (API MPMS Chapter 8.3).)

10.4.2 Crude Sample Bottles - Based on the pour point and viscosity, and testing requirements, the sample may require heating, homogenizing and compositing or other necessary steps to prepare the sample, or a portion of the sample. If heating is required, place all samples that will be used to make a composite into the appropriate mechanism to heat the samples. Heat the samples only enough to liquefy the sample, for example maybe 20 to 30°C (36 to 54°F) above the pour point. (Warning - Depending on the sample to be tested and test method to be performed, glass sample containers containing crude oil shall be vented slightly during the warming process. Samples shall remain in the heating apparatus until temperature equalizes with environment.) (Warning - Exercise special care when heating bottles that are closed with a cork. The pressure increase due to the heating may blow out the cork. Take proper measures to safeguard against such an event. Samples used for custody transfer shall be homogenized and composited following the guidance as provided in Practice D5854 (API MPMS Chapter 8.3).)

10.4.3 Crude Oil Drums, 15 to 200 L - The most effective way of achieving homogenization is mixing the contents of the drum on a roller bank in a hot room kept at a temperature between 40 and 60°C for 48 h. Alternatively, keep the drum at a temperature of 20°C above the expected pour point for 48 h and roll the drum for at least 15 min before taking a sample. If heating of the drum is not feasible, the only alternative is extensive rolling for at least 30 min to disperse the wax and wax particles as effectively as possible. In order to avoid the cumbersome procedure of (re)mixing the contents of large sample containers, it is recommended to draw an adequate number of sub-samples in smaller containers while the crude oil is considered to be homogenous. (Warning - (1) Before embarking on any heating or mixing procedure, or both, ensure that the drum and plugs can withstand the expected pressure build-up and can be handled safely without leakage. (2) Exercise care when opening the container as significant vapor pressure will have built up. Opening the container my induce foaming with resultant spillage of sample and possible injury to personnel.)

Refined Products
10.5 Gasoline and Distillate Products:
10.5.1 Gasoline and light distillate products are usually homogeneous, but they are often shipped from tanks that have clearly separated water on the bottom. Tank sampling of gasoline and distillate products, in accordance with the procedures outlined in Section 9 is acceptable.

10.5.2 Light-Sensitive Samples - It is important that samples sensitive to light, such as gasoline, be kept in the dark if the testing is to include the determination of such properties as color, octane, sludge-forming characteristics, stability tests, or neutralization value. Brown glass bottles may be used. Wrap or cover clear glass bottles immediately after filling.

10.5.3 Sample Handling of Refined Materials - Protect highly-refined products from moisture and dust by placing paper, plastic, or metal foil over the stopper and the top of the container.

10.5.4 Distillation of Petroleum Products - When obtaining samples of volatile liquids that are to be tested using Test Method D86, a sampled maintained in the primary sample container is recommended because the sample is taken directly in the bottle. Before obtaining the sample, pre-cool the bottle by immersing it in the product, allowing it to fill, and discarding the first filling. If the bottle procedure cannot be used, obtain the sample by the tap sampling procedure. Do not agitate the bottle while drawing the sample. After obtaining the tap sample, close the bottle immediately with a tight-fitting stopper and store it in an ice bath or refrigerator at a temperature of 0 to 4.5°C (32 to 40°F). Refer to Test Method D86.

10.5.5 Vapor Pressure - When sampling petroleum and petroleum products that are to be tested for vapor pressure, refer to Practice D5842 (API MPMS Chapter 8.4).

10.6 Oxidation Stability Precautions - Very small amounts (as low as 0.001 %) of some materials, such as inhibitors, have a considerable effect on oxidation stability tests. Avoid contamination and exposure to light while taking and handling samples. To prevent undue agitation with air, that promotes oxidation, do not pour, shake, or stir samples to any greater extent than necessary. Never expose them to temperatures above those necessitated by atmospheric conditions.

10.7 Sample Containers - Use only brown glass or wrapped clear glass bottles as containers, since it is difficult to make certain that cans are free of contaminants, such as rust and soldering flux. Adequately prepare and clean bottles as described in 6.6. Rinse thoroughly with distilled water, dry, and protect the bottles from dust and dirt.

10.8 Sampling - A sample maintained in the primary sample container is recommended because the sample is taken directly in the bottle. This reduces the possibility of air absorption, loss of vapors, and contamination. Just before sampling, rinse the bottle with the product to be sampled.

10.9 Aviation Fuel - When sampling aviation fuel, in addition to the individual test method, Practice D4306 should be consulted for recommended cleaning procedures for containers related to specific test methods.

10.9.1 Sampling equipment fabricated from copper or its alloys shall not be used for sampling aviation fuels.

10.9.2 Before sampling, the sampler and the container shall be flushed and rinsed thoroughly at least three times with the product to be sampled and allowed to drain before use.

10.10 Residual Fuel Oils/Bunker Fuel - Residual fuel oils usually are non-homogeneous. Tank samples of residual oils may not be representative for the following reasons:
(1) The concentration of entrained water is generally higher near the bottom. The running sample or the composite of the upper, middle, and lower sample may not represent the concentration of entrained water.
(2) The interface between oil and free water is difficult to measure, especially in the presence of emulsion layers, or sludge.
(3) The determination of the volume of free water is difficult because the free water level may vary across the tank bottom surface. The bottom is often covered by pools of free water or water emulsion impounded by layers of sludge or wax.

10.11 Asphaltic Materials - When sampling asphaltic materials that are to be tested using Test Methods D1856 or D2172, obtain samples by the boring procedure or the grab procedure. A sample of sufficient size to yield at least 100 g (3.5 oz) of recovered bitumen is required. About 1 kg (2 lb) of sheet asphalt mixtures usually will be sufficient. If the largest lumps in the sample are 2.5 cm (1 in.), 1.8 kg (4 lb) will usually be required and still larger samples if the mixtures contain larger aggregates.

10.11.1 Emulsified Asphalts - It is frequently necessary to test samples in accordance with the requirements of Specification D977 and Test Methods D244. Obtain samples from tanks, tank cars, and tank trucks by either the core thief or bottle sampling procedure using a bottle that has a 4-cm (1.5-in.) diameter or larger mouth. Also, refer to Practice D140. Use the dipper procedure to obtain samples for fill or discharge lines. Table 7 should be consulted for sampling packages. If the material is solid or semisolid, use the boring sampling procedure. Obtain at least 4 L (1 gal) or 4.5 kg (9.9 lb) from each lot or shipment. Store the samples in clean, airtight containers at a temperature of not less than 4°C (39°F) until tested. Use a glass or black iron container for emulsified asphalts of the RS-1(Rapid Setting) type, as referenced in Specification D977.

10.12 Industrial Aromatic Hydrocarbons - Industrial Aromatic Hydrocarbons - For samples of industrial aromatic hydrocarbons (benzene, toluene, xylene, and solvent naphthas), proceed in accordance with Sections 6 - 9, with particular emphasis on the procedures pertaining to precautions for care and cleanliness.

10.13 Lacquer Solvents and Diluents - When sampling bulk shipments of lacquer solvents and diluents that are to be tested using Guide D268 observe the precautions and instructions described in 6 - 9, with particular emphasis on the procedures pertaining to precautions for care and cleanliness.

10.14 Grease Sampling - This procedure covers practices for obtaining samples from production lots, shipments of lubricating greases, soft waxes, or soft bitumens similar to grease in consistency. This procedure is quite general because a wide variety of conditions are often encountered, and the procedure may have to be modified to meet individual specifications.

10.14.1 Inspection:
(1) If the material is lubricating grease and inspection is made at the manufacturing plant, take samples from finished shipping containers of each production batch or lot. Never take grease samples directly from grease kettles, cooling pans, tanks, or processing equipment. Do not sample the grease until it has cooled to a temperature not more than 9°C (16°F) above that of the air surrounding the containers and it has been in the finished containers for at least 12 h. When the containers for a production batch of grease are of different size, treat the grease in each container size as a separate lot. When inspection is made at the place of delivery, obtain a sample from each shipment. If a shipment consists of containers from more than one production batch (lot numbers), sample each batch separately.

(2) If the material being inspected is of grease-like consistency, but is not actually lubricating grease but some mixture of heavy hydrocarbons, such as microcrystalline waxes or soft bitumens, it is permissible to take samples from pans, tanks, or other processing equipment, as well as from containers of the finished product. The grease sampling method shall be applicable to such stocks only if for some reason it is not possible to apply heat and convert the material into a true liquid.

10.14.2 Sample Size - Select containers at random from each lot or shipment to give the required quantity specified in Table 8.

10.14.3 Grease Sampling Procedure:
(1) Examine the opened containers to determine whether the grease is homogeneous, comparing the grease nearest the outer surfaces of the container with that in the center, at least 15 cm below the top surface, for texture and consistency. When more than one container of a lot or shipment is opened, compare the grease in all open containers.

(2) If no marked difference in the grease is found, take one portion from the approximate center and at least 7.5 cm (3 in.) below the surface of each opened container in sufficient quantity to provide a composite sample of the desired quantity (see Table 8). Withdraw portions with a clean scoop, large spoon, or spatula and place them in a clean container. Very soft, semi-fluid greases may be sampled by dipping with a 0.45-kg (1 lb) can or suitable dipper. If any marked difference in the grease from the various locations of an opened container is found, take two separate samples of about 0.45 kg (1 lb) each, one from the top surface adjacent to the wall and the other from the center of the container, at least 15 cm (6 in.) below the top surface. If any marked variations are noted between different containers of a lot or shipment, take separate samples of about 0.45 kg (1 lb) from each container. When taking more than one sample of a batch or shipment, because of lack of uniformity, send them to the laboratory as separate samples.

(3) If more than one portion is required to represent a lot or shipment of grease softer than 175 penetrations (refer to Test Methods D217), prepare a composite sample from the containers of the same size and batch by mixing equal portions thoroughly. Use a large spoon or spatula and a clean container. Avoid vigorous mixing or working of air into the grease. As grease samples become partially "worked" in being removed from containers, the procedure is not suitable for obtaining samples of greases softer than 175 penetration on which unworked penetration is to be determined. For greases having a penetration of less than 175, cut samples from each container with a knife in the form of blocks about 15 by 15 by 5 cm (6 by 6 by 2 in.). If required, make unworked penetration tests on blocks as procured and other inspection tests on grease cut from the blocks.