ASTM D4057 standard practice for manual sampling of petroleum and petroleum products
7. Sampling Devices/Equipment and Accessories
Introduction
7.1 The preferred manual sampling devices and processes are those that do not require the sample to be transferred from the primary sample container to an intermediate container. Sampling devices shall be designed, constructed, and maintained to ensure that they perform the purpose or function for which they are intended. They shall be of sufficient strength to withstand pressures likely to be generated and sufficiently robust to withstand normal handling. Liquid sampling devices shall be leak-tight to maintain the initial characteristics of the sample. Materials of construction for sampling devices and their accessories should be compatible with the product sampled and ensure that there will be no interaction between the product and the sampling device that would affect the integrity of either.

7.2 If there is any question regarding the applicability of the sampling device to a specific product, testing should be performed to verify compatibility. Table 2 contains a listing of commonly used manual sampling devices for liquid products; categorized by the method by which the sampler is filled.

7.3 Cage Sampler:
7.3.1 A cage sampler shall be constructed of a spark-reducing metal, appropriately sized to hold the container, typically a 1 L (1 qt) bottle. See Fig. 12. The lowering and retrieval equipment shall be attached to the cage in such a manner that a stopper can be opened by means of a sharp jerk. A restricting device, such as a cap with a hole drilled in it, may be used to restrict the filling rate. The combined apparatus shall be weighted so as to sink readily in the product to be sampled. Cage samplers may be used to obtain spot, running and all-levels samples.

7.3.2 The use of a sampling cage, or any sampling process that avoids the need to transfer the sample into an intermediate sample container, is preferred for samples used for volatility testing.

7.4 Weighted Bottle - Configure the weighted bottle sampler by attaching a weighted line to the sample bottle as shown in Fig. 13. The stopper should be tied to the cord about 150 mm (6 in.) from the neck of the bottle. Attach the lowering device to the bottle in such a manner that the stopper may be opened by means of a sharp jerk of the lowering cord. A restricting device, such as a cap with a hole drilled in it, may be used to restrict the filling rate. Weight the combined apparatus so as to sink readily in the product to be sampled. Design shall allow for filling the container at any desired level. A weighted bottle sampler may be used to obtain spot, running, and all-levels samples.

7.5 Weighted Beaker - The sampling beaker shall be constructed of a spark-reducing metal and weighted so as to sink readily in the liquid to be sampled. The lowering and retrieval equipment shall be attached to the sampler in such a manner that a stopper can be opened by means of a sharp jerk. To reduce the difficulty with cleaning the beaker, any weighting material shall be fixed to the beaker in such a way that it does not come into contact with the sample. Weighted beaker sampler may be used to obtain spot, running, and all-levels samples. Caution shall be exercised to ensure that a residue from prior samplings does not contaminate subsequent samples obtained. Samples obtained using a weighted beaker requires transfer to an intermediate container, potentially affecting the integrity of the sample. See Fig. 14.

7.6 Bottom Water and Remaining On-Board/On-Board Quantity (ROB/OBQ) Sampler/Scraper - Typically constructed of copper or brass tubing, open at the top, designed with a clip on one side, and rounded bottom to allow the sampler to tip over on the tank or vessel compartment bottom. This device may have a removable bottom for cleaning. Sampler fills with product at first, hits the bottom, and falls over. Product rises to the top with free water displacing the product in the sampler. Use the sampler/scraper in a similar manner to sample very small volumes in a tank or OBQ/ROB product on marine vessels including, sludge and semi-liquid or high-viscosity material residue. See Fig. 15.

7.7 Tank Tap Sampling:
7.7.1 Each tap should be a minimum of 1.25 cm (1/2 in.) in diameter. Taps with a 2.0 cm (3/4 in.) diameter or more may be required for heavy, viscous liquids, for example, those with a relative density of 0.9465 or greater (18.0° API or less). On tanks that are not equipped with floating roofs, each sample tap should extend into the tank a minimum of 10 cm (4 in.). Some sample taps may be equipped with a delivery tube that permits the filling of the sample container from the bottom, as reflected in Fig. 16. Refer to Practice D5842 (API MPMS Chapter 8.4).

7.7.2 Tap Sampling Requirements - At a minimum, a tank should be equipped with a sample tap that is at the elevation of the main tank outlet. For multiple level samples, the tank is to be equipped with at least three sampling taps placed equidistant throughout the tank height, based on normal liquid height operating levels of the tank. Additional sample taps, for example as many as a total of five or six, may be required based on the size of the tank, type of product service, anticipated varying liquid height operating levels, and history of product homogeneity. With reference to the circumferential location, sample taps should be located a minimum of 2.4 m (8 ft) from the tank inlet and 1.6 m (5 ft) from the tank outlet/drain. If a tube is used, take steps to ensure that the tube will not contaminate the product being sampled.

7.8 Pipeline Manual Tap Sample Probe:
7.8.1 A sample probe in a pipeline is used to direct sample from the flowing stream. Manual tap sample probes are often used for product identification, testing, and calibration of online instrumentation.

7.8.2 Probe designs that are commonly used are shown in Fig. 17 and described in the following:
7.8.2.1 Fig. 17A - A tube beveled at a 45° angle;

7.8.2.2 Fig. 17B - A short radius elbow or pipe bend. Chamfer the probe end on the inside diameter to give sharp entrance edge; and

7.8.2.3 Fig. 17C and Fig. 17D - A closed-end tube with a round orifice spaced near, but not at, the closed end.

7.8.3 Pipeline Manual Tap - Free Water/Haze Verification - If the sample system is designed such that the sample point on the pipeline is primarily intended to ascertain the presence of water possibly riding the bottom of the pipe at a particular point, or intended to detect possible particulate contamination, for example, such as pipeline origin and delivery points and pump stations, the sample point may be installed such that the sample is drawn directly from the bottom of the pipe using no internal probe.

7.9 Pipeline Sampler and Probe Location:
7.9.1 Since the product to be sampled may not always be homogeneous, the location, position, and size of the sample probe should minimize any separation of water and heavier particles that would make their concentration different in the gathered sample than in the main stream. It is recommended that the probe be in a horizontal plane to prevent drain back of any part of the sample to the main stream and located in an upward flowing vertical run of pipe. The probe may also be located in a horizontal run of pipe. Extend the sample probe into the center third of the pipe with the inlet facing up stream. The flowing product at the point of sampling should be adequately mixed. This can be accomplished from the normal flowing turbulent velocity, together with an in-line static mixer; typically either a series of baffles or a perforated plate. If the line is not equipped with a static mixer, it is recommended to locate the sample point for spot samples just downstream from common line equipment that may facilitate mixing, such as 45° elbows, control valves, manifolds, strainer baskets, meters, and provers. If using the sample point for custody transfer purposes, refer to requirements as listed in Practice D4177 (API MPMS Chapter 8.2).

7.9.2 Sample lines, used in conjunction with probes, should be as short as practical and purged before each sample is taken, to avoid sample contamination.

7.9.3 When sampling heated or high-viscosity liquids, it may be necessary to heat the sample line, valves, and sample container to a temperature sufficient to keep the product in a liquid state to ensure accurate sampling. To control the rate at which the sample is withdrawn, the probe should be fitted with valves or plug cocks. Extreme caution should be exercised at all times because of the higher probability of line plugs as a result of solidified product.

7.10 Zone Sampler (Core Sampler):
7.10.1 A zone sampler, also known as a core sampler or a core–type sampling thief, shall be designed and constructed such that, when lowered slowly, it is capable of trapping a vertical column of liquid at any selected level below the surface to within 2.0 to 2.5 cm (3/4 to 1 in.) of the bottom of the tank. A zone sampler shall consist of a tube made of spark-reducing metal, glass, or plastic material open at both ends to allow free flow of liquid through the sampler during lowering. See Fig. 18 and Fig. 19.

7.11 The closing of the lower end of the tube to trap the sample at the desired level may be achieved by various means including, but not limited to, the following:
7.11.1 A closure mechanism actuated by an extension rod or sharp jerk on the cord;

7.11.2 Simply raising the sampler causing the top and bottom flap valve to close;

7.11.3 A weight falling down a suspending cable to actuate the closure mechanism, and;

7.11.4 The zone sampler shall be capable of penetrating the product in the tank and being withdrawn without undue contamination of the contents.

7.12 A zone sampler (see Fig. 18) may include the following features:
7.12.1 Extension rods for use in obtaining samples at levels corresponding with requirements for high-outlet connections or samples to determine high settled sediment and water levels;

7.12.2 Sample cocks for determining the height of sediment and water in the sampler core, as well as to place the sample directly into the testing apparatus. Refer to MPMS Chapter 18.1;

7.12.3 A clear cylinder that facilitates observing the gravity and temperature of the oil during a gravity test;

7.12.4 A cord marked so that the sample can be taken at any depth in the vertical cross section of the tank; and

7.12.5 A hook to hang the sampler in the hatch vertically.

7.13 Dead Bottom Sampler - Dead bottom samplers, such as bacon bombs, normally have a projecting stem that opens the inlet valve as the stem strikes the bottom of the tank. The sample enters the sampler through the bottom valve and air is released simultaneously through the top valve. The inlet valve automatically closes when the sampler is withdrawn. See Fig. 20. The dead bottom sampler can also be equipped with extension rods, typically 7.6 cm (3 in.), 15 cm (6 in.), and 30.5 cm (12 in.) to obtain samples from those points in a tank.

7.14 Tube Sampler - Drum or Barrel - Tube samplers are applicable for sampling liquids and semi-liquids in drums, barrels and cans. The tube is made of glass, plastic, or metal and is designed so that it will reach to within approximately 3 mm (1/8 in.) of the bottom of the container. The capacity of the tube can vary from 500 mL (1 pint) 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.

7.15 Dipper/Ladle Sampler - The dipper will typically have a flared bowl and a handle of conventional length made of material such as tinned steel that will not affect the product being tested. The dipper shall have a capacity suitable for the amount to be collected and be protected from dust and dirt when not being used.

7.16 Auger Sampler - The auger sampler is applicable for sampling waxes and soft solids in drums, cases, bags, and cakes when they cannot be melted and sampled as liquids. The auger should be 2 cm (3/4 in.) in diameter (preferred), similar to that shown in Fig. 22, and of sufficient length to pass through the material to be sampled.

7.17 Pail and Scoop Sampler - Pail and scoop (grab) sampling is applicable for all lumpy solids in bins, bunkers, freight cars, drums, bags, boxes, and conveyors.

7.18 Accessory Equipment - Ropes, chains, and cables, which could be on a reel, are used to raise and lower sampling devices. This equipment shall be clean ensuring that no residue from previous use contaminates the sample being taken. Do not leave samplers suspended in a tank when not in use, as electrical continuity (bonding) may be lacking. While Section 5 provides some guidance regarding conductivity and safeguards, there may be specific and unique requirements with regard to conductivity, grounding, and bonding of some sampling equipment. Refer to the manufacturer's instructions and facility and regulatory requirements for such guidance.

7.18.1 Rope - Do not use ropes made of synthetic fibers. They shall be made of cotton or other non-static generating material and should include some means of determining the level of insertion into the tank or vessel. The rope may have a swivel clasp to link with the attached sample device designed to minimize twisting.

7.18.2 Chain - Chains shall be made of brass or other spark-reducing material. The chain should have a swivel clasp to link with the attached sample device designed to minimize twisting. Caution should be exercised using chains because electrical continuity cannot be guaranteed.

7.18.3 Cable - Cables shall be made of spark-reducing material. The cables shall have a swivel clasp to link with the attached sample device designed to minimize twisting.

7.18.4 Rod - Used primarily for shallow-depth sampling such as with truck and rail cars. It consists of a bottle cage attached to the end of a rigid pole or rod made from spark-reducing material.

7.18.5 Bonding Cable - Conductive cable used to provide electrical continuity between the sampling device, funnel, and/or primary container and a suitable ground point.

7.18.6 Retail Dispenser Nozzle Adapter - A nozzle extender, made from spark-reducing material, is designed to be fitted onto the end of a gasoline or diesel fuel nozzle. The adapter is equipped with a delivery tube that permits filling of the sample container from the bottom. See Fig. 23.

7.18.7 Other Equipment - A funnel may be used to transfer product from the sampling device to intermediate sample containers. Also, a graduated cylinder or other measuring device of suitable capacity is often required for determining sample quantity in many of the sampling procedures and for compositing samples. All accessory equipment used shall be clean, and not affect the integrity of the samples obtained.