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Hydrological Equipment

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DH-2 Sediment Sampler

Item No.:
35.00 LBS

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The US DH-2 is a hand-line depth-integrating collapsible-bag suspended-sediment and water-quality Sampler capable of collecting a 1-liter sample. It is 20 inches long, weighs 30 pounds, and has a hollow cavity inside the sampler body. It is fabricated from a bronze casting with a plastic nose-piece and a High Density Polyethylene (HDPE) tail. The bronze casting is plastic coated with commercially available “PlastiDip.” The cavity in the bronze body is plastic lined. The plastic nose-piece holds the nozzle and nozzle holder in place and “snaps” into the sampler body with slight hand pressure. The collapsible bag is attached to the rear of the nozzle holder with a hook-and-loop strap. The US DH-2 meets protocols for water-quality sampling as outlined in the USGS National Field Manual for the Collection of Water-Quality Data.

Sampling container:  The US DH-2 has a hollow cavity in the sampler body that houses the collapsible bag. A perfluoroalkoxy (PFA) bag or a polyethylene bag can be used. The lay-flat bags are 6 in by 14 in by 0.002 in wall thickness.

Sampler function:  When the sampler is submerged with the nozzle pointed into the flow, the water-sediment mixture flows through the nozzle into the bag at a rate that is the same or nearly the same as the ambient stream velocity, within a certain acceptable velocity range. An acceptable velocity range is one at which a representative flow-weighted sample is collected at a sampler inflow efficiency between 90% and 110%. Inflow efficiency is defined as the ratio of the sample velocity in the nozzle to the ambient stream velocity. An inflow efficiency of 100% is referred to as isokinetic.

Nozzles:  Tetrafluoroethylene (TFE) and plastic nozzles and nozzle holders are available for use with the US DH-2. The nozzles come in 3 sizes“3/16”, “1/4” or “5/16” to denote the internal diameter.

Caution: plastic parts should NOT be used when an acid rinse is used in the sampling/cleaning protocol. Do no acid rinse plastic parts. Acid deteriorates the plastic and compromises the integrity of the nozzle. Only TFE parts should be used when parts must undergo an acid rinse.

Operating Limitations
Velocity: The US DH-2 sampler will collect representative flow-weighted samples in streams with velocities from 2 to 6 feet per second (ft/sec).

Depth: At a maximum transit rate of 0.4 times the stream velocity, the US DH-2 sampler is capable of sampling to a depth of 13 ft with a 5/16 in diameter nozzle, 20 ft with a 1/4 in diameter nozzle, and 35 ft with a 3/16 in diameter nozzle.

Unsampled zone: The US DH-2 sampler can sample to within 3.5 inches of the streambed. This unsampled zone is the distance between the nozzle and the bottom of the sampler.

Transit rate: The transit rate is the speed of lowering and raising the sampler in the sampling vertical. The minimum transit rate is one at which the sample volume does not exceed 1 liter. The table gives the sampling time to collect 1 liter of sample for the three internal diameter nozzles at varying stream velocities. The minimum transit rate can be calculated using the sampling time from the table and the total distance to be transited. For example, if the total sampling time is 30 sec, the minimum transit rate should be such that it takes 15 sec to descend from the surface to the bottom, and 15 sec to return to the surface. If the stream is 15 ft deep, then the transit rate would be 1 ft/sec. The maximum transit rate is 0.4 times the mean stream velocity. This limitation is based on the apparent approach angle of the flow into the nozzle that results from the vertical movement of the sampler through the water column.

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