The Model 425-D Deep Sampling Discrete Interval Sampler allows no-purge samples to be obtained from submerged depths as much as 1200 m (4000 ft).
The 1.66″ sampler is stainless steel and is connected to a length of LDPE tubing, which is wound onto a reel. The reel has a connection for a high pressure hand pump and a pressure/vent switch. To overcome buoyancy, weights are connected to the Discrete Interval Sampler before lowering.
Once the sampler reaches the desired sampling depth, it is pressurized. Using the basic principles of hydraulics, the pressure acts on the top of a piston (larger surface area) inside the sampler, overcoming the hydrostatic pressure acting on the bottom of the piston (smaller surface area) to allow sample water to enter.
As sample water fills the sampler, air from the sampler is vented through holes (covered with a vyon filter) on the side of the sampler, which are also opened with the applied pressure.
After the sample is collected, the pressure is released, allowing the piston to reseal at the bottom of the sampler. The sealed sampler is then retrieved to surface, maintaining chemical stability of the sample.
At surface, the sample is collected by reapplying pressure to the Discrete Interval Sampler. The flow of the sample is regulated by the amount of pressure applied.
The Model 425 Discrete Interval Sampler provides a no-purge sampling option for collecting groundwater samples from discrete levels, and points of inflow, in wells and boreholes. It can also be used for profiling open water bodies, and for sampling above and below oil/product layers, as well as the actual product (e.g. LNAPL and DNAPL).
The stainless steel Discrete Interval Sampler is available in 1″, 1.66″, and 2″ diameters. Operation is up to 90 m (300 ft.) below water level. The samplers are connected to a length of LDPE tubing, which is wound onto a reel. The reel has a connection for a high pressure hand pump and a pressure/ vent switch.
The pump is used to apply pressure and seal the Discrete Interval Sampler before it is lowered. This prevents water from filling the sampler, until it reaches the chosen depth. Once the sampler reaches depth, the pressure is vented and hydrostatic pressure fills the sampler. Before retrieval, the sampler is repressurized to ensure there is no mixing of water from different levels on the way up.
At surface, the pressure is released to allow the sample to be decanted using the sample release device. This regulates flow and minimizes sample degassing, suitable for VOC sampling.