VTO-standard
The VTO design provides a fitting connection to the vent (needle). In this way the vent can lead to a waste system, wet collector, scrubber, activated carbon canister, or back to the process if the process pressure allows.

VTO-NBNF (No Bottle No Flow)
The VTO-NBNF is based on the conventional Dopak VTO needle assembly. The VTO-NBNF offers additional safety features for all Dopak liquid samplers. For more information please refer to our sheet: Dopak Component sheet: VTO-No Bottle No Flow (NBNF).

Concentric needle assembly
With this design the process needle is inside the vent needle. As the two needles are using lesser surface of the septum, the sealing of the septum is optimal. This rigid design is a major advantage when taking smaller samples or when needles from a softer material are manufactured.

The VTA design allows the gas / vapour from the bottle to be vented directly to the atmosphere.

The needle assembly is the foundation of the DOPAK sampler for liquids.
It is a housing with two integrated needles.
The sample fluid enters through one needle (process) and displaced gas / vapour leaves through the other (vent).

The vent connection prevents a build-up of pressure in the sample container.
The vent line should remain open at all times therefore placing valves or any other obstructions in the vent outlet should be avoided.
To prevent any unwanted backflow of the waste system when the sampler is not in use a check valve could be installed.