Eductors / Venturis

With a vessel sampling system, vacuum is needed to draw the sample liquor up the dip tube and into the sampling system. If this isn’t available from the central vacuum system, we can supply the sampling system with an educator. The educator can generate sufficient vacuum being powered by compressed gas – either nitrogen or air.

Venturis get their name from Italian physicist, Giovanni Battista Venturi (1746-1822). He discovered that passing liquid through a tube with a constricted throat increased velocity through restriction, with a consequent drop in pressure at the throat entrance.

This main principle is still used in modern day eductors, with the drop in pressure being enough to create a vacuum. The vacuum created can be surprisingly high, depending on the choice of eductor. Drawing a 5m high column of water is not unusual.

When a vacuum service is not available, CRP use eductors on vessel samplers which are directly connected to the top manifold of the sampler. The compressed gas to drive the eductor is controlled with a ball valve rigidly mounted to a stainless steel bracket. If required, the exhaust gas can be vented to a scrubber system or piped back into the vessel.

Eductors can be provided in stainless steel, PTFE or PVDF to suit the chemistry of the sample liquid.