Diffstak Vapour Pumps EDWARD

Diffstak Vapour Pumps
The Edwards Diffstak vapour diffusion pumps are compact, water-cooled pumps with integral cooled baffles which provide exceptionally clean pumping. The proven design ensures very low backstreaming, reduced outgassing and minimized sealing requirements. These pumps are offered with integral manual or pneumatic high vacuum valves.

The compact water-cooled Diffstak pumps with an integral cooled baffle offer exceptionally clean pumping with very low backstreaming, reduced outgassing, and a reduction in the number of elastomer seals required for installation.

The Edwards Diffstak 63 (ISO63 inlet) design has been proven over many years with thousands of pumps installed. The unvalved Diffstak's are for systems requiring the highest possible ultimate vacuum or for those which do not need a high vacuum valve.

This pump has an unvalved ISO collar inlet flange and is supplied with: NW10 elbow, NW10 centering-ring, NW10 clamp, water pipe couplings and ferrules, inlet ISO 63 Co-Seal.




The Diffstak is a three-stage fully fractionating diffusion pump with an ejector-type third-stage. The pump-body is water-cooled and made of stainless steel with a mild-steel nickel-plated base. 

The interior jet system consists of a first, second and third-stage jet assembly with fractionating tubes. Above the jet system is a detachable first-stage jet-cap. The jet system is clamped together by a central tie-rod. 

The boiler is located in the base of the pump. The pump fluid is heated and vaporized by plate-type electric heater(s) (one or two, this depends on the size of the Diffstak). The boiler has a fluid filler connection and a drain-plug. The electrical supply cables from the heater are brought out to a terminal-box at the bottom of the pump for ease of connection to your electrical supply. 

Principle of Operation 

Pump fluid is heated in the boiler to produce a vapor which passes up through the interior of the jet assembly and emerges from the jets as high-velocity Vapour streams. The vapor streams condense on the cooled pump-body wall and drain into the boiler at the bottom of the pump for recirculation. 

A portion of system gas which arrives at the Diffstak pump-inlet is trapped in the vapor stream from the first-stage jet. The gases are compressed and transferred to the next stage. This process is repeated through the pump jet-stages until the gases are removed by the backing pump through the cooled backing-condenser. 

The fractionating feature of the Diffstak design provides a means of purging the fluid charge of undesirable light fractions and foreign matter and the process helps significantly towards the attainment of a low ultimate vacuum. 

The ejector jet also purges the fluid of any contaminants as it returns to the boiler and at the same time ensures a high critical backing pressure even when you use low vapor pressure fluids.

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