Improved dry vacuum pump for lab aplications

Edited by the Engineeringtalk editorial team Jan 15, 2001

Welch has introduced a new dry vacuum pump that incorporates features such as vacuum and pressure regulators, and catch pots to prevent accidental ingestion of liquids and to prevent damage

Welch has introduced a new dry vacuum pump that combines performance with affordability and incorporates user features such as vacuum and pressure regulators, and catch pots to prevent accidental ingestion of liquids and to prevent damage to the pump in an accident.

Designed to replace water aspirators, or for use in standard duty applications such as vacuum filtration, the Model 2522 dry vacuum pump uses the Wob-L principle to provide pressures to 100psi and vacuums to 78mbar, with free air flow rates of 45 l/min.

Designed and built to operate at the pressures and vacuum levels required in laboratory applications, the pumps eliminate the problems of unreliability and frequent breakdowns that beset oil-sealed rotary pumps.

At the same time, the pressure against flow rate and vacuum against flow rate curves for Wob-L pump designs are vastly superior to those of membrane pumps, giving far higher flows at any given pressure or vacuum to ensure a more consistent operation and giving longer life operation, or allowing a physically smaller pump to be used to perform any given task.

Oil free, the pump runs without the possibility of contaminating the process with oil mist.

The design is also extremely reliable compared to membrane pumps, with documented examples of Wob-L piston pumps employed in similar applications demonstrating lifespans in excess of 25,000 hours continuous running.

Developed and patented by parent company ASF Thomas, the Wob-L design is based around a small, high speed, direct connected motor compressor which has a unitary piston and piston rod whereby the piston wobbles in the cylinder as the crank shaft rotates.

The wobbling piston is sealed to the cylinder by a flanged disk of PTFE which forms both a seal and mechanical guide for the piston and which runs without lubrication in contact with a low friction, surface coated cylinder of high heat conductivity.

The circular rim of the PTFE sintered cup is warped from circular outline to eliptical outline twice per revolution, while maintaining its seal with walls of the cylinder.

Simplicity is the key to the economical aluminium design.

As the piston wobbles, air resistance on the upward stroke expands the Teflon seal on the piston to increase its efficiency, while compensating for the wobble action.

And as a piston pump, an inherent characteristic of the design is that the failure mode is a gradual wear-out, rather than the catastrophic failure mode which is a characteristic of many other designs.

A complete range of highly reliable and competitively priced Welch vacuum pumps and systems is available ex-stock across Europe from ASF Thomas, along with a correspondingly high level of local service and support.