Page 229 - WaterSense at Work

October 2012
Vacuum Pumps
remove impurities. Water requirements for both creating the vacuum and cooling the
equipment range from 0.5 to 1.0 gallons per minute (gpm) per hp.
To save water,
these pumps can be equipped with a partial or full recovery and recirculation system.
In the full recovery system, all the seal water is recovered from the discharge side of
the pump, passed through a heat exchanger (if the system configuration allows for
heat removal), and reused for sealing and cooling. A small amount of recycled water
is discharged to remove impurities, and the system is replenished with make-up
water. This full configuration recirculation system is estimated to reduce water use by
Partial recovery and recirculation systems recirculate part of the sealing water. Make-
up water is added to ensure that impurity concentration is not too high. In these
systems, consideration should be made to avoid heat buildup in the pump. Partial
recovery systems can reduce water use by about 50 percent.
Cooling the Vacuum Pump
Vacuum pumps can be water-cooled or air-cooled. Water-cooled vacuum pumps
use single-pass cooling or recirculated cooling. Either wet or dry vacuum pumps
can use water to cool the system. In single-pass cooling, water passes through the
pump only once for cooling, then is discharged directly to the drain. A recirculated
cooling system, on the other hand, passes the majority of cooling water through a
heat exchanger, and the cooling water is reused. If the cooling water does not come
in contact with the vacuumed gases or other impurities, it can be recirculated by
connecting the pump to a larger building system chilled water loop or cooling tower
water loop to remove the heat load. Air-cooled vacuum pumps use ambient air,
rather than water, to remove the heat load from the vacuum pump.
Operation, Maintenance, and User Education
For optimal liquid-ring vacuum pump efficiency, consider the following tips:
Turn off the pump when it is not in use or needed.
Ensure that the vacuum pump is set at manufacturer specifications to discharge
only the amount of water necessary to remove impurities and cool the vacuum
Periodically check the vacuum pump’s operational control schemes, if available,
to ensure optimum efficiency (e.g., timers, float-operated switches, total dis-
solved solids controllers that initiate discharge and make-up water).
Retrofit Options
If the facility is using a liquid-ring vacuum pump that continuously discharges water,
the facility can consider equipping the pump with a full recovery and recirculation
U.S. Air Force Medical Service.
Dental Vacuum Systems
Page 5.