October 2012
7-19
charged down the drain. To capture and reuse a portion of the water passing through
the ejector, a second, additional ejector with a pump and a water reservoir can be
added. This modification channels 50 to 75 percent of the water flowing through
the ejector into an uninsulated tank, where it is allowed to cool below 120°F before
being reused through the pump and ejector. If the captured water does not cool
fast enough, a thermostatic valve allows cold water to flow into the tank, and any
overflow is sent to the drain. One limitation to this type of system is that it cannot be
used on sterilizers with a sealing flange or any sterilizer that processes biohazardous
material.
31
Replacement Options
When looking to purchase a new steam sterilizer or to replace older equipment, look
for models that only use tempering water when needed and that have the capability
to cool the steam condensate prior to discharge. Look for models that have a vacuum
unit with a second ejector and a reservoir to capture and reuse a portion of the water
passing through the ejector or models with an electric liquid-ring vacuum pump.
In addition, look for models with features that can further reduce water use and
improve efficiency, such as an automatic shut-off, or a programmable control system
that shuts down the sterilizer during periods of non-use (e.g., non-business hours)
and restarts the unit so it is ready for use when needed. Models are also available
with improved chamber jacket cladding (i.e., insulation) to reduce sterilizer heat loss
and ambient heat gain.
Savings Potential
Water savings can be achieved through steam sterilizer retrofit or replacement in two
ways: reducing the amount of water required to temper the condensate, or reducing
the water used to create the vacuum.
To estimate facility-specific water savings and payback, use the following information.
Steam Sterilizer Retrofit or Replacement to Reduce TemperingWater Use
Existing steam sterilizers can be retrofitted or new steam sterilizers can be purchased
with a thermostatically actuated valve and a heat exchanger to reduce the amount of
tempering water used to cool the steam condensate.
Current Water Use
To estimate the current tempering water use of an existing steam sterilizer, identify
the following information and use Equation 7-4:
••
Flow rate of the sterilizer’s tempering water. Most steam sterilizers use tempering
water with a flow rate of 1.0 to 3.0 gpm.
32
7.4
Steam Sterilizers
31
Ibid
.
32
EPA and DOE, EERE, FEMP,
op. cit
.
