Benefits of Steam Pressure Regulation
The saturated steam tables show that with increased steam temperature comes increased steam pressure. Applying a higher steam temperature and pressure than necessary for proper operation of the sterilizer has a negative effect on the lifespan of the affected components, namely the steam-powered door gaskets and solenoid valves.
The pressure rating for the jacket and chamber pressure safety valves (PSV) is 45 PSIG. If the applied steam pressure is higher than 45 PSIG, and the jacket steam valve fails and lets steam flow through to the jacket in an uncontrolled manner, the jacket PSV will lift if the pressure climbs above 45 PSI. If the pressure is regulated to less than 45 PSIG, a possible dramatic event is avoided by keeping the applied pressure less than the lift pressure of the PSV.
Solenoid valves function better with at least a 5 PSIG upstream-to-downstream pressure differential. Most sterilizer applications call for less than 32 PSIG steam pressure in the chamber, with the exception of higher sterilizer temperatures and/or higher altitudes.
Setting the regulator for a downstream steam pressure of 38 to 40 PSIG when the machine is at rest is a good target for most applications.
Measuring Regulated Steam Pressure and Adjusting the Regulator
A pressure gauge is needed downstream of the steam regulator to measure steam pressure. PRIMUS provides a tee with a pipe plug downstream of the steam regulator for pressure measurement purposes. To measure steam pressure, do the following:
Shut off the steam supply. There should be a shut-off valve ahead of the steam regulator regardless of the steam source.
Turn the sterilizer off.
Depressurize the sterilizer steam piping by letting it cool. You may speed this process by manually firing the steam to chamber valve in Output Diagnostics with the door(s) closed.
NOTE
If pressure exists in the jacket, be very careful as the steam-to-jacket valve is now holding steam in the jacket with the valve orientation backward with respect to pressure.
Carefully remove the pipe plug from the plumbing tee downstream of the steam pressure regulator. Adapt a pressure gauge to the tee.
Slowly open the steam shut-off valve to pressure up the piping. You will see the pressure gauge respond.
With the sterilizer steam control valves at rest, turn the top of the regulator clockwise on an Armstrong brand regulator, or counter clockwise on a Miyawaki brand regulator, to increase the pressure. Bring the pressure up to a gauge reading of 38 to 40 PSIG. If the pressure is too high, adjust the regulator down accordingly.
To get an accurate reading, you will need to start and stop steam flow through the regulator after every adjustment. You can do this by turning the sterilizer on, causing the jacket valve to energize, and then turn the sterilizer off again. You may also do this in a manual mode by forcing a steam valve to open and close, e.g. jacket or the chamber with the door(s) closed. Examine the pressure gauge reading when the steam flow is at rest.
Checking the Regulator
With the sterilizer at rest, ensure that the regulator is not worn out and leaking through internally. Watch the pressure gauge so that it does not steadily climb above the pressure setpoint over time.
Watching for ten minutes is usually sufficient to see an indication of internal leakage. Just like any controlling valve, pressure regulators can lose their ability to hold back pressure. Replacement of the regulator is called for if this happens.
A regulated steam supply will help optimize the life of door gaskets and steam valves.
Have a question or having difficulties? Talk to Dave Schall, our PRIMUS sterilizer expert who is here to assist you anytime at 877.679.7800 extension 1212 or email at dschall@spire-is.com.
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