Sanitary Rupture Disc
PRIMUS has typically supplied a sanitary rupture disc as a part of Option P15 – Sanitary CIP Piping System to meet “crevice-free” bio-pharma applications.
The use of a rupture disc is appropriate in these applications, but the device is not considered to be as mechanically robust as an ASME safety relief valve.
The rupture disc is a thin stainless steel component that will protect a PRIMUS BioPharma sterilizer from an overpressure condition of greater than 45 psig, but must also be capable of withstanding close to 30 inches Hg vacuum. The combination of repeated pressure and deep vacuum cycles fatigues the metal over time. This can ultimately lead to disc failure and possibly a steam release (which should always be vented safely to a drain or outdoors in accordance with local codes).
Many rupture discs supplied by PRIMUS have a switch built in to signal the control system that a potential overpressure condition has occurred.
Safety Relief Valve
On all threaded pipe sterilizers PRIMUS supplies ASME rated 45 psig safety relief valves to protect both the chamber and jacket from an overpressure condition.
PRIMUS safety relief valves are supplied in both brass and stainless steel materials depending on the piping system specified.
One of the advantages of an ASME safety relief valve is that the valve will relieve pressure prior to reaching the set pressure, but will automatically reseal once the pressure decays to a safe level below the set pressure.
A safety relief valve is a robust component and is appropriate for most sterilizers in healthcare, laboratory and media applications. The only issue with a safety relief valve in a true BioPharma application is the presence of the NPT threads and recesses within the valve.
Safety Relief Valve over Rupture Disc Option
PRIMUS also offers an option (Option P5) to supply a safety relief valve on top of the rupture disc. This arrangement allows the rupture disc to discharge against the safety relief valve inlet and then safely to the outside discharge point.
The advantage of this option is that it resets after the overpressure condition is cleared and may allow the sterilizer to be safely operated until the rupture disc is replaced, depending upon site regulations. It also protects the facility from a release of steam due to a metal fatigue failure of the rupture disc (discussed above).
A sanitary to NPT adaptor, which allows a threaded safety relief valve to be installed on a sanitary port, is supplied when the Safety Relief Valve over Rupture Disc Option P5 is selected. This option has also been used in special applications where an end-user customer wants to replace the rupture disc with a safety relief valve.
Conclusion
The selection of the appropriate component will be determined by end-user customer requirements and the standards under which the sterilizer is being used.
End users can be confident either a rupture disc or safety relief valve will protect the sterilizer from an overpressure condition.
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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