Here's the correspondence and responses I received from SMC Tech Support (I have submitted this to FIRST Q&A to verify that it is adequate):
To:
techrep@smcusa.com
Subject: Solenoid valve rated pressure
I have ordered some SY3120 double solenoid valves which show a maximum operating pressure of 0.7 bar (~100 psi). I need to know if these valves have a rated pressure higher than the operating pressure, such that if my upstream pressure regulator fails they do not have to operate but they will not fail catastrophically under pressure. I need to put a pressure relief valve in the system set below the pressure rating of the lowest rated component in order to protect them (our normal operating pressure is 60 psi but pressure upstream of the regulator is 125 psi).
Thanks
Gary J. Dillard, P.E.
Gary,
We rate that at a maximum pressure of 100 psi due to the fact that the SY valve will shift automatically (no voltage necessary) at about 125 psi. At this pressure, the pilot section can generate enough force to shift without the assistance of a coil.
Regards,
Bryon Hartzog
Technical Support
SMC Corporation of America
Hi Bryon; if I understand your answer correctly, the valve is not designed to operate above 100 psi (with some margin), which is OK - we are running at 60 psi. My primary concern is catastrophic (overpressure) failure if my regulator fails - have these valves ever been tested to failure? We currently have a pressure relief valve upstream of the regulator set at 125 psi; I need to know if I need to add another pressure relief valve downstream at some pressure less than that to protect the valve from exploding if the regulator fails and the pressure goes from 60 psi to 125 psi. The rest of the components are rated at 125 psi or higher.
The application is a robot built by a high school team for the FIRST robotics competition (I am the mentor), and the rules for pneumatics have been modified this year; we've used these valves before without any problems (SMC used to donate some of them) but this year the extra pressure relief valve is required if any component is not rated at 125 psi, which is different from being operational at 125 psi.
Thanks
Gary J. Dillard, P.E.
Gary,
The valve will not catastrophically fail at or below 125 PSI due to air pressure alone. The proof pressure, according to JIS standards is 1.5 times the maximum operating pressure.
Regards,
Bryon Hartzog
Technical Support
SMC Corporation of America
Included Attachment: