Pressure Relief Rule 8.8

[jeremy_cuss]

I believe that the FRA rule about the need for pressure relief valves needs changing. Rule 8.8 says,

A certified pressure relief device [PRD] must be installed in each part of the pneumatics system where a different operating pressure is used (operating pressures separated by a pressure regulating device).

This should be rewritten:-

A certified pressure relief device [PRD] must be installed in each part of a pneumatic system where the equipment pressure rating is less than the pressure upstream of the pressure regulating device. (This is to protect that equipment from overpressure in the event of pressure regulator failure.)

My last heavyweight robot had 4 operating pressures (Bottle pressure, 16barg for the ram power stroke, 4barg for the pilot supply to the 5/2 solenoid valve and 1.5barg for the ram return stroke). It had 3 pressure regulators and only 2 relief valves. The high pressure one was set at 68barg and the low pressure one was set at just over 16barg. These were adequate to protect all the downstream equipment.

[m2xt]

M2 also had 4 operating pressures and 2 relief valves. This was allowed for and covered in the existing rules (rule 8.8.1 IMO refers) because all low pressure components were adequately protected by the one LP relief valve.

Paul

[dmac]

Question? If your LP section has a PRV for the components upstream of the regulator, why do you need a 1000psi PRV as well, wont the LP PRV exhaust the systen if theirs a reg failure,

[maddox]

The 1000psi PRD is more of a fair play device. That ensures people wont use dirty tricks to get more gaspressure in the bottles than allowed.

Like overfilled CO2 storage tanks, or heated tanks.

[dmac]

Wouldnt that make the burst disk go off, also how would that make a difference to a LP system that is regulated to 10 bar or so.

[maddox]

Burst disks are not proofed at 1000 psi, but rather 3000psi for most burst disk equipped bottles.
If you can find certified 1000 psi burst disks, you have a potentialy cheap, but rather annoying PRD.

The PRDs we use are self sealing when the pressure is back to 1000 PSI. A burst disk just let go, and thats it.

[pressure]

As far as low pressure systems go (up to 16 bar)all the regulators Ive seen have a built in prv so there is no need to add one in the system!

[leorcc]

As far as i know paintball regulators do not.

[maddox]

Very cheap welding regulators- like to be used on the disposable bottles- dont have a prv either.