120 psi pressure reliefg valve

[Ed Law]

I am very confused. First, update 5 says that if we use a solenoid valve rated at less than 125 psi, then we need to have a pressure relief valve in the same zone as the solenoid valve set at its rated maximum.

We are using SMC SY3000 series which is rated at roughly 101 psi. How can the pressure reach over 100 psi when it is in the 60 psi zone regulated by the primary regulator?

The second thing that confuses me is that I just read that we are not allowed to adjust the pressure relief valve. Does that mean we can not buy a pressure relief valve and adjust it to 100 psi? Are we suppose to buy one that is set to 100 psi and not adjustable?

[Alan Anderson]

Originally Posted by Ed Law

We are using SMC SY3000 series which is rated at roughly 101 psi. How can the pressure reach over 100 psi when it is in the 60 psi zone regulated by the primary regulator?

If a pneumatic cylinder is moved against the air pressure by a strong enough force, it will overpressurize the pneumatic circuit to which is connected. That's why you need a relief valve on that circuit.

I believe a relieving regulator will act as the required relief valve.

The second thing that confuses me is that I just read that we are not allowed to adjust the pressure relief valve. Does that mean we can not buy a pressure relief valve and adjust it to 100 psi? Are we suppose to buy one that is set to 100 psi and not adjustable?

You're not allowed to adjust "the" 120 PSI pressure relief valve mounted directly to the compressor. I don't think the rule applies to any other relief valves.

[Ed Law]

Thank you, I understand now. I will buy a relief valve, set it at 100psi and put it in the 60psi zone. Can I put it anywhere in the 60 psi zone or does it have to be between the cylinder and the solenoid valve?