That resembles a forklift tank relief valve.  You need to find out a couple things before selecting one.  What is the tank capacity and pressure rating?  Your photo resembles a Rego® 8540 series relief valve.

The 8546G fits a 3/4 pipe thread fitting with a discharge pressure of 250 psi and a UL flow capacity of 723 SCFM.

The 8546T is a 312 PSI valve fitting a 3/4 pipe thread fitting and having a UL rating of 880 SCFM

The 8545AK is a 375 psi valve for forklift tanks fitting a 3/4 pipe thread fitting with a flow capacity of 400 SCFM. I suspect you need a lower relief pressure setting and more capacity.