Can someone explain what "UL Listed" and "FM Approved" requirement for valves?

My current employer would like to discontinue the practice of having rupture disks ASME certified for pressure vessels. He would rather just use the graphite ones "off the shelf".

I have a water system with a large manifold feeding 10 3 inch pipes. Each pipe off the header has one 3" ball valve, about 1 ft of pipe and a nozzle.

what is piggable valve? Who can explain,please!

In the COntrolled volume pumps - (as per API 675), the set pressures for the Internal and External safety valves are differently being followed by each vendor. Some vendor set the Internal set pressur

For automatic on-off valve(ball valve), should I test seat leakage according to standard ANSI FCI 70-2(similar with Globe control valve) or API-598 (similar to all type manual valves) .

I have a refrigeration circuit with three stage compressorThere is an orifice in the bypass line. The line is the feed to the comressor suction KOD. I would like to know the purpose of the orifice.

I am not an Engineer so I decided to come here and hopefully one could help me. We have a newly installed Reverse Osmosis Water System in our facility. The piping is polypropylene and is 32mm in dia