Is there any difference between a Pressure Safety Valve and a Safety Relief Valve?or are these just 2 names for the same valve?if there are differences, what are they please?- A Safety Relief Valve (SRV) will (automatically) open in case of too high upstream pressure. And relief the excess pressure.- An Emergency Shutdown Valve (ESD) will close in case of an emergency like a high pressure. And block the high upstream pressure.- A Pressure Safety Valve (PSV) can be both. However be carefull! PSV is also often used for Pressure Shutdown Valve. Which will be the closing type again.A. Safety Valves. A safety valve is an automatic pressure relieving device actuated by the pressure generated within the boiler and characterized by full-opening pop action. It is used for steam service. Valves are of the spring-loaded pop type and are factory set and sealed.B. Safety Relief Valves. A safety relief valve is an automatic pressure relieving device actuated by the pressure generated within the boiler. It is used primarily on water boilers. Valves of this type are spring loaded without full-opening pop action and have a factory set nonadjustable pressure setting. In UG-126 the first sentences state