My berif understanding of PRV/PSV/FCV is as follow : A PRV is a device that controls the pressure in a pipe system. The PRV maintains a constant control pressure downstream of the junction as long as the upstream pressure exceeds the control pressure. If the upstream pressure is lower than the control pressure, the ability to control pressure is lost. A PSV is similar to a PRV in that it controls pressure in a pipe system. While the PRV maintains a constant downstream pressure, the PSV maintains a constant upstream pressure. If the downstream pressure rises higher than the control pressure, the ability to control pressure is lost. An FCV is a device that maintains a constant flow rate in a pipe system.The FCV can lose its ability to control flow when the pressure drop across it becomes zero or backward flow begins My specific question is : what are the differences from manufacturing point of view in between the above three control valve.Oil pumps If Cv/Kv is suitable, can a specific PRV may used as FCV.PRV (Pressure relief valve) controls the system pressure. If the pressure crosses its set value it releases a bit of fluid through its relief port to maintain the pressure back to the set value (minus the hysteresis). It is an appendage if the pressure is below the set value. It is used normally to protect the system against the over-pressurisation. fire pumpsIn the earlied thread I have given this as the pop weight of the presuure cooker. The actual PRV also is same, there is one conical orifice perpendicular to the flow direction. The orivice is closed by a spring loaded cone. When the pressure increases, the spring retracts and the extra fluid escapes, the orifice closing as soon as the pressure falls below the spring pressure.Split case pumps PSV (Pressure Safety valve) This acts like an emergency switch and opens up when the pressure crosses the set value and releases the fluid. It usually releases the whole lot of it and not closes back. The example was the blowout valve of the pressure cooker. Once this is opened, the system pressure is undefined and ideally is the atmospheric. Vacuum pumps FCV (Flow control valve) and also PCV (Pressure control valve) : This has to work on the feed back.Like the PRV there is the orifice and the cone. the opening is controlled by the down stream pressure and not by the spring. If the down stream pressure reduces, (or if the differential pressure across orifice is measured meaning flow has reduced ) then the cone is opened to allow lesser restriction to the flow and thereby increasing the flow. The reverse is the case if the downstream pressure increases and then the opening reduces to restrict the flow. In-line pumpsThis can only be effective if there is a significant flow, unlike the other two. Most of the PCVs or FCVs i have used uses a simple elastic diaphragm, pressurised by the two pressures on either side of it or the downstream pressure and a spring and the flexing of the diaphragm is translated into pin(cone) movement. This is in breif. However you can go through the catalogues of Parker and a few others like masoneilan , ForbesMarshall, Tyco etc

MORE NEWS