Cashco, a company founded in 1920, manufactures a complete line of safety valves for storage tanks, such as: pressure and vacuum relief valves, emergency valves, detonation and deflagration flame arresters and inerting valves. In this article, we will cover pressure and vacuum relief valves (PVRV).
PVRVs are installed in the ventilation ducts of atmospheric storage tanks. These valves are suitable to maintain the pressure and vacuum inside the tank, according to the pressure and vacuum calibration determined, thus reducing the loss of product through evaporation and/or contamination of the environment and preventing the tank from bursting or collapsing.
They are dimensioned in accordance with API 2000, which is in its 7th edition. Any errors in specification and/or dimensioning may lead to structural damage to the tank, as well as serious injuries, or even death to the company's technical/operational body. The main benefits of using PVRVs are:
- Precise control of pressure and vacuum inside the tank;
- Reduction of pollutant emissions into the atmosphere;
- Reduction of product losses by evaporation;
- Tank protection against bursting or collapsing.
Cashco's Pressure and Vacuum Relief Valve (PVRV)
Valve operation during pressure relief, under overpressure conditions:
Tank pressure will increase whenever product is pumped into it and/or due to thermal expansion caused by changes in product atmospheric conditions and vapors. With this, when the internal pressure of the tank reaches the value of the PVRV set-point, the pressure pallet will rise, thus allowing the tank pressure to be relieved and kept within the safety range.
Operation during vacuum relief:
The tank pressure will decrease when emptying and/or due to the “contraction” of the product and vapors resulting from atmospheric changes. In this way, whenever the tank vacuum reaches the valve set-point value, the vacuum pallet will rise, causing air to enter the tank. In this way, vacuum conditions will always be kept within the safe range of the tank.