Groth 1200A - Manual (Page 4)

Page 4 of 17
II. DESIGN AND FUNCTION
Tank protection equipment typically includes an operating valve which is designed to provide
pressure/vacuum relief under normal pump in/out and thermal breathing conditions. An
emergency relief valve can also provide both pressure and vacuum relief and normally it is sized to
provide pressure relief if there is a fire in the immediate vicinity of the tank. It may also be sized by
the tank designer to provide protection in the event of equipment failure (such as the rupture of a
process steam line or an inert gas blanketing system failing “wide open”) or operator error.
A typical tank installation is shown in Figure 1 which includes the following Groth products:
 Model 1220A Pressure/Vacuum Weight Loaded Valve
 Model 3011H Gas Blanketing Regulator
 Model 2400A Emergency Pressure Relief Valve
Pressure Relief: As the pressure in the storage tank increases, the vacuum pallet is held shut.
When the set pressure is reached, the pressure pallet lifts and relieves tank
pressure to the atmosphere (or to a header if it is a pipe away valve). See Figure 2.
Vacuum Relief: As a vacuum is drawn in the storage tank (for example, when fluid is being
pumped out), the pressure pallet is held shut. When the vacuum setting is reached,
the vacuum pallet lifts and air is drawn into the tank from the atmosphere. See
Figure 3.
Figure 1 - Typical Tank Installation
Figure 2 - Pressure Relief Figure 3 - Vacuum Relief