Pressure Vacuum Relief Valve - OPERATION & SIZING CALCULATION

According to API 2000 code, the Pressure vacuum relief valve are designed, manufactured and tested. The Pressure Vacuum Relief Valves are used on liquid storage Tanks which designed by API 520/API 650 and Others process vessels or systems to prevent structural damage due to excess internal pressure or vacuum.

This valve has functions to intake the air under constant pressure during unloading and rising Temperature, and to dis- charge the overpressure generated during pouring the liquid and falling Temperature on storage tank. This is the safe valve to control the deflation(vacuum) and inflation(pressure) of several storage tanks

THE EFFECT OF ENERGY REDUCTION 

In case of gasoline, to minimize the natural evaporation of stores saves 98m3 per year. (Based on the tank diameter: 30.4m x tank capacity 8690m)

THE EFFECT OF PREVENTION OF EXPLORATION 

With the exception of influx and efflux of stores, it is Kept always closed to prevent the diffusion of exploration into tank

 

THE EFFECT OF PREVENTION OF CORROSION (The effect of extension of life). To keep the stabilization of constant gas pressure generated pressure generated inside tank, prevents inside of the tank from corr- osion by the temperature of gas

WHEN TANK IS UNLOADING PHENOMENA AND THE PRESSURE is above the setting (operational fixing pressure), the Pressure Vacuum Relief Valves operates automatically to protect the storage tank from the deflation or malformation.

The weight loaded type models are designed to provide tank protections for both pressure and/or vacuum of set point to max 75/-43 mbarg.

Over 75/-43 mbarg set point till 900/-900 mbarg, consider to be installed spring loaded type. Safety relief valve is not used in controlling the extra setting of pressure and consider Emergency vent for External fire and Rupture case.

The set point of Pressure vacuum relief valve is fixed by the customer's order or Project´s Specification. but it is designed to adjust the pressure / vacuum setting in case. The way of change adds additional counter weight for Weight loaded type. The way of change for spring loaded as follow,

To increase the setting pressure turns the press. adjusting screw clockwise. To decrease the setting pressure turns the press. adjusting screw counter-clockwise. Before change set point of disc A’ssy, should be consulting the factory or our local representative

Latitude	Y-factor
Below 42°	0.32
Between 42° and 58°	0.25
Above 58°	0.2

Latitude	C-factor for various conditions
	Vapour pressure
	Average storage temperature, °C
	Hexane or similar		Higher than hexane, or unknown
	<25	>=25	<25	>=25
Below 42°	4	6.5	6.5	6.5
Between 42° and 58°	3	5	5	5
Above 58°	2.5	4	4	4