SAFETY/SAFETY RELIEF VALVE

 Manufactured to API/ASME codes, Full Lift, ’Pop’ type. Screwed/ Flanged models .Standardized orifice. 

Size:15NB to 300NB 

Sizing Standard  : API RP 520

Design Standard:API526/API520

When the static pressure inlet increases above the safety valve’s fixed pressure, the disk will start lifting off its seat. Then the spring begins to compress.

As the pressure increases the disc continue to lift. In order to achieve full opening from a small overpressure, the disc arrangement has to be specially designed to provide rapid opening. This is usually done by placing a shroud, skirt or hood around the disc.

As lift begins, and fluid enters the chamber, a larger area of the shroud is exposed to the fluid pressure. This rise in opening force overcompensates the rise in spring force, resulting in a fast opening

 It has to reset the valve position after the high pressure flow is reduced. But, since the bigger disk region remains subjected to the fluid, the valve will not close until the pressure drops below the initial set pressure. The distinction between the fixed pressure and the reseating pressure is called the ‘ blowdown‘.

The decreased blowdown(nozzle) ring is common in many valves where tighter overpressure and blowdown conditions require a more sophisticated built solution.
Usually the upper blowdown ring is factory set and fundamentally removes the fabrication tolerances that influence the huddling chamber’s geometry.