DN25 - DN200 (1" to 8")
2.5 – 426 bar (DIN 1092-1)
36 – 6170 psig (ASME B16.5)
DIN & ANSI Flanged
WCB, LCB, CF8M
ASME Sec. VIII Div. 1, DIN EN ISO 4126-4, AD 2000-Merkblatt A2
Applications – Functional areas
Across applications, there are four main functional requirements covered by the LESER Pilot Operated Safety Valve (POSV).
High Back Pressure Applications
Applications Requiring Set Pressure Independence of Back Pressure
The LESER POSVs open and operate independently of back pressure (within back pressure operating limits, see previous). The set pressure of the POSV is not affected by back pressure of any kind, i.e. superimposed, constant or variable.
Applications with High Inlet Pressure Losses (above 3%)
In these applications, POSVs with remote sensing should be utilized (refer to API 520 Part 2).
Applications with Increased Tightness Requirements
Since closing forces increase when approaching set pressure, LESER POSVs are particularly suitable for applications with high tightness requirements. Tightness is ensured up to 97% of set pressure because the closing forces increase approaching set pressure. Together with the defined blowdown, this allows operating the sytem close to the set pressure of the valve.
In a POSV, the system pressure acts on the main valve piston trying to push it open. It is, however, opposed by the same pressure because system pressure is also re-directed to the dome area above the piston.
Since the area of the piston exposed to pressure is larger in the dome than on the system side, this creates a greater net closing force on the main valve disc/nozzle. Approaching set pressure, closing forces increase