LFGS

Steam-service pressure relief valves

Luofu LFGS valves are for high-pressure steam up to 650 °C (1,202 °F). Inlet sizes run from NPS 1.5 to 8 with API orifice letters F to T. Pressure ratings run from Class 300 to Class 2500 with ASME flanges, or PN25 to PN420 with PN flanges. Blowdown is 4% of set pressure at most, and the nozzle is welded to the body.

3D rendering of the LFGS steam-service safety valve with the spring in an open yoke, a lifting lever, and flanged inlet and outlet — LFGS steam-service valve, 3D rendering. The spring sits in an open yoke above the body, and a lifting lever is fitted.

Where it is used

LFGS valves protect boilers and steam lines that run up to 650 °C (1,202 °F).

The series works to tighter limits than the LFO and LFB series: overpressure is under 3% and blowdown is 4% of set pressure at most. The table below gives the limits of the series.

Technical data

Series: LFGS steam service
Inlet size: NPS 1.5 to 8 (DN40 to DN200)
Orifice: API 526 letters F to T, 1.5"F2" to 8"T10"
Pressure rating: Class 300 to Class 2500 ASME flanges
PN25 to PN420 PN flanges
Temperature range: Up to +650 °C (+1,202 °F)
Set pressure: Confirmed in the sizing for each tag number
Set pressure tolerance: Under +1% of set pressure
For set pressures above 68.9 bar(g) (1,000 psig). The sizing confirms the tolerance at lower set pressures
Overpressure: Under 3% of set pressure
Blowdown: 4% of set pressure, maximum
Set with the back pressure adjusting system
Seat and disc: Hard faced with a hard alloy
Nozzle: Welded to the body

These are the limits of the series. The limits of one valve depend on its size, rating, and materials. The sizing confirms them for each tag number. The Class range and the PN range are the ranges we offer with ASME flanges and with PN flanges. One is not a conversion of the other.

Structure

The nozzle is welded to the body. The nozzle seat and the disc are hard faced with a hard alloy.

A back pressure adjusting system sets the blowdown within the 4% limit.

Standards and certifications

Orifice sizes use the API 526 letters F to T. The ASME, National Board, and TS documents cover Luofu's production of relief valves. The quotation states which of them apply to each tag:

ASME UV Certificate of Authorization — ASME UV stampCertificate of Authorization

National Board Certificate of Authorization, UV designator — National BoardCertificate of Authorization, UV designator

China TS manufacturing license for special equipment, safety valves — TS licenseChina special equipment, safety valves

What we need to quote this valve

Send these with your inquiry. A completed data sheet covers all of them, and the PSV data sheet page explains each line:

Steam condition, saturated or superheated
Required relieving capacity
Set pressure
Back pressure at the outlet
Operating and relieving temperature
Inlet and outlet size and rating
Material requirements
Design code (ASME, API, EAC, or the project specification)
Quantity, per tag number
Project country

No data sheet yet? Send what you have. We ask for the rest by email.

LFO, LFB

Spring-loaded

Conventional and bellows types for most process relief duties.

LFXD

Pilot-operated

Opens and reseats at the set pressure regardless of back pressure.

LFXY

Thermal relief

Blocked-in liquid lines, NPS 1/2 to 1.

LFNJ

Jacketed

Media that crystallize or have high viscosity.

LFCL

Lined

Wet chlorine, strong acids, and alkalis.

LFQH

Changeover valves

Switches between two relief valves on line.

Questions engineers ask

How does the LFGS differ from the LFO and LFB series?

The LFGS works to tighter limits. Set pressure tolerance is under +1% for set pressures above 68.9 bar(g) (1,000 psig), overpressure is under 3%, and blowdown is 4% at most. LFO and LFB work to ±3%, 10%, and 10%. The LFGS nozzle is welded to the body, while LFO and LFB nozzles screw in.

Is the LFGS for saturated or superheated steam?

The series runs up to 650 °C (1,202 °F). State the steam condition, saturated or superheated, and the relieving temperature on the data sheet, and the sizing confirms the valve.

Does the valve have a lifting lever?

The LFGS rendering shows a lifting lever, which lets the operator lift the disc for a function check. State on the data sheet whether the valve needs a lever, and the quotation confirms it.