Luofu makes six lines of pressure relief valve and a changeover valve for pairs of relief valves. Each line suits a different duty. The first table matches duties to lines, and the second compares their limits.
Start from the service and the back pressure. The sizing confirms the choice for each tag.
| If the duty is | Look at |
|---|---|
| General process relief of gas, vapor, liquid, or steam, with low and steady back pressure | Spring-loaded, LFO |
| Back pressure that varies, or a medium that attacks the spring | Spring-loaded, LFB bellows |
| High or varying back pressure | Pilot-operated, LFXD |
| High-pressure steam up to 650 °C on boilers and steam lines | Steam service, LFGS |
| Liquid trapped between closed valves that can heat up | Thermal relief, LFXY |
| Media that crystallize or have high viscosity | Jacketed, LFNJ |
| Wet chlorine, strong acids, or alkalis up to 200 °C | Lined, LFCL |
| Relief valves that need service while the plant runs | Changeover valves, LFQH |
Series limits from the technical data of each product page. The limits of one valve depend on its size, rating, and materials. Pressure ratings are ASME Class, or PN where PN flanges are offered.
| Product line | Series | Temperature | Size | Pressure rating |
|---|---|---|---|---|
| Spring-loaded | LFO, LFB | -268 to +720 °C | NPS 1-8 (DN25-200) | Class 150-2500 or PN16-400 |
| Pilot-operated | LFXD | -268 to +720 °C | NPS 1-8 (DN25-200) | Class 150-2500 or PN16-400 |
| Steam service | LFGS | Up to +650 °C | NPS 1.5-8 (DN40-200) | Class 300-2500 or PN25-420 |
| Thermal relief | LFXY | -196 to +427 °C | NPS 1/2-1 (DN15-25) | Class 150-900 or PN10-150 |
| Jacketed | LFNJ | -46 to +538 °C | NPS 1-10 (DN25-250) | Class 150-2500 or PN10-420 |
| Lined | LFCL | -60 to +200 °C | NPS 1-8 (DN25-200) | Class 150-300 or PN10-40 |
| Changeover valves | LFQH | -196 to +570 °C | NPS 1/2-20 (DN15-500) | Class 150-2500 or PN16-400 |
Size is the inlet size for the relief valves and the valve size for the changeover valve. The Class range and the PN range are the ranges offered with ASME flanges and with PN flanges. One is not a conversion of the other, so the PN range differs from line to line.
The cards show each line with its main limits and link to the product page.
Conventional (LFO) and bellows (LFB) types for steam, gas, liquid, and cryogenic service. The bellows type handles variable back pressure and corrosive media. Seat tightness is tested to API 527.
Pop or modulating pilot with a soft or metal seat. Opening and closing are not affected by back pressure, and the main valve opens fully without extra overpressure.
For high-pressure steam up to 650 °C. The nozzle is welded to the body, and the seat is hard faced with a hard alloy.
Small-orifice valves for thermal expansion relief in blocked-in liquid lines. Threaded or flanged connections.
A steam or heat transfer oil jacket keeps the inlet and outlet warm for media that crystallize or have high viscosity. A steam purge port is an option.
F46 or PFA lining for wet chlorine, strong acids, and alkalis. A lined valve can take the place of a nickel alloy valve in these services.
Switches between two relief valves on line, so one valve can be serviced while the other protects the system. Single and double versions, with two patents on record.
Every quotation starts from the operating data of each tag. Send the data sheet, or the medium, set pressure, required capacity, back pressure, and temperatures, and we size the valve first.
The quick form is for a short message. To send a data sheet, email it to us.
