Changeover valves
Luofu LFQH changeover valves connect two relief valves to one protected system and switch between them on line. One relief valve protects the system while the other is out for service. Sizes run from NPS 1/2 to 20 (DN15 to DN500). Pressure ratings run from Class 150 to Class 2500 with ASME flanges, or PN16 to PN400 with PN flanges. The temperature range is -196 to +570 °C (-321 to +1,058 °F).
Where it is used
A changeover valve lets a plant service its relief valves without a shutdown. The changeover valve moves the flow from the relief valve in service to the standby valve. The first valve can then come out for testing or repair.
LFQH valves handle water, oil, gas, natural gas, and steam.
Technical data
- Series
- LFQH single and double versions
- Size
- NPS 1/2 to 20 (DN15 to DN500)
- Pressure rating
- Class 150 to Class 2500 ASME flanges
PN16 to PN400 PN flanges - Temperature range
- -196 to +570 °C (-321 to +1,058 °F)
- Media
- Water, oil, gas, natural gas, and steam
- Linkage, double version
- Universal coupling and worm gear between the inlet and outlet valves
- Patents
- ZL 2011 2 0434286.6 changeover valve
ZL 2015 2 0719490.0 lockable combination valve
These are the limits of the series. The limits of one valve depend on its size, rating, and materials. The quotation 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 double version has a changeover valve at the inlet and one at the outlet. A universal coupling and a worm gear link them, so both sides switch together. The two relief valves share one outlet pipe.
The single version has one changeover valve. The drawing for each tag shows the arrangement.
Options
Choose these at the inquiry stage:
- Single version
- Double version, inlet and outlet linked
- Lockable combination valve, patent ZL 2015 2 0719490.0
Standards and certifications
The EAC documents below name Luofu's changeover valves. They cover TR CU 032/2013 for pressure equipment and TR CU 012 for equipment in explosive atmospheres:
What we need to quote this valve
Send these with your inquiry. The data sheets of the two relief valves cover most of them:
- Size and rating of the inlet and outlet connections
- Medium and phase
- Design pressure and design temperature
- Single or double version
- Back pressure in the outlet header, if any
- The relief valves to be mounted, with their data sheets
- Material requirements
- Design code (ASME, API, EAC, or the project specification)
- Quantity
- Project country
No data sheet yet? Send what you have. We ask for the rest by email.
Related series
Questions engineers ask
How does a changeover valve work with two relief valves?
Both relief valves mount on the changeover valve, but only one is connected to the system at a time. Turning the handwheel moves the flow path to the other relief valve while the plant stays on line.
Can I remove a relief valve when the outlet header has back pressure?
The double version is made for this case. With a changeover valve at the outlet as well, a relief valve can come out for service while the outlet header is under back pressure. State the back pressure on the data sheet, and the quotation confirms the version.