I. Summarize: Double interlocking switch safety device is a new product independently developed by
Luofu based on the original safety valve and changeover valve. According to the
design of API520 and BS1873, the inlet and outlet of the safety valve on the pipeline
can be switched jointly, allowing for simultaneous opening and closing. This
instruction primarily introduces the changeover valve. About the safety valve, please
refer to our Operating Instructions for Spring Type Safety Valve.
II. Use & Performance Specification
2.1. Use: The product is widely applied as an overpressure protection device on the
corrosive medium and non-corrosive medium pipelines such as water, oil, natural gas
and steam. It has the advantages of small flow resistance, flexible opening/closing,
long service life, superior safety and reliability and compact structure, it is able to achieve following functions:
<1. Non-stop operation. While one safety valve is operating, the other can be
taked down for maintenance on the premise of non-stop operation so as
to achieve the maximum economic profits due to reduce the shutdown
<2. Two safety valves share one pipeline, which can reduce both the pipeline
number and cost.
<3. The inlet and outlet changeover valve of the safety valve are allowed for
synchronous operation as well as simultaneous opening/closing, making
the operation more easily and reliably.
2.2. Scopes of application: chemical industry, petroleum refining, oil and natural
gas pipeline transportation, etc.
2.3. Performance standard (changeover valve):
Normal temperature test pressure (MPa)
and upper seal
2.4. Maximum working pressure rating of valve (pressure-temperature standard ) (gauge pressure: MPa)
Valve body material WCB:
Valve body material CF8:
Note: The temperature in the table above refers to the temperature of the pipeline media under working
condition. The pressure in the table is a sustained non-impact pressure.
III. Main Adoptive Standards:
3.1. The design and manufacture is in accordance with API 520 and BS 1873; 3.2. The flange connection is in accordance with ASME B16.5; 3.3. The inspection and test is in accordancewith API 527 and API 598; 3.4. The pressure-temperature standard is in accordance with ASME B16.34.
IV. Demonstration of the type (changeover valve):
LFQH --Luofu Changeover Valve; 150--Nominal pressure is 150Lb; C--Material of valve is carbon steel.
V. Structural features: 5.1. Device Structure:
1. Bottom reducing joint
2. Inlet changeover valve
3. Inlet reducing joint
4. Outlet changeover valve
5. Safety valveI
6. Safety valveII
5.2. Structure of changeover valve:
1. Valve body
2. Valve clack
3. Valve stem
4. Valve deck
6. Packing bushing
7. Valve stem nut
8. Valve bearing
9. Chain wheel
10. handle wheel
12. Plug Screw
5.3. The changeover valve adopts three-way structure. 5.4. The changeover valve body is connected with valve deck by MFM flange. 5.5. The changeover valve is connected with pipeline by RF flange. 5.6. Planar seal is used for the changeover valve clack.
The handle wheel and chain wheel of the changeover valves located at inlet and
outlet are all installed on the valve stem nut. The handle wheel, chain wheel and valve
stem nut will rotate together. There is a chain located between two chain wheels
through the chain, the two changeover valves and valve stem nuts will rotate at the
same time. Through the trapezoidal nut, the valve stem nut will drive the valve rod to
move up and down then the valve rod drives the valve clack so that two changeover
valve will act synchronously, allowing for simultaneous opening and closing.
As the figure shows, the changeover valve is designed with two sealing surface,
allowing one closing while the other opening. Rotating the handle wheel clockwise and
the valve clack will move far away from it so that the sealing surface which is far from
the handle wheel will be closed while the nearby one will be open. In that way, the
inlet and outlet changeover valve of the safety valve which are close to the handle will
be open so as to play a protection role, while the inlet and outlet changeover valve of
the safety valve far away from the handle will be closed, taking no effects and can be
able to disassembled for maintenance. Otherwise, rotating the handle counterclockwise
and the valve clack will move close to the handle wheel so that the sealing surface
which is close to it will be closed while the distant one will be opened. In that way, the
inlet and outlet changeover valve of the safety valve which is far away from the handle
will be opened so as to play a protection role, while the changeover valves of the safety
valve at inlet and outlet which is close to the handle wheel will be closed, taking no
effects and can be able to disassembled for maintenance.