Product - MSV Reheater Safety Valve
​Three solenoid bypass valves (SBE) are provided between the upper and the lower piston chamber of the hydraulic actuator. De-energizing one of these solenoid valves opens a flow path between the piston chambers and allows the steam pressure to open the safety valve. Due to the operating principle, the valve can be used with back pressures up to 0.5 x inlet pressure without influencing capacity or trip pressure.​
After relief operation, the valve is re-closed and kept closed with hydraulic fluid forced through another solenoid valve APL. The high force provided by the hydraulic actuator keeps the valve tight for years of plant operation. 

Three redundant pressure switches sense the system pressure and provide the trip signal for relief operation. The safety control cabinet SC contains the necessary relays to operate the solenoid valves and the test logic for regular testing of the safety valve function. Up to 4 parallel safety valves can be connected to one safety cabinet.​

​​Key features

  • Forged and bolted design with inlet separate from outlet
  • Material change between inlet and outlet is easily implemented
  • Backseat seals gland during the relief operation
  • Dou​ble acting hydraulic actuator to keep valve completely tight during the normal operation


  • Hydraulic power operated, to ensure high seat sealing force for constant tight shut-off
  • ​No spring required, steam pressure opens the valve
  • Three solenoid bypass valves are provided per actuator for redundancy
  • Complete system is type tested and has a type approval number from TÜV


  • Very high relief capacities in one valve
  • Tight shut-off over years due to high seating force
  • Valve lifts without any external energy


  • Completely testable during normal plant operation
  • No spring required
  • Safety function according to EN4126-5 (TRD421) (type approval)

​​Safety function

Reheater safety valve
Closing solenoid valve
Solenoid bypass valves
3 x SBE per main valve
Limit switches
R+4K for feedback to safety cabinet ​SC)
Safety cabinet
SC (for up to 4 parallel safety valves)

Triplicated safety device
3 x Pressure switches with lockable isolation valves and test pressure tap
N/A – Junction box only
Hydraulic power unit

​Product specification​

Design code
EN 12516-2
Others upon request
Body style
Angle type; flow-to-open
Bolted or welded
Nozzle connection
Butt-welding acc. to customer requirements
Steam data range
650ºC / 40-80 bar
Back pressure
Max. 0.5 x inlet pressure
Seat/stem tightness
Tight shut-off - EN 12266-1 Cl.B, MSS-SP61 or ANSI/FCI 70.2 Cl. V.
Double-acting hydraulic actuator

Double-acting hydraulic actuator
Typical stroking time
2-3 seconds to open
Replaceable stem/plug
Bolted bonnet or pressurised sealed bonnet
Inlet/ outlet materials for compatibility with pipe materials
For serviceability, actuator on top recommended​
Safety valve certificate
EN 4126-5 (TRD 421) - Type  approval available​

​​Operating principle

The safety system operation is based on the “1 out of 3” principle. Tripping of one of the three activation paths causes the safety valves to open. If the pressure in the steam system rises above the set pressure of one of the three safety switches, the corresponding solenoid valve on the actuator is de-energized. The solenoid bypass valve opens and the steam pressure will open the safety valve. No hydraulic energy is required to open the safety valves. Up to four safety valves can be connected to one safety control cabinet. When pressure has decreased below the trip pressure of the pressure switches, the bypass solenoid valves are energized again. Another solenoid valve closes the safety valve again and and keeps the safety valve closed under normal operation.
Manual opening by command or by an additional signal from the boiler control system are also available
The safety system has a built-in test function which serves for regular testing of the safety valves including all relevant components of the safety control system during normal operation of the plant. Therefore, the valve need never be removed during the plants lifetime. Pressure switches are checked by isolating them from the steam pressure and connecting them to a test pump. The main valve stems move during the tests. The functional test is carried out path by path.​​

​​Typical materials​​

Typical dimensions

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Product - MSV Reheater Safety Valve