Pneumatic control unit – to control  the spring-loaded safety valves

On line safety valve pneumatic controll units testing

By L-plan Legaline »CSPRS« On-site Testing Device


The combination of pneumatic loading pistons coupled with the pneumatic control  units is one of the ways to fulfill the increased performance  requirements on the safety valves in critical applications requiring one or several of the following operational features:

  • small difference between the operating pressure and opening pressure
  • increased tightness requirements
  • reduction of the opening and reseating hysteresis
  • stable blow of characteristic
  • high operating pressure applications
  • high discharge volumes
  • increased safety trough use of redundant components

L-PLAN is approved Conformity Assessment – Inspection Body by Bureau Veritas.

Such systems are offered by most of the major safety valve suppliers. Production is regulated by EN stadard: EN ISO 4126-5; Safety devices for protection against excessive pressure – Part 5: Controlled safety pressure relief systems (CSPRS).

The control unit operates in accordance with the closed circuit principle with the external medium air. The appertaining safety valves operate according to the relieving principle. The combination of safety valve pneumatic loading pistons coupled with the pneumatic control units is one of the ways to fulfill the increased performance requirements of the safety valves in critical applications.

LEGALINE CSPRS Device is used for the testing of pneumatic control units and safety valve

Legaline unit “model CSPRS” is designed specially for Testing of safety relief valves with additional assisted Pneumatic Control Units, according to EN ISO 4126-5:2013; CSPRS – Controlled Safety Pressure Relief Systems.

On the beginning of the test three “pressure gauges” are displayed on the notebook screen showing:
– pressure in the nitrogen flask
– pressure after the HP regulating valve (system)
– pressure after the LP regulating valve (pneumatic)

While the test is performed the following pressure versus time values (curves) are displayed simultaneously:
– system pressure
– pressure of compressed air fed in the control box
– air pressure in the upper chamber of pneum. piston
– air pressure in the lower chamber of pneum. piston
– spindle lift of the safety valve
– sound phenomena associated with the opening of the safety valve may be displayed

The data gathered during test are recorded and shown as graphs. Then the characteristic points in graphs are identified and based on the values recorded the valve parameters are calculated. The tests are stored in a database.

The already digitalized data supplied by several analog sensors can be processed simultaneously. The PC software, depending on the application desired / test method chosen displays the results as curves or as alphanumeric data necessary to:
– perform the test
– print the test report
– record and establish the history of the object tested

Emphasis on High Accuracy? By Legaline Device Environment Influences Validation! Standard Temperature range 0° C to + 40° C

  • The Legaline CSPRS is designed according to EN ISO/IEC 17025, EN ISO/IEC 17020).
  • Automatic calculation of measurement uncertainty.
  • Correction or compensation of environment influences.
  • System automatically calculated resultants acceptance criteria from Valves Standards.
  • Trend (history) function.


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