Excess Flow Valve with Bistable Switching Behavior

Technical background

To avoid accidents, for instance due to gas explosions, and to improve the security of gas systems excess flow valves are installed in gas pipelines. If a critical predefined gas flow rate is exceeded the excess flow valve will shut off the pipeline automatically in a very short time and uncontrolled outflow of gas is stopped. Commonly used excess flow valves with a spring-loaded pin will release the gas flow if the pressures on the front and back site of the closing disc are balanced. Because this will be a problem in the case of an unrepaired pipeline a novel excess flow valve without a spring is developed to shut-off the gas flow permanently. For the novel device a special preloaded three-ledged compliant snap-through structure with a closure body is mounted in a housing. The preloaded snap-through structure realizes a bistable switching behavior, meaning that the valve is either completely open or closed without any intermediate positions.

 

Aim

According to the principle of snap-through behavior a novel excess flow valve satisfying the requirements of DVGW-VP 305-1 will be constructed and tested. There are lots of advantages of the novel device but tilting of the closure body during snap-through motion is one big disadvantage because this may prevents the hermetic closing of the valve. By an appropriate design of the snap-through structure and the valve components we aim to build up a prototype to shut off the gas flow hermetically and permanently. This purpose will be achieved by:

  • Geometry, arrangement and number of the three-ledged compliant snap-through structure
  • Asymmetry of the system
  • Material of the three-ledged compliant snap-through structure
  • Shape of the closure body and the valve housing
 
Figure: Novel excess flow valve with compliant three-ledged structureTU Ilmenau
Figure: Novel excess flow valve with compliant three-ledged structure

Project partner

AZ Gastechnik GmbH

 

Project duration

08/2013 - 07/2015

 

Acknowledgement

Zentrales Innovationsprogramm Mittelstand (ZIM) des Bundesministerium für Wirtschaft und Energie (BMWi)