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INSTRUMENTATION • ELECTRONICS


vDEPENDABLE F


alve actuation


Richard Harvey explains why reliability in valve actuation is non-negotiable


or the optimal control of many processes, it is crucial that a valve reaches a certain position. The process of moving from one position to another is governed by the valve’s actuator, which is a type of drive that is responsible for


moving or controlling it. For safety-critical applications, the actuation of the valve (the ability of the system to move the valve to a safe condition in response to demand), is of fundamental importance. Pneumatic or hydraulic actuators are a proven


  actuators are, in turn, predominantly operated using an electromagnetic solenoid valve. Many solenoids operate within systems that can stay in one position for many years, with an overall lifetime of decades. They are often    paramount importance. In these circumstances, any failure in actuation can have catastrophic results, so reliability is non-negotiable.


BENEFITS OF SOLENOID VALVES Solenoid valves have many advantages. They are   appropriately they can provide safe switching, reliability, durability and resistance to extreme conditions, extensive lifespan and compact design. However, historically they have often been seen as the  often chosen based on cost and not design. Solenoid valves must be suitable for the


environment in which the valve operates. The valve must be able to resist corrosion, dust, water and other environmental aggression for many years, and must  But what qualities and conditions are required


to achieve optimal operation? The answer lies in a combination of unit design and the management of operating forces, as we shall see.


IDEAL CONDITIONS The reliability or otherwise of a solenoid valve is largely dictated by the forces acting within it.    retentivity, friction and spring force. For a solenoid valve to be reliable, the optimum


factors when it is closing, and those that are ideal  parameters for closure are a high force friction ratio (FFR), i.e. low internal friction and a high return spring force, and a low dangerous failure rate.


On opening, the ideal conditions are: low internal


 and a low safe failure rate. Understandably, these  and careful design.


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