Processing, April 2018

Does Valve Selection Matter in High Solid Content Mediums or Abrasive Slurries APRIL 2018 www processingmagazine com 27 Safety Integrity Levels e industry standards for HIPPS are IEC 61508 pertaining to functional safety and IEC 61511 pertaining to safety instrumented systems for the process industry sector These standards define different levels of functional safety requirements based on the likelihood that a system will fail when it is needed probability of failure on demand PFD Risk is de ned as PFD multiplied by the cost of the consequence of failure In other words if the consequence of a failure is very costly for example injury or even death the probability of it happening must be reduced to achieve an acceptable level of risk e IEC standards de ne levels of risk reduction identi ed as Safety Integrity Levels SIL SIL 1 denotes risk reduction by a factor of 10 HIPPS are typically rated SIL 3 requiring risk reduction shutting down the process is whole system must be rated SIL 3 by an independent testing organization such as TÜV For a HIPPS to be certi ed SIL 3 the PFD of all the components working together must conform to SIL 3 Note that some systems may be referred to as SIL 3 capable because they include components suitable for SIL 3 environments but to be certi ed SIL 3 the system as a whole must meet the standards Redundant solenoid valves Clearly if a process were controlled by a single solenoid valve and that valve failed to function the result would be catastrophic Besides using a solenoid valve with a PFD suitable for SIL 3 risk must be further reduced by using multiple valves backing up each has implications for process industries In the case of one out of two 1oo2 redundancy there are two normally closed valves installed to control the process valve While they are energized they remain open to keep the process owing In an emergency they deenergize and default to closed If one fails to close during an emergency a dangerous failure the other will close and shut o the ow of volatile media However if a valve fails and shuts down the process even though there is not an emergency a safe failure it can cost millions of dollars a day and cause signi cant business and operational disruption A two out of two 2oo2 redundant system will reduce the risk of these spurious trips by ensuring that one valve remains open even if one valve fails and closes without cause However once this Opposite When processes at re neries or chemical processing plants operate at different pressures a high integrity pressure protection system HIPPS rated Safety Integrity Level SIL 3 reduces the risk of over pressurization Image courtesy of IMI Norgren Inc per Shutterstock The worlds toughest pumps for the most demanding applications Our Dual Pinch and High Quality Rubber Saves Money and Increases Sleeve Lifetime Standard Pinch Valves Sleeve Life 4 Months 1 Year Opex 130 Valves 171950 5 Year Opex 130 Valves 859792 VS F lowrox Pinch Valves Sleeve Life 27 Months 1 Year Opex 130 Valves 0 5 Year Opex 130 Valves 114639 40 pumice slurry @ 60 psi valves cycling every 45 seconds Unmatched Reliability ASK ABOUT A FREE TRIAL 888 356 9797 Your productivity and profitability is our 1 concern www flowrox com by a factor of at least 1000 When a sensor detects possible over pressurization it sends a signal to the logic solver which activates the solenoid e solenoid controls the ow of compressed air or gas to the actuator which in turn moves the process control valve to the safe position other in a redundant system There are various levels of redundancy and each A four channel redundant valve manifold integrates valves with all necessary piping reducing size complexity and potential leak points to maintain 2oo3 redundancy Image courtesy of IMI Norgren Inc