Item/Function Potential Failure Mode(s) Potential Effect(s) of Failure  Sev Potential Cause(s)/Mechanism(s) of Failure  Occ Current Design Controls  Det  RPN Recommended Action(s)  
 
  Dirt / Trash in gas valve will not rotate 7 Failure mode in previous stage of compression 6 None 3 126 Filter Stream  
Valve Plates/Spring/Gaskets Corrosion of Parts due to gas type Gas leakage, excessive wear, valve failure 8 Incorrect material choice, excessive temperatures 4 None 6 192 Research all material choices  
Spring Spring failure / return mechanism failure Gas leakage, poor gas flow 7 Incorrect spring material choice, excessive temperatures, incorrect spring rate 5 Proper spring selection based on material and spring rate 3 105 Calculate all forces on valve and determine optimum spring rate and material  
Center Bolt, Threads, center bolt clearance Friction too high on mating part, Poor machining tolerances Excessive play in valve, stuck valve, excessive wear 6 Poor Machining quality, Improper material selection, surpassing valve lifetime 4 Parts are properly machined and inspected, Extensive material research 6 144 High precision machining, adequate material research
Valve Plates/Frame/Spring/Gaskets Parts over pressured Gasket Failure, Part deformation 8 Pressure exceeds designed pressure 2 Design valve with adequate safety factor 8 128 Choose more robust materials, test parts at pressure before use
Valve Housing Incorrect housing sizes not to print Valve will not fit 8 Incorrect dimensioning of design 2 Valve is designed within limits 1 16 Assemble/measure valve before use to ensure proper fitment
Valve Plates/Threads/Splines Slots incorrectly located on valve parts à not lining up Poor flow/ poor seal, won't fit 8 Incorrect dimensioning of design 2 Allow adequate gaps between holes 1 16 Assemble/measure valve before use to ensure proper fitment
Entire assembly Individual part failure  Valve is not operational 9 lack of attention to design detail 7 Extensive design analysis 6 378 calculate stresses on all parts, account for long term wear, adequate material selection, proper dimensioning
Center Bolt, Threads, center bolt clearance Incorrect dimensions on shaft, twist is not correct, incorrectly splined, not enough bolt thread Poor flow, Cant bolt together, Bolt doesn’t fit 8 Improperly dimensioned 3 Bolt designed closely to specifications 4 96 Repeat calculations, ensure proper fitment
Center bolt material, Gasket Debris in shaft Poor gas flow 6 Improper material selection, valve exceeding lifetime 5 Material extensively researched  7 210 Screen the valve, more research on proper gaskets and center bolt
Center bolt and housing Overall height of valve incorrect, Piston interference scar piston, bend rod, valve damage 9 improper dimensions 2 following design parameters closely, check valve clearance with piston 2 36 Run clearance test prior to installation
spring  Valve opens too quickly Gas not compressed, slow gas velocity 5 Spring rate too low 4 Proper force balance analysis 6 120 Adequate testing
spring Valve closes too quickly Not enough flow allowed 5 spring rate too high 4 Proper force balance analysis 6 120 Adequate testing
Spring, Center bolt Valve opens too slowly Not sufficient gas flow 5 Spring rate too high, Center bolt friction 5 Proper force balance analysis, selecting proper materials 6 150 Adequate testing and material research
Spring, Center bolt Valve closes too slowly Too much gas flow, gas not compressed sufficiently 5 Spring rate too low, Center bolt friction 5 Proper force balance analysis, selecting proper materials 6 150 Adequate testing and material research
Center Bolt, Spring Valve fails to open No gas flow 6 Center Bolt pitch too low, Spring rate to high, Friction 3 Analyze thread pitch and friction, Proper force balance analysis 3 54 Adequate testing and material research
Center bolt, Spring Valve fails to close No compression 6 Spring rate too low, Center bolt friction 3 Proper force balance analysis, selecting proper materials 4 72 Adequate testing and material research
Center bolt, Spring Valve stick partially open/closed Inefficient flow  6 Improper material selection, friction, debris in threads 4 Proper material selection, Thread analysis 6 144 Adequate testing and material research
Center bolt, Spring, Center plate Valve flutters/bounces Inefficient flow, lack of compression/gas velocity 5 Spring rate, Valve Weight, Flow frequency matching natural frequency 3 Flow analysis, spring damping analysis, vibration studies 8 120 Adequate testing and material research
     
Max RPN
 
  378