40 th Gas-Lift Workshop Houston, Texas, USA Oct. 23 27, 2017 Bellows Cycle Life & How Manufacturing Processes Can Impact it Mark Davey / Principal Engineer 2017 Gas-Lift Workshop 1
Overview API 19G2 is demanding strict set of testing requirements for gas lift components. Gas lift valve manufacturers desire to fully understand the life of their products, and key to this is bellows life. Senior Flexonics has performed our own bellows component durability testing and discovered that the manufacturing process used to make the bellows can significantly affect bellows life. 2017 Gas-Lift Workshop 2
Presentation Outline Durability testing & results of bellows components Manufacturing methods for bellows Effects of manufacturing method on bellows life Other considerations for bellows use in valves Suggestions for further study 2017 Gas-Lift Workshop 3
Overview Valve manufacturers wish to know what the bellows are capable of. All bellows are not alike. All bellows manufacturing processes are not alike. 2017 Gas-Lift Workshop 4
Bellows Nomenclature Outward Formed (Hydroformed) Outward & Inward Formed (Mechanically Formed) 2017 Gas-Lift Workshop 5
Durability Testing Bellows Components Senior performed durability cycle testing on a batch of 7 of each of the following: Mechanically formed 1 bellows Hydroformed 1 bellows Testing was accelerated to 150% of rated stroke to quickly produce failure data Why? Extension or compression? Either was verified to be acceptable 2017 Gas-Lift Workshop 6
Durability Testing Bellows Components Testing Conditions: Not in a valve bellows only Constant stroke, constant 2hz rate mechanically guided axial actuation Internally pressurized to 50 psi for leakage (failure detection) No installation loads & stresses No hydrostatic aging tests No operating pressure cycles No elevated temperatures No exposure to corrosive chemicals These can degrade bellows life. 2017 Gas-Lift Workshop 7
Accelerated Fatigue Test Test Setup Test Unit Programmable Hydraulic Actuator (1% Repeatability) Strong-back with pressure fe port Linear Guide Bearing 2017 Gas-Lift Workshop 8
Accelerated Fatigue Test Video 2017 Gas-Lift Workshop 9
Accelerated Fatigue Test Results Typical bellows fatigue failure (many cycles after initial leakage) Usually 1 st root on simple tests (especially hydroformed bellows) 2017 Gas-Lift Workshop 10
Accelerated Fatigue Test Results 2017 Gas-Lift Workshop 11
Accelerated Fatigue Test Results Reliability / Failure Probability Plots Hydroformed Avg. 28,672 Mechanically Formed Avg. 73,738 Over a 2.5 x Difference! 2017 Gas-Lift Workshop 12
Bellows Manufacturing Methods Outward Formed (Hydroformed) Outward & Inward Formed (Mechanically Formed) 13
Bellows Manufacturing Methods Method Pros Cons Outward Forming $ Manufacturing $$$Tools Inward & Outward Forming Cycle Life $ Manufacturing 2017 Gas-Lift Workshop 14
Bellows Manufacturing Methods FEA Forming Simulations - Strains Outward Forming ONLY NOTHING Inward & Outward Forming BOTH 2017 Gas-Lift Workshop 15
Bellows Hardness Readings from Forming NACE MR0175 LIMIT 35 HrC NO BENEFIT FROM STRAIN HARDENING 2017 Gas-Lift Workshop 16
Other Considerations for Bellows use in Valves Installation Loads & Stresses Don t crush bellows! Don t go past compression lockup! Rule of thumb: 30% change maximum from free length. Ageing: Don t shock it!!! Ramp up pressure SLOWLY! AP requires hydrostatic aging at 5,000 psi which can actually damage the bellows and reduce life. Bellows prefer external pressurization (eliminates squirm failure mode) 2017 Gas-Lift Workshop 17
Suggestions for Further Study Custom bellows for severe applications Higher pressure applications More extreme environments Refurbished components 2017 Gas-Lift Workshop 18
Summary Senior Flexonics bellows component durability testing reveals that the manufacturing process used to make the bellows can significantly affect bellows life as much as 2.5 : 1 Manufacturing induced strain hardening is beneficial for bellows fatigue life. Valve manufacturers can realize the best possible bellows life by avoiding damage during manufacturing & testing. 2017 Gas-Lift Workshop 19
Questions? Bellows Cycle Life & How Manufacturing Processes Can Impact it 2017 Gas-Lift Workshop 20
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