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re-useable bolts?
- Thread starter edelvi
- Start date
edelvi;
Re-use of bolts or studs depends on specific service applications. "High pressure places" is too vague. I can tell you that for service temperatures where creep is a concern, re-use of bolts or studs requires careful consideration because you have limited service life.
For service temperatures which are below time dependent properties (creep), re-use of bolts or studs should be based on a minimum of a visual inspection (check for thread condition, elongation or corrosion)and possibly nondestructive testing (NDT) to assure the bolt or stud is free of cracks or defects from previous service.
Most Codes and Standards do not address re-use of hardware because of liability concerns.
Re-use of bolts or studs depends on specific service applications. "High pressure places" is too vague. I can tell you that for service temperatures where creep is a concern, re-use of bolts or studs requires careful consideration because you have limited service life.
For service temperatures which are below time dependent properties (creep), re-use of bolts or studs should be based on a minimum of a visual inspection (check for thread condition, elongation or corrosion)and possibly nondestructive testing (NDT) to assure the bolt or stud is free of cracks or defects from previous service.
Most Codes and Standards do not address re-use of hardware because of liability concerns.
EdStainless
Materials
I used to work with downhole oilfield equipment. Our fasteners were high strength and corrosion resistant. We never reused. The risk in terms of time delay and rework if one didn't go together correctly was much greater than the cost of the hardware.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
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Rust never sleeps
Neither should your protection
As stated above it depends on the specific service conditions that the fastener sees.
We reuse thousands of of B7 and B16 fasteners in our polymer area for jacketed piping and the associated Therminol Vapor heating system. This process requires that we maintain physical integrity of the system as any outage would require an overhaul whether the system has been online one hour or one year at a cost of $150,000 to $200,000. Some of the fasteners have been in service over 30 years, each with it's on number of reuses. This is because the fasteners, studs in this case, are commingled during an overhaul with others during an overhaul. I have found some Crane Alloy studs dating from the 50's still being cycled. The operating conditions are 20-250 psig to 2500 psig @ 200C to 285C. Physical conditions determines if the stud is reused.
We also use H11 SHCS that are recycled approximately every 20 days. These fastener operate with a bolt stress around 80,000 psi at 285C and on turnaround are cycled to 485C for several hours. Again physical condition determine viability for reuse.
We also recycle B16 Studs in service at 485C. The service pressure is very lower and these studs are not highly stressed.
In the areas where we use CRS studs, mainly A193 304 Class II, we also recycle the studs. Though we don't do any formal gaging all stud and nut combination are made up prior to use. My last survey revealed that we lose 10% to 15% on each cycle.
We reuse thousands of of B7 and B16 fasteners in our polymer area for jacketed piping and the associated Therminol Vapor heating system. This process requires that we maintain physical integrity of the system as any outage would require an overhaul whether the system has been online one hour or one year at a cost of $150,000 to $200,000. Some of the fasteners have been in service over 30 years, each with it's on number of reuses. This is because the fasteners, studs in this case, are commingled during an overhaul with others during an overhaul. I have found some Crane Alloy studs dating from the 50's still being cycled. The operating conditions are 20-250 psig to 2500 psig @ 200C to 285C. Physical conditions determines if the stud is reused.
We also use H11 SHCS that are recycled approximately every 20 days. These fastener operate with a bolt stress around 80,000 psi at 285C and on turnaround are cycled to 485C for several hours. Again physical condition determine viability for reuse.
We also recycle B16 Studs in service at 485C. The service pressure is very lower and these studs are not highly stressed.
In the areas where we use CRS studs, mainly A193 304 Class II, we also recycle the studs. Though we don't do any formal gaging all stud and nut combination are made up prior to use. My last survey revealed that we lose 10% to 15% on each cycle.
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