Can a bolt be reused? If so, what grades and in what scenarios?
A bolt that has already been used in a given application may or may not be reused, depending on the grade, application, and recommendation of the “Engineer of Record”. There are a tremendous number of conflicting opinions on this subject, but the only definitive published information we can find on this issue from a reputable source is in regards to ASTM A325 and A490 structural bolts.
According to the Research Council on Structural Connections, Section 2.3.3:
“Reuse: ASTM A490 bolts and galvanized ASTM A325 bolts shall not be reused. When approved by the Engineer of Record, plain finish ASTM A325 bolts are permitted to be reused. Touching up or re-tightening bolts that may have been loosened by the installation of adjacent bolts shall not be considered to be a reuse.”
“Pretensioned installation involves the inelastic elongation of the portion of the threaded length between the nut and the thread run-out. ASTM A490 bolts and galvanized ASTM A325 bolts possess sufficient ductility to undergo one pretensioned installation, but are not consistently ductile enough to undergo a second pretensioned installation. Plain ASTM A325 bolts, however, possess sufficient ductility to undergo more than one pretensioned installation as suggested in the Guide (Kulak et al., 1987). As a simple rule of thumb, a plain ASTM A325 bolt is suitable for reuse if the nut can be run up the threads by hand.”
When reusing bolts, it is critical to involve an engineer since the reuse of the fastener depends on a variety of factors including bolt type, application, grade, finish, installation method, etc. If the bolts have been tensioned beyond their yield point, they enter the “plastic zone” (where they elongate and do not contract once the load is removed), which means they may be subject to premature failure. Since it is virtually impossible to determine visually if a specific fastener has entered its plastic zone when previously used, the decision to reuse a fastener will be determined by the price to replace it versus the potential cost and/or liability of that fastener failing.
Spending a few hundred dollars replacing structural bolts supporting an overhead sign structure on the freeway makes sense when evaluating the potentially devastating consequences and liability involved in reusing bolts that may ultimately fail. On the other hand, attempting to reuse a few hundred dollars worth of bolts instead of replacing those fasteners on a noncritical pump or other piece of equipment might make sense when a failure would only result in the piece of equipment not working.
ASME PCC-1 2019 paragraph 4(c)(1) states that: “when using bolts and nuts of common grade as fasteners, the use of new bolts and nuts up to M30 (1-1/8 inch) diameter is recommended when bolt load-control methods such as torque or tension are deemed necessary”
This is a post-construction standard published by ASME and developed by post construction commmittee. This standard is not code, but it is recognized and generally accepted good engineering practice (RAGAGEP) meant for in-service inspection and maintenance of pressure equipment and pressure piping.
More and more companies are insisting that RAGAGEP is used in lieu of code requirements, when it involves the safety, operation, operability, maintainability, and availability of your people and assets.
What is the rule for reusing anchor rods like F1554 Gr55 or Gr105?
@Hossein- Neither the AISC, ACI nor ASTM have any recommendations regarding anchor bolt reuse. With nothing published to reference, it would be left up to the project engineer.
Sir have we any tolerance bolt torqueing quantity.
@Ammar- Torque values are tricky and inconsistent. For your specific application, the project engineer should be consulted to determine proper values.
Hello,
I have Grade 12.9 Nuts and Bolts on a flange, they are torqued up to 1000nM (within last 6 months)
The Flange needs to be disconnected and reconnected, is it possible to reuse the Nuts?
Thanks in advance
@Shane- Unfortunately that is not something we are able to answer. The only published guideline we are aware of is the AISC guideline above, we do not have any information regarding the reuse of 12.9 graded fasteners.
Shall I torquing the bolt again and again..and how many times would be permitted for torquing the same bolt .if possible again’ and again the torque would be 100 or less than of next time.
@Bhanu- Reuse depends on the grade and how much the bolt has been tensioned to. We are unable to make recommendations for your application, you will need to check with the project engineer and let them determine if reuse is acceptable.
In my project Gr8.8 bolt is getting used but recently we got Bolt with grade ASTM A325 in site and our consultant refused to accept for using A325 and the explanation was grade changes. Could you tell me whats the difference of these two grades
@Sandeep- Grade 8.8 and A325 bolts are very similar in chemistry and mechanical properties, but they are not identical. They are also dimensionally different, the A325 has a larger head and shorter thread length. We would concur with your consultant that the bolts should not be substituted for each other unless the project engineer signs off on it.