Testing Tension Bolts
Testing Tension Bolts
(OP)
The special inspector said that he has to test 5-bolts from every lot and that three of which ONLY has to pass.
These are A325 tension bolts.
The 60% passing seems very high to me. What do you think?
These are A325 tension bolts.
The 60% passing seems very high to me. What do you think?





RE: Testing Tension Bolts
for lot inspection. ASTM F1470 states that five bolts are the correct number of samples to represent a lot of parts containing between 35 001 pieces and 150 000 pieces. All five samples must meet the requirements - any failure among the five pieces is cause for rejection of the entire lot.
RE: Testing Tension Bolts
MJCronin
Sr. Process Engineer
RE: Testing Tension Bolts
another day in paradise, or is paradise one day closer ?
RE: Testing Tension Bolts
The OP is speaking of the inspection of installed bolts.
CoryPad is referring to factory tests that include physical and chemical properties.
Based on my experience, 60% is a low expectation, in a properly installed joint, I would not be surprised at 100%, much depends on the method of installation.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Testing Tension Bolts
RE: Testing Tension Bolts
You used the words test and inspection. What are these? It is unlikely that anything on the bolts that can be tested or inspected is allowed to to not meet the requirements.
RE: Testing Tension Bolts
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Testing Tension Bolts
The RCSC reads: "7.2. Required Testing:
A representative sample of not fewer than three complete fastener assemblies of each combination of diameter, length, grade and lot to be used in the work shall be checked at the site of installation in a tension calibrator to verify that the pretensioning method develops a pretension that is equal to or greater than that specified in Table 7.1."
It only requires three not five and it does not indicate the passing rate. Still the 60% is way too high.
RE: Testing Tension Bolts
I pretty much became an expert on bolted connections because of the research involved, but that was long ago and I'm probably way behind now. I just counted, it was about 40 years ago.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Testing Tension Bolts
RE: Testing Tension Bolts
The only way I know to do this is to install them on a machine that measures the tension. I mentioned a Skidmore, the usual machine, or other machine. It was simply my interpretation of the requirement. You included a section of the RCSC that calls for a calibrator, again, I assumed a Skidmore or equal. I don't know how else to do it.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Testing Tension Bolts
The RCSC says to test not fewer than 3 bolts and if any fail the tension test, then the cause must be determined and resolved before they are used for work.
RE: Testing Tension Bolts
Otherwise, what is the point of doing the test ?
Cheers,
DD
RE: Testing Tension Bolts
RE: Testing Tension Bolts
RE: Testing Tension Bolts
When you put them in a skidmore ( calibrated tension checking device ) you are doing what is called " Pre installation verification " which is a 5% higher tension than what it would be up on the steel.
We'll use a 7/8" A325 bolt for example.
The required pretension for this particular bolt is 39 Kips. When you do the Pre-Installation verification you test it to 41 Kips. If this bolt snaps , like someone said before , there is an issue. You then grab 3 more bolts from that lot and try again - If they break again that particular lot of bolts is rejected.
Hope that helps and I am not sure where he came up with 5 bolts.