I saw something that I am not sure I have ever seen on an A325 bolt - a fellow inspector had a small (thumb size) brass hammer and went around to the A325 bolts (3/4") and hit them with this little hammer. Now, I am familiar with this method when you are using a castle bolt and Texas hot rod on something like an intercept valve, but on a structural connection? I didn't want to ask him, so I am asking here - what purpose does this serve? The bolts are installed with a DTI to the nut and inspection is both visual for the 'squirt' and with the .005 gauge.
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Bolt Inspection via 'Pinging' 6
- Thread starter pattimelt
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1
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Please don't tell certain folks in certain govt defense agencies that pinging isn't ever OK.
I know of a rush upgrade to a certain platform where there was some loss of traceability in some material due to the speed with which it was happening. In order to approve the parts a crude 'ping test' was performed.
I know of a rush upgrade to a certain platform where there was some loss of traceability in some material due to the speed with which it was happening. In order to approve the parts a crude 'ping test' was performed.
Posting guidelines faq731-376 (probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484
What is Engineering anyway: faq1088-1484
btrueblood
Mechanical
"My point is that if the component needs to be inspected, checked" etc.
Absolutely, and I agree with you and Ron where statements like that were made. But disagree with the statment made and referenced in the prior post, in the extent that it seems to be a blanket denial of any possible good coming from pinging a bolt. It's like saying there is no place for a Mk 1 eyeball inpsection either.
"a way for the inspector to feel like he was doing something"
Perhaps. I see it this way: I'm an inspector walking around from place to place to visit points I'm required to visit and witness inspections, stamp or write my name, etc. What harm is done if I tap a few bolts along the way? If I find a loose or broken bolt, I'm a hero. If not, I'm just some old kook with a little brass hammer. "Us mechanicals" are well versed that stuff that is bolted down does not necessarily remain that way. Buildings and structures move too, and faying surfaces may decay over time. Inspections, however precisely made, cannot and will not find 100% of flaws, even if repeated some finite number of times...and a bolt ping is probably the lowest of the rank orders of inspections...but the one time it works, again it may save a lot of money, time or lives.
Aircraft pilots (at least the ones still alive) always walk around their plane, shake the elevators, kick the tires. Sure, the FAA certified mechanic has a long checklist of fasteners that he was supposed to torque & lockwire, but the pilot is the guy who has to ride it.
Absolutely, and I agree with you and Ron where statements like that were made. But disagree with the statment made and referenced in the prior post, in the extent that it seems to be a blanket denial of any possible good coming from pinging a bolt. It's like saying there is no place for a Mk 1 eyeball inpsection either.
"a way for the inspector to feel like he was doing something"
Perhaps. I see it this way: I'm an inspector walking around from place to place to visit points I'm required to visit and witness inspections, stamp or write my name, etc. What harm is done if I tap a few bolts along the way? If I find a loose or broken bolt, I'm a hero. If not, I'm just some old kook with a little brass hammer. "Us mechanicals" are well versed that stuff that is bolted down does not necessarily remain that way. Buildings and structures move too, and faying surfaces may decay over time. Inspections, however precisely made, cannot and will not find 100% of flaws, even if repeated some finite number of times...and a bolt ping is probably the lowest of the rank orders of inspections...but the one time it works, again it may save a lot of money, time or lives.
Aircraft pilots (at least the ones still alive) always walk around their plane, shake the elevators, kick the tires. Sure, the FAA certified mechanic has a long checklist of fasteners that he was supposed to torque & lockwire, but the pilot is the guy who has to ride it.
Other than bridges, structural bolt installation gets SAMPLED. Pinging allows the sample size to be greatly increased with very little time involved. Anything that increases sample size is a good thing.
Also, the structural engineers seem to not realize that bolts get loosened and retightened at times. A good 'squirt' or a snapped-off tail of a 'LeJune' bolt is not a guanantee that that bolt is actually properly tensioned -- today. Just means that one day, it was installed correctly. Who knows about today?
A little extra care and inspection is a very good thing. When the Ironworkers know that the bolts are subject to reinspection, they suddenly start installing a new squirter or get an inspector & torque wrench to retension the loosened bolt.
Also, the structural engineers seem to not realize that bolts get loosened and retightened at times. A good 'squirt' or a snapped-off tail of a 'LeJune' bolt is not a guanantee that that bolt is actually properly tensioned -- today. Just means that one day, it was installed correctly. Who knows about today?
A little extra care and inspection is a very good thing. When the Ironworkers know that the bolts are subject to reinspection, they suddenly start installing a new squirter or get an inspector & torque wrench to retension the loosened bolt.
TXStructural
Structural
Which amplifies my point that if there is a likelihood that something has been done or redone incorrectly, or undone entirely, then it needs to be properly, 100% inspected.
As a designer, I need every bolt to be as designed, because I do not include "extra" bolts just in case. This is not something which allows a deviation from design. Theoretically, if one bolt in a set is not properly tensioned, then the slip-critical connection will fail to act as designed. Random testing is not adequate if the bolts have been tampered with after installation.
Either trust them all based on process control or test them all as a QA/QC measure.
As a designer, I need every bolt to be as designed, because I do not include "extra" bolts just in case. This is not something which allows a deviation from design. Theoretically, if one bolt in a set is not properly tensioned, then the slip-critical connection will fail to act as designed. Random testing is not adequate if the bolts have been tampered with after installation.
Either trust them all based on process control or test them all as a QA/QC measure.
TX,
I'm not a structural but when you say you haven't included extra bolts I would guess that the design codes you are following have. In the mechanical world there is a good factor of safety added on everything, that's the equivalent to extra bolts IMO.
In an ideal world everything is built according to paper and it's all perfect but in the real world people make upto 11 misakes per day (or so I've heard).
I don't see anything wrong with tapping the bolts as an extra step. If I take my car in for an oil change I always double check the oil level to be sure they put oil in, sure they're the expert but mistakes happen.
Regards,
K
I'm not a structural but when you say you haven't included extra bolts I would guess that the design codes you are following have. In the mechanical world there is a good factor of safety added on everything, that's the equivalent to extra bolts IMO.
In an ideal world everything is built according to paper and it's all perfect but in the real world people make upto 11 misakes per day (or so I've heard).
I don't see anything wrong with tapping the bolts as an extra step. If I take my car in for an oil change I always double check the oil level to be sure they put oil in, sure they're the expert but mistakes happen.
Regards,
K
paddingtongreen
Structural
The natural frequency of a string or tight bolt, with the same mass/unit of length, is inversely proportional to the length, but is proportional to the square root of the tension. For a given length of bolt, with say, the tension at 90%, the frequency would be at about 95%; with the tension at 110%, the frequency would be about 1.05.
That is a tight range. It would be neat to challenge the guy with some bolts installed in a Skidmore.
The first thing that came to mind on this thread, was watching the railway engineers walk along hitting each wheel with a hammer before he would take the train out of terminus, Paddington Station in this case. I asked one of them about it when I was a little kid, he said the "ring" told him everything he needed to know.
Michael.
Timing has a lot to do with the outcome of a rain dance.
That is a tight range. It would be neat to challenge the guy with some bolts installed in a Skidmore.
The first thing that came to mind on this thread, was watching the railway engineers walk along hitting each wheel with a hammer before he would take the train out of terminus, Paddington Station in this case. I asked one of them about it when I was a little kid, he said the "ring" told him everything he needed to know.
Michael.
Timing has a lot to do with the outcome of a rain dance.
TXStructural
Structural
Mistakes do not happen with proper procedures. It is just that simple. This is not really a mindset ingrained into construction, but it needs to be. (But we all understand that this is construction, and we have for far too long simply been told that we have to accept defects as the norm.)
We do apply load factors to account for future changes in loading, but our resistance factors (phi factors) do not contemplate missing fasteners or improperly installed connections. Resistance factors account for normal variation in materials and installation, not including failure to include all required elements. Forgetting a bolt is equivalent to reducing the size of the connection - in some cases, this could result in a 50% loss of shear resistance for the connection. This is not something which can be accounted for by the 10 or 25% reduction in capacity determined by the phi factor.
If you look at the factors for anchor strength in concrete (ACI 318 Appendix D), there is a strength reduction factor which varies by anchor type based on susceptibility to installation error. There is nothing comparable for normal structural fasteners.
We do apply load factors to account for future changes in loading, but our resistance factors (phi factors) do not contemplate missing fasteners or improperly installed connections. Resistance factors account for normal variation in materials and installation, not including failure to include all required elements. Forgetting a bolt is equivalent to reducing the size of the connection - in some cases, this could result in a 50% loss of shear resistance for the connection. This is not something which can be accounted for by the 10 or 25% reduction in capacity determined by the phi factor.
If you look at the factors for anchor strength in concrete (ACI 318 Appendix D), there is a strength reduction factor which varies by anchor type based on susceptibility to installation error. There is nothing comparable for normal structural fasteners.
btrueblood
Mechanical
"Mistakes do not happen with proper procedures. "
That is crap.
Mistakes happen because people make mistakes. They aren't robots.
Large aircraft are designed with a plethora of fasteners. Most wing skins are installed with rivets. More than 10% of them can be missing on newly built wings and they will still work, because the wings were designed that way. I.e. the designers knew that their workmen were human beings.
If you really are designing buildings with single-point bolt connections whose failures will result in loss of property or lives...please stop.
That is crap.
Mistakes happen because people make mistakes. They aren't robots.
Large aircraft are designed with a plethora of fasteners. Most wing skins are installed with rivets. More than 10% of them can be missing on newly built wings and they will still work, because the wings were designed that way. I.e. the designers knew that their workmen were human beings.
If you really are designing buildings with single-point bolt connections whose failures will result in loss of property or lives...please stop.
"Mistakes do not happen with proper procedures".
I need you to come explain why then in the "procedures-r-us" atmosphere that I work in that the constant thing being harped on by management is bringing the mistake count down.
Wow, what a Utopian statement.
rmw
PS: Ron may be onto something. As a matter of full disclosure, I am a Mechanical but I have never inspected any structural bolting. I have on the other hand inspected plenty of pipe flange bolting, turbine (shell) flange and control valving bolting, ductwork fabric expansion joint bolting, 18-Wheeler wheel hub bolting, engine head bolting to name a few. And.... along the same line, I have thumped many a truck and bus tire with a hammer or hammer handle. Didn't tell me the tire pressure, but it did tell me the one(s) that needed further checking to find out what the pressure was(n't) and the ones I could keep on walking by.
I need you to come explain why then in the "procedures-r-us" atmosphere that I work in that the constant thing being harped on by management is bringing the mistake count down.
Wow, what a Utopian statement.
rmw
PS: Ron may be onto something. As a matter of full disclosure, I am a Mechanical but I have never inspected any structural bolting. I have on the other hand inspected plenty of pipe flange bolting, turbine (shell) flange and control valving bolting, ductwork fabric expansion joint bolting, 18-Wheeler wheel hub bolting, engine head bolting to name a few. And.... along the same line, I have thumped many a truck and bus tire with a hammer or hammer handle. Didn't tell me the tire pressure, but it did tell me the one(s) that needed further checking to find out what the pressure was(n't) and the ones I could keep on walking by.
TXStructural
Structural
I realize mistakes are made. My point is that if they are getting made, the procedures are bad, and a random pinging with a hammer isn't really an adequate measure to catch random loss or misapplication of tension.
I had not heard of this... but, will try it next opportunity... just curious.
I think that Ron is trying to caution people that this is not a reliable check, and is not a substitution for proter testing. This would be foolhardy.
I usually go by random reference marks for turn of nut... with occasional torque wrench and washers.
Dik
I think that Ron is trying to caution people that this is not a reliable check, and is not a substitution for proter testing. This would be foolhardy.
I usually go by random reference marks for turn of nut... with occasional torque wrench and washers.
Dik
The concern I have is that people may think that this is a proper means of testing... and I have to learn how to spell "proper"... <G>
I just signed onto a website last night about fastening and they have some articles on ultrasonic testing of fasteners for tensioning... still have to look into it. It was a result of a link posted in a query in one of the forums about tightening bolts from the nut or head...
Dik
I just signed onto a website last night about fastening and they have some articles on ultrasonic testing of fasteners for tensioning... still have to look into it. It was a result of a link posted in a query in one of the forums about tightening bolts from the nut or head...
Dik
dik...have a friend who was involved with some field efforts to determine bolt tension ultrasonically. He is a consultant to "a major theme park in Orlando", where they routinely employ the latest methods of NDT. He started this over 15 years ago and seemed to be reasonably successful with their results.
They were looking mostly for loss of tensioning with time in dynamic structures (roller coasters, for instance).
They were looking mostly for loss of tensioning with time in dynamic structures (roller coasters, for instance).
Thanks... other than the effort in preparation, seems like something to look into...
We have on project where we are using A490's that are 10" to 12" long... found out from Portland Bolt that they get A490 blanks in 13" to 15" lengths and cut and thread them to suit...
These will be the biggest bolts that I've seen, although I galvanised a 'spare' 3" Nut when I was employed as a student at Dominion Bridge one summer...
Dik
We have on project where we are using A490's that are 10" to 12" long... found out from Portland Bolt that they get A490 blanks in 13" to 15" lengths and cut and thread them to suit...
These will be the biggest bolts that I've seen, although I galvanised a 'spare' 3" Nut when I was employed as a student at Dominion Bridge one summer...
Dik
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