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Bolt Inspection via 'Pinging'
6

Bolt Inspection via 'Pinging'

Bolt Inspection via 'Pinging'

(OP)
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.

RE: Bolt Inspection via 'Pinging'

Pinging can be used as a stress relief, but generally for welding.  I have never heard on this for structural bolts.   

http://www.FerrellEngineering.com

RE: Bolt Inspection via 'Pinging'

He is probably hammer testing for cracked or loose bolts. What were the bolts conncting?

RE: Bolt Inspection via 'Pinging'

If a bolt of a "strange" grade or alloy had gotten into the mix, it would have 'pinged' with a different tone alerting him/her to the fact that something was awry.  Same with the tightness.  Pinging to me is more subjective than objective, but I use it - not this particular test - but using tonal differences to tell me that something isn't the same as something else.

We recently had an issue where some bolts were said to be (and the MTR's said they were) A-540.  Some failed and when the set was sent in.  When I 'pinged' them, I couldn't tell what they were as much as I could tell what they weren't (they didn't ping like our A-540 set).  I could tell that we needed to send them to a lab to find out for sure what they were.  If they had 'pinged' like the known samples, we would have gone a different direction.

rmw

RE: Bolt Inspection via 'Pinging'

(OP)
Chicopee, the bolts were connections throughout the structure:  beam to beam; column to beam; monorail to column; grating platform to beam.  No particular pattern i.e., totally random.  This was done after the VT and the feeler gauge check.  Pipe stress, yes; I have seen it done there.  Also, as mentioned, I have seen it a lot doing turbine work.  I just never saw such a thing on a "regular" structural bolt.

RE: Bolt Inspection via 'Pinging'

Not required by any structural code.  However, as rmw wrote, it will find 'odd' bolts.  "Odd" bolts reqire further investigation.  It may have been removed after torquing [so feeler gauging would be ok, squirters have squirted], then reinstalled too loose or too tight.  Pining is fast & thus cheap, and the sign of a diligent and experienced Inspector.  He should be commended.

RE: Bolt Inspection via 'Pinging'

In a word...stupid.  You cannot determine the integrity nor proper tensioning of a high strength bolt with such voodoo.

Do it right with direct tension indicators, turn of the nut, or calibrated wrench.

RE: Bolt Inspection via 'Pinging'

I thought they had an instrument based on sonodur or such that used an echo effect intrumentally to check the tension in bolts.  It sounds like a similar process.  I would expect a higher pitch in bolts with higher tension acting much like a tensioned string in a guitar.
 

RE: Bolt Inspection via 'Pinging'

Purhaps in a laboratory with ideal controls the tension in a bolt can be related to the tone of a ping.   But can an inspector's ear be trained to identify this magic note, among the other job sight noise?  If so he is in the wrong profession.  And construction is far from the laboratory.   

http://www.FerrellEngineering.com

RE: Bolt Inspection via 'Pinging'

I would expect the ping method is no more that a quick qualitative inspection method.  Like plucking wheel spokes to determine if they are all similarly tensioned.  If a fastener in a pattern of fasteners sounds different then it would be marked for a more detailed quantitive inspection.

Ted

RE: Bolt Inspection via 'Pinging'

Yes, you can train your ears by pinging on a series of "good" bolts and defective bolts.

RE: Bolt Inspection via 'Pinging'

chicopee...I agree that you can probably tell the difference between a loose bolt and a tight bolt by pinging, but you cannot tell the difference between a bolt tensioned to 70 percent of yield versus 60 percent of yield.

I agree with connectegr...a construction site is not a place to depend on such a subjective measure.

RE: Bolt Inspection via 'Pinging'

I agree with you Ron ... I cannot imagine a single, useful  aspect of a bolt connection that this could possibly detect reliably.  

As a rough approximation, the value of the information provided by a particular inspection method is proportional to its ease of application.   

RE: Bolt Inspection via 'Pinging'

Sorry, but the data is VERY useful.  If one or two bolts have a *significantly* different tension - thus ping differently, a problem exists.  AISC does not make allowances for having a percentage of improperly tensioned bolts in any given connection. [Ron is correct, difference in tone between 60% and 70% yield is small].  All the more reason to pay serious attention to anomalous bolts.  They have a problem.

RE: Bolt Inspection via 'Pinging'

I'm in the skeptical crowd here.

It has no place in construction of a structural system which is designed to maintain integrity and serviceability at 90% of capacity.

RE: Bolt Inspection via 'Pinging'

"It has no place in construction of a structural system which is designed to maintain integrity and serviceability at 90% of capacity.  "

So, let the broken bolt go?  It was checked once before with a fancy digital gage, so it must be ok?  The subsequent construction and possible structural deflections arising from piling another 80% of the building's mass above that particular girder could not possibly have snapped the fastener, nor could the undocumented leak of a toilet on the floor above possibly contributed to its corrosion...etc. etc. etc.  And, of course, nobody in the construction biz EVER makes a mistake.

Get real.  Somebody raps a bolt, and instead of going "ping" like all the others, it goes "thud".  You'd wanna look into it, no?  No, it's not something you would knock a building down because of, but it might spur you to double check, right?   

RE: Bolt Inspection via 'Pinging'

I'm very intrigued. I think I'll try it on my next bolting inspection~. Early NDT methods included 'ringing' a casting to sound it out. Come to think of it, Hines's famous portraits of the construction of the Empire State building show a riveting inspector using a small hammer to do the same thing. Acoustic methods do work, look at ultrasound, harmonic bond, resonance and acoustic emission testing- it's all frequencies. It's up to us to know where to listen.
That said, I'd still take a close look at the DTI's.  

RE: Bolt Inspection via 'Pinging'

I have been pinging on stuff for years now and nothing in this thread has deterred me from continuing.  Pinging is not a "last word" test, it is only an 'initial indicator'.  I'd say that 95% of anything I ever pinged on never went past just that because the pinging didn't produce any unusual indicator that resulted in further action.  But in the 5% of cases where the ping - ping - ping - and then there was a - thud - where there should have been another resolute "ping" resulted in further testing with real instruments or testing devices and usually for good reason.  It simply told me that something wasn't quite right.  Then I had to use "store bought" testing methods to find out why.

And Cybo11, the reason that photo shows that inspector pinging at the Empire State Building is because he forgot to bring his ultrasonic tester to work that day.... (see tongue in cheek.)

rmw

RE: Bolt Inspection via 'Pinging'

My point is that if the component needs to be inspected, checked, tested, or qualified, then it needs to receive the proper inspection, check, test, or qualification, not some guy/gal walking by randomly tapping it with a small brass hammer.

If it needs to be checked, check it properly.  If it doesn't need to be checked because the quality control procedures and work processes assure it is done correctly, then stop taking time creating a false sense of security.

The OP states: "The bolts are installed with a DTI to the nut and inspection is both visual for the 'squirt' and with the .005 gauge."  This procedure is either valid or the installation procedure needs to be modified if it is not valid.  If the concern is that a bolt or connection was missed, then the quality control needs to be examined, or the inspection needs to be 100%, since all connections are life-and-death critical.

I'm on board with the idea that, as a last check, the tap tells you whether something has gone horribly awry.  However, the OP's follow-up post says, "No particular pattern i.e., totally random." which indicates to me that it was not a real inspection, but rather a way for the inspector to feel like he was doing something.  If, on the other hand, the "random tapping test" method has been qualified for this purpose, and it represents a systematic, accurate inspection, then I suppose it is fine.   

RE: Bolt Inspection via 'Pinging'

TX...well stated.  There seems to be a "discipline" split here.  Industrials and mechanicals use it for their purposes, but those of us on the structural side with prescribed procedures required for bolt inspection and testing, wouldn't use this method.

RE: Bolt Inspection via 'Pinging'

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.

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RE: Bolt Inspection via 'Pinging'

"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.

RE: Bolt Inspection via 'Pinging'

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.

RE: Bolt Inspection via 'Pinging'

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.

RE: Bolt Inspection via 'Pinging'

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

RE: Bolt Inspection via 'Pinging'

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.

RE: Bolt Inspection via 'Pinging'

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.

RE: Bolt Inspection via 'Pinging'

"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.   

RE: Bolt Inspection via 'Pinging'

I think the pinging guy is not trying to differentiate the
bolts that might be 90 percent vs 95 percent tight but find the ones that have not been tightened at all.
To ping or not to ping, that is the question.

RE: Bolt Inspection via 'Pinging'

"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.

RE: Bolt Inspection via 'Pinging'

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.

RE: Bolt Inspection via 'Pinging'

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

RE: Bolt Inspection via 'Pinging'

Dik...thanks.  You stated it better than I.

RE: Bolt Inspection via 'Pinging'

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
 

RE: Bolt Inspection via 'Pinging'

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).

RE: Bolt Inspection via 'Pinging'

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

RE: Bolt Inspection via 'Pinging'

the A490's are 1-1/2" dia...

RE: Bolt Inspection via 'Pinging'

dik...that's a good size HS Bolt!  The elongation just to get tension will be quite a bit.

RE: Bolt Inspection via 'Pinging'

Each splice has approx 100 of them... 8' deep plate girder...

RE: Bolt Inspection via 'Pinging'

(OP)
Sounds like bolts in stop valves, intercepts, etc.   BIG bolts!  Not sure if I envy you or feel sorry for you in having to do inspection!    

Thanks to all on my thread!

RE: Bolt Inspection via 'Pinging'

So, Patti... what did you decide?  Will we ever see you out with a brass hammer (or any type of hammer) on a jobsite?

rmw

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