Bolt Inspection via 'Pinging' 6

[pattimelt]

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.

 

[connectegr]

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

 

[chicopee]

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

 

[rmw]

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

 

[pattimelt]

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.

 

[Duwe6]

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.

 

[Ron]

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.

 

[dinjin]

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.

 

[connectegr]

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

 

[hydtools]

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

 

[chicopee]

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

 

[Ron]

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.

 

[Guest102023]

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.

 

[Duwe6]

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.

 

[TXStructural]

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.

 

[btrueblood]

"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?

 

[cybo11]

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.

 

[rmw]

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

 

[TXStructural]

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.

 

[Ron]

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.