Type of Bolt

thank you for your answer . however, does the plating affect the shearing of these bolts?

Not normally, but please note that the Triangle indicates that it is a close tolerance bolt which could be very important in your application.

This guy

https://www.youtube.com/watch?v=G3eH_YFTcFo

Says the triangle is just a "manufacturer's mark" (within the first 90 seconds).

Is he wrong?

I think he is right, the triangle in this case is the makers mark of Enfrasco.

I am used to a triangle meaning close tolerance, but having said that it usually surrounds the identifier which is not the case here. My bad.

I agree. Grade 5 plated bolt.

A lot of people think a bolt is a bolt. But if the failiers are frequent , the easiest is to upgrade to a Grade 8 bolt - which are readily available from any fastener store. Your point about upgrading is taken but in this application I don't think the bolts were meant to fail like a shear pin.

You might want to test a small sample of the bolts you source.

That's what we've done.

You might find that one manufacturers quality is better than another.

You might also help the manufacturer by pointing out batch quality issues. Which could lead to ..bolt samples!

I've heard that hot dipped galvanization can weaken a nail or screw ...but make it last longer.

It seems to be correct, but I have not tested that with a strain gauge.

Can a larger fastener be utilized?

Shear Madness.

The triangle is just a manufacturers idendity mark

https://www.engineersedge.com/hex_bolt_identification.htm

A phone call to the equipment manufacturer will be useful. I am sure they have seen this failure before. Ask for the field service manager.

You're assuming the OEM still exists.

I have a 40-yr old electric over hydraulic pyramid roller in my shop that I and my guys use regularly. Repairs are always a challenge, because the OEM went out of existence in the late 1980's with no successor. In fact I had to build my own set of hydraulic system schematics from scratch. My state-of-the-art Master Electrician/ PCM expert took one look at my AEG controller box and said "pray this thing never goes bad" I THINK I can get schematics on the box, because AEG is German and they are real anal about keeping historic technical documents.

FYI: Mining equipment is run until "the wheels fall off" and the CAT uses it's 9 lives and dies.

1980's! Ok.That was during the period of discreet components that can be easily replaced.

Barring a catastrophic failure,most of the electronics can be repaired.

I have even repaired boards with vaporized traces..not easy..not cheap..but doable.

I have repaired boards with no schematics by testing individual components and replacing as necessary.

My training came from the days of vacuum tubes,transistors,and experience as technology advanced.

Board replacement is easier to troubleshoot and replace than it is to repair.

I don't think they teach component level troubleshooting and repair anymore,just board level..and most modern boards are non repairable due to surface mount components becoming so small as to require a microscope and brain surgeon skills to replace.

I guess I am part of a dying breed,unless a CME or EMP wipes out the modern circuitry.

I am comfortable with progress;that is as it should be.

I can look back over 60 years of experience and the technological progress is amazing in all areas.

I have served my purpose during it's time slot and I am contentedly retired.

My E-Power guy didn't say it couldn't be replaced or repaired. He said to fear having to do it. It is a big board 18" x 24" chock full of transistors, resistors, capacitors, relays and such. Given the multi-dimensional functions, stacks of spool valves and hydraulic sensors, and remote operator's console of the machine the board is probably a dedicated custom design. If necessary I could source all the components off the net, BUT sourcing a guy with your capabilities would be a challenge even here in Houston.

In the forensic:

1. Is it a reoccurrence event?
2. If so, is the failed bolt you have the right repair bolt for the prior failure? If a Grade 5 keeps shearing should a Grade 8 be the right bolt? Since the young grasshopper is new to the world of industrial parts failure and repair he may be very well be naive to the fact some repairmen simply take the most available part (bolt) and shade tree make do.
3. If it is the right repair bolt, then something as simple as a bearing being worn causing the body that the bolt anchors to have a high frequency - low amplitude harmonic that slowly fatigues the bolt.
4. Let us not forget the little devil named torque. Even with the right bolts repairs done with regular mechanics wrenches and not torqued to manufacture's specs will have a high probability a reoccurring shear failure. The quickest way to dynamite a high powered engine is to improperly torque tighten ANY of the primary bolts.

https://books.google.com/books?id=sVTHDwAAQBAJ&pg=PA423&lpg=PA423&dq=bolts+for+vibrating+screen+in+a+dry+mill&source=bl&ots=lf_waglb7d&sig=ACfU3U2rnoLWa8Ohb9_6XOCL6JDs_Hv7Jw&hl=en&sa=X&ved=2ahUKEwiswpfgv4zqAhVvUt8KHT3gCzwQ6AEwFHoECA0QAQ#v=onepage&q=bolts%20for%20vibrating%20screen%20in%20a%20dry%20mill&f=false

https://vibrascreener.com/getting-the-best-performance-from-vibrating-screen-machines/

All the above is good stuff.

Adding some personal experience - if there is reversing torque, by design or due to resonant machine frequencies etc, then if the shear of the fixture occurs at the threads or if a clearance fit for the bolt was used instead of a close fit, then the shear problem is amplified.

I saw this in a bolted coupling where there was an AC drive and the system went into instability. Even though the drive was limited to 100% torque the resonant phenomenon created very large shear loads. It sheared 6 bolts all at once in the coupling. Part of the solution was to use high tolerance shoulder bolts where the shoulder was presented at the shear plane, and the holes in the coupling reamed to match the shoulder as a close fit. We never sheared any more bolts.

Good solution.

Threads should never be presented at a shear line.

Threads are stress risers where stresses will concentrate and focus and are especially vulnerable in high vibration applications.

The elimination of "slop" or excessive clearance in the hole is also important to prevent a hammering effect on the bolt and hole.

Even with the best possible engineering a high G force vibration application has a relatively short cycle life.

I recall an instance where a 10 hp vibrator was used to shake frozen coal from a rail car.

Very high maintenance indeed,even when using the best practices.

It actually shook buildings several hundred feet away when running.

They had recurring generator bearing failures that were unexplained.

The generator was a GE 3.125 MW co-generator on the 2nd floor of a boiler room near the coal pit.

The plant has long since shut down,and the generator has been sent to who knows where.

I am convinced that the box car vibrator was the source of their constant misery.

If only...

https://cr4.globalspec.com/thread/135283/Video-Motion-Amplification

As a Senior Test and Development (mechanical) engineer in the auto industry for more than 30 years, getting to know the means of identifying material properties of parts was essential to me. That also applies to the head markings of bolts. This is a skillset that you need to acquire. Try using Google to do this. Here is a good start:

https://www.google.com/search?rlz=1C1GCEU_enUS821US821&sxsrf=ALeKk01NwFfV5fluP0JTidkc2A7NfZgbEQ:1592568738586&source=univ&tbm=isch&q=head+markings+on+bolts&sa=X&ved=2ahUKEwjv_8Xv7I3qAhVSZ80KHUI6AyMQsAR6BAgIEAE&biw=1745&bih=886