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ASME B16.5 bolts

ASME B16.5 bolts

ASME B16.5 bolts

(OP)
Hi everyone!

I am looking for some help. I was asked to verify if the bolt size provided in ASME B16.5 is a recommendation or mandatory?
The thing is, the ASME B16.5 states that, for example 7/8'' bolt is required for 1500 RTJ flange but M20 bolt has been used. Is there something that can confirm the M20 bolt is an equivalent of 7/8'' (22.225mm) bolt? I have done the calculations for M20 bolt, but I can't find anything saying that B16.5 bolt size is just recommendation and M20 bolt will work just fine.

Regards,
Michal

RE: ASME B16.5 bolts

Refer to paragraph 5.3.1 and 6.10. Metric bolts are not referred to in the Standard. Substitution would be permitted only in accordance with your Code of Construction, but may require supplementary calculations to maintain the Pressure-Temperature Ratings of the B16.5 Standard.

RE: ASME B16.5 bolts

7/8 dia = .875 inch = 22.225 mm.

Yes, a 20 mm bolt "will fit through the holes" - which is why the "bloody idiot" who assembled the joint used that size.
22 mm => 387 area.
Now, 20 mm => 314 area, or 81% of the 7/8 capacity.

So, why would you accept the lower strength bolt?

RE: ASME B16.5 bolts

(OP)
Thank you for your qucik reply! The whole unit has been designed to ASME Section VIII division 1 which states in appendix 2, par 2-2(e) that minimum bolt diameter is not less than 1/2''.I have done the torque calculations in accordance with formulas in ASME PCC-1 and it looks like the M20 bolt is ok.

Regards,
Michal

RE: ASME B16.5 bolts

(OP)
The thing is the M20 bolt has been already supplied so I need to proof that it is still ok and there is no need to replace it.

RE: ASME B16.5 bolts

You don't understand. It doesn't matter whether a "metric bolt" is allowed or not by a US Code. The bolt installed is only 81% (or less, depending on the material grade used!) of the capacity of the required bolt. Tell them they can use a proper grade metric bolts. As long as it is 22 mm or larger.

RE: ASME B16.5 bolts

I would calculate the bolts as per asme viii appendix 2. If iT passes i wouldn’t worry about it.

RE: ASME B16.5 bolts

Quote (Michael Kolbuc)

but I can't find anything saying that B16.5 bolt size is just recommendation and M20 bolt will work just fine

Nor will you, I suspect. From B16.5-03:



So, I'd say you cannot use your 1500# flange at the B16.5 pressure-temperature rating.

You may be able to prove it by other means such as Sec VIII, Div. 1, Apx 2.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: ASME B16.5 bolts

Apparantly I was a bit to quick with my previous answer.
You should also check if BSC=1, using the M20 bolts. If BSC=1 than, in my opinion, you don't need to worry about the flange. A small side note to this is, than actually you still our in the darkish grey area of the code. If you absolutely need to be in full compliance, than you will need to do the full calculation as suggested by SnTman.
Doing the ASME VIII div.1 app2 calc you will come to the conclusion that ASMEB16.5 flanges often are not ok for ASMEVIII app2.

RE: ASME B16.5 bolts

Also, you now have over 5mm clearance in your bolt holes which can lead to misalignment and uneven load distribution (only 4 bolts in the small bore size). So even if you do a full design to appendix 2, it still probably isn't recommended. It is not like M20 was used for 3/4", where you could argue it would be acceptable, so IMO I would think the bolts should be replaced.

RE: ASME B16.5 bolts

(OP)
Hi All,

Thank you all for quick reply. The 2'' flange is 1500# so it has 8 bolts. Obviously, it is easier to say to get 7/8'' bolt but it cost a fortune to replace all these bolts. I have done the calcs in accordance wiith App2 and managed to get the hydrostatic end force per bolt. Than, I have calculated the minimum required torque value using formulas in ASME PCC-1 and maximum torque value that can be applied to the bolt. Results are satisfactory.

RE: ASME B16.5 bolts

Torque value is used for installation, not during design calculations.

Regards
r6155

RE: ASME B16.5 bolts

(OP)
Correct, that is why I have calculated total required area as per ASME VIII div 1 app2, 2-5 and the area of 8 x M20 bolt is still greater than required.

RE: ASME B16.5 bolts

Wrong design must be corrected with good design practice.
I disagree with M20 bolts instead of 7/8".
If M20 bolts is used, then two washers are required.

Regards
r6155

RE: ASME B16.5 bolts

(OP)
Hi r6155,

Can you elaborate why two washers are required?

Regards,
Michael

RE: ASME B16.5 bolts

IMO the selection of the bolting is included in the design process for any B16.5 flanges. It should be the duty of the ASME Certificate holder to indicate all the bolting that is to be used for any B16.5 flanges in the remarks section of the MDR. This is a common oversite by many ASME Certificate Holders.If accidents happen in the field the Lawyers may have a field day if it is not recorded on the (legal document) MDR.

RE: ASME B16.5 bolts

What happened to Michael Kolbuc?

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: ASME B16.5 bolts

(OP)
Nothing happened, I am still here. Thank, you all for your comments.

RE: ASME B16.5 bolts

mech8790
Assemblies often have a slotted or oversize hole: use washer

Regards
r6155

RE: ASME B16.5 bolts

(OP)
Hi r6155,

Thanks, I have got a washer in assembly either side.

Regards,
Michael

RE: ASME B16.5 bolts

mech8790,

You appear rather fixed on trying to use the wrong bolt. Just about everyone else on this thread is telling you it's the wrong thing to do and I will back this up.

If you do some searching around you'll find that use of washers is not universally accepted, in part because of issues like this where someone has tried to use smaller bolts than ones called for and hence put the washer, sometimes of unknown strength, in shear resulting in flange failure.

At the very least, you need to look at the bearing surface of the nut.

A 2" class 1500 flange requires 7/8" (22.2mm) bolts inside a 1" diameter bolt hole (25.4mm). A heavy hex nut is 1.4" (35mm) across the flats.
An M20 bolt on the other hand is 20mmOD inside your 25.4mm hole. An M20 Nut is only 30mm across the flats.

Thus at max movement of the bolt within the flange hole, the edge of your nut is in thin air.
At best (dead centre of the bolt hole), you still have significantly less surface area of the bolt and hence much higher stresses on the nut / flange interface. Add a washer into this mix and all you do is hide the visual issue, but it doesn't add anything to the strength of the joint.

You appear to be asked to verify something which is not possible "I was asked to verify if the bolt size provided in ASME B16.5 is a recommendation or mandatory?" The standard states categorically that bolt sizes are in US customary units - that's mandatory to me.

Replacing bolts is not always easy, but even on a working system, especially if you reduce pressure, replacing bolts one by one can sometimes be acceptable.

You really need to do the right thing here - Use the correct size bolts.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: ASME B16.5 bolts

mech8790

See ASME PCC-1 APPENDIX M
WASHER USAGE GUIDANCE AND PURCHASE SPECIFICATION FOR THROUGH-HARDENED WASHERS

Regards
r6155

RE: ASME B16.5 bolts

Hi might be a bit late to the party.

Gasket manufacturer here, please use the right size bolts on standard flanges, as stated for the many reasons above.. it's not just about available force, bolt stretch and yield factors.
Alignment, flange rotation, vibrations, stress distribution etc etc.. using smaller bolts/washers will have an effect... you "might" get away with it... but a class 1500# system means high pressures... so I personally wouldn't risk it.

Only takes one to go wrong and it's your signature on the paperwork.

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