When to use type of bolt for pipe system

[momo83]

Dear All,

I would like to ask for your advise on how to determine when to use stud bolt and hex head (machine) bolt for pipe systems.

Currently, our practice is to use stud bolts only when the connection is for a wafer type valve connection and use hex head (machine)bolt for all other connections.

Is there a standard for this? Is the standard usable for all types of industries (ex. water/wastewater treatment, petrochemical, oil and gas, etc)?

Thanks you in advance for your advise and answers.

 

[mk3223]

There are Industrial Codes and Standards, such as ASME B16, API, AWWA, MSS, etc., as well as the Company/Owner Standards, which may be applied to the bolting practices of the piping system.

 

[JJPellin]

I work in an oil refinery. Our internal standards do not allow for the use of bolts for pipe flanges. The additional degree of freedom with two nuts reduces the chance of a loose stud from one galled nut. The use of all-thread studs eliminates the possibility of running off the threads (possible for some bolts), resulting in a loose stud. We only allow bolts as an exception in a few locations. Our internal standards are based off of API standards in most cases. I did not review the relevant API standards before making this post.

Johnny Pellin

 

[bimr]

In Petro and chemical industry for flange connections Stud Bolts and Hex Bolts are used. The Stud Bolt is a threaded rod with 2 heavy hexagon nuts, while the Hex Bolt has a head with one nut. Nuts and head are both six sided.

For industrial pipe flanges many prefer the Stud Bolt with two heavy hex nuts, rather than Hex Bolts because of the flexibility.

For example, Stud bolts may be used in studded outlets (where one flange is female threaded). If Hex Bolts are used, you have to worry about bottoming out the Hex Bolt before the gasket is compressed or insufficient thread engagement as the Hex Bolt must be sized correctly for studded outlet.

If studs are uncoated, studs may be cut to the required length, unlike Hex Bolts which are not threaded along their entire length.

Studs may be torqued or tensioned from either side of a flange. Sometimes one side of a flange may be more accessible or one stud may be more accessible from one side.

Threaded studs may be trimmed to the particular application.

If Hex Bolts are used, the plant will be required to stock many different sizes and lengths of Hex Bolts which increases the required onsite inventory.

Bolts & Nuts for flanged connections

 

[pennpiper]

momo83,
Bolting for Pipelines and Process Plant Piping is just the reverse of what you stated.
For Flanged Joints with thru holes:
First choice - Stud Bolts (Threaded rod with one nut on each end)
Second choice _ Machine Bolts (Partial threaded rod with nut on end and head on the other end)

For Joints with flange on one side and drilled & Tapped body on the other:
First Choice - Cap Screws (Hex Head Bolt with full threaded body below the head)

Sometimes its possible to do all the right things and still get bad results

 

[GD2]

momo83,
Every facility or piping need will typically follow a construction code. once you determine the code, see what is specified and also the Owner standards if it specifies something more than the code.
For example, a facility built with ASME B31.3 adopts B16.5 flanges as listed material. B16.5 allows both stud with one nut at each end and bolt for connections. It also highly recommends to use the stud bolts for high temp service.
Usually, the standard is set by the construction code that can be modified by the Owner for specific need (Example,for same B31.3, offshore application, xylan coated bolting is typically an Owner standard for corrosion control). In absence of Owner standard, best bet will be to start with the Code.

GDD
Canada

 

[MJCronin]

An issue that has not been mentioned yet is material identification.

On job sites that use stud bolts, it should be recognized that the smaller sizes of stud bolts (say 1/2" and less) cannot be identified by any code stamped on the ends. Hex head bolt materials can be identified by the code on the head.

I have worked on job sites where this problem has been addressed two ways:

First; the site only permitted stud bolts on site that were made of premium materials (i.e. A193 studs only...no A307 permitted) This was a site where studs were cut off from longer rod stock as needed

Secondly: the more expensive solution is to stock color-coated nuts and studs (say with XYLAN) with different colors used for different materials. Identification of studs can be done at a distance and ensuring that the proper full nuts are used for the joint is easy.

Based on experience, can others share how this issue has been addressed ???

MJCronin
Sr. Process Engineer

 

[MJCronin]

https://www.eng-tips.com/viewthread.cfm?qid=355979

MJCronin
Sr. Process Engineer

 

[XL83NL]

The way we do it is as per the post in this topic. It follows your 2nd option.

Please note our company works similar to an EPC, we dont own (a) plant(s) or site(s). This gives our way of work our a different perspective maybe.

 

[KarlwithaK]

I am kinda curious that no-one mentioned the use of hardened washers for bolting up flanges. They are pretty much the expectation for studs or bolts in nuclear for many years now.
I remember having to cut studs for a large valve in a nuke on the east coast years ago. We were very careful to grind and buff the cut ends of the studs and engrave them with the code, and to use identified hardened washers.
The QA Nazi failed the first one. Why? The engraved ends were not oriented to be read right side up!

 

[MJCronin]

Karl with a K...

They are pretty much the expectation for studs or bolts in nuclear for many years now.

Washers are NOT required for the bolting of steel flanges outside of the Nuclear Industry (ASME B31.1/31.3 applications). They are optional.... I believe there may be a code case on this subject

Washers ARE required for any type of FRP, GRU, HDPE etc piping flanges.

This topic has been extensively discussed on these fora.

https://www.eng-tips.com/viewthread.cfm?qid=373310

I worked in the Nuclear Power industry for 20+ years ..

Carefully etching identification codes on individual studs and washers are what killed the Nuclear Power Industry.

Down deep, your anal-retentive QA Nazi knows this



MJCronin
Sr. Process Engineer