STUB BOLTS, NUT & WASHERS ACCORDING TO ASME B16.5 AND ASME B31.3

Aarnoud0,
All of the Flanged joints in pipework on the site I'm on do not use washers in the bolt assembly. Suggest the use of washers on flanged joints is not the norm.

Aarnoud0,

I agree with DSB123 that washers are not the norm for flanged joints. I've worked in the oil and gas industry for 12 years and it is only in a few special cases that we have used washers in our flanged joints.

If the bolt holes and fasteners, studs or bolts, are the correct size and there is a machined spot face on the back side of the flange at each hole no washer is needed or required.
It is always best to address the spot face issue rather than use an incorrect/insufficient washer.

Here are the two of the more frequent problems I've encountered.
If you have a galled spot face and use too large a washer you seat on the edge of the machined area and are in trouble.
It is the same problem if the hole or fastener are the incorrect diameter one gets into trouble quickly.

All quality nuts will have a flat seating face that is almost tangent to the flanks of the nut that is perpendicular to the CL of the threads. This face should always seat on a parallel, smooth flange surface.

One could go on and on about this, but the secret of a tight joint in a piping connection is to use the proper flange and gasket with the proper fastener and use each according to directions.

I agree with the previous posters that, for a new design, you should not need washers. If you are concerned about the bearing load on your flange material, consider using a washer-faced nut instead of a regular nut.

If you are working on an existing flange joint, there are times when you need a washer. This is especially true if you need higher bolt preloads than the flange was originally designed for, perhaps because the gasket material has changed from the original design. Then you may need washers to increase the contact area and reduce the bolt induced bearing load to a value that doesn't destroy your flange material.

The Code does not address washers or does not require the use of washers so I believe that washers are not allowed in flanged connections.
ER

generalblr,
Sec VIII UG-13(b): The use of washers is optional. When used, they shall be of wrought materials.

Agree with previous comments. The only time I've ever used washers were belleville springs, to compensate for temperature changes on start-up and shutdown. If you use washers, be sure to add the washer thicknesses to the stud length you specify. The standard bolt length tables do not include washer depths.