Valve Flange Bolting in Shear and Torsion due to side load

[Andas]

I have an end of the line valve with a 4" 300# flange with the standard 7.88 dia BC, with (8) 3/4" Bolts. The Valve is requiring a large actuator that will apply a large weight to the valve.

This setup is a cantilever beam with a support at the bolted connection and the weight applied approximatey 18" away from that support, perpendicular to the axis.

I am confused how to calculate the tension and shear that each of the 8 bolts will experience. The bolts are arranged so that they are equally spaced non-straddle the centerline. So the top bolt will experience maximum tension, while the bottom bolt will experience maximum moment.

I need to determine what strength fasteners are required to support the load, but also need to determine the max load any bolt can see so that we can illustrate to need for actuator supports.

I am not great with shear and tension in 3D and could use some guidance on how to calculate them and combine the two to compare to allowable and yield.

 

[UNSR60001]

Note, that is important to know if you are specifying/have installed a quarter turn valve or a rising steam. As each type of actuated valve would transmit forces in a different way to to the pipe/flanges.

Additionally, quarter turn valves vary greatly in their torque requirements. And can be automated with an extensive variety of actuator types and configurations.

You might want to think about considering a different valve/actuator arrangement that compensate for the cost involve to have adequate piping support?

 

[JimCasey]

The fasteners will experience tension only.

If there is enough bending moment on the bolted joint to unload any of the bolts, then the piping design is flawed or the bolts were not tight enough.

Similarly the fasteners will not experience shear... They clamp the valve to the piping flange face with enough force to keep it from slipping.

In a very simplified example with arbitrary values:
A 3/4" bolt runs through a 1" thick steel block and is threaded into a rigid fixture. The bolt is torqued to supply a clamping force of 7500 pounds force.

A lifting force of 4000 pounds force is applied to the block. What is the new force in the bolt?

Answer: it is still 7500 pounds force. BUT the pressure the block exerts against the fixture is now only 3500 pounds force.

 

[Andas]

The valve is a quarter turn valve with the actuator mounted off of an ISO pad around the stem area. The body is a single piece and is strong enough to ignore any minor deflection in the body. To simplify the problem, I was combining the force as a single force in line with the stem axis (18 inches from flange face) and perpendicular to the axis of the flange bolting.

Alternate actuators are not an easy fix since the customer spec is very specific and takes extensive paperwork to change. I am not sure actuator supports will be necessary. That is basically the reason I need to calculate the bolt loads. And before it is questioned, the flange gasket is a specialized metalic gasket that has some resilence and is expected to be able to handle the eccentric loading and water hammer. So I am back to needing the bolt load on each bolt.

 

[Andas]

Jim,

Thanks for the reply and your example.

If the bolts are not loaded enough to hold the two flanges together, then they are not tight enough. They need to be tight enough to hold the forces applied to the flange by the weight of the valve. How tight is that?

I can convert between bolt torque and tension, but I do not know how to calculate that tension on each bolt spread out in a 3D plane caused by a force perpendicular to the fastener axis.

This tension determines if a bolt strong enough exists to hold the force placed on the bolt.

If we change your example.
A 3/4" bolt runs through a 1" thick steel block and is threaded into a rigid fixture. The bolt is torqued to supply a clamping force of 7500 pounds force. Then a 18" pipe is welded to the block in the same axis as the fastener. Then a lifting force of 4000 lbs is applied to the end of the pipe, 18" away from the bolt. Is the tension of 7500 pounds force enough to hold the tension created by the 4000 lb perpendicular force 18" away from it?

How do you calculate this? Then spread it out to 8 fasteners in a 3D plane.

 

[desertfox]

Hi Andas

Have a look at this site it shows an examle of a bracket
bolted to a wall with a load at right angles to the bolt axis.
If you assume the bottom of the flange in your case is the pivot point you can follow this example.

http://www.mech.uwa.edu.au/DANotes/threads/fatigue/exampleB.html#top

regards

desertfox

 

[desertfox]

Hi Again

Here is another site that might help:-

http://www.roymech.co.uk/Useful_Tables/Screws/Bolted_Joint.html

you need to scroll down till you find the title:-

Strength of bolts in bending


regards

desertfox

 

[BigInch]

Can you post a picture or diagram of your setup?

I think if you feel you will have trouble supporting loads from opening a 4" valve, something is way way out of line. I mean its a 4 INCH. I don't believe you have the problem you think you do, unless the actuator is very UNconventional and the support is very much UNderdesigned. What torque do you need to open that thing?

http://virtualpipeline.spaces.msn.com

 

[unclesyd]

I like the post by BigInch.

If you properly bolt up the flange and then get any rotation of same you will probably loose the integrity of the joint through the failure of the gasket.

I've seen some pretty twisted pipe spools that would have imposed very high rotational forces on the flanges. I can't recall seeing any relative rotation to the flanges.

We have numerous operators of all types and descriptions mounted per the manufacturer's instruction that operate ball, plug, and disk type valves without any problem with rotation of the flanges. The only problem, major, was that some of the operators required to operate the larger ball valves twisted the valve stem trying to move the ball.

 

[JimCasey]

According to my faithful old Crane handbook, B7 bolts yield at 105 ksi. A 3/4" bolt torqued to 220 ft-lb would have a load on it of 20040 lbf, and a stess of 60ksi. 8 bolts: total clamping load 160320 lbf.

Again: The purpose of the bolts is to squeeze the flanges together firmly enough there will be no relative motion. This is true of any bolted pressure-retaining joint, such as automotive cylinder heads, too. There will be no shear, there will be no cyclic stress, there will be no bending load on the fasteners, just good ol' tension.

 

[BigInch]

I've seen a lotta' bent and sheared stems, but no broken bolts, or rotated pipe around them.

http://virtualpipeline.spaces.msn.com

 

[JimCasey]

Well I have seen broken bolts and broken flanges, but those seem strongly linked to long cheater bars and installation techs with a high-banana diet...ahem.

 

[BigInch]

Well OK discounting an explosion or two in Colombia and south Texas a long long time ago.

http://virtualpipeline.spaces.msn.com