Relation between Flow rate and Bolt stress

[Nashanas]

Hello everyone,

Imagine an L type configuration of tubes, thereis a column of 7m height with 12 inch bore connected to a horizontal line through an elbow, the bore is the same, the horizontal line is then 10m long. At the junction of column and horizntal pipe, the elblow is performing the conne connection using bolted flanges.

Now on the bolted flange which connects the column to the elbow, there is one bolt out of 24 bolts, which seems a bit deformed. The client has opened a claim regaridng that deformation. My field technician is saying that the claim is wrong and that probably the client has used a flow rate higher than deigned value.

Due to some unforeseen problems, the documentation related to the project is lost, and I am trying to recover it. But I have some questions:
1. What is the relation between flow rate in tube and bolt stress of the flange of the same tube?
2. Why only one bolt is deformed? I am suspecting that the same field technician has not used proper tightening torque while assembling the strucutre on site.
3. Is there any acceptable deoframtion range for a bolt?

 

[LittleInch]

My imagination is not working as well as yours. How about you sketch out what you are talking about and post is as an image or attachment?

Or a picture of the bolt?
Or an isometric or GA drawing
Or perhaps some details such as flow?
And what forces there are on the flange?

Why don't you just replace the bolt? You will use up 1000 x more cost in talking about it than it takes to replace the bolt.

I think your technician is talking utter rubbish, but I can't tell based on your description so far.

So my initial guess through a rather cloudy crystal ball is:

1) A complex one. Might be no stress, might be quite high. If the flow rate is a lot and the fluid gushes out of the 10m horizontal line then you might get a lot of bending force or reaction force from the change of direction of the flow. Depends on where your supports, guides and acnhors are about which you've told us nothing.
2) No idea. No data or picture so can't hazard a guess
3) No



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

 

[1503-44]

Flange bolt stress is usually related to tension, or torsion. Tension at a flange is due to one or all of operating pressure, cold temperature, or twisting and bending moments created by span load, or either hot or cold pipe stresses in the configuration. High torsion load is a bit unusual, but possible.

With one bolt out of 24 being deformed, the cause is most likely installation error. Pipe related stresses and bending moments would affect more than one bolt, likely a minimum of 4 to 8, or so in a 24 bolt pattern.

 

[Nashanas]

Thank you for responses. I have attached an image here. In this image there is one column on top of which there is an elbow connecting it to another column. The oter column turns almost 90° and becomes a straight line when the machine is employed. The flanges are joints with swivel bearings and hence they allow rotary motion.

I cant disclose the image of deforemd bolt. But as said by @1530-44, it seems like an installation error if only one bolt is deoformed out of 24 bolts. The cost of replacement might reach 10K dollars because of production stoppage.

 

[LittleInch]

Ah, Ok, so it's a swivel joint connection on a Marine Loading arm. Why didn't you say first time?

These are usually a complete vendor package? Is that who the technician is representing?

SO these are exposed to lots of other forces (wind, ship movement etc) as well as flow but you need to know what the flow is they were designed for and what the flow is that they were exposed to.

Are these used for loading or unloading or both?

Normally these are only in use during loading or unloading. So replacing one bolt can occur when not in use and one bolt in 20 you can do as a "hot bolting" exercise.

someone I feel is taking you here and you really need a bit of experienced backup locally to tell whoever is telling you it's $10K dollars to change one bolt to prove it. Or give me $5K and I'll do it for you.

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

 

[Nashanas]

Good to know you have knowledge of MLAs. Its a complicated case. We are the vendors. Our field engineer left without leaving any documents of the workdone on site on this MLA. I have taken it up, but the field technician who assembled it knows that there are no records, so if he made a mistake he can cover it up easily by saying I did my job good but the client is using higher flow rates, which to me seems like bullshit, but he has 30 years of experience more than me.

Since I am new to the field, I did not know about hot bolting practice. Now I will propose this.

Thank you.

 

[LittleInch]

I realise you might not be able to send a photo but I'm struggling to understand what a deformed bolt looks like if it was actually properly tightened up in the first place unless someone hit it with something very big and heavy.

Also 24 bolts on a 12" flange? That seems like an awful lot of bolts. What sort of flange are you using?

Also struggling to understand in this day and age how electronic copies of drawings, specifications and works packs etc are not available? 30 years ago maybe, but not in 2021.

MLAs are nice bits of kit but they are quite simple and made up of standard bits which someone in your head Office will know inside out.

But flow induced bolt failure on an MLA?? Tell it to the fairies.

If anything gets out of line your PERC should be the thing to go first, not one bolt out of 24.

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