Tips on modelling bitumen pipeline with heat tracing on Caesar II

[davincigee]

Hello guys,
Please I need some assistance on how to model a 12" bitumen pipeline heat traced with a 1/2" pipeline as shown in the attached image on Caesar II. I am particularly used to modelling and analysing single pipe systems but this has somewhat become a challenge for me. I will appreciate any help I can. Cheers!

 

[1503-44]

What is that? No notes on dwg. A pipe in a tunnel with guides? A pipe buried in soil, with soil acting as guides? Is that what you need to know? What temperatures? What wall thickness? Is the 1/2" a conduit for electric trace? Is the trace line welded to pipe, clamped on, or just placed in same trench? What depth? If you want something, you got to give some info.

Reality used to affect the way we thought. Now we somehow believe that what we think affects reality.

 

[davincigee]

Hi 7.0,
Sorry. The following will answer your queries;
1. Yes it is a 12" pipeline bitumen passing through a culvert. Please ignore the soil above it.

2. Operating temperature is 240 degrees celcius.

3. The 12" pipe is sch.40.

4. The 1/2" pipe is a conduit for hot oil and clamped onto the core 12" pipe.

5. Depth is roughly 1.5m.

So essentially, I am seeking to model both the 12" bitumen pipeline and the 1/2" heat trace pipe. It will be insulated with rock-wool of thickness 150mm and lagged with aluminium.

Thanks

 

[jojoyohan]

I'd ignore the 1/2" pipe. It is being supported off of the 12" pipe and will essentially be dragged along with it. No 1/2" line is going to put much of any stress on a pipe that large. This does assume that the smaller heat tracing line is coiled around the larger pipe and relatively free to move besides where it is clamped, otherwise I'd be more concerned with the smaller line than the 12".

 

[1503-44]

The temperature of the conduit and pipeline will be the same at all times, or will the conduit carry a higher/lower temperature during start and stops.

Reality used to affect the way we thought. Now we somehow believe that what we think affects reality.

 

[davincigee]

Dear Jojoyohan,
Thanks for your response. I see your point here. What if it's a 2" pipeline?

 

[davincigee]

Dear 7.0,
The conduit will carry a higher temperature than the core 12" pipeline.
Rdgs

 

[1503-44]

Then it will move differently than the 12". The clamps will need to allow for slide of each pipe.

Reality used to affect the way we thought. Now we somehow believe that what we think affects reality.

 

[davincigee]

Dear 7.0,
Exactly why I am requesting assistance on how to model both pipes and simulate conditions. Do you have any idea how this can be done on Caesar II?

 

[davincigee]

Guys,
Is there any previous thread that speaks to the subject matter I can follow/ I will be grateful if anyone can point me out to one.

 

[LittleInch]

I don't know of any others, but I would simply analyse the two pipes as separate pipes.

If the heating tube is simply clamped and not welded to the larger pipe, then it will move independently. Note that in a project I'm familiar with, when they initially tried stich welding a tube like this, but lower differential temp, the welds cracked when they turned it on so had to move to a fully welded tube.

I must say one 1/2" pipe keeping a 12" pipe at 240C with only 150mm insulation when stationary fluid looks rather small to me, but if that's what you've been given then so be it.

Your worst case in terms of differential movement would appear to be a cold or cool main pipe which is then being heated up by hot oil with a temperature of ?250C?. But if you've only got small lengths the 1/2" pipe will simply expand into the rockwool by a few mm. Of course it then won't be doing much to heat the pipe.

240C is nothing to be sniffed at so concentrate on the 12" pipe first would be my suggestion and then worry about the 1/2" line later.

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

 

[saplanti]

LittleInch has summerised the complexity, the half inch pipe does not have contribution to the stiffness of the bitumen pipe. Therefore ı would only model the bitumen pipe for the stress analysis. However ı would add the mass contribution of half inch pipe into the thermal insulation by changing the insulation density only.

In this way the stress analysis will give you adequate results. But you need to make sure the heater piping will not contribute stiffness of the bitümen pipe. Just watch the routing of the heater pipe.

 

[davincigee]

Thank you LittleInch and Saplanti ,
Great point. Alternatively, what if you had two 2" pipelines serving as hot oil heat tracing. Will there be contribution to the stiffness of the 12" pipe? In that case, what will be your approach?

 

[LittleInch]

All depends on the means of attachment of the 2" pipes to the 12" pipe. For sure the extra weight of the 2" needs to be added, but unless they are continuously welded to the 12" pipe, they add miniscule amounts of extra stiffness. Also depends where they are welded or connected? 12 o'clock and 6, 3 and 9, 10 and 2 ??

2 x 2" sounds a lot more like it if you're going for 240C... Mind you 240C sounds very high. Are you sure it's not 240F??

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

 

[davincigee]

Yes LittleInch,
It is indeed 240 degrees celcius. And yes I have confirmed that it will be 4 x 2" pipeline clamped onto the 12" pipeline at 12, 3, 6, and 9 o'clock respectively. Actually during operation only two heat tracing line will be heating up the core pipe at any point in time.

Thanks.

 

[LittleInch]

Well just add the extra weight and forget about the stiffness forces in those 2" lines.

Will be interesting to see a support clamp drawing for all those lines. What are they using at the supports? Foam Glas insulation? Don't tell me they are using thin welded supports??

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

 

[davincigee]

Well there will be angle irons welded to the core pipe as supports. Insulation is rock wool.

 

[LittleInch]

But how is the insualted pipe supported? Rock wool will collapse under the weight?

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