Effect of surge pressures on CML steel pipes
Effect of surge pressures on CML steel pipes
(OP)
Good day,
Are there any articles available on the effect of surge pressures on cement mortar lined steel pipes? For instance, when a cml pipe is subjected to a positive surge event, the steel will undergo a certain strain, which, depending on the pressure can be higher than the allowable strain in the cml. This will surely lead to cracking of the lining. As the lining has self healing characteristics, will the surge events be problematic?
best regards
Are there any articles available on the effect of surge pressures on cement mortar lined steel pipes? For instance, when a cml pipe is subjected to a positive surge event, the steel will undergo a certain strain, which, depending on the pressure can be higher than the allowable strain in the cml. This will surely lead to cracking of the lining. As the lining has self healing characteristics, will the surge events be problematic?
best regards





RE: Effect of surge pressures on CML steel pipes
Independent events are seldomly independent.
RE: Effect of surge pressures on CML steel pipes
Pipe OD: 1524 mm
Pipe wall thickness: 9.5 mm
Allowable operating head: 185 m (based on 145 MPa, which is 50% of yield)
Strain in steel 0.0007
Allowable stain in liner based on 4 MPa tensile strength (Young's modulus of 26 GPa) = 0.0001538, which is much lower than the strain in the steel. Am I correct in saying that if the pipeline is operated at 185 m head the liner will definitely crack?
RE: Effect of surge pressures on CML steel pipes
Is this just a general query or do you have a specific problem?
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Effect of surge pressures on CML steel pipes
Yes the problem is rather specific as im not accustomed to work with cml lining (see my previous post). We usually limit surge pressures to within 75% of the pipeline yield. As cml is not very flexible I was wondering on the effect of surge pressures on the lining. But just looking at normal operating pressure the strain seems to be too excessive for the lining. But clearly i'm missing something..
RE: Effect of surge pressures on CML steel pipes
Surge doesn't only affect the pipe, but also lots of other bits of equipment. I think what you're missing is a look at the whole system design and concentrating on a small part of it inthe middle.
I always like using electrical anlogies here - what this is is saying is my cable can withstand 660V. The rest of the system is only rated / runs at 220V. If I get a power spike of 500V, my cable is Ok, but everything else has caught fire....
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Effect of surge pressures on CML steel pipes
Independent events are seldomly independent.
RE: Effect of surge pressures on CML steel pipes
Talking about analogies... a fuse could be analog to a rupture disc..lol
RE: Effect of surge pressures on CML steel pipes
The cement lining does expand a bit in contact with water and has some self sealing / healing properties and there are some application techniques which pressure the pipe during application and curing to apply a compressive stress to the liner so especially operating mainly at 9 bar, you should be OK, but at that size of pipe, what ins't an issue at smaller pipes could be if the expansion gets concentrated one location
You could always make the steel a bit thicker.... or reduce your surge pressure. I would also question the pipe supplier a bit more to find out what he recomends / will certify or if indeed you are operating outside of the normal pressure range for this type of pipe.
For info, how did they construct the internal field joints? They could easily be your weakest point.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way