how can we stress run pipes or pressure vessels that are lined? 1

[etrobal]

we have had problems with solids in our pressure vessels ranging in sizes 0.625mm max with specific gravity of 4.58 to 5.30. the fluid is dry steam with max mass flow of 13.23 kg/sec, design pressure at 14.06 kg/cm2g, design temperature at 197.7degC, separation pressure of 11.72 kg/cm2g, separation temperature of 190degC with the solids at 84ppm at the nozzle inlet. the top ellipsoidal head is the first to leak due to the suspended solids.

we've had also leaks in our pipe elbows and other change in directions fittings in our pipelines upstream of the pressure vessel.

if we will line our carbon steel pipes with another material, or similarly with our pressure vessel of sa515 gr70 lined with another material, how will this affect our stress calculations, or stress runs? will we use the original material's allowable stresses or use the liners? will expansion affect the vessel nozzles, connections and other endpoints of the piping system?

we are bidding the design of the pressure vessel, where, if after installation, the designed vessel can provide a maximum 5ppm suspended solids at the steam outlet, the company is prepared to purchase several for its various wellheads. we've had bids ranging from usd52,000 to usd80,000. while we will be able to arrest, hopefully, the deterioration of the vessel heads, our problem will be on the upstream piping system. wil it be cheaper instead to have a lined system than a vessel designed to outsmart the solids?

 

[BigInch]

If stress is equal, but Young's modulus of the two materials are different, or stress in each material is different and Young's modulus are equal, variatioins of strains at the interface between the two materials could arise, which might cause cracking or differential strains sufficient to initiate separation and spalling of the liner.

The material properties and wall thicknesses must be carefully controlled to ensure that allowable stresses are not exceeded and strains at interfaces are within separation and/or below cracking limits.



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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[JohnBreen]

Perhaps you should look into the design of pulverized coal fuel piping systems as are used in coal power plants. You might get some ideas about how to design for internal-to-the-pipe abrasion.

http://www.abresist.com/Applications/PipesBends.htm

Also many petroleum refineries use abrasive resistant linings in their flue gas piping from the FCCU to the cyclones that remove the catalyst from the flue gas stream

http://www.blaschceramics.com/

Typically in flue gas piping, a mesh is welded to the inside of the pipe to hold the lining material in place.

We usually do not "take credit" for any additional strength due to the lining but we include the weight of the lining material. In some cases where lined pipe is used the pipe must have increased diameter so that the ID is sufficient for required flow. The increase in diameter (and as necessary, wall thickness) is modeled for stress analysis and the additional weight is also included in the model added to the model as "insulation"). The allowable stress is that of the steel piping material. Be prepared to have to modify the support system for the extra weight.

Regards, John

 

[BigInch]

We do the same on offshore pipeline concrete coating, limiting the bending radaii such that concrete cracking remains acceptable.

We also don't take any credit for the concrete in the pressure design of the pipe, which is good, since its allowed to fissure somewhat anyway.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[simplemath]

"We also don't take any credit for the concrete in the pressure design of the pipe, which is good, since its allowed to fissure somewhat anyway. "

Biginch, do you have some guidelines on how to specify bend radius for lined pipe?

--It boils down to simple math--

 

[BigInch]

Yes. Its just simplemath, but let's not hijack this thread.
Fb = Mc/S eq.1
M/EI = 1/r eq.2
Fb = allowable stress in bending
M = bending moment c = radius to OD
S = section modulus
(solve #1 for max allowable bending moment using Fb)
I = moment of intertia
r = bend radius
E = Young's modulus
(solve #2 for maximum bend radius, r)

practice with this interesting variation,

http://www.me.berkeley.edu/ME117/S07/lectures/020107.ppt#18

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[BigInch]

Make that
Fb = M/S = Mc/I

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/