Welded Cr Moly for high temperature piping 1

[SPLIT]

Does anybody has used A335 Gr P11 welded pipe for 85 bar 485 °C 24" steam pipe. According ASME B31.3 is OK.?Any restriction ?

Regards,

SPLIT

 

[NozzleTwister]

Yes, I have seen this. 1 1/4 Cr is a common material for high temperature steam systems. No restrictions.

Good luck,

NozzleTwister
Houston, Texas

 

[xhpipe]

Look up the design S vslue in Table A-1. if the material is listed for the temperature you need then your home free.

Even if it is not listed B31.3 provides a basis for you to determine an apropriate S value...

Bottom line read the code

Regards,
XHPIPE

 

[rjstephens]

Hi SPLIT,

Do you know what design life you will be designing the pipeline for. The temperature takes the material into the creep range and depending on the layout of the system, you may want to consider pre-stressing the material to reduce the end reactions on your equipment, read up on this in the code. I personally would not use welded pipe for a high pressure/temperature pipeline. The components that fail in the creep range are generally related to the heat affected zone of the welds and the in-line fittings(bends, tee's etc)

The pipe line will also require maintanence and inspection of the welds & in line items, this is a costly exercise so welded pipe is not generally used. A metaligist can put together an inspection program for you.

Just another note on the prestressing of the pipeline, due to the "shakedown" effect, the pipeline will undergo self induced prestressing to various degrees of magnitude. Depends on the forces applied to the pipework. You may want to control this amount by inducing the required amount of cold pull yourself. A proceedure needs to be established to control the implimentation of the cold pull to reduce rotation at the closure weld.

Be careful.

Hope this helps

Regards

Rob

 

[DSB123]

SPLIT,
As stated by rjstephens welded pipe means that the longitudinal weld is subject to long term creep loading. Also you should note that the long awaited 2004 version of the B31.3 Code will include Weld Strength Reduction Factors for materials operating at high temperature to address the fact that the welds in certain materials are "weaker" than the parent metal which could result in you needing a thicker pipe.

 

[xhpipe]

There will be options associated with the WSRF i.e., if you have test data available for the filler you use that shows it holds up well at creep then you can adjust the factor accordingly.

The bottom ine is some people were not using a filler metal that shared the same and or similiar creep strength properties of the base metal, this change will penalize those who continue to do so.

Regards,
XHPIPE

 

[SPLIT]

Thank you anyway

My concern was related with the existence of some local code or engineeering practice that avoids to use welder Cr Moly for high temperaturs.

 

[MJCronin]

Ahhhhh!!!!!!

There is a long sordid history of failure of A335-P11 "long seam welded" piping failures in Main Steam and Hot Reheat piping systems !!!!! People have been killed at a power plant when this particular material has failed in high energy piping systems (Hot Reheat System- Mojhave Steam Plant in California)

"Nozzletwister" is wrong....he may have seen this material in older plants, but it is subject to failure

P11 materials are subject to creep failure in a relatively short time. Many utilities have ubdergone a program of replacement of all p11 materials in steam piping systems.

You are much, much better off specifying and using SEAMLESS a335 p22 or p91 (higher chrome moly) materials at slightly increased cost

Admittedly, many of these failures have occured in systems operating over 1000F for several years.

I suggest that you GOOGLE "p11", "piping" and "failure"....... see what you get

Also see this link:....read PSB-1 and the several other reports on this website!!!!

http://www.babcock.com/pgg/tt/plantservicebulletins.html

My opinion only.....


MJC

 

[xhpipe]

MJC

Good article... those code guys!!!! Well better late than never....

Regards,
XHPIPE

 

[MJCronin]

Split,

Review this thread and come back......

http://www.eng-tips.com/viewthread.cfm?qid=114837

Post your e-mail address on this thread and I will send you other documents.

MJC

 

[JTHEVENET]

for commodities as steam, Welded pipe is strictly forbidden in most engineering. you should us seamless pipe