Steam Pipe Line

What size is it?

Hi aligillani,

The specification that governs the piping design is:

ASME B31.1,power piping.

herein a quick selection guide:

ASTM SA-335,Grade P11 for design temperature less than 510 degree cent.

Grade P22 ( 2 1/4 Cr ) for temp.between 510 and 566 deg. cent.

Grade P22 for temp. between 510 and 574 deg. cent. in the DN 150 and smaller size range.

Grade P91 for temp. between 538 and 593 deg. cent.

Regards,

Sayed

Let us understand- you are working in superheated steam over 90m length and you don't know the pipeline specification (i presume it is the material you want) -

With all due regards, don't try to guess these areas. The ASME PV is highly specialised area. get hold of some consultant who is qualified to do the design. The material of the pipe is only one, small, part of the pipe line.

I can list out factors that will have the effect - and that may not only have on material , but on schedules too, to certain extent.

Get help from an expertises in steam pipeline, it is impractical to do this by your self

Dear Mr. aligillani,

Your point is what is the material specification for of steam pipe line between Boiler to Turbine? for 62 Bar and 480 deg. C supper heated steam. You have not mentioned about the turbine house, position, and total length is it horizontal length or inclusive of bends and if bends are included how many etc. to be taken in to account.

It is not the specification alone to be noted. Even if you know the specs. the steam pipe lay out design is not simple as if it is water line. The FLEXIBLITY ANALYSIS is to be made since the Thermal Expansion of the pipe material and its resultant forces to be analysed, and thermal expansion will be considerable level for the temp. and length you have mentioned.

Assuming the ambient temp. is 40 Deg.C for a length of 90 Metres the pipe expansion will be about 285 MM in total, (11.22 Inches) and this expansion to be taken care with proper expansin loop, bends supports and anchoring etc., If expansion loop is accounted the total pipe line length will be more than 90 Metres.

Further the Turbine Manufacturer must have given the maximum Forces and Bending Moment allowable on inlet flange and exhaust flange and this is to be done properly which is a specialised job.

Hence my suggestion is mere knowing specs alone is not sufficient. Do not take risk as the safety is prime consideration for the equipement and staff. Do not think you are being discouraged.

Dhayanandhan.S

You have some very good advice stated above....

I have been involved with the specification, design and analysis of piping systems for over 40 years. The engineering and analysis of Superheated Steam piping systems is at the top of difficulty of Piping engineering and is certainly no place for a beginner to learn. Designing the correct piping supports for such a high energy systems is a separate and not insignificant challenge

Spend the money and engage the services of an experienced professional for your powerplant high energy systems..... Despite what an MBA might tell you, do not assign a young fresher just out of the University.

I have another issue with material selection ...

I would not use or specify the ancient ASME SA 335-P11 (low alloy material) for this system. P11 has a forty year history of catastrophic failure when supplied in an axially seam welded configuration. Use the higher alloy P22 material in the seamless condition (which gives you margin on slightly higher temperature usage) .... It will be nearly the same cost.

The P22 will protect you against the inexperienced boiler operator who will accidentally (ooopps!) run the boiler above its design temperature.

The P91/P92 materials are also acceptable, but are more expensive and difficult to weld into place.

Good luck ....Please tell us more about your project and do not be afraid to continue to post questions...

Regards

Thank you Mr. MJCronin for your observation on my above posting

Another important issue is (though the original post did not ask for ) is the STEAM LINE BLOW-OUT and conclusion on the observation of Target Plate. This subject does not get the due importance and attention for the proper support for new steam line blowing-out and I am the witness for a case where support has failed and caused problem.

Luckily no injury to anybody or serious damage except a bend totally damaged near the turbine side or else the twist and swing, due to reactive force, could have damaged the turbine governor and shattered to pieces and a fatal blow to near by staff.

The narrow escape was due to just a gap of 12 MM between the governor and pipe swing path and no staff with in 10 feet distance, while the bend swing was 180 degrees. This happened 43 years back, and in those days to get a new turbine governor will need minimum 8 months.

Incidentally what was the practise of pressure for line blow-out and criterion for the target plate you have followed - is it for the full working pressure and temp. or less than that. I insisted on full working pressure and temp. and cleared the target plate blow of less than 10 dents of 0.2mm size for 3 consecutive blows.

Thanks,

DHAYANANDHAN.S

A good, but somewhat dated summary of HP steam piping system design is contained in "The Piping Handbook" by Nayyer (Chapter C3 and B4 B5).

The governing code for these steam systems is typically ASME B31.1

Generally speaking, each and every pipe support on these systems requires detailed engineering as well as periodic re-adjustment after system shake-down.

There should be some evaluation of steam system transients "Steam Hammer" due to rapid valve closure.

After installation, there should be a detailed periodic inspection plan developed for the Main Steam and other High energy piping systems.

Again, high energy piping system design is not for beginners .....

Tell us more about your system

- Are allowable loadings on nozzles a consideration ?

- Do you have a piping layout with pipe support locations determined ?

- Do you have safety/relief valves on your system ?

- What is your code of record ?

An excellent background document about boiler and steam systems:

https://portal.endress.com/wa001/dla/5001084/9862/000/00/CP01195DEN_0117.pdf

This document explains some of the subtlties and important design issues related to steam piping hanger design.

Remember, the hanger components that touch the high temperature steam piping must also be designed to operate at the high temperatures.... i.e. alloy materials are required.

https://s3.amazonaws.com/s3.anvilintl.com/resources/literature/PipeHanger_DesignEngineering_Catalog.pdf

According to some preliminary estimates I have made, based on your 100ton/hr massflow rate, pressures and temperatures, your system is probably 10" or 12" NPS and schedule 80....

Again, this is PRELIMINARY, because you have either lost interest or stubbornly refuse to give us any more information...

Based on this sizing and pipe schedule, you should probably select the ASME SA335-P22 alloy steel material. Your modest massflow and relatively low design temperature does not justify the extra capital and installation cost of the higher alloy P91/P92 piping material.

It is too bad that there is no more interest in this thread. High temperature piping design is certainly an important and interesting engineering topic that seems to be slipping into the sands of time .....

Thank you Mr. MJCronin for your valuable inputs on this topic. I hope the original poster has taken note of it and give due importance for the steam piping design - which is a highly safety related subject, expert's job as expressed, and certainly IT IS NOT A JOB of FOR A BEGINNER.

Thanks.

DHAYANANDHAN.S