If we consider 100% cold spring in a typical main steam piping to steam turbine with NEMA SM-23 load allowable, as per eqn 22 clause 319.5.1(a) of ASME B 31.3, thermal expansion load R can be reduced to (1-2/3C)* Eh/Ec * R. With C=1.0, Eh/Ec=0.73, the expansion load gets reduced to one-fourth of R. Only risk is that the expansion load will come back at installation temperature which can result in leakage at start-up.

For steam turbine piping, is cold spring a safe option ? As it is simpler compared to complex anchor/restraint arrangements, constant/softer springs, low diameter/low thickness (better material) pipings or additional piping loops, can this option be tried ?

regards,

sam

What I don’t like about the cold springing is the construction face of these cuts. We talk about tolerances that I would find hard to achieve with a blue torch and a grinder. No matter how skilled is the welder I wouldn’t trust in that any precise fraction of an inch that you could ask for. That’s my concern about cold spring.
By means of controlling the expansion (loads) around a steam turbine, I would most likely consider expansion joints instead of expansion loops. I think that you would be facing less pressure head loss (and les condensate formation) with the expansion joint. Remember that condensate in a steam turbine will become as pellets to the turbine blades. You can check which one would generate less condensate with the process engineer.
Springs guides and stops would, in my opinion, be always more achievable than a cold spring.

Regards

Dear Massabie,

You have overlooked the fact that "typical main steam piping to steam turbine" in my problem, where expansion joint can't be used for such high pressure service. At the TTV valve inlet flange three direction coldsprings can be accurately introduced. I have seen some cold springs in older day nuclear plants steam piping. After tuning the spring hangers optimally, one can bring down the load & then to reduce the creep at high temperature, cold pull can be used. How do you, all, feel- am I right ?

regards,
sam

regards

Sam,

Probably I did overlook the high pressure!
However check this link and ask the vendor what are thier pressure limits.
http://www.usbellows.com/products/inline_joint.htm
Regards,

Cold Spring is in the same category as snubbers a method of very last desperate resort.

Add flexibilty to the system that is what we are paid to do... the original paper that became the analysis portion of the B31 code was entitled "Flexibilty Analysis"

Thank You, Sir. Your advise paid. By adding flexibility & directional restraints, we could bring down loads & moments within allowable limits. At first, we were not confident that we could achieve NEMA allowable or not.

regards,

sam

for me, I think use constant effect spring hanger is a another safety method

Sam,

You are welcome... in the 35 years in this buissness I have never had to resort to cold pull to meet an equipment allowable... Our work is made difficult by politics and often times the analyst is told by people who have no idea what in the world is going on "You have to make this work"

Its easy to knuckle under such misguidance but what I always remember is that I will get the call from the field if the design does not work out... not the person telling me "you have to make it work"

Often times besides a detailed knowledge of the code(s), CARSAR II, statics, dynamics, etc. one must also have a degree of courage and a comittment to act appropriately. The shame is most management types think that all you need is a copy of a pipe flex program.

So good luck and be strong (Lance Armstrong)

To John C. Luf,

Sir,

While viewing "The Science of Lance Armstrong" in Discovery channel, I remembered your advise. Even cancer in lungs,brain & abdomen could not destroy Lance Armstrong. His years of training in high altitude has made him so strong & efficient! If any one trains like him, he can be as strong, too.

You are right in your comment, that management types feel that only a pipe flex program counts, because we, just like mindless robots, churn out anything to justify any stiff layout they want by manipulation of support stiffness, friction coefficient, gaps in restraints etc, knowing very well that they may not work at site, at all.

Without persistence & determination, we can't be strong; education or experience are not enough !

regards,

sam

Sam,,

Watch the discovery channels program on the design and construction of the Titanic... the orginal designer of record resigned and walked away from the ship over a disagreement on the number of lifeboats to be installed.

His strength on the subject matter is recorded for all posterity whereas the other people involved with the ill advised choice of too few a number of life boats are not dealt with as kindly.

Where have the strong people of Titanic designer's days gone !

Today, we are training engineers to be managers, not to be doers at first,with hands-on touch of cooperation in problem solving. Conflict has replaced harmony & teamwork in meetings. We teach before we learn, try to be leader before becoming a perfect follower. We learn to cover up our mistakes as failures are not acceptable in working life.

Class teacher of my class-VIII daughter told the other day that she is a follower type, must be a influence of which TV channel she views often. She told, ask her to view CNN, not DISCOVERY, to know who really lead & survive!

Fortunately, in our field of work we have great people like John C. Luf for inspiration. The values & qualities we learn from them to stand for in professional life may not make us great managers, but sincere engineers, no doubt.
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I have noticed that European steam turbines have quite higher nozzle load allowables - both individual & combined. Why is not NEMA SM-23/24 follwing API-610 & making american steam turbine nozzle allowables higher in these days of so high fuel price ?

regards,

sam

My guess is $$$ the stronger you make the machine the more it will cost.... so to compete in the Turbine buissness my guess is that price rules in whose turbine is purchased.

What everybody fails to see is the lower allowables drive up the installed cost of the attached piping system, so I guess its good for us (more work).

Markl and Rossheim had proposed load limits for non-rotating equipment to be designed to back in the 50's they were ignored so PV's are often nozzle weak when they need not be.

TO

John C.Luf

Sir,

"What everybody fails to see is the lower allowables drive up the installed cost of the attached piping system, so I guess its good for us (more work)."

This shows that we have become commodity purchased in hourly rate not for our quailty of work, but the sheer volume. In today's lingo of adding "value" to our service sold, we need to evolve with time. Just like in India, "Volvo" does not mean only safety, but style & comfort -free, we have to show to customer how to reduce the life cycle cost of the plant built, not only the installed cost of piping, but the O&M cost added for the related piping & machinery. This is the only way to fight with 'low-cost' service of low or no quality. We must show to customers that our personal signatures cost because we add value !

Otherwise, in the interesting times of tomorrow, we will have none to follow. You only have instructed us to be strong (Lance Armstrong)!

regards,

sam