Gentlemen,
I have questions regarding Cold Spring application for main piping of 320 MW thermal power plant

First, system description:
main 34" CRH, 34" HRH and 20" MS lines from boiler connecting to steam turbine via this route: 50 meters down, 40 meters east and 40 meters north.
I don't need cold spring in the turbine side as routes are flexible enough. BUT due to huge displacements I get very large reaction moments (moments only) at boiler side. As I use restraints to limit displacements at boiler side, the turbine loads/moments exceed allowables (the thicknesses are so high making the system so rigid). I'm thinking of having cold springs on the three main pipes connecting to boiler.

Now my questions:
1- Is it a good way to solve this problem via cold springing the system? Is cold spring still used in such systems?
2- I put in line ANC-CNODEs to read the required forces for implementing cold springs and I get extremely high moments (500,000 N.m)! How big should be the pulling forces to close the cold spring gaps? Is it possible to apply moments when cold springing?
3- I'm thinking of three locations for cold springing on each line, each in one direction. Is it a good idea? Is it possible to have a 3D cold spring for such large sizes?

Sorry my story went so long. Your help is really appreciated.
Best

Any ideas? ...

Micvanzil,

Generally, cold spring is not a very good idea to implement to bring the nozzle loads within allowable for various reasons such as it is difficult to maintain record for the cold springing after every shut-down etc etc. Nowadays, cold spring is either not allowed at all by various clients or require client approval.

Try with some other options or if couldn't come up with some thing plausible, then think about using an expansion joint.

Hope this helps.

Keep Smiling...

It always helps....

SJ

Micvanzil,

I had a same problem in one of my project of 1600MW, in that case we had opted for expansion joint. it will be great if you can share some pipe routing, So that the discussion will be more realistic.

Regards,
RK

hi friends,
how we can use expansion joint in ms, crh & hrh line?
i feel that your solution is impossible.

We had used cold spring on main steam turbine line during one of the projects. I dont remember the turbine size, but the line size was 14". Steam properties were 525 deg C and 125 bar.
The plant is running as of today.
Using cold spring is not such a bad idea if you really know how to use it.
Also you have to convey the same to the site.

To get a feel, do some trial runs with small lengths of cold spring.

Dear all,
Thank you for your kind replies,
As you are suggesting, cold spring is the last solution when no flexibility can be added to the system due to the piping stiffness (Very thick material), hydralic calculation limitations and ...
But in most main steam piping it is inevitable as it can control restraint loads where the system conects to steam turbine.

Babasaheb,
I've done many trials and faced the problems I've shared with you in earlier posts. I'm still getting very high loads for In-line ANC-CNODS which I don't know how they can be implemented during th esystem construction. That would be great if you could send a sample or sketch of what you have done for the system you described.

Best
Mic

2- I put in line ANC-CNODEs to read the required forces for implementing cold springs and I get extremely high moments (500,000 N.m)! How big should be the pulling forces to close the cold spring gaps? Is it possible to apply moments when cold springing?

- 1.) do not have anc-cnodes. model the system as you would normally do.
2.) Insert coldspring element (mat. no. 18) from ceaser database, this can be done where-ever you think (trial and error) cold spring might help.
3.)Yes at the cold spring element (start with 5mm of mat. no. 18) you will see a lot of forces and moments. But we shall care only for forces and moments at our equipment nozzle.
4.) Check these w.r.t. allowables (probably NEMA SM23).

3- I'm thinking of three locations for cold springing on each line, each in one direction. Is it a good idea? Is it possible to have a 3D cold spring for such large sizes?

- Try to restrict cold spring with one location.

- Theoretically you can have as many cold spring in the system as you want, but I will surely spare a thought for the construction guys who have to install such a system on field. It is really easy for us to have cold springs in our system (thanks to coade team) but very difficult to install them on field.

(pipe mat.)
(Noz)|----------|
|
| - Cold spring mat. no. 18 (say 5mm to start with)
| -(pipe mat. continues)
|
|-------------

Check the noz. loads with this 5mm first.
Now you can change this 5mm or the location anywhere you want as per your
line routing.
I will suggest you get some information (read) about cold spring before you apply it.

Regards
Ashish G

(pipe mat.)
|----------|(Noz)
|
| - Cold spring mat. no. 18 (say 5mm to start with)
| -(pipe mat. continues)
|
-------------|


horizontal and vertical lines are your pipe elements.

Regards

Ashish G