Guide for repair and welding cage on control valve

[Rio Risnaldi]

Dear Engineers,



How are you mate?
Trusted you very well, right?
by the way, I have some issue that we not have detail guide that its refer or available with standard for repair from (scratch, corrotion, erotion, pitted,ovality, etc) and welding (instruction and material available) for Cage on control valve. could yu haelp for give your guide for reference, mate?


Looking forward to hear from you.

Thanks
rio

 

[Rio Risnaldi]

Dear Engineer,


Could you help or any advice?

Thanks
Rio

 

[Danlap]

Dear Rio,

There is only two solutions, repair the existing cage as per existing detail drawing (if you have the detail drawing of the cage) or replace it. Most of the cases, replacement is would be the path forward.
Main two reason:
- Most likely no body except the manufacturer has the detail drawing
- Cage function is one or more of this: noise reduction, mitigating cavitation and/or flashing, streamlining the flow, etc. Any slight changes in the dimension will alter the efficiency of cage's function, or sometimes may not even work as intended.

Root causes that you've just mentioned if not in major state such as (small) corrosion, erosion, pitting can be repaired by (step by step):
- removed by means of sand-paper, sand blasting or other similar removal method --> this will for sure causing volume removal of some part of the cage. Read: design change
- after removal then followed by polishing --> again causing volume loss/design change
- if ones want to restore the "volume loss" back to its preliminary design, then hot work required e.g. welding, machining, etc. Given cage have small "holes", then hot work most likely will cause holes or if not dimension distortion.
On top of that, let say you've manage all of that and cage fits "perfectly" inside the body and also the Plug. It is very unlikely that you could function test the cage with given flow and pressure. Most test benches are using static pressure, and only small numbers of manufacturer have this dynamic (pressure+flow+control-ability) test bench. Flowserve Villach is one of them.

For scratches and oval it is truly depending on engineering judgement. Some cases required to be replaced, and some is not (only standard cleaning required). Usually if scratches and current oval condition do not "block" Plug movement and valve URGENTLY required to be installed back, then leave it as is. But then again, one who is in direct contact with the real Cage/Plug should know when to replace.

Cage re-engineering/re-fabrication in principal can only be done by its original manufacturer. If deemed current design is not suitable then retrofitting might be required, IMI/CCI engineering maybe one of well-known cage retrofitting company.
I have seen so many contractor fail when attempting to repair cages, and often make the situation even worst.

Kind regards,
MR

https://nosuchvalve.com

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

http://www.eng-tips.com/faqs.cfm?&rat1=2&fid=376

 

[Rio Risnaldi]

Dear Mr Danlap,

Good morning and hope you very w, well today, mate.

Thanks for your information and your advice.

inform to you that we work for service valve that as your information,"Most likely no body except the manufacturer has the detail drawing". So, what we can do is inspect by visual and measure for actual. Then we restore the "volume loss" back to its preliminary design.


the problem is, we not have standard procedure for detail, step by step for repair this cage (trim component).

may be you have advice for detail procedure repair cage (trim component) base on defect type (scratch, erotion, pitted, ovality, crack, etc), dimension of defect and process repair that recommended base on dimension defect ( spot weld/overlay,machining, NDT/blue chack,lapping, roughness chcek,hardcrome/metal spray).


Actually we only have this procedure for other parts, but we dont have for cage that its have specific and crutial function on control valve.


If you have advice for detail procedure or have some reference standard, mate?


Looking forward to hear from you.


Thanks
Rio

 

[Rio Risnaldi]

Dear Engineer,


could you help for my issue, mate?

Thanks
Rio

 

[Danlap]

Hi Rio,

I don’t think I anybody can help you, and I will try to elaborate why:
a.Control valve cage have hundreds of design, and each detail dimension and configuration have a specific function. The passage/holes have different complexity in order to be able to be refurbished.
Photos below courtesy of MASCOT and Flowserve

b.Repair by Merriam Webster meaning to restore by replacing a part or putting together what is torn or broken into good order
Good order means an itegrated part will be able to perform its function as new, or within acceptable tolerance objective by subject matter expert (SME) assessment.
Assessment means that SME will compare final result after repair vs original drawing (including holes diameter, its shapes, roughness, etc.) AND/OR flow characteristic after valves’ vena contracta (or in this case Cage) on its original design vs after repair

There is no way a detail repair procedure for can cover “simple” cage as above-left picture and applicable for “more sophisticated” above-right picture. And there is no way anybody aside from manufacturer can have a detail dimension and configuration of the passage/holes and other features. This is a proprietary rights, and if someone leak this information, they will got sued.

You can Clean it, restore it the best you could make it fit for purpose (from valve point of view only) for another xx years. But it is very unlikely you can repair under given budget constraint.

http://knowledgelovingsociety.blogspot.com/2012/06/control-valve-operation-and-design_05.html

Decision to repair should be with a flow chart. More or less as follow:
-Dismantle valve
-Cage found to be damage
-Obtain drawing of Cage -> IF NOT, then order OEM part and replace it; IF YES, go to next step
-Clean surfaces from corrosion and sharp edges
-ID and OD check of by micrometer (check 5 or more different spots)  let say tolerance 0.2 mm. IF ABOVE tolerance (read oval), order OEM part; IF NOT go to next step
-Erosion check -> passage or hard facing missing more than 1-3% of its volume. IF YES, replace; IF NOT go to next step
-Others
-Do hypothesis or define the root cause of above damage. We can repair “it” but if we don’t know the root cause, shortly the failure will reoccur.

Please note that most and if not all cage are hard faced. So if you find gauging, scores or eve scratches, it may subject or re-hard facing. If you know original hard face composition, you might overlaid it.
It is not suggested to use existing dimension as reference, since it might be already eroded due to years of service.
If you have the time to procure OEM cage or engineering it by control valve expert, then suggest to do it. It would be safer, beneficial for all parties (yours, client, and OEM/3rd engineering party). Plus you can still claim that you’ve repair it
Why I put small margin of tolerance prior Replace decision? It would cost you more to make round of something already oval, weld/hard face something that already eroded in comparison with buying new Cage.

Good luck,
OOT,cmiiw seeing your name I assumed you’re Indonesian.

Kind regards,
MR

https://nosuchvalve.com

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

http://www.eng-tips.com/faqs.cfm?&rat1=2&fid=376