Shell and Tube rusted heat exchanger cleaning

[setrite]

I have a Centrifugal chiller that was full of water for about six months until the customer decided to call for service to fix it. Did the usual leaking tube replacement, compressor repairs and re-insulated the motor stator. But, now the difficult part is to clean the heat exchanger of all the rust that has formed on the shell surface. I do not want to cut the shell as advised some colleagues and would need advise from Guru's here for any alternative method that will help to rid the shell of maximum amount of rust.

Trenching it out.....

[RANGER1]

setrite,
Any chance of a picture to help give you the right advice.

[Magoo]

Hi.
what brand of centrifugal chiller are you dealing with. R11 . Have not worked on or seen one for years but have some back ground and experience with Carrier and the problem you have.
magoo

[setrite]

@ Ranger1/Magoo - This is a large 1000 tr R134a Centrifugal Chiller that had condenser tubes puncture, customer did not pay immediate attention as 6 months ago they had no load to operate this chiller, now they need it up and running yesterday. I am attaching pics of the compressor section which may give you fair idea of the rust that could be in the heat exchangers. Being 11kv compressor motors I want to ensure that all or most of the rust is gone so that it does not get back to the compressor. I am also installing additional liquid line drier cores that can catch any remaining moisture and rust in the system after start-up.

[setrite]

To continue with this, decided to do the following:
1. Take the customer in confidence, be very clear that there is a 50-50 chance of the system working OK.
2. No time line set. Work, work work but I don't know when it will finish.
3. Think of a way to get all that $#!& out of the shell.
4. Guts - To stop all other works and concentrate only on this one job.

This is the biggest challenge in my career so far. It will test my patience as well as the customers.

Work is in Progress....

[RANGER1]

For moisture lots of heat in a controlled way over time as well.
Rust will have to be collected in filters once running over time.

Good luck, no guarantees

[Magoo]

Important to get motor stator to a re-winder for drying and confirmation that it will operate. Strip and clean everything and anything, then filtration filters in refrigerant lines, parallel so as can be changed out with out interruption. Good luck you will be there on site for a long time, do not offer client any guarantees of success.

[Tycho]

Wilhelmsen ship service has something called "descaling liquid", we use it mostly on the seawater side of condensers and oil coolers, but have also used it on the refrigerant side of systems that have been submerged.

http://wssproducts.wilhelmsen.com/ma...g-liquid-25-l/

you need to circulate the mixture via an external tank with a pump to pull out the particles, if it had been on the seawater side you could have just left it for a while and then replaced it.

I'd also put a filter on the return hose from the heat exchanger, I've only done this on smaller parts of systems so my return hose hasn't been bigger than 2-3" and I have just ziptied a rag over the end.

Hope it works out for you

[Tycho]

also, Descaling Liquid should not be used on aluminium, zinc, tin, stainless steel or any galvanized surfaces for which a special grade cleaner should be used.

so if any of those materials are involved I would use descalex
http://wssproducts.wilhelmsen.com/ma...escalex-25-kg/

[setrite]

Wilhelmsen ship service has something called "descaling liquid", we use it mostly on the seawater side of condensers and oil coolers, but have also used it on the refrigerant side of systems that have been submerged.

http://wssproducts.wilhelmsen.com/ma...g-liquid-25-l/

you need to circulate the mixture via an external tank with a pump to pull out the particles, if it had been on the seawater side you could have just left it for a while and then replaced it.

I'd also put a filter on the return hose from the heat exchanger, I've only done this on smaller parts of systems so my return hose hasn't been bigger than 2-3" and I have just ziptied a rag over the end.

Hope it works out for you

Tycho Thank You for the advise. I guess that is the only way to remove most amount of rust and debris from the shell side. In talks with a de-scaling company here who will be able to arrange a de-scalant to do the job. After its done will be passing dry hot air at 70 deg C through the shells for a week so that the water dries up.

Meanwhile compressor is dis-assembled and stator sent to the oven for cleaning and heating.

Thanks for all the advises flowing In.
Cheers!

[setrite]

Compressor is ready. But haven not installed it on the heat exhanger after they were flushed with Water + chemical to remove the rust inside. I was surprised at the amount of rust that actually came out of that thing. The water was draining all yellow for atleast 4 hours. Flushed with OFN cut open tubing at the lowest part to ensure that all water drains out. Pressure tested the heat exchangers separately without the compressor and started vacuum after heating the shell and circulating hot water through tubes. Holding vacuum at 6500 microns to prevent water from forming ice. Every time it rises beyond 12000 microns start vacuum again to hold again at 6500 microns. Today was the tenth time the vacuum was held at 6500 hope there is no rise tomorrow so that I can go further down to 500 microns. Phew!!! Vacuuming needs patience........

[setrite]

Today Finally the vacuum held at 6000 microns, so I am sure that there is no more liquid water in the Heat Exchangers that will freeze at triple point. Now will install compressor and pressure test and operate vacuum pump continuously to acheive 500 microns.

Hope to close this job before Christmas... Any advise to ensure a proper dehydration will be of great help.

[Rob White]

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What an excellent write up.

Very interesting. I hope all is OK when the big switch on happens.

Keep us updated.

All the best

Rob

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[Magoo]

Hi
You have been on a mission to this point, with the final vacuum use short and large diameter pipes between vessel and multi pumps, a cold well in lines will reduce moisture contamination in vac oil. You will still use a truck load of vacuum pump oil all the same. Keeping vessel warm will also speed things up. One of those LPG heaters that look like a jet engine with a bottle attached, are really effective.
From memory it is a 6Kv drive motor. Scary stuff when you push button for first start up.
Keep us all informed with progress. Keep up the good work.
magoo

[setrite]

Returning with an Update. It's been three weeks the machine's running OK. Used two vacuum gauges and targeted a vacuum of atleast 500 microns, A final vacuum of 450 microns was achieved. The circulating hot water in tubes helped to a great extent.

Have changed Oil once, however the first Oil charge when tested indicated all parameters normal.

So, the customer saved $$$ from buying a new machine, and a sense of achievement for me. I hope it works well in the days to come.

Thanks to all the advises from the experts here.

[Grizzly]

Returning with an Update. It's been three weeks the machine's running OK. Used two vacuum gauges and targeted a vacuum of atleast 500 microns, A final vacuum of 450 microns was achieved. The circulating hot water in tubes helped to a great extent.

Have changed Oil once, however the first Oil charge when tested indicated all parameters normal.

So, the customer saved $$$ from buying a new machine, and a sense of achievement for me. I hope it works well in the days to come.

Thanks to all the advises from the experts here.

Brilliant News for you and all concerned.
You deserve all the credit you can get!
Because you did the best you could for the customer without Bull**** and total honesty.
Guess what. Good news travels and You deserve it Well Done!
An Interesting read throughout as well.
I tried to add a rep point to your post but apparently I have to "spread the Love" more first!
So just accept my genuine congratulations.
Grizzly

[Magoo]

A painstaking job well done and a good result, no doubt a very happy client. Thanks for coming back with final outcome.
magoo

[setrite]

Thanks Magoo and Grizzly. It was indeed painstaking and at the back of my head there was also the pressure of the challenge that was taken when the OEM gave up and suggested to scrap it. In the End it was all worth it.

[Rob White]

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Just read the follow up.

Well done. Just shows what can be done.

Regards

Rob

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