PCHE cooler low perfomance due to block

[binbin93]

Hello,

our PCHE cooler is using for cooling down gas temperature with medium cooling water, but it's partially blocked (fouling) to cause cooler low performance. it's indicating DP across high and gas outlet temp high also.
please tell me a method to clean cooler

thanks

binbin93

 

[vpl]

What does PCHE mean?

Is the heat exchanger plate, shell & Tube, spiral?

Patricia Lougheed

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[binbin93]

it means Print Circuit Heat Exchanger
this use for cooling down gas compressed

 

[che68]

Do you know which side of the cooler is fouled? Fouling of either side will lead to loss of performance but its actually more common that the utility cooling system is the source of the fouling (PCHE's are generally used in clean process services because they are so prone to fouling). The high DP is presumably measuring the process gas side? PCHE almost always have a strainer in the compressor discharge line before the cooler - is there a DP measurement over this as well? You might want to double check that the strainer mesh hasn't failed and ended up in the PCHE. Either way, best method is to UHP jet but its likely you'll need to get the cooler ashore (most PCHE's are offshore) for a specialist contractor - Google "PCHE cleaning". The manufacturer or their local rep will likely be able to help you find a UHP contractor as well. If you are lucky, the fouling will be on the coolant side and should be controllable by maintainence/chemicals. Other methods of cleaning depend on knowing more about the nature of the fouling - chemicals might work if its not too heavily fouled or its lube oil carryover. Final comment - delaying the clean will only make it harder to rectify in the long run and might cause other problems (corrosion, localised boiling leading to thermal cycling & leakage)

 

[fazrul03]

Hi binbin93,

My client also face the same problem with this PCHE. The outlet T of Gas is high. So the main cause can be from water side which fouling may present.

Thus they requested us to service PCHE. So for time i still searching the best method to clean it and found several methods:

1. Back puffing - using high pressure N2 from outlet to inlet nozzle, with rupture disc installed at inlet nozzle, and puff away foulant or loosen it.

2. Back flushing using water. But water shall contain low chloride (<30ppm)

3. Chemical cleaning - can use organic acid with no chloride contain to dissolve foulant (mostly calcium carbonate).

I still study the back puffing method. So if some here knows how to carry out this method, please give some opinions. Tnx.

 

[vpl]

fazrul03 - If your fouling is calcium carbonate on the water side, the back puffing is not like to be successful.
One possible method is a soak with a mild vinegar solution to disolve the calcium carbonate followed by flushing.

Binbin - depending on what's causing your fouling, fazrule has given some suggestions on cleaning methods.

Patricia Lougheed

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[fazrul03]

I contacted the chemical company and they propose me the descaler chemical with composition as below for cleaning of foulant at water side:

Chemical Name % Concentration
Secondary Alcohol Ethoxylate - > 2
Polymeric Emulsifier < 5
Tricarboxylic acid < 5
Special Corrosion Inhibitors < 5
Phosphoric Acid < 20
Nitric Acid < 20

PH = 1 @30deg C

At first they proposed me hydrochloric based chemical, but i'm not prefer to use that because the PCHE core is SS316 material. As far as i know, it will cause Chloride stress corrosion.

Thus, if to proceed with chemical cleaning using the above chemical, will it harm to the SS316?

 

[binbin93]

thank you very much.
yes, we have used N2 back puffing and chemical cleaning also.
we use both chemical: acid photphoric and aci sulphamic
please advice me these chemical are good for cleaning?

thanks

binbin

 

[gr2vessels]

binbin93,
Can you answer the question of which side you think is fouled (refer che68 reply). Then can you advise the materials your PCHE is made of? Without this information, how do you imagine that someone can advise which of your chemicals are good for cleaning?
Fazrule, you have crossed enough binbin's post, please open your own post.
Cheers,
gr2vessels

 

[binbin93]

dear ALL,

our heater is fouling at gas side and it made by SS316.

thanks

 

[vpl]

If it's the gas side, I'd suggest the back puffing. There shouldn't be anything requiring chemical cleaning on the gas side.

For the water side, flushing should be sufficient unless you have some sort of participate like fazrul03 has with the calcium carbonate. If you do, then go with the chemicals his vendor suggested. Neither the phosphoric acid or the sulphuric acid should harm the cooler in the concentrations normally used.

Gr2vessel: since both binbin93 and fazrul03 are asking the identical question, it makes sense for there to be one thread addressing both of them. If fazrul03 started his own thread, someone would probably just refer him back to this thread, totally confusing him.

Patricia Lougheed

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[fazrul03]

Dear All,

Maybe i'm a bit cross over about the topic. But i do really interested in back puffing method to clean PCHE. Any one can help me in detail procedures? How to contact people here in personal?

As i'm new, do forgive me if i'm breaking the forum rule.

 

[vpl]

fazrul03 (and binbin93)

To start off you both need to look at your coolers and the type of environment they are in. My experience, because of my line of work, generally involves room coolers that range from about a minimum of 27 cubic feet (i.e, about 3 feet in each direction) to about 125 cubic feet. They are indoors in a generally clean environment with a plant cooling water running through the tubes. The plant cooling water, depending on the plant location, can be clean soft water, heavily sedimented (silt, sand, clams, mussels, and -- one very smelly time -- ground up fish)water, or hard water with a lot of minerals that can precipitate out over time.

You may have a cooler that has a lot of particles or sediment in the air -- if the cooler is outdoors, or if the particular area has a lot of dust or other particles in it. The water that is in your cooler could be soft, silty or hard. The method to clean the cooler has to depend on what the problem is.

If you have an air cooler that is susceptible to air side fouling then you can clean the air side by providing a flow of clean air in the opposite direction from normal. This will remove particles that have settled on the cooler. As I stated, this is really only needed if the cooler is in an area where there are a lot of particulates in the normal air (such as this one person who posted several years ago that had an outdoor air cooler that was picking up sand.) If your cooler is inside, you can do it, but it will probably not result in much better performance.

If your cooler is dirty on the water side, then you need to decide why it is dirty (which usually requires opening up the water box so you can look in the tubes.) If it's silt or sand -- or even fish -- you can probably remove the blockage by flushing with a high pressure hose. If it's clams or mussels, you'll probably need to kill them off with a biocide and then flush. If it's mineral deposits (I believe fazrul03 mentioned calcium carbonate), you'll need to use a chemical to get the deposits back into solution and then flushed out of the system. I have seen places where the "chemical" was nothing more than several gallons of off-the-shelf vinegar flushed through the cooler a couple times followed by a clean water flush.

The important thing is to figure out as much as possible what's causing the fouling in your cooler before you take it out of service. Take care of your biggest problem areas -- coolers with calcium carbonate deposits are definitely going to be underperforming. Getting those deposits removed will do you far more good than cleaning the air side.

My two cents ...

Patricia Lougheed

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[binbin93]

thank you very much for your cooperation and give me advice.

below is our cooler performance for your reference:

1. DP across cooler (gas side): 600Kpa. (inlet = 10000kpa, outlet = 9400kpa), this is not including inlet strainer and strainer is clear.

2. Gas Inlet temperature: 123oC.

3. Gas outlet temperature: 86oC. (setpoint at 70oC).

4. Cooling water inlet temperature: 31oC.

5. Cooling water outlet temperature: 55oC.

6. Gas flow thru cooler: 60mmscfd.

that's mean gas side of cooler partial blocked (DP=600Kpa) and gas outlet temp is high 86oC, it can not down to setpoint 70oC.

we have cleaned many times (back puffing and chemical cleaning) but no much improvement. do you think the mechanical problem of this cooler?

 

[gr2vessels]

binbin93,
If it is the gas side fouling, as you stated, then the gas is normally very dirty, probably includes high quantity of oil droplets which tend to condense in your exchanger, causing loss of heat transfer efficiency. Back puffing could only help (if any at all), to remove some loose dust, but no oil condensed in those tiny channels. It is common in a compressor station to lose oil at the seals, which end up in the pipeline, causing all sort of problems in the next station...
The only thing I can see to help is a big separator coalescer at the inlet of the compressor station, to separate the oil droplets, or ditch the PCHE and use either a water cooled standard TEMA exchanger or a nice big air cooler. Noisy, but efficient.
Cheers,
gr2vessels

 

[rlepierres]

Dear Binbin93,

Have you found a solution for cleaning the PCHE so far? Have you found the reason for the PCHE performance drop? Was it due to fouling? If so which side? What is the cooling water you are using (fresh water? Sea water? open or closed loop?). Do you have issues operating at the designed inlet conditions? As well how long has this PCHE been in service before you started to experience some performance issues?

VPL has a very good point as the solution to solve your issue with the PCHE is to know exactly the reason why the PCHE is not performing as per your expectation. It is a lot of questions but hopefully the more you can disclose about this unit, the easier it will be to advise a solution.

Dear fazrul03,

I would advise to contact the PCHE manufacturer as I am sure they will be the best to advise about any cleaning method and potentially giving you details about the cleaning procedures (it would be in their interest). They must have an aftersale team that could assist you. The same advice to Binbin93.

I would be very interested to know about your progress.

Cheers.