Corrosion information for evaporative equipment

[US Iceman]

Here is an interesting link on corrosion in cooling towers. I think this will also provide some insight into the same problems associated with evaporative condensers or closed circuit fluid coolers.

http://www.corrview.com/index.html

[aawood1]

Hi US Iceman, Had a good look at the link and some good info. in it. We had a change of water treatment this year and the new service company that looks after it should change the drums and service the pumps and pipe work upto the condensers. But they only seem to come onto the site at the weekend's, We run out of water treatment and the pumps brake down and the pipe's split. We cleaned out one of the 7 condenser,s to find pinhole pitting in a 2 year old BAC condenser and small holes in a 4 year old Evapco unit. What away to save some money on water treatment.
Arthur

[smpsmp45]

This is a nice article. One of our customers is now going in for evaporative condensers & was highly worried due to his earlier experience. We have now recommended him to use SS 316 tubes ,l though the enclosure still is a factor to worry.
But this article shall make us relook at the whole issue once again.

[smpsmp45]

By any chance have you used these?

[Andy P]

Hmmm....seems a bit like using your airbags to tell whether you drove into a wall or not!

cheers

Andy P

[US Iceman]

I posted this link because they had what appeared to be some good information on corrosion formation, pictures, etc.

I was thinking more along the lines of mechanical integrity issues than gadgets. As the old saying goes let the buyer beware.

[TXiceman]

As a point of interest, The most recent RETA Breeze has an article about ammonia-water contamination.
Ken

[Sergei]

As a point of interest, The most recent RETA Breeze has an article about ammonia-water contamination.
Ken

Do we need a device to remove water from ammonia system?

[smpsmp45]

As a point of interest, The most recent RETA Breeze has an article about ammonia-water contamination.
Ken

Can we get a copy?

[TXiceman]

The article is on the www.reta.com site and you have to be a member to gain access to the articles. I will try to up load the article here.

Ken

[Sergei]

The article is on the www.reta.com site and you have to be a member to gain access to the articles. I will try to up load the article here.

Ken

I have 2 concerns about this article.
1. Liquid injection oil cooling from intermediate pressure receiver. Never heard about this.
2. Do we need ammonia regenerators? We have them in the systems. These are oil pots.

[NH3LVR]

I have 2 concerns about this article.
1. Liquid injection oil cooling from intermediate pressure receiver. Never heard about this.

New one on me as well. Possible, but seems like it could be a problem.

2. Do we need ammonia regenerators? We have them in the systems. These are oil pots.

We have just recently became aware of the problems water can cause in a NH3 system. Many older systems have a LOT of water in them. 20 years of running in a vacuum tends to do that.
Oil Pots do nothing to remove the water from an LPR, unless you have oil to drain. Many Screw Compressors will pump less than a gallon a month. Even then the efficacy is doubtful.

[US Iceman]

We are getting off track a little bit, but I will add some quick comments about the liquid injection using medium pressure liquid.

As long as the liquid injection valve is sized accordingly for the lower available inlet pressure (lower differential pressure between the liquid injection port and the liquid feed pressure) you are OK.

The only criteria is the liquid injection supply pressure has to be slightly greater than the port pressure at the compressor (which is between suction & discharge pressure).

Oil pots don't do anything except collect oil and let some of the ammonia flash off to the connected pressure of the equalizing line.

You need a heated still essentially do drive off the water.

[TXiceman]

Hansen makes an Auto-Purger that will remove water as well. What US Iceman, says about the the liquid injection cooling is correct. With the electronic liquid expansion valves,we are able to control over a much larger range.

I posted the article for the content on system performance as well as the mention of internal corrosion due to the water.

Under ideal conditions and with PURE anhydrous ammonia, you can use copper. But we all know, there is no such thing as pure ammonia in a system.
Ken

[Sergei]

I don't see significant difference between oil pot and ammonia regenerator.
Oil pot takes liquid ammonia from suction side of ammonia pump. Ammonia boils off. Residual(oil, water) is drained.
Ammonia regenerator takes liquid ammonia(the same liquid) from discharge side of ammonia pump. Ammonia boils off. Residual(oil, water) is drained.

[NH3LVR]

I don't see significant difference between oil pot and ammonia regenerator.
Oil pot takes liquid ammonia from suction side of ammonia pump. Ammonia boils off. Residual(oil, water) is drained.
Ammonia regenerator takes liquid ammonia(the same liquid) from discharge side of ammonia pump. Ammonia boils off. Residual(oil, water) is drained.

Good Morning Sergei!

I believe the difference is that water will pass through the Oil Separator, although it might catch some. It does exist as a liquid at discharge temperatures however.
In any event it would do nothing about the water in a flooded vessel, such as a LPR.
I have had success however in trapping water in Intercoolers.

[Sergei]

Good Morning Sergei!

I believe the difference is that water will pass through the Oil Separator, although it might catch some. It does exist as a liquid at discharge temperatures however.
In any event it would do nothing about the water in a flooded vessel, such as a LPR.
I have had success however in trapping water in Intercoolers.

Good morning NH3LVR.
I'm talking about LPRs and Intercoolers. Water in these vessels will be in solid form and will be separated from ammonia in oil pots or in ammonia regenerators. Function of oil pot and of ammonia regenerator is the same. They take some liquid ammonia from the system, boil off ammonia and residual(oil, water and etc.) is warmed and drained.

[US Iceman]

Let's not forget the ammonia we use is anhydrous, so it has a high affinity to absorb water. Oil is not the only substance that will hold water in an ammonia system.

[TXiceman]

The article I supplied list the percentages and the temperature penalty for the water. Water will readily be absorbed in the ammonia. This is the principle that ammonia absorption refrigeration works.

Ken

[Sergei]

We are getting off track a little bit, but I will add some quick comments about the liquid injection using medium pressure liquid.

As long as the liquid injection valve is sized accordingly for the lower available inlet pressure (lower differential pressure between the liquid injection port and the liquid feed pressure) you are OK.

The only criteria is the liquid injection supply pressure has to be slightly greater than the port pressure at the compressor (which is between suction & discharge pressure).

Oil pots don't do anything except collect oil and let some of the ammonia flash off to the connected pressure of the equalizing line.

You need a heated still essentially do drive off the water.

Regarding to liquid injection from intercooler. Theoretically it will work, but not practically. Usually, intercoolers have pressure 15- 25 psig. Liquid can be injected into compressor at early stage of compression. First, it is not efficient. Every compressor manufacturer designs liquid injection at the latest stage of compression to minimize penalty related to liquid injection. Second, when screw compressor unload, sooner or later injection port will be exposed to the suction and this factor will reduce efficiency as well.

[US Iceman]

Regarding to liquid injection from intercooler. Theoretically it will work, but not practically. Usually, intercoolers have pressure 15- 25 psig. Liquid can be injected into compressor at early stage of compression. First, it is not efficient. Every compressor manufacturer designs liquid injection at the latest stage of compression to minimize penalty related to liquid injection. Second, when screw compressor unload, sooner or later injection port will be exposed to the suction and this factor will reduce efficiency as well.

I do not disagree with what you stated above Sergei. But let me clarify my earlier point, I only mentioned medium pressure liquid, not intercoolers.

In order to use the liquid injection port you need a liquid pressure greater than the port pressure. For a high stage compressor you need liquid at condensing pressure (or a pump).

For liquid injected boosters you can discharge into the booster discharge line or the liquid injection port.

In either case, the liquid supply pressure has to be greater than the port or connection pressure.

In most screw compressors I am familiar with, the liquid injection port is close to the discharge cut-off prior to the discharge port. This is how the manufacturers minimize their power penalties for liquid injection. In other words, the additional mass flow used for oil cooling is only compressed from a pressure not much lower than discharge cut-off.

I am not advocating liquid injection into the suction lines.

[nh3wizard]

RS has a purger that they claim will remove water from an NH3 system. Havent seen one installed, most of our plants have the Hansen Autopurger.

[Andy P]

Per Nielsen (co-author of the article Ken posted) used to work with Danfoss, then York, Denmark and now runs his own consultancy. There are more articles, with better information at

http://www.coolingconsult.dk/pollution.html

cheers

Andy P

[US Iceman]

Thanks for sharing the link Andy. The site contain some good material.