Solution to Corroding Pipes Near Cooling Towers

Dear Mr. sanjayb,

You have to provide additional information, such as

1. Whether you treat the circulating water, and what is the quality of make-up water.?

2. Whether the minute water particles spill over the pipe and causes corrossion.?

3. If pipe is laid below the ground, whether pipe-metal is eaten away by corrossion, and do you mean painting is internal or external.?

4. If spilled water is causing corrossion means, pl. check the RYTZNER FACTOR,for the water, which indicates CORROSSION Character of water. Treatment of water is the solution.

We have cooling tower, and we have wrapped ASHPALTED SHEET by HEATING and fixing tight. This will take care whether the pipe is below ground or above round, near by cooling tower or a little bit away from the cooling tower.

DHAYANADHAN.S

1. Whether you treat the circulating water, and what is the quality of make-up water.?

No idea

2. Whether the minute water particles spill over the pipe and causes corrossion.?

yes , i think so

3. If pipe is laid below the ground, whether pipe-metal is eaten away by corrossion, and do you mean painting is internal or external.?

pipe is above ground at Terrace, painting is external

4. If spilled water is causing corrossion means, pl. check the RYTZNER FACTOR,for the water, which indicates CORROSSION Character of water. Treatment of water is the solution.

...Treating water is a solution. I agree.

but What according to you should be the best way forward to protect the pipe , replace ( if yes, with what) it or paint it again ?

Dear Mr. sanjayb,

In my reply, I have said, RYTZNTER FACTOR is to be CHECKED. For CORROSSION, it is LANGELIER FACTOR is to be checked for Corrossion,and NOT RYTZNER Factor.

The RYTZNER FACTOR is applicable for deciding the SCALING EFFECT of Circulating Water.

By mistake I have not mentioned correctly. After posting, it struck to my mind and hence this correction is sent. Sorry for inconvenience.

Now that it has been clarified that the CORROSSION is EXTERNAL, THE Water Quality hence the LANGELIER FACTOR appears to be alright.

Try to wrap ashpalted rubber sheet over the pipe, CORROSSION problem can be solved.

You have mentioned in your post, "CHILLED WATER" and what is the Temp.of Water entering and leaving the Cooling Tower and what is the Wet-Bulb Temp. ? This will help to understand that the cooled temperature cannot go down below Wet-Bulb Temp. This is purely Thermo Dynamics.

DHAYANANDHAN.S

Are they corroding from the outside, or from the inside?

I'm currently designing a Cooling Water expansion in one of our facilities. I'll share with you what I know.

While well into it, I was informed of AquaTherm. I wish I knew about that in the on start.

What I saw and understand of it is,

• It is more pricey
• Installation seems to be quicker
• Lighter and easier to handle

Over and above their warranty, they also have a 10 year ~$20,000,000.00 insurance policy from Zurich???, if there is a failure to cover your liabilities, (Injuries, lost production, damages, ect....) takes some risk away.

They seem to really pushing for this in the U.S., it's pretty popular in Europe. But thats salesmen speaking.

I would definitely look into this.

If I recall, the 'R' Value of this is only about 1.7, in the Northern Climates this may not be enough??????. also you may need it to protect against condensation.

As far as your corrosion issue, doe you have your cooling water treated, or even tested?

The other issue of corrosion, on your cooling cell, what type of basin Galvinized or stainless?

There may something going on with galvanic reations with the minerals in you cooling water thats affecting your pipes. (and valving as well, not to mention pumps)

This stuff looks very good, after you get through the purchase and installation phases.

It's a co-extrusion of straight poly pro resin on the outside and a core of glass filled resin in the center.

It will require welding or fusion welding to install, but that's no big deal with the right equipment.

No maintenance for years.

You send your people to your supplier for training, or your supplier will train at your facilty. It's only a 1-2 day certification to get certified.

And the smaller fittings say up to 2-4 inch pipe, You can buy the fixtures for welding immediate repairs or projects at the plant.

and on the larger piping, you can rent them from your supplier. Yes, your right, it doesn't look like a big deal.

Setting up takes longer then the actually welding, but total time is cut.

On exterior piping you would have to U.V. protect the pipe, or insulate and jacketed.

I talked to all of our contractors that will be doing this, but they had very little experinence with this.... actually none.

I wish I knew about this at the beginning, our biggest concern in our expansion, we have to take the cooling tower out of production which means a 100% shut down for us.

And some of the footages, shows one guy carrying what looks like a 20', 10" length of pipe on his shoulders. (of course you will nee more supports on this type)

because the water is chilled you need to focus on insulating the pipes. any small exposed area will case sweating and eventual rusting/corrosion. so if its chilled, paint isnt your issue. hope that helps

Dear Mr. Fredski,

You have referred in your post, "because the water is chilled you need to focus on insulating the pipes. any small exposed area will cause sweating and eventual rusting/corrosion. so if its chilled,....."

I am of the view, IF SWEATING HAS TO OCCUR over the Pipe Surface, the CHILLED WATER TEMPERATURE SHOULD BE BELOW THE WET-BULB TEMPERATURE. In a COOLING TOWER - which works on EVAPORATIVE COOLING PRINCIPLE, Cooled Water Temp. will be always more by 3 to 5 Deg.C of WET-BULB Temperature,and IT CAN NOT EVEN GO NEAR TO WET-BULB TEMPERATURE.

Hence in my opinion, sweating over the pipe surface can not happen, on account of chilling. On the other hand, if the DRIFT-ELIMINATORS of the cooling Tower is NOT effective, then minute water particles will escape and will fall on the adjoining land surface - in this way the pipe may get water particles deposited, leading to corrossion.

DAYANANDHAN.S

yes i think the drift eliminators in these towers are not effective.

The OP stated that these pipes were near the cooling tower, and contained chilled water, not that the pipes that were part of the cooling tower's connections were sweating.

Fredski is correct. It is the chilled water pipes that need attention. If they are sweating, then apart from anything else relating to the structure of the pipes and their corrosion, there is an energy loss of ambient heat into the chilled service, and the chiller plant is having to work more than it would if the pipes were properly insulated.

Those chilled pipes need protection from corrosion with some sort of coating, then lagging properly afterwards, otherwise the corrosion may recur; eclude moisture from their surface, and they will last longer and the energy costs at the plant will fall.

Dear Mr. PWSlack,

Thank you for your posting. I want to understand how "CHILLED" temp. (as posted in the OP) can go below Wet-Bulb Temp, WITH OUT ANY MECHANICAL AID/MEANS like Refrigeration.

Expecting your posting.

DHAYANANDHAN.S

In order for the water to become chilled, there has to be a refrigeration plant, even if the original poster hasn't stated this. No mention was made of cooling water pipes and the original poster's problem is with the chilled water pipes, as stated in the original post.

Here are Few pictures

Thanks for the pictures. Years ago, the plant I worked at had a similar problem. We used a coat-and-wrap system like used for underground pipelines. It worked fine, but our system was less congested and larger diameter and lengths. If your pictures are representative, and the return temperature is not too high, I would replace with polyethylene, PVC, or fiberglass - maybe the system somebody recommended above. Because of the lower strength, you may have to add pipe supports as recommended by the vendor. Some of these systems use thermal welding, some solvent welding, and fiberglass uses adhesive. I would first check out PVC because of the ease of installation and cost. One big consideration of any system you consider has to be UV resistance - some plastics are great until they see long term exposure to sunlight.

From these pictures I would say it looks like the paint may not be suitable for the location. Try having a good sandblast to base metal and paint with a good primer then topcoat with a marine or wet area tolerant paint.

Depending on the age of the equipment or our facility it may not be financially responsible to replace all the pipes. If a quality coating is applied correctly you may get the pipes to last as long as the rest of the system. I always thought it was bad form to see brand new parts on a piece of equipment that was being scrapped.

Drew K

I agree with Drew here...It doesn't look like the pipes were properly coated and maintained...They might be salvageable but it might just be easier and cheaper to replace with PVC....

If the paint is the correct type for the situation then to me the pics show that poor preparation of the pipes is at fault. I would look at the condition of the pipes & the process preparing the surface prior to painting.

Even though I am not qualified in the painting industry, the 1 thing I have learnt from associates that are in the industry "preparation is every thing" to achieve a lasting result & to stop rust from reoccurring.

So unless the pipes are damaged beyond normal allowable limits & before investing a lot of money replacing the pipes I would look at the painting process & preparation of the surface to make sure it meets the standards needed to achieve the required results.

It appears that there are anti-scaling chemicals being used in the water that is attacking not only the pipe but everything metal in the area.

Are you sure your chemicals are in balance?

If they are in balance you need to identify the chemicals being used then contact a reputable coating vendor and they will be able to provide you with the correct coating(s) to prevent and/or at least slow down the damage.

New information!

Right, so is there now a problem with the cooling water pipes as well as the chilled water ones, or is the term <...chilled water pipes...> actually a misnomer for the cooling water pipes? Cooling water pipes are never lagged, as the whole purpose of the cooling water is to dissipate process heat to atmosphere. Their temperature is usually at or above the wet-bulb temperature. Chilled water pipes, however, will be below the wet-bulb temperature and will require lagging.

Fixing the drift eliminators might not be the whole solution, for the pipes would seem to be in a place where rainwater might still fall upon them.

It would be worth checking the electrical installation in the area to make sure that there is no unintended current flowing to earth via these pipes, which would exacerbate the problem of corrosion. An unintended cross-over between earth and neutral somewhere in the area might make a lot of difference to the longevity of metal pipes. Pipes should never be used as the link between the electrical installation and an earth electrode, as one cannot ensure the continuity of an earth path with any confidence owing to the growing use of non-metallic pipes.

There is a very cool solution to the corrosion problem. I have seen it in Accion at a very wet salt mine. We all know what WET Salt does to steel. And this stops it dead in it tracks. It uses a negative charge that is very mild to stop the electorolasis. Here is a link to the company. http://counteractrust.com/Aviation.htm I have not tested it but a friend of mine was using this or another brand on little trains at a salt mine in the bay area where they dry sea water for sea salt. It just stopped the rust on the trains. Give this a look or a try or search for more powerfull or call them and ask what you need based on your situation. Jim

You are talking about cathodic protection. This is a well known practice but only works if the metal to be protected is in an electrolytic solution. It will only work if there is enough water on the surface to complete the circuit. Cathodic protection is intended to be used in addition to an effective coating.

Drew K

Hi Sanjay,

There is firm in Mumbai called Kitec Industries India Ltd. they mfr. composite pipes in Swiss collaboration. Their web site is www.kitecindi.com. e-mail:

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HDPE pipe is a viable alternative to schedule 40 carbon steel piping commony used for condensor / cooling water supply and return provided it is not an insulated /heat traced system exposed to extreme cold temperatures. HDPE is joined by the fusion method - depending on specifying engineer - butt fused or socket fused ( electro-fused). Simply heating the material to change of state where it is fused together - "welded". I would recommend prefabrication of the piping and using lap joints/flanges and backer rings to erect and connect to tower. The vendor of the HDPE material usually provides the fusion machines at a weekly rate. Depending upon pipe sizes it can be expensive. A more economical application would be schedule 80 PVC solvent weld fittings depending upon the use of the cooling tower. Is it for process or HVAC? If HVAC it could winterized during the winter season but if for process it is used year round and PVC may not suit the application-susceptible to freeze and bursting. Victaulic or grooved fittings are also commonly used in steel pipe systems for cooling water - but this does not address your corrosion issue. You may want to look into the water treatment system and ensure that is operating correctly. Good luck.

I agree with those who suspect drift eliminators- Especially If the corrosion is predominantly on top of the piping vs the underside. If the eliminators are failing, replace them. Shift them from side to side to eliminate any wide gaps. If the tower has excess capacity, consider slowing the fan speed; Even a small reduction will reduce spitting markedly while capacity will drop off proportional to fan speed. Consider alternative water treatment chemicals. Chlorine as a biocide is especially corrosive.

Yes HDPE pipe can be used for cooling tower service.

Be aware there are different types and different service ratings so be sure to selct the correct type for your application.

Also I would suggest you use HDPE with "tracer" wires on all underground applications so that they are easily identified during/for ease of future excavations and for safety reasons.

HDPE is "fused" (welded) using a special machine that hydraulically clamps the two peices to be joined in the same plane, cuts the ends of the pipe square, de-burrs the inside and outside pipe edges, and then uses heating plates to heat the pipe to proper temperature and finally hydraulically presses the ends together at the proper pressure to attain a fault-free connection without any voids and/or distortion.

Be aware HDPE pipe is very sensitive to temperature changes so it expands and contracts a great deal which can cause joint failure if the pipe is not properly secured and the movement controlled/offset.

The HDPE supplier will assist you and provide you with all the information you need.

I've used this product with great results.
http://www.tnemec.com/Industrial
http://www.tnemec.com/project/view/?j=161
http://www.tnemec.com/product/view/Series-73-EnduraShield

FRP/GRP pipe is what you want. Offers many years of service and can easily be repaired.

HDPE needs twice as many supports and will end up to be more expensive to install.

We can even provide pipe stress analysis though our partner in Germany.

Contact ZCL Composites/corrosion division.

HDPE pipes have minimum resisatnce against ultra violet rays. They become brittle after some exposure. PVC pipes also have a problem of getting brittle.

PP pipes (Polypropylene) are better. They could be threaded or even flanged pipes are available. They can stand even temperature upto 110 C. They will not need painting.