JACKET WATER TREATMENT

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offshoresnipe
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JACKET WATER TREATMENT

Postby offshoresnipe » Sat Apr 21, 2012 3:50 am

Looking for info on J/W treatment, having a bit of a discussion in the control room on this.
Any info would be great.
Thanks

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Big Pete
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Re: JACKET WATER TREATMENT

Postby Big Pete » Sun Apr 22, 2012 1:38 pm

Lots of different ways of treating cooling water:-

If the water you use is always distilled or shore water from a region where the water fallsand is collected on hard rocks, it will be acidic because it absorbs CO2 gas from the air and forms a weak solution of Carbonic Acid, hence it will cause corrossion.

If the rain falls on chalk or limestone or goes througjh a "Hardening Filter" the Carbonic Acid will dissolve the rock and the water will become hard and cause scale deposits at high temperatures.

You have to treat the water to prevent both these outcomes.

The Germans used to use Soluble Oils emulsified into cooling water to prevent corrossion, (The same as the soluble oils used to cool and lubricate machine cutting tools on lathes etc until they were proved to cause skin cancer and banned) as this formed a stable emulsioin it was death to the OWS and 15 ppm monitoring so it is now banned for this use too.

Chromate based corrosion inhibitors were used next (Remember Julia Roberts chasing the Hexavalent chrome deposits around the cooling pools for a Natural Gas pumping station? (Erin Brokovitch))That also got a resounding NO from the 'elf & safety people.

What is used now was originally called NC (NO CHROMATE) treatment and is Nitrite based, same as fertilisers. It reacts with air so it is continually depleted and has to be tested regularly and topped up as required. The drawback for this is that it is a fertiliser and encourages bugs etc to grow in your cooling water.

Hope this helps.

BP
It is always better to ask a stupid question than to do a stupid thing.

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offshoresnipe
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Re: JACKET WATER TREATMENT

Postby offshoresnipe » Sun Apr 22, 2012 1:46 pm

Thanks BP, helps with the heated discussion in the control room. [no pun intented]

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JK
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Re: JACKET WATER TREATMENT

Postby JK » Mon Apr 23, 2012 3:15 am

With the Cats, I switched to the Cat coolant. It really made a difference to the life of the engines.
Before we were getting pitting on the outside of the liners to the point that they were almost perferated. I suspect that checking the treatment levels was not part of the ER routine over the years.
BP, you made me choke on my coffee with the comments on the chromates. Another product to add to my list for the Doctor for exposure, along with the asbestos, formyeldehyde and fuel bug killer. Sigh.

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Big Pete
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Re: JACKET WATER TREATMENT

Postby Big Pete » Mon Apr 23, 2012 11:48 pm

Some more information to add to your heated disscussion, anyone lifting safety valves yet?

I have seen some engine makers, Deutz for one, that supply "Filter Cartridges" to fit in the water circuit, usually in a bypass line, these are solid blocks of chemical, in a metal case, that dissolve and maintain the coolant saturated, you weigh the cartridge to check if it is depleted or not. The new filters weigh a ton, the empty one is not much heavier than an empty beer can)

Some suppliers, such as Unitor supply the corrossion inhibitor as a powder (Dieselguard NB) or a liquid (Rocor NB Liquid). These are Chemically the same, a Nitrite/ Borate based compound with organic corrosion inhibitors) Usually the liquid is much easier to use, but the powder has to be mixed with water to ensure it dissolves, before being added to the header tank. However, if you buy the liquid, you are paying for packaging and transporting a lot of water, so the powders are usually much more cost effective.

These Chemicals attack Aluminium and Zinc, so if you have these metals in your coolant circuit, you have to use other coolants, I know Unitor make one but I can't remember the name.

In the case of lifeboat engines and emergency generators, on a World Wide Trading vessel or one trading to cold areas, these coolant systems should always be treated with a combined anti freeze and corrossion inhibitor. Don't mix the antifreeze with your usual corossion inhibitor!!
(The should also be fueled with "wax free" winter grade DERV.)

Keep discussing and asking questions, it is the best way to learn.

BP
It is always better to ask a stupid question than to do a stupid thing.


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