Sea Water Cooling Loop Offshore Rigs - Marine Growth Problems

Copper bands on the pipes. Tin based paints are banned now. Any chemicals would be classed as marine polution. Silver kills bacterial growth. Best I can do for now.

Hi George,

On a smaller scale, 10000 gallon cooling systems with 3 - 5" lines and good flow, we use a closed system heat exchanger with conditioned water. This prevents the scale, mineral build-up, continual maintenance issues, and the related cooling efficience decreases. I'm not sure if you can justify the extra expense for such as system given your industry, but, might be a thought.

Then again, how about using a closed system on and around the "critical parts" then add a flushing system with an open design with access for "power washing" the exchanger coils at the interface. Might be best of both and the least overall cost - without doing the calculations.

Paint might only reduce heat transfer efficience.

Unless the correct grade of SS is used paint reduces corrosion problems. Anti fowling paint can help but it must be looked into first. A closed loop is no good for a sudden high demand system you have to rely on like a fire fighting inlet system. Copper was first used back in the 1700's as an anti fouling material. It does keep down the growth of algae.

Thanks very much both of you!. Further clarification: I use a closed loop for the engine cooling (ethylene glycol for the -35*C weather), and the sea water side of that loop is raw unfiltered (you can't filter out small animals) sea water at 3-4 barg at 750 litres/min. The sea water carries small bits of animals and veggie growth. The firewater pumps that just sit in sea water waiting to start up some day, for example, are full of barnacles and the 16 inch pipe reduced to 3-4 inches from growth. And the heat exchangers that are not running when equipment is switched off, sit for months and things grow inside if you don't drain them and blow them down. I'm an equipment expert, not a offshore process expert, so, I was hoping someone had exact experience designing such things working for engineering firms that design offshore platforms and such. Maybe a sea chest system with dosing of hypochlorite, or UV lights . . . ???? I too far out of my element to know.

Thanks again !

I read somewhere years ago that the larvae of these little beasties cannot settle if the fluid velocity is above a certain level. Once settled they can filter feed and grow quite well, as you know. It is possible that if you can find this velocity and actively maintain enough water through the pipes to be well above this velocity 24/7.??

Another method is the chlorine slug once/day that will kill the nascent beasties. Chlorine not being a toxin like tin can be used as long as the rate is low. The slug passes down the pipe and does the job.

Some marine fouling people should be able to enswer this? or do they guard their knowledge for fee charging encounters?

yeap my friend

yous could try with CATHELCO MODULES UNITS..

THIS MODULE CONTROL MARINE GROW, BYA MEANS OF A SMALL CURRENTE APPLIED ON CATODES ZINC AND ALUMINIUM. DEPEND MARIN GROWTH OR CORROSION.

THEY CALLED MG, AND TC.

IS A GOOD SYSTEM, ACTUALLY I AM WORKIN IN AR SEMI SUMERGIBLE VESSESL WHERE WE HAVE THIS SYSTEM..

HAVE A GOOD ONE.

EL TEHUANO

Thank you. Can you end some links to web sites of the system you have tried? I found only one, but I'm sure there must be more. Maybe I spelled something wrong in Google ??!! Thanks again.

years ago I worked on a system for sterilsing bilge water on international ships to prevent unwanted lifeforms if foreign harbours.

that system worked by pumping the water through the boiler before dumping it. the hot water kills the bugs.

We later modified it to reverse the flow to clean the hips inlet pipes. This process had a second step of blowing high pressure steam into the water filled pipes a few days later. This removed all teh dead debrie stuck to the pipe walls. Can't leave it too long between flushes or the rubbish blocks the pipes and the expanding steam blows the pipes apart. Otherwise system worked really well.

another addition was to polish and hot wax the pipe interior. It didn't stop the growth but it made the barnacles come off easier!

Cheers

another 'boat' thought...

many vessels run the heat exchangers external to the hull, (one coil immersed directly in the water. This saves the entire seawater circuit and the crap on the pipes doesn't reduce the cooling significantly as the heat kills it off, there is no 'flow' to restrict AND it is largely heat transparent anyway. In addition, the seawater isn't going to freeze in the pipes. You can run straight pipes between piles with huge gaps for eventual cleaning.

Good Luck.

Copper nickel pipe works well to prevent bio-fouling in marine systems. For suppression, copper anodes or chlorine producing anodes work will also. I think US Filter makes some type of marine growth suppression system.

See CAPAC -http://www.usfilter.com/en/Product+Lines/Electrocatalytic_Products/

George,

Contact Pete Hellwig at Mariners Choice, 904-425-1234,

marinerschoicecorp.com....

ecologically friendly acid replacement for marine cooling systems...

Bob

read the information that the Royal navy has on this subject, they they have been dealing with that problem for centurys now.

http://www.google.com/search?hl=en&sa=X&oi=spell&resnum=1&ct=result&cd=1&q=+Cathelco&spell=1

Thanks !

George,

What is your constant flow rate? and what do you expect it to be with fire pumps on?

Wangito.

Wangito

I'll have about 1000 gpm (3785 l / min or 3.785 m^3 / min) in a loop that I need to design so maybe 8-10" pipe and the take offs to each heat exchanger for each engine will be about 4" pipe at 250 gpm each leg through a double pass shell & tube heat exchanger, tube side. The shell side is closed with antifreeze to the diesel engine. No FW pumps are involved, that was just an example of another problem on this same rig that was amazing to see how blocked things can get from beasties! Flow rates above 2-3 metres / sec (I've been told) keep critters from grabbing on to pipes and such, but I'll have some circuits at zero flow when equipment is off, or, redundant lift pumps are submerged in sea water.

No hypochlorite treatment is allowed due to environmental reasons and other caustic type paints are not allowed for the same reason. I see a few 'electrical' solutions via Google hits but I need to know if someone is using these in practice with years of success in my similar duty. This is not a boat or yacht where if I make a mistake, there is an angry owner and we do something else, this is an entire off shore platform that is converting to air blast coolers since we cannot use hypochlorite any longer and all the sea water pipes are blocked now. To change over to air blast coolers is difficult with ice, snow, wind, ducting, noise, space, piping, aux pumps, etc etc etc.

Thanks for the note.

George

Hmmm...

You've got a problem on your hands...

Assuming that solids are not a problem and Ignoring the fire pumps, as you have said that they are not a problem here, and due to relatively high flow rates, Chemical treatments even if they were legal, would be difficult to apply and VERY expensive. The first step to take, is to have the pump intake as DEEP as possible. If you can reach depth of at least 500' or more it will reduce your algae growth significantly, if you can take it from 1000' or more you might have none at all. The very low TDO₂ at these depth and the lower temp will help in corrosion protection and better heat losses. Trick is, Keep Oxygen out, and temperatures low.

It is a serious undertaking. If I were you, the first thing I would do, is take water samples from varying depths measure total dissolved Oxygen, And in a lab run some tests to study the flora/fauna. And with the help of a marine biologist take it from there. Life from these depths wouldn't survive when brought to or near sea level. Your biggest enemy here are still water. you should find a way to continuously circulate some (?) water through the system at all times. Pumps are another problem but not a very difficult one. SS/ submersible pumps with bronze impellers are almost maintenance free and will last relatively long time. Problem is to install them. They must be anchored together with the discharge pipes at the bottom. and be left in suspension at all pumping rates. And about a zillion more details...

My 2 cents..

Wangito.

Thanks. I'm in 40 m of water so plenty of O2 there. As there are hundreds of platforms around the world taking sea water for cooling I'm trying to find people with experience at doing this without caustic chemicals, and there were 3 links on these posts that look promising for technology. Now, to find someone who is using this technology at my flow rates for 1-2 years and without problems is a different story. I'm waiting for replies from 3-4 companies that I learned about thanks to the kindness of people on CR-4. No replies as yet, but in one more rotation of time zones I'm sure things will pop.

George

At the Monterey Bay Aquarium they have an extra water intake pipe. When the pipe in use clogs to a certain point, they switch to the back-up pipe and cap the clogged one. The capped pipe goes anaerobic and, what was growing dies out.

You're right. We do the same where I work. By shutting off one intake line, the water stagnates, the suspended solids in the water decompose and create hydrogen sulphide (H2S) which kills the biological life in the water. When flushing out the line the water is black and smells of rotten eggs. H2S is toxic to humans too and I've been told that when you can smell it you are OK but it can smell of nothing and if you are in an enclosed area you can die from over exposure.

We also use UV sterilisers and while these are good at killing off micro organisms they are not 100% and you still get build up in the pipes. For the system talked about here I would not recommend spending money on UV's cos they only work if you have filtered water. With raw sea water there are too many nooks and crannies for the little beasties to hide in till they are past the UVC. If you are wondering we filter to 1 micron nominal.

Thanks - Appreciate the affirmation! Cheers!

Thanks all for comments. It is difficult situation environmentally. I can't shut in one circuit since building totally redundant circuits is space and cost prohibitive. This is an offshore platform with only X quantity of beds (warm bed rotation) and life boats so if projects during revamp take X days = X beds = X life boat loads they just prioritise projects and my 'double loop' gets scrubbed from the program. Good idea though. I'll think of a loop to a loop concept and may build a short sweet redundant first loop only 200 m long, and use that to cool a closed treated fresh water loop that goes throughout the rig an into the other heat exchangers here and there. Hmmm. Then what to do with H2S 'black water' full of dead beasties. I wonder if the environmentalists would see this back washing of black water as fouling the environment even if done only 2 x a year. Maybe I can back wash to my black water tanks on the rig and haul it away or treat it as we do now. Hmmmm. Thanks

Would you like to contact me regarding a potential resolve to your fouling problem?

I guarantee copper bands work the best for the least effort and money.

If there is little or no circulation in the pipes for any amount of time you will have growth. Copper is good if you have enough. Marine applications use copper in anti fouling paints for vessels...

Does not work as well as TBT.....Tri-Butal Tin..which is outlawed for all but military ...it was the best....

We have been using Muriatic acid in a reduced solution to remove grasses, mussels, etc..from A/c raw water cooling pipes...

The new fix all is an acid replacement that is ECo-friendly...this stuff dissolves calcium on contact...AND you can put your hand in it...NO PROBLEMS...

Give Peter Hellwig a call...in previous thread...

Maybe an option for part of your problem is to use a pig to scrape the insides of pipes. I believe some aquariums use them. I imagine there is potential for one to get stuck, though. It is another possible consideration.

Good idea and thanks, but not practical in the exact situation as pumps and heat exchangers, hundreds of elbows and joints are involved in the loop. It only takes one little 'un-pigged' section to block it up, plus debris from pigging would be an issues rattling down through heat exchangers. But, thanks for the note. Good idea if we had straight pipe!

Just another thought. Can you flush the line with fresh water from time to time. Most organisms which live in sea water cannot survive in fresh water due to the differing salt levels and reverse osmosis.

It has been found that the marine larvae are unable to settle on the pipe if the water is flowing above a certain velocity, so if this piping can be kept running 24/7 above that speed the adherence of the larval forms is prevented.

They have used bubble curtains to help with this on stationary ships, as the larvae do not settle on ships in motions - most ships spend some stationary time at various places - and once they have colonized the ship - motion will not dislodge them - it just feeds them.

I have used bubble curtains as well for heat exchangers with amazing results. I've been able to keep systems from fouling for close to 4 years.

Chemcal cleaning using GOTAR Technologies products would remove growth, scale and buildup in piping and heat exchangers. periodic cleaning could keep things cleaned well. more info can be found at www.gotar.com or email me at jstefanowicz@gotar.com

I can provide you chemicals and expertise to remove organic marine growth in the piping systems going to the diesels. it would remove soft marine growth with a GOTAR DG-500 and remove scaling or barnacles using GOTAR D-500.....removal of the growth would entail a chemical loop flush cleaning the piping systems and heat exchangers in the piping system.... email me ...jstefanowicz@gotar.com

Dear,

I would like to answer your question in two parts.

1. Sea water Marine growth prevention.

When we are talking about offshore conditions or offshore platforms, mostly sea water will be used for Well fluid cooler. To avoid the marine growth in the stand by pump (considering working & stand by pumps are connected to common header.). General practice in the offshore is to provide the hypochlorite injection piping below the suction strainer (hard / flexible piping running inside the caisson) of the working pump as well as stand by pump (at least 1m below the strainer. Manufacturer's recommendation is required to avoid the ingress of air bubbles in the pump). All standard manufacturer's will provide the same like DMW, CLYDEUNION, Hayword-Taylor etc.

Now when you are talking about the fire water pumps; it will be having separate injection system like oxygen scavenging & bactericide preventor because these circuits will be operated maximum 52Hrs in a year so separate injection is required. I hope you know that fire water headers shall be always pressurised by sea water stream supplied either by sea water lift pump or utility water pump or any other pump called as a jockey pump. In case of SWLP & UWP will have hypochlorite injection system.

2. Sea water usage for cooling.

In case you are using sea water for other HE's like pump seal plan, cooling jackets etc. you are suggested to have separate cooling system with potable water.