Sea Water Service Pipeline, 316L? 3

[mufasa1]

I am a mechanical engineer at a large petrocehemical complex in Turkey. We are located on the seaside and we have decided to feed our fire water pipeline with sea water during an emergency such as lack of fresh water or very low fresh water pressure. In the project the suction line from sea to the main collector (serving three centrifugal pumps) is about 50m long. What kind of material is appropriate for the suction line? It will be full of sea water at all times. Is 316L OK? We do not want to have corrosion problem in the near future.

 

[ENC]

Dear Mufasa,
I am working on a project in Mexico which uses seawater as the cooling media. There are several materials that can be used but few are perfect. The original design engineers used carbon steel piping which holds up well with the proper coating system and a cathodic protection system. We also used 316L in areas of the facility. However, 316L will pit from under deposit corrosion yet it can also be cathodically protected. I would not consider 316L in the application that you describe. I would consider several other materials depending upon the service pressures, line diameters and technical skill of the contractors in the area. I would consider the following, in no particular order

Carbon Steel with a protective coating system and cathodic protection system

Cement piping

HDPE piping

Ductile Iron piping with a coating system

I will be publishing a paper on design guidlines for seawater piping systems shortly. Would you like a copy?

 

[mufasa1]

Thanks, ENC. Appreciate the feedback. I will be glad to receive a copy of your paper. Yesterday I found a related paper on the net. You can check it out. It is,

"Materials Selection for High Reliability Seawater Systems"
Brian Todd, Consultant to Nickel Development Institute.

I found the article very helpful, but the materials suitable for high reliability seawater systems such as 10/90 CUNI or 254SMO need higher initial investment.

For our system we may go for coated carbon steel. In this case what can we do for couple valves on the line? What do you think about plastic lining (polyethlene or whatever ..)?

 

[ENC]

Mufasa,
I you go with coated carbon steel, you should make sure there is a cathodic protection system installed, because the coating will get small surface cracks. Most common is carbon steel with an outside surface of cement to protect the metal.

The valves should be installed above ground and a good valve is the BRAY Valve make with rubber lining and DI disk coated with Nylon 11. These are used in seawater service and mud slurries.

You should check the quality of the water. If storms in the area create high suspended solids, then abrasion may become an issue and determine the final coating selection.

If this is for period service such as a fire system it may be fine.

 

[rustbuster1]

If you bought a sai boat, you would probably be very well advised to buy one made of Fiberglass reinforced Plastic (FRP).

This is a good indicator that you should give serious consideration to FRP pipe (there also is sand-filled resin pipe made by Hobas) because it is immune from corrosion inside and out and has no problem handling seawater up to 75C (you won't go that high, I know). You do not mention sizes but this can be obtained in almost any size up to 1 meter. You should decide how t you will do the joints and then do a cyclic hydro test to verify good joint quality. There are many web sites with helpful information on FRP pipe. Second choice could be UHMW PE pipe, for many of the same reasons. This is in wide use as ocean outfall piping and as sheathing for vertical pilings in marine service. Metals will just be too costly if you want intrinsic corrosion resistance and require too much checking and maintenance if you rely on protective coatings.

Happy piping!

 

[mufasa1]

Thanks guys,
forgot to write the location of the paper.

marine.copper.org/2-toc.html

 

Don't waste your time and money.The best coating near or in saltwater is pure Aluminum or Zinc over carbon steel etc. A metallized coating of Alum or Zinc act as a barrier plus an inhibitor, while providing electrolytic protection. In 1974 the AWS completed its test and has over 20 plus years of test of both material in saltwater with no problems at all. Overtime the cost is lower because of no maint. If you have any questions about this type of service contact me a knorris@hvof.com ,Good Luck.

 

[takoot]

We're doing a project for a client that has more than 30 years experience in handling Dead Sea brine (10 time more concentrated than normal sea water). We're using caoted carbon steel with CP, which proofs ENC 100% right. We're also using Titanium Gr.2 and 7 wherever the brine temp goes beyond 90 deg C. FRP is excelent but due to its high cost we're replacing it with cement lined ductile iron whenever possible. However, for the storage of two end products (CaBr2 and NaBr), we're using SS304. I used to think that NaBr forms most of the brine content!!!??? Anyway, my question is: what exactly happens to SS in sea water service? is it stress corrosion craking? does chlorides contents have anything to do with this?

I appreciate a briefing. ENC, I would like a copy of your paper. Thanks

 

[stanier]

In respect of this topic one should be careful with the design of FRP pipelines as this material has a lower strain tolerance than other materials. The product mentioned admittedly is a sand filled resin however the reinforcement is random orientated chopped glass filaments.

A risk assessment must be made as to the consequences and likelihood of any events when selecting materials.

Another material you consider that has been successfuly employed on sea water is ABS. refer

http://www.eurapipe.com.au

for details.

 

[mufasa1]

I have started the same thread also at the following forum.

Mechanical Engineers Area - Piping & fluid mechanics engineering Forum

There are other views for the same question..

 

[rustbuster1]

It is not responsible to make throwaway statements like "FRP is excelent but due to its high cost we're replacing it with cement lined ductile iron whenever possible." Properly made FRP pipe is not "high cost" when you consider all the additional components that must be applied internally and externally for ferrous materials like cement-lined ductile iron or coated steel. The primary appeal should be to achieve lowest "Total cost" which includes inspection and maintenance costs. I have no axe to grind for any particular material. I 've just been regularly disappointed with the long-term performance of coated steel or other internally lined pipe.

 

[Pommy]

All 300 series are not suitable for sea water because they are susceptible to Cl Stress corrosion cracking and Cl pitting. If I were you I will consider cost between the following options which have just about the same performance in sea water:-
1. Cement Motar lined CS pipe
2. HDPE lined CS pipe
3. HDPE pipe
4. FRP pipe

However if HDPE or FRP is selected, you have to consider about pump incase of fire because if there is a fire HDPE and FRP will not last very long and can do great damage to your pumps.

Hope this helps...

 

[joeswoes]

For your valves, go to

http://www.pureflex.com,

fully lined composite butterfly valves