Mesh For Sea Water Suction Line

If you Google "bronze screening" you can find many suppliers. Some of them might not be located nearby, but would be able to ship anywhere. Stainless 316 would be a good material, and there may be others, but you still may need to order from afar.

304 stainless?

Glassfibre reinforced plastic?

Oak?

Choose your screen materials acording to the suction hose material. If this is fire (fighting) water then it will be used only occasionally but electrolytic corrosion will be working 24/7.

if it is to be fine enough to stop sand then it will need to be a very fine screen and thus a very large area to avoid an unacceptable pressure drop across the screen.

saludos

Capblanc

Ask around for what other people are using for anti-fouling in your area. Boats and businesses using seawater will be able to tell you what works for the sea life you will encounter. Usually any object submerged in the sea becomes a habitat. Coral, seaweed, sea sponges, sea squirts, sea moss, etc. will attach all over your screen.

I would consider using just an over-sized copper pipe for the submerged suction pipe. Sea life doesn't like copper. Then have a huge suction filter at the pump to catch what has grown in your pipe, which will get sucked down the line when the fire pump operates.

Once the pipe has been cleared of the growth, you will have unimpeded flow to the pump. I can not think of any screen that will not run the chance of being clogged when you go to use it after being submerged for a while.

Even a screen will not keep sea life from attaching to the inside of the pipe, or screen, as it enters as a microscopic seed.

I don't think normal stainless steel works well for seawater application. Maybe only SS904L or duplex SS.

How about considering plastic, like PP or PVC?

Exactly; normal stainless steel will corrode within few weeks. You need to use Super Duplex (SAF 2507 or UNS32750) not JUST duplex. This will be much expensive but will work. Best and cheapest is to use plastic - PVC, PP or FRP.

Either use Bronze if it is available or 316 St Stl., go by the price.

304 St Stl in 10% NaCl has a corrosion rate of less than 0.0007 "/yr but has does it with "worm hole" type corrosion.

316 St Stl in same has a corrosion rate of < 0.0001"/yr without the "worm hole" type corrosion.

I have a 50 yr old sailboat with a 45 yr old 316 St Stl centerboard in it that is immersed 6 months/yr is salt water and it has no corrosion at all on it.

In my professional career in the chemical industry we always used 316 when using a metal for salt water.

Good Luck, Old Salt

Old Salt knows what he's talking about. 316 SS fittings work fine in salt water applications where duty is not 24/7 or in waterline or splash zone locations. And of all materials you have a high liklehood of finding the right screen mesh and wire size for your application in 316 SS and at a good price.

Ed Weldon

Agreed 100%. As long as this is not a round the clock operation as you have specified that it is not, the 316 SS wire mesh should be fine. As far as finding the correct wire diameter and opening sizes in the screen mesh. I would search the net, including several manufacturing sources, may want to check with Mcnichols or http://www.bwire.com/ and also check out Mcmaster Carr.

All these sites have photos of the mesh and I think Bellevill will even send you some samples to take a look at before purchasing.

All the best -

Jack

just beware of interfacing SST with dissimilar metals in seawater.

firebreglass mesh, and as noted it should be over a large box / entry section to avoid suction issues.

Hi,

My background is in desalination, and we use sea water intake systems to draw feed water for the desal plants.

Some common SW intakes are as follows ...

Vertical Beach Wells – Vertical beach wells are shallow intake wells that make use of beach sand or other geologic structure as a filter medium. They have the advantage of delivering "pre-filtered" water that may greatly reduce additional filtration requirements.

Cylindrical Gravel Pack – Provides a very rough filtration / distribution of flow.

Metal Screen – manufactured of Super Duplex (SAF2507) typically 3-6mm holes/slots.

All of these need to be well designed to prevent NPSH problems with the feed pump. The gravel pack and metal screen will eventually clog with bio growth. This growth can be tempered, with Air Scour of the screen (properly designed this can work very well). For it's simplicity the vertical beach well, is the simplest and easiest system (however it becomes harder to design with larger water flow requirements).

To prevent biological growth in your intake line, I suggest periodic chlorine dosing (at low level), with irregular shock dosing to discourage biological growth.

Hope this helps.

Anthony

Hi clperera,

I found the cheapest (and possibly the best) is a plastic drum (size to suit)
with small 5mm holes drilled all around it, about 50 mm apart. (yes, a lot of holes)
starting approx. 300mm above the base. (which also has no holes.)

The hose is fixed at the top (one end) of the drum and the base, which is
solid (no holes) can sit on the sea/lake floor without collecting sediment or weeds.

If anything is drawn into my home made filter, it has to be smaller than 5mm, and
most hoses/pumps can cope with this. In practice, very little gets into the drum,
which can be opened (at the hose end) and emptied of debris if necessary.

This is very cost effective (apart from the little time to make it) and the filter can
be easily and cheaply replaced with a copy, perhaps of improved design.
(but mine works ok.)

In an earlier model I made a small wooded surround (case) to protect the plastic
drum, but it was not really necessary, and just made handling the hose awkward.
My best model was detachable from the hose, and I did think of selling them,
(as usual) but thought that there would not be a sufficiently large market.

Will send a drawing if you need one, but it's only a plastic drum with holes in!
Hope this helps. jt.

(If visiting the UK please try my new web site www.mycall.mobi, thank you.)

Appreciate everyones input. I think I have received the answer. Thank you all of you.

vortex filters

like the dyson cyclone vacume cleaners

http://www.google.co.uk/search?q=vortex+filtering&sourceid=ie7&rls=com.microsoft:en-US&ie=utf8&oe=utf8&rlz=1I7GPCK_enGB411&redir_esc=&ei=QBEuTbiHL8KKhQeY2smoCQ

Does it have to be submerged 24/7 or can it be set up to drop at time of use?

This way you cold use a less expensive material (plastic, Bronze) for the screen. Keep it supported near a splash zone and make it part of your daily maintenance to rinse it with fresh water. You would prevent microbe growth and reduce the corrosion factor and as previously posted it will not be come a habitat.

Install a quick release solenoid to drop it to the ocean for fire use.

Line is submerged in sea water

Angle the suction portion of the line up away from the sandy bottom. Install a copper/bronze/stainless flapper valve on the end of line (like that of a diesel trucks exhaust) or a gate valve that slides open at the lines pick up point, no suction strainer keep the line in free water and electronically energize the flapper/gate valve.

Install over sized strainers at the inlet to the fire pump's. No matter what you do under water regular maintenance must become a part of your daily routine so that would insure no growth over the valve.

I was trying to imagine some small fans made of a sand and salt type of material that continue circulating materials out,yet are unable to move water or maybe something simple resembling a revolving door or even an old water mill,there has to be plenty of data on those since they've been around so many years. connected at the mouth of the pipe.ds

Ajwinemaker has a good point. Submerge the screen below the sand, and sea life won't be able to grow on it. There are special pipes for this made of plastic. They have lots of slits in them to let in the water, but keep out the sand.

Another solution, expensive though, is to have a well put in. This will also keep sea life out of your intake. You can also go with a submersible pump, so there would not be a prime problem, the pump would always be ready.

If the bottom is very sandy you will have to elevate the pipe. I have done a lot of underwater repairs on these and on intakes on ships. On ships the gratings are just made of steel with good underwater coatings and zinc anodes. You want your underwater grating to stop your bigger debris and filters topside that are easily cleaned you can get dual filters so you can change one without disrupting flow. Underwater you would want a long elevated perforated pipe, a dead end or small screen could easily be clogged. I may still have some plans from some that we have inspected or worked on. Another thing you could do is install jet nozzles around intakes to blast sand away keeping intake clear

Appreciate evryone's input which have been very encouraging and useful. apologize for not replying to individual replies.