Rubber-Lined Valves for Sea Water Service
Rubber-Lined Valves for Sea Water Service
(OP)
We continually have reliability problems with industrial-grade, rubber-lined butterfly valves that we use for onstream isolation of our cooling water (sea water)exchangers. We have tried them all --- Crane Centerline, Keystone, etc. We need to be able to find a source for this type of valve (or perhaps an alternate valve type) that we can rely on for both high reliability AND on-the-shelf availability. I am considering trying-out some rubber-lined knife gate valves that are apparently used for corrosive slurry applications. Does ANYONE have any suggestions? This has been a long-term problem at our plant. Thanks for your cooperation!





RE: Rubber-Lined Valves for Sea Water Service
may I ask what kind of "reliability problems" did you have? Did you try to analize the root causes?
And... why "rubber-lined" only?
Perhaps switching to much higher reliability and longer useful life durations (e.g.: with metal seated valves) may justify higher costs and make the on-the-shelf availability requirement superfluos...?
Thanks and Regards, 'NGL
RE: Rubber-Lined Valves for Sea Water Service
Some butterfly valves with buna-N lining and seats had swelling of the rubber so that the valves could not shutoff. Replacement valves with EPDM rubber seats appear to have better life. Other butterfly valves with metallic disk (AL-BRZ, or 316SS epoxy coated) with the EPDM seats are also being tried.
Supposedly some epoxy FRP valves are in seawater service, and the unique feature about them is a fire-test rating(!) for oil production platform firewater installations.
wwww.advalve.com
RE: Rubber-Lined Valves for Sea Water Service
RE: Rubber-Lined Valves for Sea Water Service
I suppose you could go down to your local marine supply store and buy some zinc anodes to bolt to the discs for galvanic protection.
If the pressure is low and the seawater is laden with sand, valve companies may optionally reduce the diameter of the disc a bit. An "undercut" disc carries a lower shutoff pressure rating, but does not scrub the sand against the liner as forcefully, so it lives thru a greater number of cycles.
We can speculate all day. Both Gerhardl and Anegri have asked about the specifics of the reliability problems.
What's going wrong, and what's your pressure, flowrate, temperature, and particulate load?
RE: Rubber-Lined Valves for Sea Water Service
RE: Rubber-Lined Valves for Sea Water Service
Valve internals in contact with the river water (body, stems, seats, discs, etc.) shall be
internally coated with two (2) coats of coal tar epoxy to a minimum dry film thickness of
20 mils.
Any comments??
RE: Rubber-Lined Valves for Sea Water Service
I pulled this up from the epoxyproducts.com website:
"Coal tar epoxies are essentially a mix of coal tar and epoxy resins (and not all epoxy resins are the same). Coal tar epoxies were at their peak of popularity in the 1960's (???) through about 1990. After that, non-coal tar epoxies replaced coal tar epoxies due largely to health concerns over long term exposure and direct contact (by coating applicators) to the 'tar'."
I would not think that the sealing edge of the disc would maintain a coating of CTE after a few cycles.
RE: Rubber-Lined Valves for Sea Water Service
These materials are used in desalination plants.
For high pressure aplications the body can be in super duplex also.
If you do specifiy super duplex use ASTM A995 gr 5A or 6A as it requires more testing at the foundry.
RE: Rubber-Lined Valves for Sea Water Service
C. Valve body shall be cast iron, ASTM A 126, class A or B, with extended neck to suit
insulation thickness.
D. Disc shall be cast iron or nickel alumnimum bronze.
E. Valve seat and stem (shaft) shall be nickel aluminum bronze.
I can get an oppportunity to talk with the specifying engineer to recommend better, newer, more economical and/or long lasting solutions that may be advantageous to the end user (and me if I get to sell this stuff!)
RE: Rubber-Lined Valves for Sea Water Service
From my experience, following:
1. International companies in the cooling business tends to choose cheapest possible 'standard solution acceptable valves' and could end up with standard wafer or U-flange type elastic lined, centric butterfly valves.
2. Note: Operation could require different operational modes from the valve, involving at least two-step emergency closing and different throtteling situations, and again have or give requirement for hydraulic, electro-hydraulic or pure electric control operation.
3. If yes to point two: beware of possible cavitation by throtteling, and water speed plus general torque requirements. Weakness for centric valve type is as given by others: increasing torque when swelling and agening of sealing.
4. Materials: stem and stem sealing details super duplex and seawater resistent stem seals, solid construction for longitudal firm positioning, stem construction overdimensioned for torque and at least solid key positioning of disc.
5. Alternative valve construction to improve expected lifetime: double eccentric, double flanged, with seat ring either acceptable ring material walzed into housing or none, against a hard wallcoating itself. Plus for double eccentric valves: no rubber-sticking disc, sealing ring placed on disc and almost plan-parallell closing and opening of disc the first few degrees. Disc free of seat already at the first 2-3 degrees opening.
6. Housing inner coating: modern plastic based more easily accessible and perhaps as good or better/cheaper than older rubber lining. Different types available: enamel 8glass based surface), or probably better for abrasiveness (shell and sand in cooling water) EPC (epoxy ceramics, good resistance to abrasiveness) are available. If enamel is acceptable towards existing degree of abrasivenss the valve does not need a walzed in seat. EPC and seating: unknown but seating ring super duplex could probalby be done.
7. Note: abrasiveness of coastal seawater by sand and shells is often underestimated, storms and floods can stir up and fill water intake area with lots of hard particles, not easily filtered or felled.
8. Erhard, Tyco Waterworks, Germany, among others, can offer this type of double eccentric valves for seawater in different pressure classes, unknown if other than European standard flanges can be offered.
Good luck!
RE: Rubber-Lined Valves for Sea Water Service
RE: Rubber-Lined Valves for Sea Water Service
Regards to All, 'NGL
RE: Rubber-Lined Valves for Sea Water Service
RE: Rubber-Lined Valves for Sea Water Service
Other links and references about this kind of valve are listed in thread408-190488: 4 offset Butterfly Valves ( Quadruple Eccentric ).
Hope this helps, 'NGL