Valves on steel hull?
OK, I have the oldest Feadship afloat, she is 56' and built in 1952, powered by twin Detroit 6-71's.
When she was built they welded steel pipe to the hull, threaded the end and screwed on steel valves. Needless to say that over the years many have siezed and are inoperable, others have corroded where the threads are on the pipe and have broken off in my hand. (I have been restoring her for 2 years now and any valve that would not open easily I waited to test until I was hauled, there I broke 4).
In replacing them I have the following options:
1) Weld a new mild steel nipple to the hull and screw a bronze valve to it
-dissimilar metals below water
a) Same but with a SS nipple welded to the hull
2)Weld a new mild steel nipple to the hull and screw a SS valve to it
- dissimilar metals below water
-when sitting the water in the thru hull will lose all 02 content and the SS will suffer crevice corrosion.
a)Same but with a SS nipple welded to the hull
3)Weld a new mild steel nipple to the hull and screw a Marelon valve to it
- not a fan of plastic below the water line.
a)Same but with a SS nipple welded to the hull
4) Weld a pipe to the hull with a flange welded to the end and use a flanged valve.
a) the same but take care to isolate bolts as well
b) the same but connect the flange to the valve with a wire to insure bonding
5) Weld a pipe to the hull, weld a flange to the pipe, remove one face of a stainless valve and bolt it to the flange.
- crevice corrosion again
I have been reading and reading on this for about three months and still have no answer.
The vessel is fitted with an impressed current cathodic protection system (CAPAC).
I intend to paint the inside of the pipes attached to the hull with an eopxy paint before installing the valves.
What material pipe? Steel or SS?
What style? Threaded or flanged?
What material for the valve? SS, marelon or Bronze?
This question gets opsted many times but there never seems to be a clear answer
I dont like Stainless steel. It has some applications in plumbing but best to stay clear.
Welded on threaded nipples will work, but take up to much space , make installing the valve with the correct torque and at the correct angle troublesome and make future servicing a nightmare. Welded flanges with studs...set on a standpipe if required ..work well.
Repair the boat exactly like the boatbuilders built it...dont change anything. Well prepared and painted steel will last many many years.
thin walled Plastic or fibreglass tube inserts glued into the bore of the thru hull pipe will keep the steel bore from rust bleeding down the side of the hull and keep bottom paint gangs from scratching the epoxy primer off inside the pipe when chasing barnacles.
Nothing wrong with Marlon. Ive never used them on a big metal boat. I prefer Bronze valves that can be disassebled and serviced.
On Brigand Feadship had used steel pipe welded to the hull and threaded, onto these they screwed iron valves, mostly gate valves. Most have failed by jamming tha valve, others had corroded at the threads to the point where they leak or break off when the jammed valve is operated.
The issue with Bronze is that it will be in contact with the steel flange unless I isolate the bolts with sleves, even then it will be in contact with the steel via the seawater passing through the valve. Some articles I have read advise mechanically bonding the bronze to thye steel...
Ive been working with steel vessels for many years and have never had any galvanic problems with bronze valves installed on threaded steel nipples. It works. I just dont like them because they take to much space ,its hard to align the valve and difficult to unscrew and service downstream plumbing legs. . Flanges make the installation and service of plumbing easy. Flanges, because they rely on gaskets between valve and flange effectively isolate the different metals from metal to metal contact.
If youre doing a complete plumbing job you would be wise to check out the Georg Fischer or another plumbing suppliers catalogue, draw a plumbing layout, then contact them to put together a package. Down stream components are 90 percent of a plumbing refit. PPR tubing and fittings are widely used in the marine industry. As for stainless, I only see it used on the sea chest construction .
I understand the use of flanges and am a welder and own a fab shop. Simple gaskets will not isdolate the metals, the bolts connecting the flanges conduct unless you line the bolt holes with non-conductive material and use non-conductive washers under the bolt and nut, or in the case of tapped threads, just between the bolt and flange and under the bolt head. Even if you do this the water passing through the fitting still contacts both metals. Dissimilar metals in water form a battery, isolating the metals in theory makes this worse and many think that the metals should actually be electricly bonded thereby reducing the current potential to zero...
Bronze is quite noble, mild steel is not, the bronze will slowly make the area that is threaded crystaline in structure. The real question is wheather or not I will still be alive by the time this happens.
I am not looking for a cheap or simple answer, I am looking for the right answer.
I am looking for the right answer.
Whatever you chose , exercise the valve once a month for longest life, and no surprises .
Marlon is fine .
Circuits' Piping - Manners to be fitted on Hull
Since the Auxiliaries were become absolutely necessary for a Ship to run, was born the issue of Piping maintenance.
A "Vector analysis" that will find answers to the issue should be based on sensitive subjects like:
Low Maintenance Cost.
The main factor that affects to "middle life" of piping instruments is the corrosion.
Corrosion appears as a matter of "what" is involved.
Analyzing the possibilities and the application causes we should refer some main points:
1. Where the pipes are installed (bilges - in or out of liquid bath / upper deck - touch or not the sea water spray / bulkheads - strain stress affected through the Hull elasticity , vibration , temperature lengthening) - Environmental Conditions which affect to the physical Properties.
2. The matter of Liquid that will be transfered inside. (Sea Water - Oil - Soft Water - Fuel - Bilge Liquids - Waste grey or black - High Pressure Oil - .....)
3. Temperature of transfered liquid and/or the difference against to environment temperature.
4. Speed of the transferred Liquid and the Sectional Velocity profile of its mass that should be ideal continuous or with low level of changes to avoid cavitation.
, and  are Operational Conditions which affect to physical properties
4. The existed Electric Current Density (J) to the Pipes' material structure, is detected through the measured Electric Potential Difference (V) between the Hull's Electric Charge and the Sea's one.
It is important to be mentioned that the Electric Current Flow to the Sea is a certain and continuous condition and at most is presented to the parts like pipes which are flowed in by Sea water.
Electric Field Interactive Conditions which affect to the material structure
Based to the Hull's Electric Isolation as an effect of special antifouling and anti corrosion paints (last fifteen years all of them ("green" paints) have been eliminated [Zn] into their composition) ; the Hull's Electric Charge couldn't be discharged to the Sea Water except through the Propeller's Surface and the internal Pipes' surfaces. Of course a low conductivity (σ) "Ground" Protection solves the Issue. This is applied through an Sea-Water immersed low Electric conductivity electrode (material: Al-Bronze) into Central Sea Water Injection Case. The Electrode is isolated to its based point on the Case and should have been connected by cable on it to any of machinery parts should be Electric discharged-protected (Pipes - machines - etc).
Following an Galvanic Current Protection like that we are able to choose install steel composed materials physically connected between them (welding - contact by fasteners - pressurized by circular joints - etc.....) at low damage's possibility.
Finally without compromise we can choose any material that affects to the highest resistance against other special conditional factors like:
Mechanical Stresses/Loads (AISI 316L or CuNiFe or Rubber Shore 60/80 with compound Net Steel Layers in Hydraulic Applications )
Thermal loads ( CuNiFe )
Chemical influences ( AISI 440 / 631)
Vibration ( PVC / Polyamide)
Fluid Cavitation (CuNiFe and Section Design that keep continuous the flow profile and constant the internal Diameter as far as is possible regarding to avoid turbulence because of small sectional dimensions compared to the flow vector and intercepts on the flow field when is divided or rejoined).
Mechanical or Electric Spark possibility on fuel pipes (Cu / Polyurethane)
and to be improved the Safety and the Maintenance durability.
If these are overboard lines I would use schedule 80 pipe with weld on flanges and flanged gate valves. Screw piping is no go in the workboat industry for overboard discharges/sea chests. For internal transfer piping you could use screw pipe and schedule 40. Also be sure to provide doublers where pipes penetrate the side shell and bulkheads/tank tops.
Nothing is perfect thus there is no perfect answer(solution). Consider the age of what you are removing and if it is acceptiable re install the same. I do agree with one common theme, no stainless where it will be emerged in water. Bronze mated with steel will last 20yrs. no prob. Before installing any plastic class of material check with your insurance co. first, you might be surprised on their outlook regarding melting and failure due to even a small fire. What ever you do, do a better job of welding than shown on Michaels post #2, I could be wrong but it looks like a bubble gum job in the photo. No offence Michael, I know this is not your boat or your work and is for illustration purposes only --Geo.
A yacht is not defined by the vessel but by the care and love of her owner.
I believe that you are correct and that there is no perfect solution. I am leaning toward the following:
Removal of all extraneous thru hull fittings
Replacement of existing ones with new pipe welded to the hull, flanged face, bronze valves.
While the bronze is more noble than the steel, the steel will be coated with epoxy paint, possibly lining the steel with plastic. The vessel is protected by a CAPAC system and unless something goes terribly wrong, corrosion should be kept to a minimum. Regualr excercise of the valves and annual inspections should show anny issues before they become serious.
The Illustration shows a steel "Hat" flange welded to a section of tube, the tube is welded to the hull, painted with epoxy paint completely, then I intend to coat the inside of the tube and the outside of a section of PVC pipe with 3M 5200 and install the pipe in the tube. In theory this will isolate the metals via coatings and will allow the inlet to be cleaned without damage to the coatings.
INexpensive, simple, repairable, limits corrosion, allows cleaning, eliminated plastic valves below the water line.
I wouldn't be at all concerned about galvanic action between the steel and the bronz.You have the Cadillac of corrosion control in your active system, overkill as far as steel and bronz interaction is concerned. a simple bolt on zinc would be more than ample. While the plastic liner is not needed it will have one good feature, being very smooth and slippery it will deter growth of those pesky little buggers disrupting a good flow of water. Yup good design. Is that your little ship in the photo, man thats just plain class. Thats what a power yacht should look like, I wouldn't even remove the RDF antenna, it just adds to the vision. I can hear the gurgling rumble of those big 671's ticking over at 1/4 speed just idling along with the bait out. If I ever go over to power it'll be this style. AAAhh, A smoking jacket, a good cigar, a glass of red wine, sitting on the fantale with the sun setting in the Keys, Look out Hemmingway i'm moving in.--- Burn a good rod (a nice artistic lay)---Geo.
A yacht is not defined by the vessel but by the care and love of her owner
Best practice is to use a flange or doubler on the hull skin side , with the intake tube protruding thru the hull skin.
The doubler flange need not be circular if space for welding is tight.
Best practice is to over size the flange to valve mounting holes and use plastic bushing to line these holes. Over size these flange holes so that when inserting the bushing you do not violate the epoxy paint system on the flange.
SS studs set in helicoils are used when space prohibits thru flange bolting.
Not big on stainless in areas where it will be deprived of 02, it tends to suffer crevice corrosion
The two bottom bolts were used to secure a rudder shoe on a vessel for 5 years, the bottom is stainless and the one above is obviously bronze.
Simply oversizing the flange hole is not enough as the head of the bolt will still contact the upper flange, I would need to use non-conductive washers below the head of the bolt as well...
" a simple bolt on zinc would be more than ample."
Not really, the electrical potential changes all the time, coatings decay, things get scratched, salt water vs fresh, speed of liquid across the hull, static charges, magnetic fields created by things in the vessel. Over-zincing will create a battery as will under-zincing. Now I know that people have been using zincs since I was but an itch in my fathers loins and that God made Zinc for a reason, and that you are saltier than Lot's wife and have sailed the 7 seas in a teacup, etc. But the fact is that steel boats in practice have a pretty limited lifespan. In commercial applications they haul all the time, hack a hole in the side of the boat, swap motors and fittings and weld the hull back up. The military hauls and replaces stuff constantly, divers plugging things from outside, repairs being made inside. The Cruise ship industry, military and commercial steel ships have quite short lifespans and most end up in Alang inside of 50 years, many in as little as 20.
When I first pulled Brigand the straps broke two 16" x 16" holes in her sides, s simple water trap had caused spaces to decay from the inside out, in other places I found crevice corrosion where a single spot of paint had been weak near the huge bronze wheels, it looked as though someone had taken a drill to the hull and made holes of varying depths and widths at random. She was zinced but not sufficiently and the PO had gone to the trouble to install a complete CAPAC system just as is used on oil rigs and submarine pipes - but they had never hooked it up! There it sat without the wires connected to the unit, rotting at anchor.
The only way to protect a steel boat is by doing everything possible to idiot-proof the protection, then accept that no matter how clever you are, nature will always create a newer, better, faster, idiot. Coatings, coatings, coatings, limit possible potential, limit exposed metals of any type and limit the possibility of charging the hull - then you get to check your neighbors boats and the marina as well. A hot dock can rot the outdrive mount off a I/O in a few weeks!
Is that your little ship in the photo, man thats just plain class. Thats what a power yacht should look like, I wouldn't even remove the RDF antenna, it just adds to the vision. I can hear the gurgling rumble of those big 671's ticking over at 1/4 speed just idling along with the bait out. If I ever go over to power it'll be this style. AAAhh, A smoking jacket, a good cigar, a glass of red wine, sitting on the fantale with the sun setting in the Keys, Look out Hemmingway i'm moving in.--- Burn a good rod (a nice artistic lay)
The vessel is "Brigand" and she is the oldest Feadship afloat, built in 1952 in Holland for A.J.Seamon as the baddest sportfisher ever made. The hull was designed as a patrol boat nd 4 such hulls were built, two were partol boats and vanished within a decade, the third was "Caprice" a bridgedeck cruiser "Deep sea Motor-yacht", she too is long gone. Brigand was based in NJ in the summer and Bimini in the winter. Seamon ordered a larger vessel and Brigand lay in Florida for some time as a corporate yacht then vanished for decades from the Coast Guard Register reappearing in Seattle where she lay for many years at the end of the dock at Rosario resort, again vanished only to reappear in a boat house on the Colombia where the PO purchased her. He did as little as possible and lost interest leaving her to lay in salt water untouched for better than a decade.
She came to me via a crooked Broker and Surveyor, I moved her 50 miles to Seattle only to find every thruhull frozen, few if any systems working, motors in need of complete rebuilds, miles of braided steel over lead over cotton insulated wiring, a windlass that fell to pieces when attempting to emergency anchor after losing both motors dropping a 200lb hook and about 75' of 3/8 chain, etc.
Unfortunately I, like you, fell in love with her and being a metal worker, diver, fab shop owner, mechanic, etc. I took her as a challenge and began. Had I known what I was in for I am sure I would have run screaming.
Pulled her and replaced 64 sq ft of steel below the water, painted her and splashed. Both motors were hard starts and smoked until warm but she ran. Found some lose planks on deck (1-1/4" Burmese teak over steel) and when I tried to re-bed them, the deck came up like a zipper with only tissue paper under. I cut it all out and replaced the steel, milled the teak and began reinstalling it. At this point i also cut off the hideous boxed wheelhouse and restored it to the original lines, stripped and finished all the bright house, rails, etc. Restored the coach roof, gutted the salon and about 6 trash cans filled with wire and started fresh. Along the way I have fallen even more in love with the style and rebuilt and/or restored as many of the original features as possible including a Sailor VHF, Westinghouse Air Compressor that looks like a BSA motor, vintage Iron Mike, etc. Everything looks period with modern materials hidden below.
The 6-71's were a refit to replace the Chrysler royals she left the ways with, this was done early in her life as they predate her. Probably war surplus originally destined for Landing Craft. I found again that the surveyor was a crook and both motors needed complete rebuilds which I am just now finishing - hence the need to address the thru hulls now.
Here she was two years ago
Notice the Skull and Crossbones on the maidenhead. A.J.Seamon was apperantly a "Bad Boy" at 60 and ordered her delivered with the custom maidenhead, flying the Jolly Roger and named "Brigand"
The object behind plastic bushings is to keep the fastening....bronze ,steel whatever you choose from, chipping, violating , the barrier coating of epoxy primer. On steel boats you must follow proper assemble techniques and never damage the paint coating. You will also use plastic washers under the steel washer. Steel fastenings are preferred but are hard to paint...hence SS. SS inside the boat is dry..and will not suffer. .
Examine the photo carefully. That thru hull flange installation has plastic bushings and washers, it is 17 years old and the paint has never...never... been renewed.
One tip I can pass on from working with Dutch built metal boats for the past 30 years is that all metal joints must be watertight. even on the inside of the boat. When you install a piece of equipment use best practice , then bond the joint with bedding compound. The joint must be waterproof or rust will form in the joint and its all over...the paint system has been ruined. . The bedding compounds used are...Sikaflex, Welcon or Teffgel paste. The pastes..tefgel or Welcon waterproof the joint and are used for joints that must be frequently serviced.
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