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Old 07-07-2013, 16:23   #16
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Re: Yanmar SD20 Kingston Seacock raw water valves

Thanks for all the help and info.

I think we will go with DZR brass or bronze, depending on what is available locally (in Tahiti). I think either is a bit better than SS with the aluminum, and I tend to be on the conservative side with this. Prices are similar for all three materials.

Have to figure out what type of pipe dope we should use, or ask around. I don't think using both tape and dope is normally done, seems it is advised to use one or the other. Seems the thicker the better based on the two installs discussed here.

Since they are tapered threads, and seal from the threads more then the dope or tape, I wonder about using tape, and then coating that in Tef-Gel to minimize any chance of corrosion. Just don't know if the Tef-Gel and teflon tape can live happily together.

I am pretty sure the threads are 1/2" BSP based on a post on another forum, for others looks for the correct parts.

Thanks again for the help, now to find the parts.
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Old 07-07-2013, 16:33   #17
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Re: Yanmar SD20 Kingston Seacock raw water valves

Let us know how it turns out.
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Old 17-07-2013, 12:27   #18
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Re: Yanmar SD20 Kingston Seacock raw water valves

Don't know if it will help, but there is a yard in oriental, NC - boatyard@deatonyachts.com - that may be of help. The owner John Deaton has worked on Yanmars for some 20 or thirty years, it's his specialty. I'm sure if you emailed him he'd respond promptly as to the thread type and best metal options. My guess is it's a tapered metric thread.

I think you'd be better off with a good thread sealant than tape or tape/thread combination. The metal threads tend to cut the tape exposing the metal. The sealant would tend to create a more even and consistent barrier.

Another option might be to put in a thread to barb elbow and have the valve insulated completely from the engine by way of the hoses. I'd use a very high quality hose between the engine and the valve. It would address the corrosion issue and mean that you weren't dependent on any specific threads for the valve especially where you're sailing.

Fair winds
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Old 17-07-2013, 13:34   #19
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Re: Yanmar SD20 Kingston Seacock raw water valves

Thanks.

I am waiting for an update from Torrenson Marine (from Yanmar), on the threads and the metal that is used in the OEM valves.

I am fairly certain the threads are 1/2" BSP based on a thread on another forum by someone who changed them with SS parts. Pretty much all pipe fittings are BSP (except in the U.S.).

I will probably go with DZR brass on our replacements, but am still waiting to hear back from Torrenson. Once I know more, will post it here.

Do agree with using thread sealant, think it will protect a bit better. On the existing OEM valves I have replaced, I always used tape, probably because that was what was used when I took them off the first time. I have a suspicion the OEM valves are DZR brass as well, but am hoping for confirmation from Yanmar.

I will email your contact as well to get his thoughts and re-post here as well.
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Old 17-07-2013, 19:45   #20
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Re: Yanmar SD20 Kingston Seacock raw water valves

It's amazing no one has a good answer to this issue.

Here is a link to the thread size info:

Saildrives?

It should be 1/2" BSP.

As far as material, still waiting for a response from Yanmar, but not expecting it to be honest. Seems Volvo folks have tried to find out the material on their's as well with no luck:

VP Saildrive- Seacock Material? [Archive] - Yachting and Boating World Forums

The reply I got back from John Deaton was:

"With respect to the ABYC standards, bronze or brass should not be in contact with aluminum in an underwater setting; with that, SS would be the best choice unless you could find an aluminum bodied valve in BSP."

Interesting, but does not jive with what is installed on most boat's SD's it seems (except some who have installed SS valves/fittings), and certainly not the OEM stuff from Yanmar or Volvo.

Wow, who would have thought this was all such a mystery.

As I find out more, I will share.
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Old 17-07-2013, 20:11   #21
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Re: Yanmar SD20 Kingston Seacock raw water valves

When you say, BSP you mean BSPT or BSPP? My guess is it's BSPT?

And isn't everything else on the Yanmar metric?

Sometimes you need to know the answer, before you can ask the question.

Again,

Fair Winds and best of luck on getting the right answers.
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Old 18-07-2013, 02:23   #22
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My understanding is that with BSP, the male thread is tapered and the female parallel. But I think that is all standard when you order BSP fittings. I am pretty sure that is the only way they come.

Also, John confirmed that he believes they are BSP as that is what Yanmar typically uses.
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Old 19-07-2013, 11:32   #23
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Re: Yanmar SD20 Kingston Seacock raw water valves

Kiltym -

First, you state, " John confirmed that he believes they are BSP as that is what Yanmar typically uses."

BSP (British Standard Pipe) is simply a set of thread standards. You need to know whether it is BSPP (British Standard Pipe Parallel) or BSPT (British Standard Pipe Tapered if you want a correct fit. What I've seen is that NPS is considered to be an acronym for National Pipe Standard when it is National Pipe STRAIGHT (all threads the same.). The British use the term PARALLEL to define all threads being the same. Tapered is tapered, where female threads start with a thread or two equal to the straight thread dimensions and then taper down and the male threads start small and taper up to the straight thread dimensions. All John is confirming is that it may be a BSP thread.

NPT: National Pipe Taper correspond to BSPT
NPS: National Pipe Straight correspond to BSPP

You stated, "My understanding is that with BSP, the male thread is tapered and the female parallel."

The answer to this is NO. BSPP (parallel) and BSPT (tapered) threads are not compatible and the same would be true for NPT and NPS threads.

And, YES the male BSPT fitting will thread into the BSPP female fitting. The reverse will not work. However, the male thread will have most likely only one or two BSPP threads at the back end of the fitting. Neither a good sealing option or thread purchase option, but it will work in a pinch.

Here's a thought, on the old Yanmar fitting/valve that screws into the engine block, was there a gasket or O-ring as part of the fitting? Or is there an internal shelf that will stop the male fitting. Or did you simply use some paste or tape on the threads and then screw it in till it stopped turning. If there is no shelf or O-ring/gasket as part of the original Yanmar valve/fitting assembly then the threads are most likely tapered. Most pipe threads are tapered if they have no compression gasket or o-ring. I very much doubt that Yanmar would use a female BSPP thread on the engine and a male BSPT thread on the valve/fitting. Just simply not good engineering.

Here’s some additional food for thought info.

I'm not an expert on BSP threads, but do know that the differences between NP and BSP do not effect the thread type, tapered or parallel. In other words, NPS (National Pipe Straight and BSPP (British Standard Pipe Parallel) have the same basic configuration and function. They all screw in till they bottom out, and their sealing quality is by a bottom or top compression, usually with an O ring or gasket. They are basically the same as the threads on a nut and bolt.

If you look at an NPS and BSPP set of threads you'll see that every thread is the same. If you put a caliper on them both the internal fitting surface and the thread peak surface would be parallel.

I call these threads "sloppy" when it comes to sealing. Again, all the sealing is done by top and bottom compression.

NPT (National Pipe Tapered) and BSPT (British Standard Pipe Tapered) are designed to seal, not by compression, but by the meshing of the threads with one another (with the help of a little paste or tape. Although, given the low pressures involved on most thru-hull related applications a paste or tape on a parallel thread will suffice.

A tapered thread is designed to thread in only so many turns before maximum sealing occurs. And should require only minimum sealant to achieve reasonably high pressure sealing. In fact, there is a form of tapered threads NPTF (National Pipe Tapered Fine) that is so close tolerance machined that it will seal with no sealant.

An NPT 1/2" tapered thread according to the ASTM standard should have 14 threads/inch and have a hand-tight engagement of 4.48 turns. The BSPT 1/2" threads will have a similar, but slightly different, set of specifications. In theory, you should get maximum sealing at a point just over the number of hand tight turns.

The BSPP female thread needs to accept 6.48 threads to get any real mechanical purchase; the 4.48 threads with a 3.20 inch length – the are in effect doing very little with regard to either mechanical purchase or sealing.
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Old 19-07-2013, 12:12   #24
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Re: Yanmar SD20 Kingston Seacock raw water valves

Thanks for all the clarification.

There is no O-Ring, only the threads seal, so I will assume it is BSPT. I guess my quick look online may have provided slightly wrong information. Have used tape before when changing them out, and all has been fine.

However, not to start an argument, but based on the links below to the products I ordered, I also assumed only the male threads were tapered since the male state BSPT and the female BSP. From Wikipedia (not that I believe everything I read here, but where I got some of my limited info).

British Standard Pipe - Wikipedia, the free encyclopedia

"These can be combined into two types of joints:
Jointing threads: These are pipe threads where pressure-tightness is made through the mating of two threads together. They always use a taper male thread, but can have either parallel or taper female threads. (International standards require all female threads to be parallel.)

Longscrew threads: These are parallel pipe threads used where a pressure-tight joint is achieved by the compression of a soft material (such as an o-ring seal or a washer) between the end face of the male thread and a socket or nipple face, with the tightening of a backnut."

So you stating they are not compatible (tapered and parallel), may not be correct and hence my comments from before.


Some feedback as well from people over the past 24 hours. I think this pretty much sums things up now.

From Mastry:

"I think you are correct my information tells me it is ½ BSP"

Also from Mastry:

"The material is brass."

From Torrenson;

"The metal used to make the 196420-02290 valve very likely is a brass alloy rather than bronze; while more noble than brass, bronze has certain properties which make it less suitable for manufacturing things like little valves out of it. Brass is easier, and still decent nobility-wise. ABYC doesn't like brass in underwater fittings, though - when subjected to a galvanic environment, brass can "bleed" out the component zinc, and can thereby become quite brittle. ABYC guys have nightmares about somebody's raw water intake seacock snapping off without warning because it got the zinc sucked out of it over time.

Stainless offers less opportunity for disaster, hence their rule. However, Yanmar chose brass, regardless of ABYC rules (which are guidelines, not law), for reasons probably entirely logical and defensible to them."

Note that using DZR brass avoids the "bleed" issue mentioned above, which is why I ordered DZR Brass (mostly available in Europe is seems).

I have ordered the following parts, for anyone else looking to replace these:

DZR CR Ball Valve Seacock (Note the product info at the bottom, BSP FEMALE PORTS)

DZR 1/2" Male Equal Nipple (Note the product info description, BSPTM (BSP Tapered Male))

The hose barb on the OEM part is 5/8". I could only find a straight barb that size, so if it is important to have 90 degree turn, will have to look elsewhere.

Hose Tail DZR 1/2" BSP to 16mm (Note the product info description, 1/2"BSPT MALE)
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Old 24-07-2013, 11:00   #25
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Re: Yanmar SD20 Kingston Seacock raw water valves

Mark,

I don’t consider your comments to be in anyway argumentative.
I really appreciate the dialogue and information, in particular the WIKI statement “They always use a taper male thread, but can have either parallel or taper female threads. (International standards require all female threads to be parallel.)” Especially, with regard to what ISO calls joining threads (BSPT or NPT). It forces me to think and I learn every time.

To be honest the ISO statement makes no sense to me. I tried to find the source of the original statement to see if it was an editing error. No luck one-way or the other.

My basic response is that I stand by my original statement.

“The answer to this is: NO. BSPP (parallel) and BSPT (tapered) threads are not compatible and the same would be true for NPT and NPS threads.

And, YES the male BSPT fitting will thread into the BSPP female fitting. The reverse will not work. However, the male thread will have most likely only one or two BSPP threads at the back end of the fitting. Neither a good sealing option or thread purchase option, but it will work in a pinch.”

The reason is simple. As I said the male BSPT part will screw into the BSPP female part easily. But the male part is then nothing more than a longscrew (BSPP) threaded part with the first .320” threads (4.5 threads) being BSPT. A ½” male BSPT fitting that has ½” of thread will have, approximately 4.5 tapered threads (BSPT) with an additional 1 or 2 parallel threads (BSPP).

Functionally, the male BSPT part becomes nothing more than a 2 threaded BSPP fitting. The 4.5 BSPT threads in this scenario have no real sealing or purchase value. Think of it as a set of lines, the female threaded part is a straight line (say 2”) and the male threads are a combination of a short straight ¼” line (the 2 BSPP threads) followed by a ¾” downward tapering line (the 4.5 BSPT threads). This combined line sets slightly below the straight line. In effect, you get none of the sealing qualities of the BSPT threads and marginal threaded capacity of the BSPP threads. What you do get is an unnecessary gap caused by the tapered BSPT and the BSPP threads.

You now come under the guidelines of “Longscrew or BSPP threads and they are: parallel pipe threads used where a pressure-tight joint is achieved by the compression of a soft material (such as an o-ring seal or a washer) between the end face of the male thread and a socket or nipple face”

If both your parts are tapered, then using tap or paste is a matter of choice. If you use tape, use as few wraps as possible, you want to try and not have the threads cut the tape. Parallel threads without a gasket probably a combination would be best. Paste wrapped with tape?

With a tapered/parallel joint the issue is really how to fill in the tapered/parallel gap without cutting the tape. Maybe a lot of paste on the tapered threads and 2 wraps of tape?

I understand the constraints that you’re under, especially where access to parts is difficult. And I’m sure you’re end product will work just fine. I felt I had to comment on the ISO statement about using BSPP and BSPT threaded parts. My position is simply parallel with parallel, tapered with tapered whenever possible and know the function of each.

Fair winds,

Jed
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