Safety Concern - Blow Off Valve

[JonRiley56]

Hi All,

I was out running my boat yesterday and pulled into a dock to take on water. (I am running on salt and my condensing system is not operational right now). I figured I would build steam while I was tied up but was confident that the safety would go if necessary.

I came back with my filled buckets, (I only had to go about 50 feet to the water source), and there was steam leaking from my water gauge, the water in the gauge was very turbulent, and the pressure was at 225 #.

My safety is set to blow at 150 psi and it did not go off. I dumped steam and added make up water to settle things down, but i was very unsettled that the safety did not blow.

I do not have anything between the safety and the boiler, I also made a point of buying a brand new safety valve rather than picking up a used on somewhere. I am pretty sure it is a kunkle.

Any ideas ? Do I just pull and replace the valve ? I have another port on my steam drum and after that episode I am thinking about adding another safety. I dont want that to happen again.

jon

[gondolier88]

Am I to understand you've been out with the boat in steam without actually testing the safety valve?

Greg

[JonRiley56]

Nope,

I ran it up to blow off at the beginning of the season and multiple times since. It has always worked before.

jon

[fredrosse]

I have experienced a safety valve not lifting at its setpoint, but only about 10% higher pressure and the valve then lifted. A 150 PSI safety valve not lifting until 225 PSI is very unusual. Pop the valve with the manual lever at 150 PSI, the valve should open fully, and reseat at a lower pressure, 130 - 140 PSI. Remove the valve and check that deposits have not clogged or otherwise fouled the valve.

Sometimes a valve with a slow leak will accumulate dissolved solids. This occurs when water laden with dissolved solids leaks past the valve seat, and immediately the water flashes to steam, leaving behind the solids. These residual deposits can often be very much like concrete, solid and strong. Periodic blowing of the valve will keep this from accumulating to the point where the valve no longer functions. On a steam boiler the safety valve should not be exposed to the boiler water, (should see steam only) but many are by high boiler levels, or general sloshing of water within the boiler.

Is it possible that the setting was tampered with? Safety valves should have a lock wire and lead seal to indicate that the settings have not changed.

Having two safety valves works OK, and certianly increases reliability of the relief function, but you should still confirm their function frequently.

[JonRiley56]

Hi Fred,

I ordered a replacement. I will see if I can figure out what is wrong with the current one, but for now I will have a new one that should be relaible. I will run it up to blow off the fisrst time I use it.

In the past I have seen some leaking by etc at about 125, not so this time.

jon

[barts]

After you're done with the yearly hydro, replace the safety valve, drain the water back to a normal level and then fire until the safety pops. Then, during the year, flip that little lever at the top of the safety when within 20 psi or so of popping to verify that it lifts properly.

- Bart

[JonRiley56]

Hi Bart,

So if my safety is set for 150, just pop the lever at 130 and make sure it lifts ?

jon

[DetroiTug]

Hi Jon,

I would advise purging the boiler repeatedly to get rid of loose rust. Fire it up and blow it down, add water, build pressure and blow down repeatedly. Do this over concrete, until the blow down is clear.

When I disassembled your Southworth pump in the spring there was a build up of rust sediment in the corners in the bottom of the steam cylinder as I mentioned in an email. A trace is to be expected, but it was excessive. And now the relief valve is not functioning properly, I'm betting that is the result of rust sediment contaminating the valve and binding it and rendering it inoperable which is unsafe to say the least. This is obviously not good for the engine as well.

In conversing with steam car folk, that is one of the issues with water tube boilers, they do not control sediment very well in comparison to a firetube which is much more stable due to it's less active higher reserve volume, sediment has a chance to settle for expulsion from blowing down. In the case of a monotube their saying is "Whatever goes in one end, comes out the other end"

-Ron

[Steamboat Mike]

I had this problem ten years ago. Safety set at 150, I left the boat for a few minutes to get wood, came back and the safety was wide open and a little noisier than usual. Just about fell off my perch when I saw that the pressure was at 225 on a 150psi boiler. I took it back to the distributor and before I could get past "This valve seems to have stu..." he had the offending valve out of my hand and yelled over his shoulder as he headed for the dark recesses of the stock room "Wouldja like a replacement?" We then had a brief conversation in which it was established that "this probably never happened". Shortly after this they came out with a curious notice that said these valves are safety valves and therefore should not be used to relieve steam. They are not suitable for solid fuel or manual control and should never be opened by the lift lever in spite of its name. They regard them as a safety device more like a fuse that is used once as the last resort than a circuit breaker that is designed to be used repeatedly. They recommend only going to 80% of opening pressure to prevent simmering and drooling. I have since heard that sticking is a problem with top guided safeties such as Kunkle and Conbraco. What Fred said makes complete sense. I feel the the fact that the valves are no longer made in Indiana but are assembled at various places from parts sourced all over the world can not help the situation very much. Three years ago I finally got rid of the Kunkle and got a Conbraco 29 series. The valve now weeps a tiny bit and yesterday it stuck closed for a 25 psi over pressure event. Kinda like the dog that bit you, you are always looking at them to see if they plan to do it again. I have been looking for a suitable Lunkenheimer bevel seat, bottom guided safety. All this being said I think safety valves are a maintenance item. In the days of steam railroads the boilers were washed at least every month or more often if needed. The first things to come off the boiler were the safties to be shipped to the home shops for overhaul. There was a giant fleet of valves so replacements were always available. Locomotive safties opened repeatedly and often loco was worked many hours a day. I am not sure what the answer is, I think two safties would be a start. It would give a favorable statistical boost to the probabilities of a positive boiler pressure outcome.

Best regards, Steamboat Mike

[JonRiley56]

Hey All,

My new valve from Mcmaster carr arrived yesterday. I will get it put on this weekend. What do I need to know as far as cleaning the "sticky one" goes. If I go after it with a wrench will it be obvious ?

Mike talks about different types of valves. Is there one type that is inherently more reliable than the others ? I do have a manual steam dump on my set up so I can release pressure without going through the safety. It is actually a neat old piece that will automatically go at 15 psi so I have a valve ahead of it.

Is there such a thing as a "dump valve" that is designed to dump steam at a certain pressure ? I dont know how that would be different than a safety blow off, but figured I would ask.

jon