Safety Concern - Blow Off Valve

[mtnman]

Something I learned back when I had a Traction Engine was that once you start a fire you never leave that boiler unattended, never.

[DetroiTug]

"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 ?"

I wouldn't touch it. I would contact Kunkle and get a return authorization for a new replacement. As a manufacturer of something so critical to the safe operation of a steam boiler, they are going to want to see that valve to determine what caused it to malfunction. It would be very irresponsible for a manufacturer of a safety device to handle it any other way.

That's the reason these safety valves cost so much. The customer is buying a guarantee that it works, and they are covering their posterior if they get sued.

They'll want to see it..

-Ron

[fredrosse]

"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."

Almost all large power plant boilers use these, called "Power Opreated Relief Valves", or "Pilot Operated Relief Valves". They open more slowly in a controlled fashion, and re-seat more reliably than the spring type valves. Many plants have main steam "Dump Systems", otherwise known as "Bypass Systems".

ASME Code requires good old spring type safety valves on all boilers, relatively simple and reliable, although from this forum thread, not as reliable as we would wish. Since the spring loaded valves pop open, wake up the neighborhood, and often weep after lifting, the industry usually opens one of the Power/Pilot valves to avoid popping the main spring loaded safety valves.

The Bypass systems usually dump steam into the condenser when there is a steam turbine trip, and the fires (or the reactor) cannot be shutdown quickly enough to stop continued steam production. Gas turbine combined cycles (where the hot exhaust gas from the gas turbines is passed thru a boiler to generate steam, which is then used in a steam turbine) generate full steam flow even if the steam turbine is shutdown, so they may be dumping full steam flow for hours, days, or even months, continuously.

[Oilking]

Navy 600 & 1200psi propulsion boilers had in total four safety valves, three on the drum and one on the superheater outlet.
The two lager drum valves were identical, and the smaller "pilot" valve, set to open first, would send steam to the superheater valve actuating chamber, opening it, thus maintaining flow through the superheater. Total relief capacity was designed to handle the boiler out put at full firing rate with the steam stops closed.

Regardless of the specific design, a true safety valve should lift with a crisp pop, and then plop shut after blow down, with little or no simmer. Lift and blow down should be able to be set independantly.

I agree with Ron, if a recently manufactured valve is giving trouble I'd send it back before ripping into it.

Steam On - Steam Safe

Dave

[Lopez Mike]

All pretty horrifying. In fifty years of being around steam this the first time I have heard of a malfunction of this magnitude. A little set point creep. Maybe some groaning and a less than crisp closure. But never going out of sight like that. Definitely send it in.

As others have suggested, one wonders if the quality and precision of the product has declined. My safety, stamped 150, has slowly crept down to 140 over a year or so. The action, though, has improved greatly. Maybe a wisp before popping and sometimes a bit more fussing on close.

With my hand fired wood burner in stop and go service, I open the safety several times a day. I suspect that there were some rough surfaces in there that have smoothed out with time. The drift to 140 is in the safe direction so I'm going to live with it for now.

Mike