Steam explosion

SlamDunk

https://www.courant.com/breaking-news/hc-br-west-haven-va-hospital-explosion-20201113-7kwigxujpbgqvia36ze3wnmzxq-story.html

george_42

what pressure do they run on those type systems?

PerryHolzman

The pressure is most likely between 50 and 150 PSI.

If the article is correct in that this happened when pressurizing the new piping system; then the most likely cause will be cheap foreign (Chinese/India - most common) non-spec pipe with faked certification papers. Unfortunately, it's a known problem and has killed many people.

My condolences to the families of those killed.

Perry

cutter

Did they replace a piece of threaded pipe, or cut out a bad section and weld a new piece of pipe in.

I was in the forward fire room of a Navy Destoryer, The fire room had a excess amount of steam in the fire room. There was also a roar of a noise behind # 1 boiler. # 2 Boiler was lit off but not up to steam yet. Those boilers run at 600 lb's of saturated steam and 1200 lb's of super heated steam. Forward fire room supply's steam to forward engine room. I wasn't in that fire room more than 10 minutes when the roar got loud enough for the top watch to call after fire room and say cross over. The top watch then yelled for us to wrap it up. That roar was the main steam line leaving # 1 boiler having a crack in it and getting worse. If that line would have let loose the 4 of us in that fire room would have been scraped up off the decking.

jumper

What does a hospital use 50 psi steam for?
Do sterilizers or kitchens require more than 250°?

SlamDunk

Regular boiler steam to "clean steam" generators which uses purified water to provide steam for autoclaves. Typically 100psi.

EBEBRATT-Ed

My guess would be water hammer. You shut some valves and isolate a section of pipe. If the upstream valve does not have a trap near by to keep it drained that leg fills with water.

Then the valves get opened and bad things happen with a pipe full of water.

Sad two people were lost. Condolences

Lard

I am going to guess water hammer too.  

A similar incident happened at an automotive plant we were installing equipment in a couple years ago, though just low pressure steam.  Valve opened and blew the rotted overhead pipe apart from water hammer, showering several $1.5 million CNC machines below with condensate.  Luckily no injuries, just some rusty guideways and ballscrews.

SlamDunk

I really would like to think pipes can handle water hammer. On the rare occasion when I bring my system down, I get a lot of hammer on start up.

If you run at 100psi, then everything should be rated for 300psi.

As for foreign pipe vs US pipe, I buy US pipe but I have not seen any measurable differences in longevity. My system's pipes say made in china or hyundai for every five feet for thousands of feet. Condolences to the families. Something to be learneed here.

ChrisJ

SlamDunk said:

I really would like to think pipes can handle water hammer. On the rare occasion when I bring my system down, I get a lot of hammer on start up. If you run at 100psi, then everything should be rated for 300psi. As for foreign pipe vs US pipe, I buy US pipe but I have not seen any measurable differences in longevity. My system's pipes say made in china or hyundai for every five feet for thousands of feet. Condolences to the families. Something to be learneed here.

My understanding is high pressure steam has killed many from water hammer.  Not only pipes but heavy valves have been blown apart by it.

I don't believe a heavy steel pipe can handle severe water hammer any better than it can handle ice.

Steam hammer in high pressure systems appears to be very different than in home heating systems..   

I have zero experience with it but did a little reading on some articles on it and was amazed.  I recall one where simply removing pipe insulation caused hammer and killed someone. 

SlamDunk

Maybe. I have not read many investigation reports on root cause of failures. I like to tell visitors to my boiler/chiller rooms that these are the safest rooms in the building because we maintain them to be the safest rooms in the building. I hate to think I've been telling lies. We get pretty serious hammer when we screw up. The system is not shy about telling us when we screw up , things shake, pipes move, but I have yet to see a life threatening result.

ChrisJ

SlamDunk said:

Maybe. I have not read many investigation reports on root cause of failures. I like to tell visitors to my boiler/chiller rooms that these are the safest rooms in the building because we maintain them to be the safest rooms in the building. I hate to think I've been telling lies. We get pretty serious hammer when we screw up. The system is not shy about telling us when we screw up , things shake, pipes move, but I have yet to see a life threatening result.

If you take the threat serious and keep everything in good working other I don't think you've been lying.

EBEBRATT-Ed

@SlamDunk

Many systems run 100#s with schedule 40 pipe and 125# cast iron fittings. Nothing wrong with using 300#fittings though

It's not the pipe, schedule 40 pipe is good for way more than 100psi. It's the valves and fittings that fail. Pipe is rated for different pressures depending on the diameter of the pipe and the temperature it is subjected to. 1/2" pipe can take more pressure than 6" pipe.

Sure some systems hammer on start up, that's when the condensate load it the highest when the system is warming up slow by starting the boiler and bringing the whole system up.......that's usually not a problem.

But that's not what I was talking about. I am talking about a high pressure system where a valve is closed to isolate part of the system for maintenance. Water may back up behind this closed valve due to a failed trap or poor design.

Now you have a big slug of water in the pipe causing no issue just sitting there until the valve is opened causing a battering ram driven by 100psi steam.

Don't know what happened but that's my guess

SlamDunk

Everything on our system is sced80 and most of it is welded. Valves rated for 300psi. But, i cant help but think we dont do anything differently than these guys.

Leon82

They released the initial investigation.

https://www.wtnh.com/news/breaking-news/west-haven-pd-responding-to-incident-at-va-hospital/

According to state police, the CSP-FEIU investigation determined that a “pressure event” occurred within the steam system that was being worked on. “This caused super-heated water vapor to rapidly fill the room and building.” They said that this was not a fire or an explosion.

jumper

Two dangers. A slug of water moving very fast. And a rupture with high pressure steam. Oddly steam has low energy on a volume basis compared to high temperature water but latter is considered safer when there's a rupture. Hear about these issues when district heating is being planned.

Jamie Hall

I'm not about to comment on this particular case, but... the kinds of water hammer we experience are within the capability of the pipes we use to manage. But a big slug of water moving at speed is a very different matter. The shock loading from bringing it to a stop is terrific and good engineering practice requires measures be taken to keep it from happening -- or to dissipate it.

ssnowder

Did opening the isolation valve too much too soon have anything to do with the thermal shock and/or water hammer?