Flooding boiler

[TGTimm]

Whenever we shut the boiler (Col. WL90) down, it floods as it cools. I then have to drain water down to the proper level before we can use it again.

I recently bought and installed a proper (Kadant Johnson) vacuum breaker made for use on a boiler to replace the sticking swing-gate check valve I'd been using. It sticks. I now am using both valves and they both stick as if they were being glued shut.

Any ideas? Something in the water treatment (which I can't afford to use until I fix this)?

[gitchegumee]

My best practice....

... is to use Spirax Sarco parts on a steam install. Awesome equipment and depending where you are, great customer service or none at all. I install a Spirax Sarco VB-14 on every independent jacket. Not that it would help if downstream of a closed control valve when you are shutting down a boiler. But maybe it would be the ticket to your problem if installed on the steam header just out of the boiler and main steam isolation valve? I haven't had this problem before, but it might be because I blow down the boiler after every use pretty hard--boiler bottoms, control column, and any other gauges or equipment that might be prone to gunk. Best of luck!

[TGTimm]

Howdy, Phillip.

Are these Spirax parts another form of vacuum relief valve? I believe our steam traps also have VRVs in them, 'though I'm not 100% sure of that. Leaving the main steam header valve open on shut-down doesn't help at all.

What really confounds me about his problem is that the TWO VRVs I have installed are both outside the water jacket--they should only be contacting clean steam. I'm currently considering adding another VRV at a high point in the condensate return line between the boiler and the condensate return pump to see if that would stop the problem, but there will probably be some leakage which complicates the plumbing.

The strange thing is that this problem started recently on a 4-year-old boiler replacement. The old boiler--identical to the new one--never had this problem, and until six months ago, neither did the new boiler.

I've had the brewers throw the breaker for the condensate return pump on shut-down to see if, for some reason, it was the culprit. No luck.

[siebeer22]

I've had a similar issue

TGTimm-
We were having the same issues last year with our boiler. We replaced a lot of VRV's and other valves.Nothing helped. It ended up that our float on the condensate return tank had so much build up on it was stuck in place. Replaced the float, got a entire new tank and put in a water treatment system. prrrs like a kitten now.

Hopefully it's your float sounds the like the same issue, off the top of my head it was $60 replacement. The reason I replaced the condensate tank is that we ran for a year with no water treatment.(installers said Eugene's water was soft enough, NOT TRUE!) The tank had so much scale in it once the treatment system was in place it started to break up calcium deposits and thus tear the gaskets in the condensate pump.

oh yeah forgot to clarify it was the float on the make up water for the system was stuck so city water was consonantly flowing into tank. May be the reason why the boiler still flooded with your pump turned off.

Howdy, Phillip.

Are these Spirax parts another form of vacuum relief valve? I believe our steam traps also have VRVs in them, 'though I'm not 100% sure of that. Leaving the main steam header valve open on shut-down doesn't help at all.

What really confounds me about his problem is that the TWO VRVs I have installed are both outside the water jacket--they should only be contacting clean steam. I'm currently considering adding another VRV at a high point in the condensate return line between the boiler and the condensate return pump to see if that would stop the problem, but there will probably be some leakage which complicates the plumbing.

The strange thing is that this problem started recently on a 4-year-old boiler replacement. The old boiler--identical to the new one--never had this problem, and until six months ago, neither did the new boiler.

I've had the brewers throw the breaker for the condensate return pump on shut-down to see if, for some reason, it was the culprit. No luck.

[TGTimm]

Thanks, siebeer.

I'd considered that problem early on, but unfortunately... our make-up water float valve screams like a banshee when it's asking for water (or stuck), the condensate return tank is vented directly to the outside, and it's 20' up, 100' over, then 20' down from the tank to the boiler. A siphon is possible--without professional surveying equipment it's hard to get the exact elevations, but boiler and tank are within a few vertical inches of each other. I think contraction of the steam and water within the system is causing a vacuum; starting the siphon.

Again, the strange thing is this just started up after nearly 20 years with the same set-up. The VRVs are definitely sticking as if they were glued shut.

I need to get a treatment system going on this boiler, but until I can quit dumping 30 gal of water every time we use it, it would be a massive waste of money. Until this problem cropped up, I'd been adjusting pH with caustic and using our hot liquor for make-up water (our HL system is vented and pumped, and so de-aerated).

[lhall]

TGTimm,

I had a similar problem, maybe not the same issue though. Our feedwater tank had a steam line and control valve that would inject steam into the feedwater to try to maintain it at 200 F. When we shut the boilers down, the water in the feed water tank would gravity feed backwards through that steam line, once the steam pressure was low enough. It would fill the boilers full of water, since the float valve on the feed water tank would continue to fill the tank.

If that is not it - why not just open some steam vent valves once the boiler pressure is down? I've never had much luck with vacuum breakers on our boilers too.

[TGTimm]

Thanks, Linus.

Unfortunately, that ain't it, neither.

I did try leaving a vent valve open after the boiler had cooled some. That resulted in boiling water spraying all over the boiler room because a particular brewer was too busy to close it before turning the boiler on (even with a note on the boiler switch).

I'm kinda thinking an electrically-driven valve might be the trick--in the condensate return line. Unfortunately, not cheap....

[Starcat]

Feedwater Control

I have only rarely and in such cases not for long run any boiler system without a Pneumatic control valve in the return line. That valve cycles with the McDonnell switch.
AS thus you use a steam rated NC valve that is wired in parallel with your return pump control signal.
The package boilers like Hurst that come with double check valves after the return pump are essentially useless. Those check valves being good for a matter of weeks depending on your water and duty cycle. Pneumatic control are how all the boilers at A&M were set up, so I have never known any different or better way to configure, though some different methods are described in boiler schools and texts.
At the University we ran mainly Johnson V-3000 series, but I went with Spirax on this job.
As Phillip has stated its very rugged gear.
All you need is the valve and actuator, an EP switch, and a regulated air supply of about 20 PSIG.
This will also generally stop any steam cavitation issues with your return pump if they are happening.

[TGTimm]

I'm having some difficulty understanding some of this.

So, the Spirax or Johnson controls you're mentioning are pneumatically-actuated valves that go in the condensate return line between the pump and the boiler, controlled by the float switch that calls for make-up from the condensate return pump?

I'm aware of the problems inherent with check-valves. Our water renders them useless in days or weeks.

[BrewinLou]

Could your condensate tank be gravity feeding into the boiler? Ours has a check valve, but when I do shut it down for inspection I have a gate valve I can manually close to make sure the condensate stays in the tank. We have a municipal make up water line piped directly into our boiler, very poor choice for whomever installed it. But if you have a water source hooked to the boiler... have you checked to make sure the valve is not leaking into the boiler? I shut everything down on ours to do and internal inspection not too long ago and just could not get water to stop coming out of it, at least a small stream the whole time it was open. I chalked it up to condensate coming back down the header, because I had all valves closed right at the boiler. The only pipe without a valve was the steam header coming off the top.

[TGTimm]

Thanks for the reply, Joel.

No, our make-up water goes to the vented, ambient-pressure condensate return tank. The problem is likely exacerbated by siphoning once the pressure drop gets things going, but it's not gravity-fed.

[BrewinLou]

No I am not saying ours IS gravity fed, we also have a pump and check valve. But, in the event we shut down if I do not close the manual gate valve the condensate tank will gravity feed into the boiler until it reaches the same level inside both. Add in siphoning and you may have found your culprit. Just a possibility.

[TGTimm]

Crikey.

Last night, the boiler flooded WHILE IN USE. I'm now replacing the float switch with an old one I have from the previous boiler. The new boiler's switch uses micro-switches, while the old one has mercury switches--it seem now that, among all the other problems, the switch for the return pump MUST be sticking--the mercury switches should solve that problem.

That is, after I get down from cleaning the top unit of the grist lift, which has gotten gummed up to the point of jamming from the torrential rains of the last few weeks. one of my favorite jobs....

[TGTimm]

Well, it looks like I finally fixed it.

I added a second check valve for vacuum relief--no joy. Then the boiler started flooding while under pressure and that could only be the high-pressure condensate return pump. One of the microswitches in the float valve was intermittently sticking. Fortunately, I still have the old mercury switch float switch from our old boiler, and it was a quick and easy swap out. Two weeks, numerous brews, and no flooding.

Yeah!