Near boiler piping issue?

steamyjoe

First post here, please be patient.



I'm at a pharmaceutical facility that's been facing some issues for a couple of years with its boilers. Many contractors have had opinions and none of them have turned in to real solutions, so I'd like a consensus on the problem.



We have 2 low-pressure Burnham firetube boilers, I'm currently at home and don't have any specs with me, and they've been going off on low water in the early morning a couple of times a week(or more) for as long as I've been at this facility. From what I've seen, we've had some carryover issues, even in the summer, and this has lead to a feed water tank that has overflowed more times than I would care to count.



My boss dug up a steam survey today from 7 years ago that's mostly relevant, but after adding in the new loads, it looks peak load is at 95-110% of boiler capacity. This is one major issue that will be addressed(hopefully before winter); it's in management's hands. So this overcapacity could really explain the problems we've been having in the winter, but I'm not sure why it's persisting(thought not to such a great degree or as frequently) in the summer. We have a boiler chem contractor that says the chemistry is fine, so I'm not too sure that that's the problem. However, after reading some stuff on this site and from various other sites, I noticed what could be a problem in the near boiler piping.



If I can, I'll provide a drawing tomorrow. But, for now, let me attempt to explain.



The larger boiler's riser(Boiler 1) goes up maybe 24" from the top of the boiler before turning at a 90, continues straight from there for about 30" before turning at another 90 and then about 5' before turning down into the common header. In that 30" section, the "equalizer" taps into the side of the horizontal pipe.



The smaller boiler's riser(Boiler 2) goes up about 36" from the top of the boiler before turning at a 90, continues straight from there for about 24" before turning at another 90 and then about 3' before turning down into the common header. In the 36" section, the "equalizer" taps into the side of the vertical pipe.



The common header, from end to end goes in this order: HX feed, HX feed(NIU),HX feed, Boiler 1, Boiler 2, Building system main(mostly AHU coils and another HX), drip leg with F&T trap. That F&T trap goes down to a condensate pump that pumps into the feed tank. I've seen that condensate pump overflow quite a few times, also.



The problems I see with the piping are that the boilers don't really have individual headers before going to the common header. The equalizers aren't in a good position to catch carryover at a point where the direction of the steam will change. Additionally, the common header is set up wrong. The order should be as follows: Boiler 1, Boiler 2, load, load, load, load, drip trap.



I don't have much experience with boilers, so I'd like some input from some more qualified people. We also have our usual boiler/steam pipe contractor coming in tomorrow, and I plan on pointing these things out to him to get his opinion. Let me know if you have any questions.



Links of reading that I did to get me to this conclusion:

<a href="http://www.tazeandhewitt.com/Multiple%20Steam.pdf">http://www.tazeandhewitt.com/Multiple%20Steam.pdf</a>

<a href="http://www.burnhamcommercial.com/resources/product-information/pdf/i-o-manual.pdf">http://www.burnhamcommercial.com/resources/product-information/pdf/i-o-manual.pdf</a>

<a href="http://www.heatinghelp.com/article/323/Boilers/151/Modular-steam-boilers">http://www.heatinghelp.com/article/323/Boilers/151/Modular-steam-boilers</a>

<a href="http://websupport.completewatersystems.com/entries/21713737-Multiple-Issues-With-Multiple-Steam-Boilers">http://websupport.completewatersystems.com/entries/21713737-Multiple-Issues-With-Multiple-Steam-Boilers</a>

<a href="http://www.manualslib.com/manual/189601/Weil-Mclain-80.html?page=19#manual">http://www.manualslib.com/manual/189601/Weil-Mclain-80.html?page=19#manual</a>

<a href="http://www.comfort-calc.net/steam_Multiple_Boiler.html">http://www.comfort-calc.net/steam_Multiple_Boiler.html</a>

<a href="http://www.heatinghelp.com/files/posts/2455/Header.pdf">http://www.heatinghelp.com/files/posts/2455/Header.pdf</a>

SWEI

Can you post some photos

of the boilers and associated piping?  The "steam survey" you mentioned would also be helpful.

nicholas bonham-carter

Pictures necessary

Besides the possibility of an improper piping issue, there is always the chemistry contractor. Would he ever say that it is not fine? The best additive to our heating boilers is H2O, unless there is some clear water problem which needs a Ph adjustment.

Drain off some of the boiler water in to a pan, and place it on the stove. It may behave like a pot with potatoes, covered and boiling too fast. The resulting overflow, will swiftly empty the pot of water, and dry out the potatoes, just as it can empty the boiler.

What is the steam being used for-process, or heating purposes?--NBC

steamyjoe

Steam survey

It's just a breakdown of loads in lbs/hr, but I don't feel comfortable posting that because my employer doesn't like sharing information on what types of processing equipment we have. However, I'll try to get some photos when I go in today.

steamyjoe

Water chemistry

I imagine the contractor would point to anything being wrong in his opinion, if his opinion is worth anything. I'll try to boil a sample today, but it may be difficult to locate a stove to use in a commercial facility. Maybe I can borrow one from the lab guys.



On this topic though, I should note that a saturation of chemicals has always been thought of as a potential cause. I've seen the water coming out of the cool down tank on some of the rough days become foamy and the chemicals can be smelled when the feed tank overflows. I've assumed that this was because the boiler would go off on low water so many times, that the feed pump would run too much, making the chemical dosage too high as it runs in conjunction with that pump. To my knowledge, the daily tests and the chem contractor have never pointed to any real issue in a normal operating condition. Nevertheless, we've turned off the chemical feed pumps for days at time before, and it's never stopped the issue of low water.

steamyjoe

Steam application

The steam is all heating, some for heating process air in production equipment. The HX's are for hydronic loops and a domestic HW.

JStar

Steam

You are correct that the piping is not correct and will lead to carry-over and innefficient steam production. We see A LOT of poorly installed commercial/industrial systems like this. Usually, the cost to repair the piping is seen as excessive by management. In reality, you'll make a large improvement in most of your problems by fixing this. And you'll save on fuel costs as well.

steamyjoe

Boiling pot test

The chemicals were turned back on yesterday after being off for a few days. This morning we got some low water bells going off again; we turned the chemical pumps back off. I took a boiler water sample later in the day and put it on a hot plate in the lab. It came to a boil and I let it go for a few minutes, but I didn't see any foaming. Maybe if I had gotten the sample sooner, when I expect the chemicals were in higher concentration, then it would have gotten foamy.

steamyjoe

Since it's incorrect

Could you tell me if I'm right on how it should be?

lza

Carryover

Steamyjoe,



What do you mean when you say that the system is having issues with carryover?  Do you mean impurities in the steam, or is the issue priming of the boiler water?  And why are you connecting the feed water tank overflowing to the carryover issue? 



You say that the boilers have been having low water conditions, but the feedwater tank overflows.  Maybe you need to take a look at your feedwater pumps...they may need maintenance, or they may be undersized.   It sounds like your facility is asking more out of the steam system than when it was originally installed.  If so, you need to take a good look at your equipment and figure out what you need to upgrade.  If you are pushing the boilers to the max, that may lead to excessive carryover of boiler water. 



Although you need to be discriminating with anyone who is trying to sell you something,  I would skip the contractors and contact the manufacturer's rep for Burnham in your area.  They will probably charge you to come out, but they will be much more knowledgeable than the vast majority of commercial mechanical  contractors. 

steamyjoe

Carryover

I'm meaning steam quality, whether it is caused by a mechanical/piping issues or the boiler water. I'm definitely connecting the condensate pump thats overflowing from the drip leg on the common header as a result of carryover. I think it makes sense that if the boilers are losing water through carryover and going off on low water that the pumps run more often, lowering the feed water tank level, causing city make-up to come in, then the carryover returns and overflow the tank.



Pump sizing was one of the first things we looked into. Both pumps are capable of keeping up with the boilers. The pumps have received their needed maintenance and at least one has been replaced because of a leak. Strainers on the lines have been cleaned regularly and the two check valves have been checked.



We are definitely pushing the boilers to keep up with the system in the winter, especially if we are running processing equipment air handlers, but our load in the summer is significantly less, so I'd expect the issue to cease, however it only lessens. We are in the process of figuring out how we are going to add more boiler capacity, so the load issue is in the process of being solved.



I like to take the contractors' advice with a grain of salt and get multiple opinions if I can. However, our near-boiler piping design is not remotely close to the manufacturer's recommended design(which I believe is that same for all of their forced draft steam boilers; I can't find an installation manual for our models). I'll keep in mind bringing out a Burnham rep, but that's ultimately management's decision.

steamyjoe

Correction!

I just realized that I was wrong on how the trap on the common header ties into the return. It goes straight to the feed tank, not to the condensate pump. The condensate pump only receives the condensate of the HWHXs.

So pump over flow was due to excessive water carried into that system, or the pump is undersized(I don't think it is).

Feed tank overflow would be coming from the regular condensate returns and the trap on the common header

RobG

Stupid Questions

I have a couple of stupid questions. Did the system ever work correctly? If the answer is yes, what's changed?

steamyjoe

System functionality

The system has been here for a few decades. Many changes have occurred over the years. To my knowledge, this facility originally had one boiler, the larger one. Then there was a second boiler added, and then that second boiler was replaced with this current, smaller, one.



Aside from the boilers themselves, a feed water tank was changed over to accommodate two boilers and numerous additional loads have been added on, removed, and reconfigured.

RobG

When?

Do you know when the last time it worked normally was? If there are records, sometimes it is easier to work from the back to the front. When did it work last and what did the last knucklehead do to it?

steamyjoe

Most recent change

It was working well a little over 2 years ago, then an air handler was added that has a significant load, and the problems started around that time.