How often should LWCO controls be tested?

elfie

how often should the low water cutoff devices be tested on a 14 section commercial steam boiler?



is just once at beginning of season adequate?



thanks

Jamie Hall

What kind of control?

If it is a float type, you should be blowing it down regularly and, ideally, when you do it should shut off the burner.  Regularly is one of those comments, but more than once a week is probably unnecessary... and less than once a month is probably not enough.

gerry gill

float type

controls are supposed to be blown down weekly.

elfie

LWCO testing/blowdown

so when the LWCO blow down is done it should drain enough water from boiler to cause the LWCO to shut down the boiler



seems this might be alot of water and goes beyond cleaning out the LWCO devices (ie. maybe doing the LWCO test monthly while doing weekly blow downs of the LWCO device.might be OK)

Jamie Hall

Actually it may not take

as much water as you might think -- if the LWCO is connected through relatively small pipes -- which is often the case -- and has a nice big blowdown valve, the water in it will drop a lot faster than the water in the boiler, and it should trip.  Try it...

cn30

boiler feed pump

Is there any way to shut off the boiler feed pump while doing this? My pump refills the boiler at a pretty good pace.

Dave in QCA

Not a good idea

CN,    You may be able to kill the power feed to the feed pump separately from the boiler, but it's not necessary and not a good idea.  If you are like me or people that have worked for me, something will happen to distract you and then you forget to turn it back on.



At any rate...  When you open the drain on the bottom of the LWCO/Feed pump controller, you open the valve all the way, and you do that fast.  If the boiler is firing, you will observe two almost immediate reactions.  1) The feed pump will start to run, 2) The burner will shut down.   As you are doing this, you observe for brown dirty sludgy water.  It will probably only take a very short time to clear up, say between 3 and 10 seconds, but every situation will be slightly different.  As soon as the water runs clear, shut the valve.  As soon as the float chamber refills the firing sequence will begin and the feed pump will shut off.



As Gerry and Jamie have both said, this needs to be done at least weekly.  If this is a larger capacity boiler that runs at a maintained pressure, such as a school, hospital, etc.  This is a routine that should be done daily.  This is nothing to mess around with.  Proper operation of the LWCO is the link that stands between proper operation and catastrophe.  All you can ever know is that it worked property the last time you tested it, and that you flushed out the sediment.  If the boiler is destroyed by dry firing, and the operator states that he tested it a month ago, or last September, it will look like serious negligence. 

FJL

LWCO w/Auto Water Feeder

I blow down mine once a week. My LWCO, however, has an auto water feeder attached to it, so that when I am blowing down and the water level drops, it automatically refills. Should this be disabled? Also, I was told to do this while the boiler was off, i.e., not firing and after it had cooled down a bit so as not to crack it? I don't know how, maybe b/c the auto feed might send too much cold water in at once? Anyway, does it matter whether the boiler is running or not or hot or cold when you do this?



Thanks.

nicholas bonham-carter

How often is natural?

I blow down my 1,050,000 btu's as often as the water in the discharge bucket dries up, about twice a week.

Just as important as the frequency is the method--open the discharge valve, and let the water run until it is clear, and not brown and rusty.

While you are there, have a look around the boiler, and see if there are any leaks.

Once a month, I use the jumper cable I have to fire the boiler, and verify the lwco turns off the boiler as I drain it. I also use that time of firing to see whether my main venting seems to be doing its job, by looking at my 0-15 ounce gauge, to see the back-pressure of venting, and if it is an ounce or so as the air is escaping, I know all is well.

Finally, since I have no auto-feed, I can check the water-level against the clothespins I have on the rods next to the gauge-glass, and add water if needed.--NBC