Page 256 - Boiler_Operators_Handbook,_Second_Edition

Consumables 241

we never make mistakes, right? Now that I know a few sound indication of high degrees of hardness in the wa-
people that have been seriously injured handling treat- ter. When I asked about the regeneration of their soften-
ment chemicals I can honestly say that the wise operator ers I was told they did it just like they always did, every
uses all the protective gear. Wednesday. It didn’t seem to matter to them that the
I regularly thank God that I’m not one of those steam demand on the plant, and makeup, had tripled in
hard heads that got hurt handling chemicals, there’s the last three years. The softeners ran out of sodium ions
nothing other than will and dumb luck that prevented on Monday.
it. You may feel you look stupid in the clunky rubber Applying the chemicals in a uniform matter, con-
boots, silly rubber apron, klutzy rubber gloves and the sistent with the rate of boiler water makeup will mini-
face shield that steams up so it’s hard to see what you’re mize their use by making them most effective. Some
doing—but you’re safe. Not wearing that outfit is taking systems, such as low pressure hot water heating sys-
a chance on living with a serious injury for the rest of tems, require very little treatment because the system
your life; wear it. is closed and losses of water are very limited so shot
Frequently people don’t think of salt as a water feeding of chemicals using a shot feeder (Figure 7-2) is
treatment chemical. It is, and it’s one of the cheapest capable of providing adequate treatment.
and safest to handle so you want to make sure you make Those shot feeders do, however, often look much
the best use of it first. Ensure the water softeners are like a mess where it’s evident that the chemicals were
regenerated with adequate brine concentrations and re- spilled and wasted as opposed to injected into the sys-
generate them before they’re depleted to minimize con- tem. Proper use of a shot feeder requires closing the
sumption of phosphate or other scale treatments which isolating valves and proving them closed by slowly
are a lot more expensive than salt. cracking the vent valve while holding a bucket under
Take regular samples of the incoming makeup the vent pipe to capture any discharge. It’s possible for
water to check for changes in hardness that will alter the shot feeder to accumulate some air or gas from the
the capacity of the softeners and adjust the softener system so the contents could expand out dramatically
throughput accordingly. You don’t want to be like one when it is opened to atmosphere. It may require waiting
plant I visited for problems with their new boiler. Blis- several seconds or even minutes to allow pressure to
ters at the bottom of the boiler’s waterwall tubes were a bleed off slowly before it’s relieved. If only liquid flows
out that’s an indication that one or both of the isolating
valves are not shut. Be sure you wear the silly outfit
because expanding gas can carry out slugs of water that
could still contain concentrated chemicals and splash
them on you.
Once the pressure is relieved the shot feeder
should be drained by opening the drain valve with a
bucket under it to capture the contents. If the contents
are system water it’s the best thing to use for mixing
the new charge for chemicals. If the contents appear
to be a concentrated mixture of chemicals it means the
feeder didn’t discharge its contents; in that case, close
the drain, open the fill valve, pour it back in and return
the feeder to service to get the chemicals where you
want them, in the system. Be certain the drain is closed,
checking it by adding a cup or two of fresh water, then
open the fill valve and slowly pour in the new mixture
of chemicals.
To charge the chemicals close the fill valve, close the
vent valve down then crack it a little and crack the feeder
outlet valve to fill the feeder pot. Hold a small container
under the vent line to capture the first shot of water and
close the vent valve as soon as the water appears. Finally
Figure 7-2. Shot feeder open the feeder outlet valve and the feeder inlet valve to