Page 94 - Boiler_Operators_Handbook,_Second_Edition

Boiler Plant Operations 79

recommend you go to the hardware store and get some on the correct boiler, pull on it and let go of it. Repeat
lightweight welded chain, machine screws and nuts that for each safety on the boiler allowing a few seconds
fit through the chain and two pulleys per valve that will between lifts to let things stabilize before doing the
carry the chain. Figure out where you’re going to put it next one. What should happen is you’ll hear the steam
before you go to the store then add twenty feet per boiler belch out of the valve and then stop—pop and stop. In
to have enough chain to do the job. You may also need the very unlikely situation (which normally occurs only
some clamps to attach to building steel, screw eyes for when you haven’t tested the valves regularly) that you
wood structures, or lead anchors and eye bolts to attach hear steam weeping through the valve after a lift test
to a concrete ceiling to suspend the pulleys. Connect one you should operate it again as soon as possible to blow
end of the chain to the eye that’s at the end of the safety whatever got under the seat out.
valve lifting lever (that’s what the eye is there for) and Pop testing of a safety valve is normally done as
run the chain through the pulleys so it drops to a reason- part of the semi-annual inspections on high-pressure
able height above the operating floor near a walkway. boilers and during annual inspection of another boiler
Finally, to prevent the chain running out on you, you in low pressure plants. That operation is described in the
need something at the other end to offset the weight section on annual inspection.
of the chain between the two pulleys. I always suggest What about safety testing on hot water boilers?
making a combination operating handle and weight that Well, you can test the safety valves on HTHW boilers
looks like the one in Figure 2-5. Yes, it looks sort of like using the same rules as steam boilers. Always make it
a stop sign and that’s intentional. It should have a red a point to ensure everyone is clear of the vents on the
background with white border and lettering to add to boiler room roof before testing because the discharge
that effect. That’s because you don’t want some visitor will include water as well as steam. If problems occur
to come wandering by and wondering what happens when testing (like hot water splashing all over) the valve
if he pulls it. Making it about 2½ inches wide makes it discharge piping is not arranged properly.
relatively comfortable in the hand. It you make it from Regular hydronic and hot water heating boiler
at least 10 gauge steel with the edges ground smooth is safety relief valves shouldn’t be tested by lifting them.
should be very comfortable to operate the lifting lever Normally the system pressures are nowhere near 75% of
with it. Finally, mount it so it’s above the top of the head the valve setting and that’s one reason why. When asked
of the tallest Operator in the plant and low enough for what to do about them I only recommend that they be
the shortest one to reach it. You can make a wire hook removed from the boiler during each annual or biannual
from an old coat hanger wrapped to a pipe off to the inspection and examined by looking at the inlet and
side of the walkway to store it to keep it from knocking outlet. If you see scale buildup on either side replace
heads or catching on something you’re carrying down the valve. Hot water boilers are typically equipped
that aisle. with PTV valves (pressure and temperature relief) The
Oh! I didn’t say how to do a lift test? Well all you temperature relief is accomplished by a small diameter
do is check the pressure, the boiler load, and make sure cylinder that hangs out of the bottom of the valve and
you’re grabbing the handle that’s attached to the safety contains a fluid or wax that expands with temperature
and will force the valve open at the set temperature. Un-
like steam safety valves they do not have to be installed
vertically and must be installed so that cylinder is in the
heated water.
A hot water boiler explosion occurred several
years ago at a school in Oklahoma with several children
and some teachers injured. It was because a contractor
didn’t understand the application of a PTV valve and
changed its mounting. Another hot water heating boiler
generated steam in a school in Baltimore in 1999 so the
water was pushed back through the cold water line by
the expanding steam to flash out a toilet as a little girl
flushed it with disastrous consequences for her. Those
valves have to installed according to the manufacturer’s
Figure 2-5. Safety lift grip instructions and inspected regularly.