Page 313 - Boiler_Operators_Handbook,_Second_Edition

298 Boiler Operator’s Handbook

pressure. Don’t be like one laundry I encountered a few turn and are fitted with a T type handle so they can be
years ago where the procedure was to close the valves closed by pulling a chain hanging from the ends of the
every time the boiler was shut down. It’s no wonder that handle. For more effective shutoff a chain link or small
they had dry fired the boilers so frequently that they had triangle shaped piece of metal is attached to the bottom
to replace all the boilers in the plant and that was only valve handle and connected to balance the force of the
since they were all replaced six years earlier. pull chain between the two valve handles (Figure 78) for
Piping connecting the water column and boiler a positive shutoff.
must be installed so it can be inspected and cleaned. The purpose of that valve arrangement is to permit
That normally results in the installation of crosses in an operator to close them when (not if) the gauge glass
the piping. I always insist on the opposite end of those breaks. On any ship I worked on I added a little style to
crosses being closed with nipples and pipe caps. It those chains by making two different tabs for the ends
provides two possible joints that will break so you can of the chains, one that was a miniature copy of a stop
gain access to inspect the piping and it’s a lot easier to sign and one looking like a yellow yield sign. The stop
remove a pipe nipple than a pipe plug. In a plant with a sign shape had “shut” instead of “stop” and the yield
boiler damaged by dry firing, and after several hours of
effort to remove the plugs, we found the piping hadn’t
been inspected for years because the operators couldn’t
get the plugs out. No matter how good you think your
water treatment is there is a potential for those pipes to
plug and you must inspect them annually.
Another important consideration with the piping
is connections. Nothing more than operating pressure
switches should be connected to the water column pip-
ing. In one plant I found someone had decided to con-
nect the atomizing steam line to the column piping. All
they had to do was remove the pipe cap and hook up
to it! The pressure drop of the steam flowing from the
inside of the drum to the cross immediately outside it
was twelve inches of water column when the atomizing
steam was on. Luckily the boiler had a separately piped
low water cutoff because the level at the gauge glass and
water column read a false twelve inches higher than it
actually was in the boiler.
You should never accept a leak in that water
column piping for the same reason. Any small flow
of steam out a valve packing or leaking pipe joint can
change the indicated level of the water.
Another important factor with the column piping
is it must be installed so it stays in position relative to
the boiler. Any maintenance activity that involves re-
moving the water column or part of its piping should be
preceded by measuring the height of the column relative
to the steam drum or above the boiler room floor so you
can confirm its proper reinstallation later. Most columns
will have a mark in the casting that’s the normal water
line. You can use it as a reference.

Gauge Glass
The gauge glass is normally mounted on the water
column and can be isolated with special shutoff valves.
The valves are designed to shut off in about one quarter Figure 10-33. Gage glass shutoff chains