Page 109 - Boiler_Operators_Handbook,_Second_Edition

94 Boiler Operator’s Handbook

That doesn’t mean that you have the credentials that are testing is performed. Pressure testing is normally limited
required to perform certain repairs. Even what are called to hydrostatic testing but that’s not always possible. The
“repairs of a routine nature” which appear to require procedures you use should be consistent to ensure the
little skill are still required by Law (because your State, systems are safe for operation under pressure and not
Commonwealth, or Province, has adopted the National damaged while pressure testing. I’ll cover hydrostatic
Board Inspection Code) that not only addresses the re- testing first, because it’s common and preferred.
quirements for inspection of your boilers but includes As with filling there should be a person assigned
requirements for the repair of your boilers. Any repair to control the pump or valve that is pressurizing the
within the environment of a boiler or pressure vessel re- system. Be as certain as possible that you have removed
quires the work be performed by an organization (which all air from the system. A system is usually air free if
can be a one man shop) that has Authorization to use the the water pressure increases rapidly once everything
National Board “R” Symbol Stamp or ASME Authoriza- is closed. If the pressure doesn’t jump to city or system
tion to use the applicable Code Symbol Stamp. Without pump pressure there may be air. Once you’ve started the
those credentials you’re not qualified to perform the hydro pump look at the gage. If pressure isn’t jumping
repair. You should also be wary of Contractors that may up with each cycle of the pump then there’s still air in
have convinced some purchasing agent that they can do it; get it out. If the system ruptures with compressed air
the job cheaper but don’t have those credentials. It costs in it the air and water will pass out through the point of
a considerable amount of money to satisfy the National failure with dramatic force.
Board Inspectors that review firms to determine if they Hydrostatic tests should be conducted with wa-
are qualified to do the work and that expense has to ter between 70°F and 120°F for reasons of safety, that
be included in the cost of the work. The firms have to temperature range is also required by code. Normally
repeat qualification every three years so it doesn’t matter hydrostatic test pressure is 150% of the maximum allow-
how long they’ve been in the business. If the Contrac- able pressure or the setting of the safety valves.
tor can’t produce the Code Symbol Stamp or a copy of Newer equipment is manufactured with steel at
their authorization to use it they shouldn’t be working higher rated pressures than when I was designing their
on your equipment either. installation and, because higher stresses are allowed,
You should be impressed by the skill of the welders the requirements for a Hydrostatic test pressure may
and boilermakers that work on your boilers and pres- be 125% of the design pressure instead of 150%. There’s
sure vessels. Once you’ve seen the result of a window still a lot of equipment out there that was tested at 150%
weld to replace a blistered or bulged boiler tube in a and I still insist that it be tested at that pressure after any
watertube boiler you’ll be convinced that they’re the repair or for a preventative maintenance check. When
right people for the job. If, however, it looks sloppy, questioned by the repair or maintenance crew I always
inconsistent with anything you’ve seen before, or just use the same answer, “The boiler / pressure vessel had
plain wrong in your mind ask to see their Authorization to pass a 150% hydro when it was made. Don’t you want
or the Code Symbol Stamp and report them to the State, to prove that it is as good as new?” And, when discuss-
Province, or Commonwealth’s Chief Boiler Inspector if ing it with a repair contractor I always add “You did
they can’t produce it. That should get rid of any unquali- repair it so it’s as good as new, right?”
fied contractor. I think the days of Contractors buying Of course you can’t just apply 150% test pressure
their authorizations is long gone, at least for now, so you to a system without concern for what’s attached to it.
shouldn’t have to accept shoddy or inadequate repairs. Many pressure switches, transmitters, etc., can’t with-
Maybe you don’t know what to look for in terms stand the hydrostatic test pressure so they have to be
of a good weld. What you can do to inspect welding is disconnected. That includes some thermal wells and
described in the chapter on maintenance. temperature switches and sensors so be certain they’re
okay or remove them for the test. It’s all that cumber-
some removing stuff and putting it back that many con-
PRESSURE TESTING tractors wish to avoid so they’ll try to get away with a
lower test pressure.
The most catastrophic incidents within a boiler Many times even boiler inspectors permit testing
plant are due to sudden releases of steam and water un- at normal operating pressures but I consider that foolish
der pressure. To help ensure the equipment, piping, etc. because the system can fail and allow pressure to reach
is capable of operating without rupture, regular pressure the settings of the safety valves plus the valves can stick