Chemical Engineering May 2020 - 39

* Control valves and linkages may
loosen with cycling
* Debris accumulates in fans,
burners and air piping, altering
air-to-fuel ratios and reducing
energy efficiency
* Incorrectly vented valves, relief
devices, regulators and pressure
switches can fail to properly respond
upon use, or not react at all
* Gas pressure switches should
be wired with a means to prevent
fuel from a failed switch
from flowing through a conduit
or wiring to an electrical enclosure.
Such a failure could cause
an explosion if the fuel were to
reach an arcing contact inside the
electrical system
* If plug valves are installed, they
must be properly serviced with
the correct sealant. Plug valves
that are low on sealant may leak
externally, or permit fuel to bypass
a closed valve. Excessive use of
sealant can build up in the piping,
which may subsequently flow into
other components
yet,
* Worse
an
employee may
defeat, bypass or jumperout
safety controls, creating
unknown hazards
Add up all these dangers and
the need for maintenance by
trained technicians becomes
readily apparent.
Inspection requirements
Different components of the valve
train may be on their own unique
inspection frequencies set forth by
the manufacturer or established by
codes. It is strongly recommended,
however, that the entire combustion
system be inspected at least
annually, both internally and externally
while out of service, to assure
compliance. Consult with the specifications
set forth in NFPA 86 (Standards
for Ovens and Furnaces) from
the National Fire Protection Association
(NFPA; Quincy, Mass.; www.
nfpa.org) as a starting point. It provides
guidelines to establish these
measures, clearly stating: " The user
has the responsibility for establishing
a program of inspection, testing
and maintenance with documentation
performed at least annually. "
NFPA 86 applies to both new installations
and modifications to existing
equipment. Yet because NFPA
86 is only a minimum standard, the
Authority Having Jurisdiction (AHJ)
has the final say. The AHJ could be
an insurer or the local fire marshal,
for instance. Whoever it is, the AHJ
is the point of definitive reference for
all compliance matters.
Does this mean that you are in
the clear if the AHJ gives your valve
train approval? The short answer is
no. Annual testing and preventive
maintenance are typically requirements
of insurance agencies, but
other (often overlapping) codes and
standards may need to be adhered
to in addition to NFPA. These may include
codes from industry organizations,
such as the American National
Standards Institute (ANSI), American
Society of Mechanical Engineers
(ASME), National Electrical Code
(NEC), the Underwriter's Laboratory
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39
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Chemical Engineering May 2020

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