Chemical Engineering May 2020 - 38

Cover Story
Part 2
Turning Up the Heat
on Valve Train Safety
Despite their nearly universal use in industrial combustion processes, valve trains are not widely
understood. Here are some guidelines to help ensure their safe and effective operation
Robert Sanderson
Rockford Systems, LLC
D
oes your manufacturing facility
have a smoke stack? If
it does, it also likely contains
a valve train, commonly
known in industrial circles as a fuel
train. This complicated series of piping
and components needs regular
inspections, accurate record-keeping
and preventative maintenance to avert
very serious safety and productivity
issues (Figure 1).
If you aren't sure what a valve train is,
you're not alone. It is one of the most
misunderstood pieces of equipment
in a plant, even by those conducting
work on it. As a result, it rarely receives
the consideration it should from plant
managers and safety professionals.
While it is not necessary for engineers
to know every engineered component
of a valve train, they should be
aware of what it does and why it
demands attention.
Essentially, a valve train controls the
flow of pressurized gases into fuelfired
industrial equipment (Figure 2).
For safe and proper combustion, the
flows of air and gas to the burners are
controlled by the valve trains feeding
the burners. The burners then mix the
combustible gases and release the
thermal energy needed to safely heat
furnaces, boilers, heating, ventilation
and air-conditioning (HVAC) equipment,
thermal oxidizers and other
equipment to a specified temperature.
In turn, the fuel-fired equipment performs
critical industrial tasks, such as
drying gypsum boards, roasting and
baking foods, heat-treating metals,
heating fluids and abating pollution.
38
What could go
wrong?
Owing to the presence
of hazardous
vapors and gases,
a poorly designed
or inadequately
maintained
train can lead
catastrophic
cidents,
from
valve
to
acranging
explosions
and
fires to employee
injuries and
death. When this explosive force is
unleashed, the shockwave carries
equipment, debris, materials, pipes
and high temperatures in all directions
with tremendous force.
The following incidents are examples
of why it is important to use a
high-quality valve train, and to keep it
professionally maintained, inspected
and tested:
* In 2018, a furnace explosion at a
Massachusetts vacuum-systems
plant killed two workers and injured
firefighters as a result of fuel
malfunction
* In Japan, an automobile manufacturer
lost tens of millions of dollars
when it was forced to shut down
production for almost a month after
a gas-fueled furnace exploded due
to flammable fumes building up in
the tank
* In a Wisconsin bakery, an employee
was seriously injured when
he ignited an oven's gas and was
struck by a door that was blown
off. A malfunctioning valve had allowed
natural gas to build up inside
the oven
* In 2017, a van-sized boiler exploded
at a St. Louis box company, killing
three people and injuring four
others. The powerful, gas-fueled
explosion launched the boiler more
than 500 feet into the air
* In 2016, a boiler explosion in a
packaging factory in Bangladesh
enveloped the five-story building in
flames, killing 23 people
The need for maintenance
Many such explosions are the result
of a lack of maintenance. Valve trains,
like all industrial equipment, wear with
use. The following are some considerations
that should be taken into account
when maintaining valve trains:
* Fuel flowing to a system can convey
condensate, piping scale or
other
foreign
materials
that
will
either damage or block a safety
valve from fully closing
* Diaphragm valves are vulnerable to
embrittlement, aging and rupture
* Outdoor valve trains must endure
seasonal extremes, adverse
weather and exposure to
ultraviolet (UV) light
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM MAY 2020
FIGURE 1. A valve train consists of piping and several essential
components that help to facilitate industrial combustion

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