By Bob Boyer
In the process of oxyfuel cutting, preheat flames from a cutting torch bring a piece of steel to a cherry red color. Once kindling temperature is
reached, applying pressure to the torch’s oxygen
lever releases a stream of pure oxygen, initiating
rapid oxidation. This is oxyfuel cutting.
As operators focus on the cut path, they rarely
think twice about the regulators that are supplying
oxygen and fuel to their torch. What’s happening inside a regulator that enables it to provide for a trouble-free cutting process? How do regulators help
provide safe, consistent operation? Can a regulator
design even enhance operator experience?
What Is a Regulator?
The technical definition of a regulator, as defined
by ISO regulator standard 2503 (Section 3. 12), is a
device for regulating a generally variable inlet pressure to an outlet pressure that is as constant as possible. Inlet pressure sources include high-pressure
cylinders, liquid cylinders, bulk supply systems, and
air compressors. Outlet pressure management is required for oxyfuel torches with cutting, heating, and
welding attachments; welding systems; and plasma
cutting operations. (This typically involves air or nitrogen cylinders used for field fabrication.)
Regulators come in many di;erent forms, depending on performance needs, size constraints,
maximum inlet pressure, type of gas being used,
purity requirements, and even personal “look and
feel” preferences (see Figure 1). Modern regulator
design can be traced back to William Stettner, the
founder of Victor, who developed his first product
in 1913 a;er losing an eye in a regulator explosion.
As Figure 2 shows, his design has withstood the
test of time, with many modern regulators retaining
a similar look. Figure 3 highlights the major internal components of a regulator, and color codes the
high- and low-pressure areas.
Within the regulator, the diaphragm is the sensing
element that does most of the hard work—which is
to open and close the seat that controls gas flow
from the high- to low-pressure chambers of the regulator. Gas flow control is a three-step cycle:
1. As the operator turns the regulator knob, it
compresses an adjusting spring that sits atop the diaphragm. When the adjusting spring exerts enough
force, the diaphragm pushes open the seat to begin
gas flow, which allows gas to start filling the low-pressure chamber.
2. The resulting pressure in the low-pressure
chamber increases to the point where the upward
force on the diaphragm is su;icient to overcome
the force of the adjusting spring, causing the dia-
phragm to rise and the seat to close. This static state
becomes the adjusted delivery pressure seen on the
regulator’s low-pressure gauge.
3. As gas flows downstream equipment, pressure
drops in the low-pressure chamber, which creates
an unequal balance of forces, allowing the adjusting
spring to push the diaphragm down, which opens
the seat and begins the cycle again.
During use, the regulator is constantly refilling
itself to replace the gas being withdrawn from the
low-pressure chamber (see Figure 4). What the
operator perceives as constant delivery pressure is
actually continuous action inside the regulator to
Two Key Components
Because the diaphragm and seat do most of the
work, they also are the two main components that
drive flow performance in a regulator. Diaphragms
o;en are constructed from elastomeric materials,
such as neoprene, as well as from metals, such as
thin stainless steel sheet. A neoprene elastomer
diaphragm has incredible flexibility, making it suitable for use as a regulator diaphragm, where it’s
constantly moving to open and close the regulator
seat. However, any elastomer material naturally
degrades over time, is prone to absorbing contaminants, and is susceptible to performance impairment caused by extreme high or low operating temperatures. Stainless steel generally is perceived as
a more durable material. It does not rust or absorb
contaminants and is nearly impervious to extreme
temperatures. But like any metal, it can only go
through so many cycles of flex movement before its
grain structure degrades, causing a loss of mechanical properties.
Underwriters Laboratories (UL) standard 252
requires a stainless steel diaphragm to withstand
10,000 endurance cycles before it is considered
safe, but elastomer diaphragms require 25,000 endurance cycles because of the inherent flexibility
characteristics of an elastomer over steel. The perfect diaphragm would combine the durability of
stainless steel with the flexibility of an elastomer for
the best of both worlds. Newer diaphragm designs
are looking to surpass current performance expectations (see Figure 5).
The physical size of the diaphragm is important
to performance, as a larger surface area provides
greater sensitivity to pressure changes, and it can
allow for greater flow output. However, a larger diaphragm means a physically larger regulator, which
can add size and weight to the portable regulators,
which have to be attached manually to cylinders.
The gas pressure regulators on the cylinders may not
be the first thing that you notice, but the fabricator has
his eye on them. Di;erences in gauge size and color-coding enable him to evaluate gas flow and cylinder
contents, even from a distance.
While current regulators use more modern materials,
their look is strikingly similar to a design patented in
What’s there to know about
They keep fabricators safe and productive
as their design continues to advance