december2022january2023 - 36

Product Profile
A DP Indicator for
Smaller Applications
BY REBECCA KANABLE
T
o determine whether a filter is
functioning correctly, fuel handlers
rely on differential pressure
(DP) readings.
The differential reading reflects how
clean the filter element in the housing is.
In other words, explains Jim Gammon,
president at Gammon Technical Products,
how difficult is it for fuel to flow through the filter element.
As a filter plugs, it requires more force (pressure) to push the
fuel through.
Gammon Technical Products, an aviation fuel quality control,
refueling and handling equipment manufacturer that
manufactures more than 3,000 products and components in
the United States, offers the Mini Gammon Gauge to assist
fuel handlers with DP readings.
The Mini Gammon Gauge from Gammon Technical Products
isn't really " a gauge " that reads actual pressure. Rather,
the Mini Gammon Gauge is a differential pressure (DP) indicator
that reads the difference between the pressures at the fuel
filter inlet and outlet.
" Everyone calls DP indicators 'gauges' because they are so
similar, " says Gammon.
Differential pressure is indicated as " psid. " If the inlet pressure
is 287 psi and the filter outlet pressure is 277 psi, the
gauge reads " 10 psid. " It would have the same reading if inlet
pressure is 17 psi and outlet is 7 psi.
The actual system pressure, meaured in psi, has no effect
on the Mini Gammon Gauge.
The Mini Gammon Gauge was first introduced in 2017,
about 50 years after the original Gammon Gauge. Jim Gammon's
father and company founder Howard Gammon, who
has been referred to in the industry as " the father of aviation
fuel quality control, " developed a wide range of products
to fill the needs of the aviation fuel handling industry. The
Sampling Probe was first, followed by the MiniMonitor and
Gammon Gauge in addition to many other products.
" The Mini Gammon Gauge was invented to provide a
less expensive alternative to the original Gammon Gauge, "
Gammon says. " The problem was that the original gauge is
expensive to make. On a large filter housing, costing many
thousands of dollars, this is reasonable. On a small filter, it
can cost as much as the small filter housing.
" The industry needed a smaller, less expensive, yet high
36 || Ground Support Worldwide || December 2022/January 2023
quality differential pressure indicator
for small filter vessels, " he continues.
" For example, the Gammon Gauge is
used on filters up to 2,500 gpm (gallons
per minute) in refineries and airports,
and typically 300-800 gpm for airliners,
but when refueling a private
aircraft, the flow rates are typically
under 200 gpm for jets and 50 gpm for
smaller aircraft. "
While meeting the needs of smaller applications, the mini
version is made to the same standards.
" Our manufacturing standards are based on always being
the best possible for the price, " Gammon says. " For a piston-type
DP gauge, we machine our clearances to be no more
than about 0.0002 " at any temperature. A piece of paper is
about 0.003 " thick, about 15 times of the clearance we have.
Why is this important? Because any fuel that gets past our
piston goes downstream and into the aircraft, having never
passed through the main filter vessel, we want that amount of
DIFFERENTIAL PRESSURE
FOR AVIATION FUEL FILTERS
According to the Energy Institute (EI), understanding the
importance of differential pressure (DP) is critical to a fueling
operation.
Every drop of fuel delivered to an aircraft is typically cleaned
down to a few microns. Dirty fuel can impact aircraft
operations.
To determine whether a filter is functioning correctly, a DP
gauge is used. As trace levels of dirt accumulate on filter
media, there is a progressive rise in DP. Large plumes of debris
or large volumes of water hitting the filter may cause a more
sudden increase in DP. An increase in flow rate through a filter
causes an increase in pressure at the filter inlet.
A steady gentle increase in DP is normal. It means trace
levels of dirt - or for filter monitors, water - are gradually
accumulating on the filters.
A rapid rise in DP means something has blocked the filter. A
large drop at the same flow rate means the restriction to fuel
flow has been reduced. Something has happened and must be
investigated.
Source: Differential Pressure for Aviation Fuel Filters video by the Energy Institute
The Mini Gammon
Gauge is mounted
to a small filter
vessel head.
GAMMON TECHNICAL PRODUCTS
FACET FILTRATION CORP
december2022january2023

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