INSTRUCTION MANUAL Revised Jan. 2012 GAMMON GAUGE

INSTRUCTION MANUAL
Revised Jan. 2012
GAMMON GAUGE™ DIRECT READING DIFFERENTIAL PRESSURE GAUGES
MODELS GTP-534 AND GTP-534PB
PRINCIPAL OF OPERATION:
The Gammon Gauge™ is designed to measure the difference between two pressures. With the high pressure
connection made at the side fitting near the top of the gauge, the piston (3) (Refer to drawing GTP-534 or GTP534PB) will move downward in the glass cylinder (2) against the spring (8 or 9). When the total of the pressure
under the piston (low pressure) plus the spring force equals the high pressure is very little, the spring will compress
very little. If the difference is large, the piston must move a longer distance downward until the spring is compressed
enough to compensate for the pressure difference. A gauge protection filter element (1) prevents dirt from entering
the glass cylinder (2) from the high pressure connection.
The pressure differential or “pressure drop” across the filter is read on the gauge scale (14 or 15) at the top of the
piston. The scale is calibrated in PSI and KPA on one face and in Bar and KG/CM² on the reverse face. Two basic
models are available. One has 0-15 psi range and the other has a 0-30psi range.
GTP-534-15A
GTP-534-30A
GTP-534-15S
GTP-534-30S
Aluminum body, 0-15 psi
Aluminum body, 0-30 psi
Stainless Steel body, 0-15 psi
Stainless Steel body, 0-30 psi
GTP-534PB-15A
GTP-534PB-30A
GTP-543PB-15S
GTP-534PB-30S
INSTALLATION:
Mount the gauge in a vertical position using ¼” (6mm) screws in the four holes in the cage (12 or 13). If the surface
that the gauge is being mounted on is not flat within 1/16”, do not warp the gauge by tightening the 4 attachment
screws. Use shims to compensate for the non-flatness before tightening. Make tubing connections at the high (filter
inlet) and low (filter outlet) pressure fittings on the gauge. The high pressure connection is on the upper side; the
low pressure connection is at the bottom.
If you intend to attach a pressure gauge that will show system pressure, the ¼” npt port in the bleeder plug (10 or 11)
contains a pipe plug when shipped, but is easily removed for installation of a pressure gauge.
If you have purchased a model with suffix letter “D”, two selector valves with ¼” npt threads are included. These
valves permit one Gammon Gauge™ to be used for measuring two different differential pressures. For example,
the up and downstream fittings on filter A can be connected at ports A of each valve. The filter B connections can be
made at Ports B of each valve. The suffix letter G denotes ¼” BSP threads for these valves.
CAUTION: If the Gammon Gauge™ is installed with gauge-line shutoff valves, never leave both valves closed at
the same time because fuel thermal expansion will break the glass cylinder.
CORRECT CONNECTION OF MODEL GTP-534PB ONLY:
A tubing connection from the inlet side of the filter vessel must be made at the upper (side) port of the gauge.
The downstream connection from the filter vessel must be made at the center bottom of the gauge. The side
fitting at the bottom of the gauge is a vent port which should be connected to the slop or fuel recovery system.
NOTE: This version of the Gammon Gauge™, GTP-534PB, has an integral pressure relief feature that is set to
relieve thermally built up pressure at 300 psi to protect the glass cylinder. Such a condition may occur if gauge
line valves on both sides of the gauge are closed on a very hot day.
PERIODIC INSPECTION:
Periodic calibration of this instrument is unnecessary because the graduated scale is made to match the
characteristics (load/deflection curve) of the spring.
If the spring loses some of its strength for some reason, the ”free length” must be shortened. A full length spring will
always provide accurate readings. This is a fundamental truth about compression springs.
This spring is at its “free full length” when there is zero differential pressure; the top of the piston is then in the “zero”
band of the graduated scale.
-2PERIODIC INSPECTION CONTINUED:
Therefore, if there is no differential pressure imposed on the Gammon Gauge™ and periodic inspection reveals
that the piston does not return to “zero”, either the spring has failed and should be replaced or the piston is binding
in the glass cylinder.
CAUTION: If it is determined that the spring must be replaced, follow the disassembly instructions. Red springs are
for gauges that are calibrated to 15 psi while blue springs must be used only with gauges that are calibrated to 30
psi.
FUNCTIONAL INSPECTION per EI-1581 FOR GTP-534 ONLY:
The specification for filter separators states that all piston-type differential pressure gauges should have a 3-way
test valve at the low pressure connection so that the action of the piston can be observed by venting the underside
of the piston. The objective of this test is to determine whether the piston or glass cylinder have collected a coating
or deposits that would interfere with the free movement of the piston. You can purchase a suitable stainless steel, 3way valve retrofit kit for existing gauges by ordering model GTP-8304. See Diagram A.
1. Turn the valve so that the arrow shaped handle is pointing to the right. The letter P (pressure) is visible at the
pointed end. This is the normal operating position. To perform a test, the system must be at operating pressure.
Turn the valve handle so that the pointed end is to the left with a letter V (vent) now visible. This blocks pressure
from the downstream side of the filter separator and opens a flow path to the vent port from the lower side of the
glass cylinder under the piston. Pressure on the piston will force it downward, displacing fuel through the vent
port. Collect this fuel in a cup or it can be directed to the slop tank or fuel recovery system.
2. While the piston is moving downward, note whether it moves smoothly or erratically.
3. After the piston has stopped moving turn the valve handle back to the starting position with the letter P visible.
The piston will return to its original position. Observe the motion of the piston on its return.
4. Stop flow. The piston should move back to a position within the zero band. Accuracy of the gauge is within ± 0.5
psi if the piston returns to the zero band.
NOTE: If the piston moves erratically in either direction, down or up, this means that the glass cylinder and piston
need cleaning. The only acceptable cleaning material is Scotch-Brite. This is a non-metallic scrubbing pad
normally used in kitchens.
5. Repeat the test after cleaning and reassembly. If the piston will not return to zero, the spring must be replaced.
Refer to page 3.
FUNCTIONAL INSPECTION per EI-1581 FOR GTP-543PB ONLY:
EI-1581 Specifications for jet fuel filter separators requires that piston-type differential pressure gauges be
installed with a 3-way valve at the low pressure connection so that operation of the gauge can be inspected. The
Gammon Gauge model that you have received has a push button 3-way testing valve with a spring return feature. A
vent connection is located either on the right side or the rear of the lower end of the Gammon Gauge as shown in
Dia. A.
1. With the system operating at normal flow and pressure, push the valve button inward. This blocks pressure
from the downstream side of the filter vessel and opens a flow path to the vent port from the lower end of the
glass cylinder under the piston. Pressure on the piston will force it downward, displacing fuel through the vent
port. Collect this fuel in a cup or it can be directed to a slop tank, where it normally should be routed.
2. While the piston is moving downward, note whether it moves smoothly or erratically.
3. After the piston has stopped moving, release force on the button so that it will return to its original position.
Observe the motion of the piston on its return to a normal position.
4. Stop flow. The piston should move back to a position within the zero band at the top of the scale Accuracy of the
gauge is within ± 0.5 psi if the piston returns to the zero band.
NOTE: If the piston moves erratically up or down, this means that the glass cylinder and piston need cleaning. The
only acceptable cleaning material is Scotch-Brite.
5. Repeat the test after cleaning and reassembly. If the piston still will not return to zero, the spring has taken a
permanent set and must be replaced.
-3MAINTENANCE:
A. Slow reaction to changes in differential pressure.
Filter (1) may be plugged with dirt and must be replaced. Cleaning is not practical because the dirt may plug the
inner pores of the filter media and will not flush out.
B. Piston does not return to “zero” when there is no system flow to cause a differential pressure.
See sections titled Periodic Inspection and Functional Inspection
C. Leakage
Replace seals as necessary but they must be made of Viton, not Buna N. However if the gauge is used at very
low temperatures. (below zero degrees F or -20°C), it should have been ordered with Option O special
compound o-rings shown in the parts list.) Refer to drawing No.GTP-534 or GTP-534PB, attached.
DISASSEMBLY:
To Replace Gauge Protection Filter Element (1).
Remove bleeder plug (10 or 11). The element is removed by pulling it straight upward. This can be done by prying
upward through the high pressure connection port, but an easier way is to use a hook bent on the end of a wire,
such as a heavy paper clip. The hook need be only 1/16” long to hook on the under edge of the filter element end
cap. Install new filter element by pushing downward. Reinstall the bleeder plug.
To Remove Piston (3) and Glass Cylinder (2)
Remove 1 screw (20) located at lower end of the
scale. Remove 4 screws (22) located at the lower
end of the cage. It is unnecessary to remove the 4
similar screws at the upper end of the cage (12 or
13). Carefully pull downward on lower flange.
Remove flange, spring and glass cylinder. The
piston will tend to stay in the glass cylinder, but can
be removed by pushing upward with a small wooden
stick. Do not use metal. Be extremely careful not to
scratch the piston or allow any metal part to touch its
outer surfaces. Clean the piston and glass cylinder
as described in the section titled Functional
Inspection. See note at step 4. To determine
whether or not the piston and glass cylinder are
thoroughly cleaned, dry both parts and then install
the piston. Gently push it through the cylinder in both
directions.
After 3 or 4 cycles, the piston should slide freely in
both directions due to its own weight when the
cylinder is tipped.
To reassemble, simply reverse the disassembly
procedure, but be sure that the seals are not cut by
the glass cylinder. To prevent this, use a slight
amount of lubricant, such as petroleum jelly. Rotate
the lower flange while applying force to ease the oring into the glass cylinder.
This diagram is for GTP-534 gauge only
-4REPLACING SEALS IN THE PUSH BUTTON FLANGE MODEL GTP-534PB ONLY:
If leakage occurs at the push button fitting, the o-ring on shaft (27) is the most likely seal to need replacement.
However, without a special tool, it may be damaged during replacement so we recommend a new shaft and o-ring
assembly, P/N GTP-552-8J. Refer to diagram C. Remove the push button (29) by loosening the set screw (30).
Remove the actuator body (28) from the lower flange (4, 5, 25, or 26). Then push inward on the end of the shaft (27)
to remove it. To install shaft (27), first apply a thin coating of petroleum jelly to the o-ring. Then install the push button
(29). It is advisable to replace o-rings (23 and 24). Use petroleum jelly as a lubricant on both o-rings.
Internal leakage of seal (23) will not be evident unless the piston fails to move downward when the push button is
pressed to its full travel.
If leakage occurs through the vent port (31), the o-ring on the poppet valve must be replaced. This requires that the
valve, spring, and spring adjuster screw be removed and then replaced so that the valve poppet will relieve
pressure at 300 psi. This requires special fixtures and instrumentation so we have an exchange/replacement
arrangement for the vent port assembly shown in Diagram B. It is factory set for 300 psi. If you request P/N GTP552-8G, we will quote a price for the exchange arrangement. If you request P/N GTP-552-8GR, we will quote the
price for the outright purchase of the factory set assembly. A new o-ring (22) is included.
ONLY
Location
Company Name
[email protected]
GAMMON TECHNICAL PRODUCTS, INC.
2300 HIGHWAY 34
MANASQUAN, NJ 08736 USA
PHONE (732) 223-4600 FAX (732) 223-5778
Sign here
TEST PERFORMED BY
TEST CONFIRMATION
Steps 1-5 above were successfully performed on gauge/filter/vehicle#
DATE
FORM# GGTC2-11/11
5. Repeat the test after cleaning and reassembly. If the piston still will not return to zero, the spring must be replaced.
NOTE: If the piston moves erratically and/or it does not return to zero, disassemble and clean the piston and
glass tube with jet fuel and Scotch-Brite. Refer to Installation and Maintenance Bulletin, for instructions.
4. Stop system flow. The piston should move back to a position within the zero band. In the case of a Peak Hold gauge, turn
the green reset knob to release the piston. Accuracy of the gauge is within ± 0.5
psi if the piston returns to the zero band.
3. Actuate the test valve on the bottom of the gauge to vent the underside of the piston. The piston should move to the
bottom of its travel smoothly without evidence of sticking as it moves. Be prepared to collect approximately 50 ml of fuel
from the outlet of the 3-way valve. Return the test valve to the normal position by releasing the button on GTP-534PB or by
turning the valve handle of GTP-2305.
2. Establish full system flow. The gauge should read a differential pressure greater than zero.
1. With no flow in the system, read the gauge; it should read within the zero band.
Unlike common pressure gauges, Gammon Gauges do not require periodic bench/laboratory calibration. A complete test of the
Gammon Gauge consists of the following steps. If all steps are conducted with the correct results, the gauge is calibrated. To
perform this test in accordance with EI-1581, the underside of the piston must be vented by blocking pressure from the
downstream side of the filter vessel. A 3-way valve, such as our GTP-2305, can be installed, but we strongly recommend the
Gammon Gauge with a built-in 3 way push button valve, GTP-534PB.
GAMMON GAUGE GTP-534 SERIES
OPERATIONAL CHECK AND CALIBRATION CERTIFICATE