sive pressures to achieve the desired flow rates; these may result
in leakage and undue wear on the pump.
Although all flowmeters are carefully calibrated and tested after
assembly and no changes should be necessary; field calibration is
recommended after installation is complete.
While the installation is still new, clean the strainer frequently. Af-
ter the system has been in service, only periodic cleaning is neces-
sary.
MAINTENANCE
General Maintenance
For sustained accuracy of flowmeters, little maintenance is re-
quired other than to see that the proper conditions of operation
are preserved. Once the flowmeter has been installed correctly,
these conditions consist merely in guarding against foreign mat-
ter, such as vapor, sediment or water entering the measuring
chamber. However, should any malfunction develop, do not dis-
mantle the flowmeter until the cause of the trouble has first been
determined. (Refer to TROUBLESHOOTING .)
Sediment- The liquid passing through the measuring chamber
must be free of grit and other forms of sediment to prevent unnec-
essary friction and to eliminate scoring of the piston and chamber
walls. Evidence of trouble from this source will be found in un-
der-registration of the flowmeter. Periodic cleaning and inspection
of the flowmeter strainer will help to insure against this form of
trouble.
Vapor - Being an instrument that measures by volume, a
flowmeter will record the passage of vapor as well as the liquid
being measured. Over-registration will result. Where this condi-
tion exists, check for adequacy of the vapor elimination system.
Water - Incidental water will cause no damage to the flowmeter.
Trouble from this source may be expected when water is allowed
to remain in the flowmeter.
Erratic Registration
Erratic registration is usually caused by vaporization of the prod-
uct, faulty differential valve or vapor release valve
(over-registration), or by dirt or pipe scale in the measuring cham-
ber (under-registration). Clean the flowmeter if necessary, as di-
rected in MAINTENANCE. If flowmeter continues to creep when
outlet valve is closed, check differential valve seals. (Refer to
TROUBLESHOOTING.)
Consistent Over- or Under- Registration
When the flowmeter consistently registers either more or less than
is delivered and no other cause in system function can be deter-
mined, calibration of the metering system is recommended.
CALIBRATION ON UNCOMPENSATED
FLOWMETERS
Test the flowmeter using a volumetric prover large enough to per-
mit the flowmeter to operate for at least one minute at normal
flow rate. Slip tube and rotary gauge reading are not sufficiently
accurate for proving flowmeters. A detailed description of an
LP-Gas test procedure may be found in the National Bureau of
Standards Handbook 99, “Testing Liquefied Petroleum Gas Liq-
uid-Measuring Devices”.
A thermometer well is provided for taking temperature readings
while calibrating. It is covered by a snap plug to keep dirt from en-
tering the well.
When temperature readings are to be obtained, the well must be
filled with permanent type antifreeze, or with a light oil.
If a gravimetric test method is used, the conversion to gallons
must be on the basis of: (1) specific gravity determined at the time
of the test (not an assumed value), and (2) the temperature of the
product as it is passed through the flowmeter. The volumetric test
method, however, is considered to yield more accurate results and
is preferred. After performing the test procedure:
1. Determine the percentage of over-or under-delivery for each
test conducted.
2. Remove the register screws and take off the register.
3. Note the numbers stamped on the register change gear (on
register spindle marked “R” on the adapter plate) and on the stuff-
ing box change gear (or flowmeter spindle marked “S” on the
adapter plate). Locate the gear tooth combination on the Change
Gear Chart.
4. Add the step-wise increments of change in registration until the
desired amount is reached. If the flowmeter is under-registering
(delivering too much), select a new pair of gears farther down the
chart. If the flowmeter is over-registering (delivering too little), se-
lect a new pair of gears farther up the chart.
5. Remove the old change gears and replace them with the new
pair. Always place the change gear with the smaller number of
teeth on the “R” shaft and the gear with the greater number of
teeth on the “S” shaft as indicated on the adapter plate. To remove
change gears, close the split end of the spindle slightly with a pair
of pliers to permit removal of the change gear. After slipping on
the new gear, spread the ends of the spindle slightly.
6. Reinstall the register, run several gallons (liters) through the
flowmeter, and retest.
CALIBRATION ON COMPENSATED FLOWMETERS
1. Remove the two seal screws and cover from the temperature
compensator.
2. Move the anchor pin from “Compensated Anchor” to “Uncom-
pensated Anchor”. (Flowmeter reading will now be uncompen-
sated.)
3. Perform the same LP-Gas flowmeter test procedure as outlined
for uncompensated flowmeters.
4. If necessary to change flowmeter calibration, refer to
CALIBRATION ON UNCOMPENSATED FLOWMETERS, steps 1 to
6.
5. Move anchor pin to “Compensated Anchor”, and operate
flowmeter for at least 50 gallons (189 liters) before proceeding
with calibration tests. (Flowmeter readings will now be tempera-
ture compensated.)
6. Perform same flowmeter test procedure used for uncompen-
sated flowmeter. Temperature reading must be taken at the prover
only. (Temperature at flowmeter is assumed to be 60ºF.)
7. If necessary to adjust compensated registration, turn calibra-
tion dial located on the right side of the Lever Arm (to turn adjust-
ment, use wrench on hex hub of dial). Turn clockwise “To Give
More” or counterclockwise to “To Give Less”. Each dial gradua-
tion will change compensated delivery approximately 0.15%.
MEASURING CHAMBER MAINTENANCE
CAUTION: Be sure meter is completely relieved of pressure
before performing any internal maintenance. Pressure must
be 0 psig. Failure to properly depressureize and evacuate the
system could result in serious injury or death from explo-
sion/fire.
Perform the following outdoors, away from buildings and
sources of ignition. Before opening any part of the flowmeter,
close all valves between supply tank and flowmeter. Replace-
ment gaskets should be on hand.
To Remove and Disassemble
This operation is not difficult and may be performed by any com-
petent mechanic. No special tools are required. No trouble need
be expected, if these few simple but important directions are fol-
lowed. Do not open the flowmeter until you have checked over all
other possible causes of erratic registration. (Refer to TROUBLE
SHOOTING.)
1. Prepare a clean surface on which to place the parts as they are
removed. (The parts are machined to close tolerances and should
be handled with care.) Also check that a replacement gasket is on
hand before opening the flowmeter, it may need to be replaced.
2. Remove the flowmeter top taking care not to damage the gas-
ket, it is to be reused.
3. Lift the measuring chamber from the flowmeter casing.
4. Remove the top plate by inserting a screwdriver in one of the
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