Honeywell RABO Instruction Manual page 7

8) Connect the inlet and outlet pipe flanges using
appropriate bolts and gaskets. Inlet and outlet pipe
ELSTER RABO Rotary Gas Meter
flanges should be parallel and should not introduce any ®
bind on the meter body when tightened.
9) Level meter to within 1/16" per foot in all directions and
tighten flange bolts evenly (maximum 80ft-lbs).
Pressure test ports are provided for simplified pressure
c) Adding Oil
connections [Figure 9].
!
WARNING
Add oil only to the index end of the meter.
Below 45 F the neoprene core of the Pressure test ports
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does not recover its original shape as rapidly as it would
1) Ensure gas valves are closed and meter and piping are
at temperatures above 45
depressurized.
the probe used for pressure or temperature readings, the
valves may not close fully and immediately or the valves
!
WARNING
may remain slightly open until the operating temperature
is above 45 F. Duration of probe insertion and pressure
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Failure to depressurize the meter prior to removing
are also factors in the rate of valve closing. For this reason,
meter and/or components could result in personal
plugs should not be used in applications where discharging
RABO Rotary Gas Meter
® injury and/or property damage.
gas or liquids would create a hazard. The gasketed cap
is supplied to eliminate the small amount of leakage that
2) Remove oil fill plug in the counter end case cover using a
may occur at lower temperatures after probe insertion and
5mm hex key [Figures 5 and 6].
removal. The cap should be left on the plug at all times
3) Using the supplied syringe and oil, slowly add oil until
Pete's Plugs ® are provided for simplified pressure connections
and tightened to deter unauthorized removal. Special care
it is +/-1/16" of the center of the sight glass [Figure 7].
[Figure 9]. Typically, when proving a meter, both the meter
should be taken to assure that readings are taken in the
DO NOT OVERFILL. Only use Shell Morlina lubricating oil.
pressure and meter differential pressure are used and
shortest space of time and that a probe is never left in a
recorded. The RABO meter differential pressure ports are not
plug for a period of hours or days. Severe deformation of
!
WARNING
full bore and most temperature probes will not fit through
the valves may occur if the probe is left in the plug for a
into the gas stream. Installing the temperature probe in the
long period of time.
DO NOT remove any sight glasses. No maintenance
provided thermowell ports is recommended.
can be performed through these openings.
PRESSURE TEST PORTS
PETE'S PLUGS
®
4) Reinstall the oil fill plug.
Figure 9. Pressure test ports Figure 9. Pete's Plugs
The meter volume is determined though a device that senses
Typically, when proving a meter, both the meter pressure and
the meter revolutions. An optical pickup can be used on the
meter differential pressure are used and recorded. The RABO
index proving wheel or an index pulser may be used.
meter differential pressure ports are not full bore and most
On-site proving, performed in-line, also requires connections
temperature probes will not fit through into the gas stream.
that allow air flow through the meter to the prover. This is
Installing the temperature probe in the provided thermowell
accomplished by use of pipe Tees upstream and downstream
ports is recommended.
of the meter. A bypass loop is recommended for uninterrupted
The meter volume is determined though a device that senses
gas supply to the customer.
the meter revolutions. An optical pickup can be used on the
While performing an accuracy test, the meter is tested for
index proving wheel or an index pulser may be used.
a specified volume of gas at each flow rate test point. Poor
On-site proving, performed in-line, also requires connections
repeatability at a given rate may be caused by a test volume
that allow air flow through the meter to the prover. This is
that is too small. It the meter does not repeat within acceptable
accomplished by use of pipe Tees upstream and downstream
limits (0.1%), try increasing the test volume and retesting
of the meter. A bypass loop is recommended for uninterrupted
the meter. Most companies have developed test plans
gas supply to the customer.
that include the volume of gas for each size meter at a
given flow rate. Consult your Elster representative for
applicable volumes.
F. Therefore, upon removal of
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®
07 Honeywell
OIL
LEVEL
SIGHT
GLASS
While performing an accuracy test, the meter is tested for
a specified volume of gas at each flow rate test point. Poor
repeatability at a given rate may be caused by a test volume
that is too small. It the meter does not repeat within acceptable
Figure 6. Vertical installation
limits (0.1%), try increasing the test volume and retesting
the meter. Most companies have developed test plans
that include the volume of gas for each size meter at a
given flow rate. Consult your Elster representative for
applicable volumes.
b) Differential Pressure Testing
A differential pressure test is not an accuracy test, but it can
be used to gauge the relative performance of the meter.
Rotary meters are made from solid parts, machined to tight
06 Elster Instromet
tolerances with close clearance fits, and the energy it takes
to turn the meter is generally used to overcome the friction
Figure 7. Sight glass
of the bearings and other rotating parts. If this friction value
increases, it will take more energy to overcome it. This
additional energy is measured as an increased pressure
b) Differential Pressure Testing
drop across the meter.
A differential pressure test is not an accuracy test, but it can
The increased friction is caused by contamination of the
be used to gauge the relative performance of the meter.
measuring chamber and/or bearings.
Rotary meters are made from solid parts, machined to tight
Contamination in the measuring chamber can cause the
tolerances with close clearance fits, and the energy it takes
meter components to wear against each other. Contamination
to turn the meter is generally used to overcome the friction
in the bearings makes them harder to turn.
of the bearings and other rotating parts. If this friction value
increases, it will take more energy to overcome it. This
Comparing the pressure drop reading when the meter is new
additional energy is measured as an increased pressure
to the reading collected after time allows the performance to
drop across the meter.
be monitored.
The increased friction is caused by contamination of the
RABO meters are supplied with Pressure test ports installed
measuring chamber and/or bearings.
in the meter differential pressure ports [Figure 9]. This faci-
litates differential meter testing. A differential pressure test is
Contamination in the measuring chamber can cause the
performed using a differential pressure manometer. The test
meter components to wear against each other. Contamination
is to measure the pressure drop across the meter at a given
in the bearings makes them harder to turn.
flow rate, under known operating conditions at a known date
Comparing the pressure drop reading when the meter is new
and time.
to the reading collected after time allows the performance to
The meter differential curve of flow rate vs pressure is not
be monitored.
linear. Testing at multiple flow rates is suggested. It is
RABO meters are supplied with Pete's Plugs
preferable to test at 3 rates between 25% and 100% of flow
meter differential pressure ports [Figure 9]. This facilitates
if possible. Differential pressure tests at flow rates under
differential meter testing. A differential pressure test is
25% are hard to interpret because the meter differential
performed using a differential pressure manometer. The test
pressure at the lower flow rates is quite small. The errorin
is to measure the pressure drop across the meter at a given
measurement is almost as large as the reading itself.
flow rate, under known operating conditions at a known date
The meter differential pressure is also a function of line
and time.
pressure and increases as line pressure increases. Testing
The meter differential curve of flow rate vs pressure is not
the meter at the same conditions (line pressure and flow
linear. Testing at multiple flow rates is suggested. It is
rates) yields comparable data.
preferable to test at 3 rates between 25% and 100% of flow
A change in the differential pressure indicates a change
if possible. Differential pressure tests at flow rates under
in performance. Testing has shown that a 50% increase in
25% are hard to interpret because the meter differential
meter differential pressure (at flow rates over 25%), indicates
pressure at the lower flow rates is quite small. The error in
almost a 1.0% change in meter accuracy.
measurement is almost as large as the reading itself.
Baseline data must be captured during initial start-up to
The meter differential pressure is also a function of line
which future data can be compared.
pressure and increases as line pressure increases. Testing
the meter at the same conditions (line pressure and flow
If the differential pressure test shows an increase in the meter
rates) yields comparable data.
pressure drop at a given flow rate of more than 50% from the
original value (1.5 x original value), then it is recommended
A change in the differential pressure indicates a change
that the meter be removed and serviced.
in performance. Testing has shown that a 50% increase in
meter differential pressure (at flow rates over 25%), indicates
The frequency of deferential testing is at the discretion of
almost a 1.0% change in meter accuracy.
the user.
Baseline data must be captured during initial start-up to
which future data can be compared.
If the differential pressure test shows an increase in the meter
pressure drop at a given flow rate of more than 50% from the
OIL
DRAIN
installed in the
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