Liquid Controls M-MA Meters - Manual (Page 8)

operatIon requIreMents
▪ the Meter Must reMaIn full of product
at all tIMes.
An easy way to accomplish this is to put the meter assembly in the
line below the piping center-line (a sumped position). This requires
adding elbows and flanges prior to installing the meter. The meter
should be installed in a bypass loop, below the pipe center-line,
with block valves upstream and downstream of the meter inside
the bypass loop. A block valve should be located in the main
pipeline and labeled as the bypass valve.
▪ pIpInG pressure relIef
Any portion of pipe system that might isolate or block flow should
be provided with a pressure relief to prevent damage from thermal
expansion. There are excellent benefits to this type of installation.
First, the meter is kept full. Second, this type of installation
allows the meter to be isolated for servicing and calibration while
continuing flow through the bypass valve.
▪ MaIntaIn upstreaM lInes
Upstream lines must be maintained full to prevent air from entering
the meter. If upstream or inlet lines are constructed in a manner
which allows reverse flow, foot valves, or back checks must be
installed.
▪ underGround tanks, subMersIble puMps
Underground tanks that are furnished with a submersible pump
will eliminate many problems that occur with positive displacement
pumps (suction pumps) when suction piping is incorrectly sized or
when the lift is too great.
▪ apI Manual of petroleuM MeasureMent
standards
Every meter should be calibrated under actual service and
installation conditions per the API Manual of Petroleum
Measurement Standards:
The following chapters of the API Manual of Petroleum Measurement
Standards supersedes the API standard 1101.
Chapter 4 - Proving Systems
Chapter 5 - Metering
Chapter 6 - Metering Assemblies
Chapter 11 Section 2.3 - Water Calibration of
Volumetric Provers
Chapter 12 Section 2 - Calculation of Petroleum
Quantities
▪ provIde a Means of convenIently
dIvertInG lIquId for calIbratIon
purposes
▪ evaluate puMpInG equIpMent
Give careful attention to your system’s pumping equipment and
piping. Because of their influence on liquid being measured as it
enters the metering assembly, systems should be made free of
conditions that cause or introduce entrained air or vapor.
▪ folloW the Manufacturer’s
recoMMendatIon fully When InstallInG
puMps
Give particular attention to factors like: use of foot valves, pipe
size to the inlet, and conformance to net positive suction head
(NPSH) conditions when suction pumping is required. Follow
the manufacturer’s recommendations to minimize air and vapor
elimination problems.
▪ lIGht hydrocarbons and sIMIlar lIquIds
For liquids such as light hydrocarbons that tend to flash or
vaporize easily at higher ambient temperatures, it is advantageous
to use flooded suctions and piping sized larger than the nominal
pump size.
▪ vehIcle tank InstallatIons
On vehicle tank installations, the layout of the system’s piping
is crucial in preventing problems with split compartment
test conformance. Piping should slope away from a positive
displacement pump to prevent resurgent re-priming of the pump
due to drain back.
▪ avoId hydraulIc shock
Hydraulic shock is harmful to all the components of an operating
system, including the valves, the meter, and the pump. Because
of the high precision with which they measure products, meters,
in particular, must be protected against hydraulic shock. The best
protection against hydraulic shock is to prevent it from occurring.
To prevent hydraulic shock, adjust the closing rate of the valve
until shock does not occur.
▪ avoId therMal expansIon
Thermal expansion, like hydraulic shock, can easily damage
meters and other components in the system. When designing the
system, include pressure relief valves in any portion or branch of
the system that might be closed off when an operating or block
valve is closed.
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