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PTFM 1.0 Portable Transit Time Flow Meter
SENSOR MOUNTING LOCATION
The position of the sensor is one of the most important considerations for accurate Transit Time flow
measurement. The same location guidelines apply to Transit Time as most other types of flow meters.
Before permanently mounting a Transit Time sensor onsite testing is recommended to determine
optimum mounting position. Use the sensor coupling compound (supplied with each Greyline flow
meter, or petroleum gel, acoustic compound or electrocardiograph gel). Take several readings around the
axis of the pipe and then at several points upstream and downstream from the selected position,
checking for consistent readings. Avoid high or low reading areas. Mount the sensors where consistent
(average) readings were obtained or continue testing on another pipe section.
VERTICAL OR HORIZONTAL PIPE - Vertical pipe
runs generally provide evenly distributed flow. On
Horizontal pipes and liquids with high concentrations
of gas or solids, the sensors should be mounted on the
side (1 to 5 o’clock positions) to avoid concentrations
of gas at the top of the pipe, or solids at the bottom.
VELOCITY INCREASING DEVICES: Generally the sensors must be mounted away from flow
disturbances such as valves, pumps, orifice plates, venturis or pipe inlets and discharges which tend to
increase flow velocity. Velocity increasing devices often cause cavitation, or rapid release of gas
bubbles, and readings both up and downstream may be intermittent or inaccurate. As a guideline, mount
the sensor at least 20 diameters upstream or 30 diameters downstream from velocity increasing devices.
Required distance from a velocity increasing device will vary in applications depending on the flow
velocity and the characteristics of the liquid itself.
TURBULENCE INCREASING DEVICES: Elbows,
flanged connections and tees tend to introduce
desirable conditions of an evenly distributed flow
profile. Sensor mounting 6 pipe diameters upstream
and 10 diameters downstream from these disturbances
is generally optimum.
The sensors are designed to mount longitudinally on a straight section of pipe. Do not attempt to mount
it on bends, elbows or fittings.
VERTICAL PIPE USUALLY
HAS EVENLY DISTRIBUTED FLOW
1 TO 5 O'CLOCK POSITION
ON HORIZONTAL PIPES
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