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PTFM 1.0 Portable Transit Time Flow Meter
TRANSDUCER MOUNTING
LOCATION
The position of the transducer 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 transducer onsite testing is recommended to determine
optimum mounting position. Use the transducer 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 transducers 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 transducers 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 transducers 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 transducer 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. Transducer mounting 6 pipe diameters
upstream and 10 diameters downstream from these
disturbances is generally optimum.
The transducers 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
FLOW
TRANSDUCERS MOUNT 6 DIAMETERS
UPSTREAM OR 10 DOWNSTREAM
FROM AN ELBOW
