Our vast knowledge and experience
of providing solutions for organisations worldwide has proven our understated
capability to provide the complete range of flow measurement equipment.
Our custom-designed measurement solutions are typically of the differential
pressure (DP) type, including orifice plates, Venturi tubes, Pitot tubes and
flow nozzles.
Orifice
Plates
The most common and widely used differential producers, suitable for a wide
range of flow measurement applications in line sizes of 50 mm and above. Choose
'concentric square edged' for general application, 'conical entrance' or 'quarter
circle' for low Reynolds number flows, and 'segmental' or 'eccentric' for
flows containing light solids and slurries.
Flow
Nozzles
For measurements where high temperatures and velocities are present, the flow
nozzle may provide a better solution than an orifice plate. Its construction
makes it substantially more rigid in these adverse conditions and flow coefficient
data at high Reynolds numbers is better documented than for orifice plates.
The inlet is contoured, and may be either radius entrance (ISA1932) or elliptical
entrance (ASME long radius). The flow nozzle has about a 65% greater flow
capacity than an orifice with the same diameter.
Venturi Tubes
There are two common types of Venturi tube - the Venturi nozzle, and the classical
Venturi. Both feature a convergent inlet section and a divergent outlet section.
The major advantage of the Venturi over orifice plates and flow nozzles is
in the area of pressure recovery. Typically, unrecovered pressure is in the
region of 10 - 30% of measured DP as opposed to 40 - 90% for an orifice plate
(depending on beta ratio). Although the cost of a Venturi can be comparatively
high, where pumping costs are important the initial outlay can be warranted.
Another advantage of the classical Venturi over the other differential pressure
producers is that the requirements for upstream and downstream straight pipe
lengths are somewhat less onerous.
Pitot
Tubes
These practical and effective DP primary elements can, in some applications,
match Venturis in terms of performance at a substantial cost advantage, especially
for large diameter pipelines. A number of upstream facing ports effectively
average the velocity profile and allow for measurement of impact, or stagnation
pressure, and a pressure port (or ports) located behind the tube measures
the static pressure, the difference being used to infer the flow rate. The
differential pressures produced from such devices are considerably lower than
from the other DP elements, which can limit their usefulness in certain applications.
However, they present little resistance to the flow and as such exhibit excellent
unrecovered pressure loss characteristics (it may be considered as negligible
in many circumstances). Installation of averaging Pitots is simple and inexpensive,
and since there are no sharp edges to wear, averaging Pitot tubes offer good
long term accuracy.
Other Products
We also provide a wide range of other flow measurement technologies including electromagnetic, Coriolis, vortex and ultrasonic solutions.
Why not allow Thermocouple Instruments to provide all you need for a complete mass flow solution? Through our Solutions range, we can supply all your requirements, including computers, manifolds, valves, DP and pressure transmitters.
Please click here to go to the literature download page