Dwyer UFB - Manual (Page 14)

2: Installation
10
To obtain the most accurate results, the condition of both the liquid and the pipe wall must be suitable to allow the
ultrasound transmission along its predetermined path. It is important also that the liquid flows uniformly within the
length of pipe being monitored and that the flow profile is not distorted by any upstream or downstream
obstructions. This is best achieved by ensuring there is a straight length of pipe upstream of the transducers of at
least 20 times the pipe diameter and 10 times the pipe diameter on the downstream side, as shown in Figure 2.2.
Flow measurements can be made on shorter lengths of straight pipe, down to 10 diameters upstream and 5
diameters downstream, but when the transducers are positioned this close to any obstruction the resulting errors
can be unpredictable.
Preparation
Before you attach the transducers you should first ensure that the proposed location satisfies the distance
requirements shown in Figure 2.2, otherwise the resulting accuracy of the flow readings may be affected.
Prepare the pipe by degreasing it and removing any loose material or flaking paint in order to obtain the best
possible surface. A smooth contact between the pipe surface and the face of the transducers is an important
factor in achieving a good ultrasound signal strength, and therefore maximum accuracy.
2.3.2 Transducer attachment
Figure 2.4 Transducer attachment (completed assembly)
Key Point: Do not expect to obtain accurate results if the transducers are positioned
close to any obstructions that distort the uniformity of the flow profile.
Rectangular Upstream
Downstream
Stainless steel bands
transducer
opening transducer
Nylon Flag
Transducer
Cable Connector
Thumb screw
Transducer Holder