Dynasonics DDFXD Doppler Ultrasonic Flow Meter - Manual (Page 19)

06-DPP-UM-00147 02/12 19
PROBE INSERTION
Before inserting the DP7 probe into the piping system, it is necessary to calculate the probe insertion
depth that will place the measuring electrodes at the proper position in the pipe. In order to complete
this calculation, some knowledge of the piping system must be known. Refer to the paragraphs that fol-
low and Figure 2.6 for information regarding this process. The variables required are:
t The overall probe length.
t Pipe internal diameter (I.D.).
t Pipe wall thickness.
t The length of the valve stack.
t Amount of straight pipe diameters in the system.
Using this information and referring to Figure 2.6, proper insertion depth can be determined.
Measurement A — The typical depth that the DP7 probe tip is inserted into the piping
system is 1⁄8 (12.5%) of the pipe internal diameter.
Measurement B — Pipe wall thickness. This information can be obtained from standard
pipe wall charts See the Appendix of this manual) or ideally can be measured using an
ultrasonic wall thickness gauge.
Measurement C — Measure the distance that is going to be taken up by the pipe tap,
nipple, full-flow ball valve and the insertion fitting. DP7 probes utilize 1½” NPT hardware
and the insertion fitting is approximately 2.5” in height.
Measurement E — This is the overall length of the probe measured from the black mea-
surement tip to the top flange on the probe.
Measurement D — This is the length of DP7 probe that will be protruding from the inser-
tion fitting after it is inserted to the proper depth in the fluid stream.
1) Lubricate the O-rings located within the DP7 probe seal fitting so that the seals are not damaged
during probe insertion.
2) Run the lower jam nuts down to a point that approximates the final insertion position or at least
far enough to allow insertion into the insertion fitting. Using the threaded rods as a guide, posi-
tion the probe in the insertion fitting. Continue to insert the probe as far into the isolation assem-
bly as possible. The probe tip will come in contact with the closed “ball” in the isolation valve.
CAUTION: Do Not Force the Probe Tip Against the “Ball”, as damage to the probe tip may
result.
3) Replace the upper jam nuts (2 on each rod) and the cotter pins. The nuts should be run down to
the top side of the retaining collar and the cotter pins replaced. Orient the probe in the direction
of flow as indicated by the FLOW direction arrow located on the top of the probe flange. See Fig-
ure 2.8. Lock the probe in position with the enclosed Allen wrench.
CAUTION: The nuts on both ends of the retaining rods must always be in place as a safety
measure to prevent possible probe blow out. Inserting cotter pins is a further safety measure.
4) Slowly open the isolation valve. When the valve is fully open, use the proper size wrench on the
insertion nuts, alternately tightening each nut about two complete turns to avoid uneven seal
loading.