Meriam 70H_72H High Pressure Wet Tap Accutubes with Integral 3-Valve Head and Optional RTD - Manual (Page 28)

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7
MAINTENANCE AND REPLACEMENT PARTS
7.1 Cleaning
Accutube performance is generally not sensitive to dirt and film buildup. However, if
contamination can build up to the point where internal or port hole blockage is
threatened, then precautions must be taken to prevent this. One method commonly used
is occasional probe removal for thorough cleaning. Purging systems are also used which
on regular intervals inject air or fluid through the probe into the pipe line system, thus
flushing out the probe interior. A pressure source and a system of control valves are
required to do this.
7.2 Replacement Parts
Accutube probes are completely welded sealed units for greatest integrity and reliability.
No parts within the probe are replaceable. Mounting hardware and accessory parts can
be obtained from the factory as replacement parts.
8 TROUBLESHOOTING
8.1 Should measurement problems occur with an Accutube probe, the following is a check
list of possible causes:
8.1.1 Probe Position: Verify orientation of probe as stated in Section 1.0.
8.1.2
Upstream/Downstream Piping: Verify proper straight pipe run is as
recommended in Section 1.0. (Table 1)
8.1.3
Pipe I.D.: Verify the inside diameter is nominally the same as that for which the
probe is designed (standard product is Schedule 40 on 20” line size and less, and
Standard Weight for larger line size).
8.1.4
Flow Magnitude and Direction: Verify that the reference source for expected
flow is accurate.
8.1.5
Indicator Calibration: Verify indicator accuracy.
8.1.6
Indicator Scale: In installations where the scale is calibrated in flow units for
specific flowing conditions, verify operating conditions agree with scale design
conditions. Correction factors may be necessary (see File No. 957:081).
8.1.7
Air Entrapment: In liquid and steam applications, air trapped in high pockets of
instrument piping can cause erratic/erroneous signals.
8.1.8
Blockage: Internal blockage will give an incorrect or no flow indication.