DH Instruments E-DWT-H, Operation And Maintenance Manual

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5. MAINTENANCE, ADJUSTMENTS AND CALIBRATION
Page 103 © 2009 DH Instruments, a Fluke Company
Use [SPECIAL] , <8cal> , <1Hi Q-RPT > or <2Lo Q-RPT > , <1edit> , to read and record
the current values of PA and PM for the Q-RPT to be calibrated.
AutoZ the RPM4-E-DWT with the reservoir shut off valve close, TEST shut off valve open
and open to atmosphere at the E-DWT-H TEST port.
Run the recommended calibration point sequence for the Q-RPT (see Section 5.3.4).
Record the pressure applied by the standard and the RPM4-E-DWT reading at each
calibration point. Dwell at least 60 seconds at each point after setting the reference
pressure to allow full stabilization.
Enter the calibration pressures and RPM4-E-DWT readings into a spreadsheet.
Calculate the “non-corrected” RPM4-E-DWT readings by backing out the PM recorded in
Steps above, following:
non-corrected reading = corrected reading/PM [Note: PA should be 0]
Perform a linear regression to find the offset and slope that best fit the non-corrected
RPM4-E-DWT readings to the calibration standard pressures. The offset is the new
value of PA, the slope is the new value of PM. If the RPM4-E-DWT was AutoZeroed
properly to calibration, HEAD was set to zero and the pressures from the calibration
reference were properly adjusted to the RPM4-E-DWT reference level (TEST port), the
value of PA should be very close to zero.
Press [SPECIAL] , <8Cal> , <1Hi Q-RPT > or <2Lo Q-RPT > , <2edit> and write the new
calibration date and the new values of PA and PM for the Q-RPT calibrated (see Section
5.3.6).
Calculate as left data for the calibration if desired following:
as left reading = non-corrected reading • new PM [Note: PA should be 0]
Perform additional verification pressure runs as desired.
5.4 E-DWT Maintenance
There are no E-DWT-H maintenance procedures other than the overhaul procedure.
5.4.1 E-DWT Overhaul
E-DWT-H is generally overhauled as one common assembly. Removal of RPM4-E-DWT from
the E-DWT-H is not recommended.
Any or all of the following items may be included as part of an E-DWT-H overhaul:
•
Check that RPM4-E-DWT rear panel mounted cooling fan operates when RPM4-E-
DWT is powered.
•
Clean and inspect E-DWT-H TEST port connection.
•
Purge and clean reservoir and internal hydraulic circuit. Replace used oil with clean oil.
•
Check that internal fittings, screws, bolts and nuts are tight.
•
Perform system leak and operational check.
•
If the RPM4-E-DWT has two Q-RPTs, check Lo Q-RPT pressure relief valve for
proper operation. See correct relief valve cracking pressure in Section 1.2.1. Do not
apply pressure greater than 110% of the to the RPM4-E-DWT Lo Q-RPT maximum
working pressure as it may be damaged beyond repair. The RPM4-E-DWT warranty
does not cover damage due to Q-RPT overpressure.
•
Clean RPM4-E-DWT and E-DWT-H front panel.