Yokogawa DO402 Dissolved Oxygen Analyzer - Manual (Page 75)

IM 12J05D02-01E
Maintenance 7-1
7. MAINTENANCE
It is important for maintaining the measurement accuracy of the EXA DO series of wire dissolvedoxygen
metering system to perform inspection and maintenance at fixed intervals. It also serves to prevent prob-
lems from arising.
This chapter describes daily inspection and maintenance for the purpose of maintaining system perform-
ance.
7-1. Overall dissolved oxygen metering system
Tables 7-1 and 7-2 show the inspection and maintenance items for equipment composing 4-wire dis-
solved-oxygen metering system. The procedure of inspection and maintenance for the dissolved oxygen
converter is described in Section 7-2. For inspection and maintenance of the sensors and holders, see
each user’s manual respectively.
7-1-1. Inspection and maintenance to be implemented periodically
Table 7-1 shows the items which are recommended to be inspected and maintained periodically.
Table 7-1. Items for periodic inspection and maintenance of 4-wire dissolved-oxygen metering system
7-1-2. Inspection and maintenance to be implemented on occasion
Occasionally implement the maintenance that is not directly related to measurement functions and main-
tenance associated with errors.
Table 7-2. Items for occasional inspection and maintenance of 4-wire dissolved-oxygen metering
Instrument or apparatus Item Recommended Interval
All equipment a. Calibration a. 1 to 2 months
Dissolved oxygen sensor a. Clean the tip of the sensor a. 1 to 2 months
b. Polishing of (silver) electrode b. 6 to 8 months
surface and replacement of electrolyte
c. Replacement of membrane assembly c. 6 to 8 months
d. Replacement of sensor cap d. 6 to 12 months
Dissolved oxygen converter a. Inspection of temperature indication a. 6 months
(error check)
b. Replacement of fuse b. 1 to 2 years
Float holder a. Sweeping of winch mechanism a. (depends on installation
environment)
Immersion holder a. Inspection of sensor holding O-ring a. 6 months
b. Sweeping of cleaner nozzle b. 1 to 2 months
c. Inspection for leakage from the solenoid c. 6 months
valve for cleaning utility
Faulty phenomenon System content of inspection
Error E2 occurrence Check whether the dissolved-oxygen sensor membrane is
contaminated or not.
Check whether the nozzle is clogged or not.
Error E3 occurrence Polish the silver electrode surface of the galvanic dissolved-
oxygen sensor, platinum surface of the polarographic dissolved-
oxygen sensor, and replace the electrolyte. Check that the
connection between sensor and sensor cable is fit, and LED
emission of the optical dissolved-oxygen sensor.
It is difficult to see the inside Wipe off the dirt on the transparent window using tissue paper or
of the converter through the the like. (Use detergent for hard-to-clean dirt.)
window