8 IM-P402-37 AB Issue 9
6. Maintenance
5. Wiring
4.2 Subsequent removal and refitting
Cabling should be installed in accordance with BS 6739 - Instrumentation in Process
Control Systems: Installation design and practice or local equivalent.
Warning: Ensure boiler or vessel is depressurised and vented to atmosphere
before attempting to unscrew or remove the probe.
- Always use the correct size spanner - not a pipe wrench.
- Inspect male and female threads for signs of damage, which may have occurred through
overtightening, leading to torn threads or even localised cold welding (galling / picking up).
- If damage has occurred replace the probe.
- Carry out an electrical continuity check to ensure that the resistance between the probe
body and the boiler or tank is less than 1W.
- An 'O' ring is supplied with both the LP20 and PA20. Ensure only one 'O' ring is fitted
between the probe and the PA20 preamplifier (see Figure 2).
The preamplifier must only be screwed on hand tight to avoid damage to the 'O' ring.
Refer to the preamplifier IMI for further information.
Refer to the preamplifier and controller / transmitter Installation and Maintenance
Instructions for wiring details and diagrams.
Note: Read the 'Safety information' in Section 1 before starting any maintenance.
No special servicing, preventative maintenance or inspection of the product is required.
Level controls
Boiler water level controls and level alarms, however, do require testing and
inspection. General guidance is given in Health and Safety Executive Guidance
Notes BG01 and INDG436.
For specific instructions for the Spirax Sarco system please see separate literature.
Cleaning instructions
Use a cloth dampened with tap / de-ionised water or isopropyl alcohol. Use of other
cleaning materials could damage the product and invalidate the warranty.
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