21
Preventive maintenance
General
The OTS is a HV instrument generating up to 100 kV (model dependent) and is not user serviceable. The user should
ensure that the lid is not cracked or distorted before use. The only internal part of the instrument that is accessible to
the user is the printer paper housing allowing renewal of paper and ribbon when required. Opening the instrument
is strictly forbidden and will constitute a breach of warrantee. There is no need for any tools to be used with this
instrument other than the supplied gauges and magnetic bean retriever. Printer cover locks can be turned using a
suitable coin.
Cleaning
To clean the outer surfaces of the instrument, first disconnect from line power and then wipe the instrument using a
clean cloth dampened with Isopropyl Alcohol (IPA).
The user must ensure that the test chamber is always kept clean, particularly prior to a test. Wipe away any spilt oil in
the chamber or on the outside of the test vessel with a lint free cloth. When a lot of oil is spilt in the test chamber the
unit is designed with a drain facility at the rear. Simply unclip the clear tube and drain oil into a beaker or other suitable
container.
To clean the inside of the test vessel follow the instructions given in the relevant test specification or, in the case of no
instructions, cleaned with a small volume of the next sample of oil to be measured.
Care for OTS electrodes
Brass electrodes supplied with the Megger oil test sets will show signs of deposits built up from insulating oil
breakdown testing. If left they will oxidise and appear dull.
New electrodes
Megger electrodes are supplied in a kit with gap gauges and magnetic stirrer beans and retrieval stick. The electrodes
have different shapes but are cared for in the same way. If new electrodes require cleaning, isopropyl alcohol (IPA) may
be used to clean them off. It is advisable to immerse the electrodes in clean insulating oil for a couple of hours prior to
use.
Electrode storage
Electrodes may be stored in a suitable container or immersed in clean mineral insulating oil. Electrodes in a test vessel
left to stand overnight may be left with the last oil sample tested in the vessel.
Cleaning oxidised/dirty electrodes
Dirty electrodes may be cleaned with a clean, soft cloth and brass cleaner but care should be taken to use minimal
pressure to avoid removal of excessive electrode material. After removing the dirt clean the electrodes with a clean
cloth and IPA. It is advisable to immerse the electrodes in clean insulating oil for a couple of hours prior to use.
If electrodes are pitted or scratched they should be discarded and new electrodes fitted.
