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OTS80PB and OTS60PB OTS100AF, OTS80AF and OTS60AF
19
Preparations for use
the plate without flowing over its top surface.
When testing to ASTM D1816:
ASTM D1816 specifies that the oil is stirred throughout the test sequence, and a two bladed motor-driven impeller
is specified. The standard prescribes the impeller dimensions and pitch as well as the operating speed, which must
be between 200 rpm and 300 rpm. But remember, with this stirring requirement it is vital that air is prevented from
coming into contact with the oil as described above.
When testing to ASTM D877:
ASTM D877 does not specify oil sample stirring
7.5. Calibration
The Oil Test Sets are calibrated in the factory prior to delivery so there is no need to calibrate on initial setup.
A calibration certificate is supplied.
7.6. Stirrer options
Megger supplies a range of impellers to optimise the stirring set-up.
Magnetic
bead
IEC60156 ASTMD1816
Fig 8: Impeller and bead
Megger supplies as standard with the stirrer lid assembly two impellers.
The Impeller on the left is optimised for IEC 60156, whilst the one on the right is ideal for ASTM D1816.
Vigorous circulation can exacerbate the inclusion of any moisture captured on the surface film of oil left behind after
rinsing at the vessel preparation stage, making the need for rapid filling even more critical, so as not to detrimentally
affect breakdown results.
7.7. Ordering Information
For ordering information please refer to OTS60PB--OTS80PB--OTS60AF--OTS80AF--OTS100AF Datasheet.
Oil dielectric breakdown voltage testing can provide a quick, first line evaluation of the condition of insulating oils.
However, cleanliness, and good preparation is key to obtaining accurate and meaningful test results. Information on
the Megger range of test instruments can be found on the Megger website www.megger.com. Further information
can be found on the Megger booklet “The Megger guide to insulating oil dielectric breakdown testing”, part number
2003-149.
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