Oxidation Stability Of Mineral Insulating Oil

Compliance Standards

ASTM D2440, IP 335 ASTM D943

Introduction

This test method determines the resistance of mineral transformer oils to oxidation under prescribed accelerated aging conditions. Oxidation stability is measured by the propensity of oils to form sludge and acid products during oxidation.

Significance & Use

A test specimen of mineral transformer oil is oxidized at bath temperature of 110°C/95°C, in the presence of a copper catalyst coil, by bubbling oxygen through duplicate test specimens for 72 and 164 h, respectively. The oil is evaluated at the end of each aging period by measuring the amount of sludge and acid formed. The test specimen is diluted with n heptane and the solution filtered to remove the sludge. The sludge is then dried and weighed.

Brief Construction Details

The complete unit comprises of following main parts and accessories

Oil bath

• Double walled oil bath with inlet provision
• Rectangular shape
• Stainless steel structure
• Outer body fabricated from Stainless Steel 304
• Inner chamber fabricated from Stainless Steel  316
• Heavy insulation between inner chamber and exterior body
• Inner chamber is fitted with efficient heating element  and PT 100 Sensor
• Bath temperature is controlled by Microprocessor based dual display PID Temperature indicator  cum controller
• Temperature control accuracy :± 0.5°C
• Temperature display                   : LED
• Temperature range                     : 5°C above ambient to 200°C
• Supplied with over temperature protection safety

Oil Receptacle and Head

• 4 nos of test tube
• Made of  borosilicate glass

Provided with B 24 cone having the following dimensions:

• Overall Length          :    210± 2.0 mm
• External diameter    :    25± 0.5 mm
• Wall thickness           :    1.25± 0.2 mm
• Height of head          :    28± 2.0 mm
• Side outlet tube        :    5.0 mm outside diameter

Oxygen inlet tube (Delivery Tube) Dimensions

• External dia                :    5.0± 0.4 mm
• Wall thickness           :    0.8± 0.1 mm
• Inside diameter         :    3.0± 0.1 mm

The test tube is  fitted with a Drechsel head to which is attached the inlet tube which will extended within   2.5± 0.5 mm mm  of the bottom and  its  end ground at an angle of 30° to the horizontal axis.

Nos. Metallic Copper Catalyst of following  dimension

Copper  catalysts consist of a wire of  non annealed commercial electrolytic copper of diameter between 1.00  and 1.02 mm. And  wire shall have a length of 305 ± 1.0 mm  rolled into a spiral of approximately 20 mm external diameter and 50 mm in length.

4 nos. rotameters (flowmeters) of following features

These are rotameter type flowmeters with the capacity to measure the flow rate  of oxygen in the range  (1± 0.1) litre / hour in case of ASTM D2440  test method or  (3± 0.1) litre / hour in case of ASTM D943 test method.

Following accessories will be the part of standard supply

• Oil bath for the immersion of 4 standard test tubes held by a double bottom
• Stainless steel structure
• Insulated double wall
• Four independent flow meters that transfer oxygen at (1± 0.1)  l/h or  (3± 0.1)  l/h  rate
• Heavy duty motor stirrer
• Outlet system
• Complete of glassware

Note:

• Please refer to the recommended accessories section to carry out the test as per ASTM Standard
• Hot air oven for glassware drying
• Membrane filter holder for filtering out the test sample oil at the end of experiment, so that generated sludge and oil can be separated.
• Conical flask, 500 ml, to collect the filtered test sample (oil) at the end of the experiment
• Burette with 10 ml capacity and 0.05 ml accuracy to carry out Neutralization value test using titration solution.