A case of premature failure of (after 8 months of service) of bolts located in column flange of one of CCW – vertical centrifugal pumps of a thermal power plant was received at ERDA, for investigation   It was analysed using metallurgical failure analysis methods.  

Fractography indicated that the bolt had failed in fatigue - manner at head to shank fillet portion. The chemical composition of bolt material revealed that the material used was SS 201 grade instead of SS 304 grade. (i.e lower chromium and Nickel content than 304 grade), which can give rise to lowering in fatigue strength.  Also, the metallography showed that the material had a abnormally coarse – grained structure instead of preferred fine – grained structure.  The hardness values were lower than required, as expected for such material.  

From analysis, it was concluded that the bolt had failed in fatigue manner due to faulty material composition as well as faulty heat – treatment.  

Micro-switches used in auto – mobile application were tested for its vibration and shock endurance as per Japanese specification.  

The switches were tested with power supply given as per its rating, and checked for its malfunctioning in vibrating and shock environment.  

Also, the oscillograms for the power supply as well as vibration and shock signals were recorded during testing as per the requirement and specification.  

This testing first of its kind was completed successfully to the customers satisfaction.  The manufacturers / purchasers of electronic items regarding similar tests to be done may contact, HOD (MT) for their requirement.  

The short circuit laboratory is upgraded to meet the testing needs of higher ratings of power equipment. The details are as under;

1. Distribution Transformer

• Up to & including 1600kVA,

11/0.4333kV

• Up to & including 500kVA,

22/0.433 kV and 33/0.433kV

1. L V Switchgear

• Up to & including 65kA for 1 sec

Short time withstand test

• Up to & including 65kA, 525 V

Short circuit-breaking capacities

• Up to & including 44kA for 3 sec
  

• Up to & including 80kA, 525 V

Breaking capacity test

• CT – Short time current test at

40kA for 3 seconds on 132kV

class outdoor type as per IS:2705

ERDA has upgraded the pump test facilities as per relevant IS. The upgradation of facilities include the installation of:

1. Magnetic flow meter for different flow ranges of accuracy class 0.5%

2. Digital pressure gauges of accuracy class 1.0%

3. Digital ammeters, digital voltmeter and digital wattmeters

The above facilities have reduced the testing time. With addition of these facilities, we can now provide faster services for certification and evaluation testing.

Test set up to determine oxidation stability of mineral insulating oils as per IS:12958-1990 by Rotating Bomb method

Oxidation plays a major role in aging of mineral oil. There are several methods to assess the quality of insulating oil by measuring oxidation stability in various conditions. New mineral insulating inhibitor (e.g.2,6 di teriary butyl para cresol – DBPC) for more oxidation resistance. The inhabited unused mineral insulating oil is evaluated as per IS:12463-1988, IEC:60296 Class A, BS:1982, BS 148 Class A – 1984 and ASTM D3487 – Type Ii-58. Oxidation stability test by rotating bomb indicates the time in minutes required for the complete oxidation of oil sample under test.

ERDA has established this test facility for determining oxidation stability of inhibited mineral insulation oil by rotating bomb as per IS:12463-1988 and ASTM D-2112-1986.