Quality

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Whenever people from the world of giant Transformers think about Quality – ASTA flashes in their mind first. A sense of satisfaction and tranquility of trust – that naturally come on their faces, have been earned by ASTA through centuries of hard work and total commitment to meet customers toughest requirements – many a times working together with them.

It would not have been possible without rigors of intense Research & Development and impeccable Quality management systems to achieve such feats – some of them still preserved as exclusive and joint-patents. The hallmark of ASTA Quality has been its uncompromising and perhaps the most severe test routes etched out after in-depth study and understanding of customers needs. The carefully selected test facilities are, therefore, one of the best available in the world. The comprehensive set of tests, as listed in ASTA Quality Plan encompasses requirements of all latest global specifications related to the product.

The journey of assuring quality begins right at the receiving stage. Conductor materials constitute over 97% of CTC – hence rightly deserve the best attention. Metallographic and torsion tests ensure that only the flawless copper rods are made available for processing. While the first process of Round-wire drawing delivers perfectly round (achieved by special rotating die) and blemish-free, bright wires to the next process of Flat-rolling, it is the unmatched process control at this 2nd stage which produces flat strips with incredibly narrow tolerances of ± 5µ in thickness and ± 10µ in width – against an internationally accepted tolerance of minimum ± 30µ for both thickness and width for the smallest size of strip (for higher sizes of strip, the allowable tolerance goes up to ± 70µ). This not only consistently gives strips of uniform dimensions, it also helps in reducing the designed bundle dimensions of finished CTC and eventually, size of the transformer.

If the proof-stress requirements are high (> 200 N/mm2), the rolled strips are passed through off-line annealer and re-rolled to have a controlled proof-stress. Otherwise, they are moved directly to Enameling – the  3rd process.

The most exhaustive tests are conducted on the strips when they are coated with enamel/epoxy during this process. On-line HV testers, capable of detecting each and every pin-hole fault (in case, pops-up on enameled strip during coating), prevent any bad spool from going to the next stage.  ASTA, at this stage, does not merely conduct customer-specified tests, but also performs many special tests to reinforce confirmation to customer requirements.

Hot-bench test to know about the epoxy curing stage, Tan-delta to determine enamel curing, Lap-shear test at elevated temperature to ascertain bonding properties, Bending-press test for Low-Chip CTC, long-duration (168 hrs) Hydrolysis test for determination of hydrolysis and oil resistance at elevated temperature in moist transformer oil of enameled winding strip – are some of such tests that are included in ASTA Quality Plan.

Once cleared, the enameled strips are made available for final stage of processing – the Transposing. Type/grade/construction of Insulation papers, as specified and bundle dimensions, as approved by customers are the minimum check points at this stage. ASTA, in some cases, also suggests the desirable pitch of CTC which is so critical for the transformer winding to be stable. Here again, true to its stringent way of testing, ASTA uses a High Voltage which is almost double the HV specified by the customers for CTC inter-strand short circuit test – just to make sure the customers get a Quality product with higher level of satisfaction.

Finally, the Customer satisfaction survey and valuable feedback from customers form an essential part of ASTA’s routine life. Being an ISO 9001 : 2008 certified company, it strongly believes in what ISO 9001 says with regards to Customer satisfaction. ASTA understands and respects the Voice of Customer and acts promptly on any issue related to its product, quality, logistics, technical and innovation – as ASTA is not just a supplier to its customers, it is a partner in their growth.