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Re: [MW:31981] Accuracy of PMI

By Materials & Welding
Dear Pravin,

Normally PMI is performed for High alloy welding consumables to ensure that there is no mix up of consumable during welding and it is not an accurate method and tolerance is always allowed; PMI performed by below methods.

1. X-Ray Fluoroscopy
2. Optical Emission spectrometer
3. Atomic Emission spectrometer
4. Volumetric Analysis (Chemical Analysis).

For carbon steel used for NACE service to ensure Nickel Kept within 1%, we control the issue of welding consumable from the stores. Only welding consumable containing 3.1/3.2 certificate batch Numbers are identified and electrode issue slip from the supervisor to stores will contain the batch Number.

But your case seems to be special since carbon steel is not PMI tested but it is your client requirement and need to be complied.

Moreover it is understood from your mail that you have performed Chemical Analysis (volumetric Analysis) at chemical lab which always gives accurate results.

Below are considered the way forward for your problem.

1. Check the Batch Number to ensure traceability to certificate to ascertain the use of correct welding consumable.
2. Perform proper sampling and redo the test.
3. Perform an Hardness test. The purpose of restricting Nickel is to ensure that it does increase the Hardenability (Hardness).
4. Check whether it is a Specification requirement or Additional client requirement and then take up with the client accordingly.

Thanks & Regards

J.Gerald Jayakumar




On Wednesday, 3 February, 2021, 09:17:31 am IST, Pravin Poornachandran <htcispravin@gmail.com> wrote:


Dear expert, 

Good day. 

Recently I performed WPS for ER70S-G for nace requirement project. 
Based on welding consumable mill certificate as per EN10204 3.1, Ni <1% and these chemical analysis is conducted in authorised laboratory following the method specified in industrial code. It is laborious procedure and accurate. 

But when we perform PMI, Ni values shows 1.2-1.5, which client is questioning now. 
I did contacted consumable supplier and they are very certain Ni is less than 1%. 

Can anyone advice how should I handle this situation. 

Best regards,
Pravin Poornachandran 

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