March / April / May 2016 : Electrical heaters in the dust storm cabinet

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Written by Laurence
Monday, 04 April 2016 19:13

The ISO 3452-4:1998 standard, quite old, though still enforced, requires that the dust storm cabinet be fit with a heater, to prevent any contamination of the powder by the air moisture.

We have been unable to find any similar requirement in the ASTM standards dealing with Penetrant Testing.

Is such a requirement in this ISO standard justified?

Many dust storm cabinets, be they in manual, half-automated or fully-automated process lines, are void of such an equipment.

Thus, we may be inclined to think this is a useless requirement written in the standard, with no-good reason attached.

When the dry developer is contaminated, lumps appear, which make it improper for use. If these lumps are put in the drying oven of the PT process line, the moisture will evaporate. However, the lumps stay there, due to the Van der Waals forces between the dry developer particles.

Therefore, regenerating dry developer, when contaminated by water, is impossible.

In fact, the purpose of these electrical heaters in the dust storm cabinet is to prevent humidity from condensing in the cabinet, for instance, at night, when ambient air cools down, taking into consideration, on the one hand, the capillary properties of the dry developer, hygroscopic, hence, hungry for water, on the other hand, the relative humidity of the ambient air.

It is sufficient to have electrical heaters in the dust storm cabinet, set to maintain the temperature at about 40 °C (104 °F) 24 hours a day, 7/7, except for maintenance purposes.

This may seem as a small detail...able to ease the life of users!

Normative references

ISO 3452-4:1998, Non-destructive testing -- Penetrant testing -- Part 4: Equipment, International Organization for Standardization, Geneva, Switzerland, 1998.

ASTM Volume 03.03 Nondestructive Testing

ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA, 19428-2959, USA. Website: www.astm.org/Standards

 

 

Last Updated ( Wednesday, 06 April 2016 08:18 )