Consulting About Steam Blowing

A few days ago, we were consulted about a very interesting case that I would like to share my opinion as it would be useful for engineers involved with commissioning:

Can carryovers and/or water droplets affect the target plate during steam blowing?

Yes indeed. Carryovers can affect final results, specifically magnetite particles in the outer oxide layer that are not consistently attached to the surface and are driven off the drum.

Solution

This can be solved running the boiler at high pressure for a few days right before steam blowing starts, to allow steel increasing thickness, degree of compaction and hardness of the protective layer.

However, there are other few factors that may contribute to this happening and should be avoided, for instance, intermittent decompressions, chemical instabilities, defective chemical cleaning, insufficient blowdowns, operation with high level in the drum or low steam quality, among other deficiencies. Water droplets can also be a source of impingement and produce false reading of the pipe cleanliness.

For this purpose, it is recommended to place the target upstream temporary desuperheaters, prevent drains from clogging that can overflow driplegs and get dragged by steam, and finally make sure to get rid of all condensation during warmup stage.