PetroStreet

we just fabircated ammonia storage tank as per API 620 App R
now its in stages of painting.

before painting we want to sand blast all the tank but contractor is not agree for it. as condition of plates are so severe as it is near the cooling tower zone.
my question is that is there any reference of NACE that will show the extent of sand blasting required

The level of cleanliness is mentioned by the designer of the tank in project specifications.
NACE only provides you a reference / details of all the surface preparation grade.
Normally, for such tanks surface finish with sandblasting or garnet is ensured to SA2.5 grade which corresponds to grade 2 of NACE (near white metal finish).

Dear Sakib,

Extent of sand blasting is always given by the tank designer in his "Painting Specifications" which should be recycled and approved with Contractor upfront.
Here are some relevant Standards on Sand Blasting, refereing the extent / degree of cleanliness:

- ISO 8501-1: 2007 Preparation of Steel Substrates before Application of Paints
- SSPC SP-5 White Metal Blast Cleaning
- SSPC SP-10 Near-White Metal Blast Cleaning
- SSPC SP-6 Commercial Blast Cleaning
- SSPC SP-7 Brush-off Cleaning
- NACE TM 01-70 Visual Surface Standard of Airblast Cleaning
- NACE TM 01-75 Visual Surface Standard of Centrifully Blast Cleaning

Regards

We have recently erected a hydrogen tank.
The surface finish was made to SA 2 1/2.