NB/T 10558-2021Coating and transport packaging for pressure vessels (English PDF)

1.1

This document specifies the relevant requirements for surface treatment, coating and packing for pressure vessels and components transport.

1.2

The surface treatment, coating and packing for pressure vessels and components transport shall comply with the requirements of design documents and ordering technical conditions in addition to this document.

3.1 Method for surface treatment

The methods for surface treatment of pressure vessels or components include grinding, derusting, polishing, pickling and passivation.

3.2 Conditions and timing for surface treatment

The surface treatment of vessels or components shall be carried out after the pressure test (leakage test or hot gas cycle test) and surface cleaning, and welding, heat treatment and other operations damaging the surface state shall not be carried out after surface treatment, otherwise, surface treatment shall be carried out again.

3.3 Grinding

3.3.1

The surface grinding of the vessel specified in GB/T 150.4 shall be completed before the pressure test. For the surface defects that affect the appearance and coating, such as uneven surface, scratches, grooves, etc., the grinding method shall be adopted to remove these defects and make a smooth transition, and the method of puttying shall not be adopted to replace grinding.

3.3.2

Appropriate grinding tools shall be selected according to the material of the repaired parts, and grinding tools made of different materials shall not be mixed.

3.4 Derusting

3.4.1

The outer surfaces of carbon steel and low alloy steel vessels or components, the inner surfaces that can be derusted and other surfaces to be coated shall be cleaned and derusted.

3.4.2

Rust removal can be carried out by manual and powered tools, blasting or ejecting. During rust removal, damage to the surface of vessels or components affecting product quality shall be prevented.

3.4.3

Before surface derusting, thick rust layer, visible grease and dirt shall be removed; after surface derusting, dust and debris shall be removed, and the residue inside the vessels or components shall be cleaned up.

3.4.4

The effect of derusting shall be evaluated according to the typical sample methods specified in GB/T 8923.1, and shall meet the coating requirements or the grade specified in the design documents (see Table 1).

Table 1 Grade of derusting

Grade Treatment method Degree of treatment Cleaning requirements

St2 Derusting by manual and powered tools Thorough When visually inspected without a magnifying glass, the surface shall be free from any visible oil, grease and dirt, or loosely adhered scale, rust, coatings and foreign matters

St3 Derusting by manual and powered tools Very thorough When visually inspected without a magnifying glass, the surface shall be free from any visible oil, grease and dirt, or loosely adhered scale, rust, coatings and foreign matters, but the surface treatment is much more thorough than that of St2, showing the metallic luster of the base metal

Sa2 Blasting or ejecting Thorough When visually inspected without a magnifying glass, the surface shall be free from any visible oil, grease and dirt, or any loosely adhered scale, rust, coatings and foreign matters; and the surface shall only have firm residue contaminant

Sa2.5 Blasting or ejecting Very thorough When visually inspected without a magnifying glass, the surface shall be free from any visible oil, grease and dirt, or any loosely adhered scale, rust, coatings and foreign matters; any residual sign on it shall be point-like or parallel-strip with slight stain

Sa3 Blasting or ejecting Make the appearance clean When visually inspected without a magnifying glass, the surface shall be free from any visible oil, grease and dirt, or any loosely adhered scale, rust, coatings and foreign matters; the surface that has been treated shows uniform metal luster

3.5 Polishing

3.5.1

When required by the design documents, the surface of the vessels or components shall be polished according to the requirements of the design documents.

3.5.2

Polishing may be carried out manually, mechanically or electrochemically.

3.5.3

Before polishing, the surface to be polished shall be ground and pretreated to remove oil, grease and dirt that affect the polishing operation; after polishing, the residue attached to the vessels or components shall be cleaned.

3.5.4

The polishing effect shall be evaluated according to the tactile and visual comparison method or instrumental measurement method specified in GB/T 10610, and shall meet the requirements specified in the design documents. Common polishing effects are shown in Table 2.

Table 2 Polishing effect

Surface condition after polishing Micro-distinguish the direction of machining traces The direction of the machining trace is indistinguishable Dark varnish Bright varnish Mirror varnish

Corresponded roughness Ra/µm <=0.4 <=0.2 <=0.1 <=0.05 <=0.025

Note: Ra is the arithmetic average deviation of profile.

3.5.5

Measures shall be taken to protect the polished surface, and the operation damaging the surface quality shall not be carried out.

3.6 Pickling and passivation

3.6.1

The surface pickling and passivation for vessels or components shall be carried out according to the requirements of design documents.

3.6.2

Pickling and passivation may be carried out by soaking in pickling solution, passivation solution or brushing with pickling passivation paste.

3.6.3

Before pickling and passivation, the treated parts shall be ground first, and appropriate methods shall be taken to remove oil, grease, oxide scale, dirt, etc. on the surface of the treated parts; after pickling and passivation, the surface of the treated parts shall be washed with clear water, and there shall be no residual dirt, liquid, etc. If necessary, phenolphthalein test paper may be used to check the washing degree.

3.6.4

The effect of pickling and passivation may be inspected visually or by blue dot method. If the visual inspection is adopted, its surface color shall be basically uniform; if the blue dot method is adopted, prepare the solution containing 1g of red blood salt + 3 mL of 65%-85% HNO3 + 100 mL of water, then soak the filter paper into the solution and attach it to the surface to be inspected, or brush the solution directly on the surface to be inspected. If there are no blue dots within 10s, the parts shall be judged as qualified.

3.6.5

Measures shall be taken to protect the surface after pickling and passivation, and the operation damaging the surface quality shall not be carried out.

4.1 Coating condition

The coating operation can only be carried out after the vessels or components pass the manufacturing quality inspection (including surface treatment inspection) carried out by the quality inspection department of the vessel manufacturer.

4.2 Coating scope

4.2.1

In general, only the outer surface of vessels or components is coated. Unless otherwise specified in the design documents, anticorrosive coatings may not be applied under the following conditions:

a) The inner surface of the vessel;

b) The surface of the inner parts leaving the factory with the whole vessel;

c) High alloy steels, non-ferrous metals and alloy vessels or components surfaces.

If vessels or components made of high alloy steel, non-ferrous metals and their alloys need to be transported by sea or used in coastal areas, whether to be coated or not and the coating requirements shall be specified in the design documents.

4.2.2

The following grooves shall not be coated within at least 100 mm from the edge of the groove, and shall be coated with protective films which are harmless to welding quality and easy to remove if necessary:

a) The cut-off surface groove of the segmented ex-factory vessel;

b) The peripheral groove of the sliced parts;

c) Other welding grooves on the vessel shell that need to be assembled and welded at the site.

4.2.3

Finished surfaces such as threads and sealing surfaces shall not be coated, but shall be coated with protective films that are easy to remove.