Philosophy for Painting/Coating Systems Requirements

  1. PURPOSE

 

1.1       This engineering standard defines the philosophy for painting/coating systems requirements.

 

 

2. SCOPE

 

2.1       This standard applies to all painting/coating applications, unless otherwise specified by our customer, and excluding standard catalog purchased items (for example, pumps and motors). There are specific specifications for painting of bulk distribution equipment (rolling stock) (4AEQ-68585), and for underground pipelines (4APL-20001).

 

  1. RELATED DOCUMENTS

 

3.1       Air Products Engineering Documents

 

3EQ68001           Selecting Paint Systems and Identifying Paint Codes, Including Requirements for Under Thermal Insulation

4AEQ-68585        Painting and Decaling of Liquid Bulk Distribution Equipment (rolling stock)

4APL-20001        Pipelines External coatings for Underground Service

 

3.2       International Organization of Standards (ISO)

 

ISO 12944        Paints and Varnishes – Corrosion Protection of Steel Structures by Protective Paint Systems

 

 

  1. GENERAL

 

4.1       Painting/coating systems shall be selected to provide the lowest total evaluated cost. Total cost shall consider initial cost of painting/coating, cost and frequency of maintenance painting, safety, and other considerations such as wear and tear on equipment. The painting/coatings selected in the specifications must achieve, at a minimum, all of the following objectives:

 

  • Provide protection against corrosion.
  • Provide visual identification of safety hazards.
  • Meet the aesthetic requirements.
  • Meet customer specifications.

 

4.2       All selected painting systems shall be in compliance with all national, provincial, and local environmental laws and regulations, and shall be applied according to the manufacturers’ recommended procedures. Of particular concern in some locations are the emissions of volatile organic compounds (VOC) and avoidance of isocyanates.

 

4.3       A paint system is to be used which is appropriate to the corrosivity of the environment and the expected longevity. This is in accordance with ISO Standard 12944. See Engineering Standard 3EQ68001. Special paints are designated for cryogenic and elevated temperatures, and for corrosion protection under thermal insulation.

 

4.4       For SOE (sale of equipment) projects, the customer’s specifications for paint need to be known and accommodated.

 

4.5       The aesthetic requirements of painting vary depending on the public visibility and the particular item. Large storage tanks, tall TSA vessels and cold boxes, which are in public view, should receive the specified paint and color. For structural steel framing, and items which are not in public view, the color requirement might be compromised for cost savings. For example, flat gray-green inorganic zinc is acceptable for structural framing, if it offers a significant cost savings. Similarly, silver-colored high temperature paints are acceptable. At minimum, all items shall present a clean and well-maintained appearance.

 

4.6       Some judgment should be used when specifying paint. The written documents have limitations, as they address only the normal shop painting applications of Air Products standard products. Actual situations will not always fit into the simplified terms and categories of the specification. Consideration should be given to micro-environments, such as water mist from cooling towers, which warrant greater corrosion protection than the balance of plant. If there is uncertainty or confusion regarding painting, then the SME (Subject Matter Expert) should be consulted.

 

4.7       Equipment and structure should be designed to avoid areas which are difficult to paint, or that are prone to greater corrosion. Narrow gaps and deep inside corners are difficult to paint, and thus are prone to corrosion. When designing structural framing, it should be recognized that back-to-back angles can be difficult to paint. Concrete foundations should extend above grade to reduce the exposure of steel structures to moisture. The design of equipment and structures should provide good drainage of water (rain).

 

 

  1. PAINTING

 

5.1       Uninsulated, Aboveground Steel Operating up to 93°C (200°F):  A paint system is to be used that will provide the needed corrosion protection, which depends on the environmental conditions and expected longevity. This is in accordance with ISO Standard 12944, and is described in Engineering Standard 3EQ68001. The default should be a three-coat paint system of zinc-rich epoxy primer, epoxy intermediate paint, and polyurethane top coat. In low-corrosive environments, a two-coat paint system is normally adequate. Inside dry buildings, where there is no corrosion, a single-coat paint system might be adequate.

 

5.1.1   Other considerations include aesthetic requirements, the accessibility for re-painting, and expectation of mechanical damage. Tall cold boxes and vessels, which are difficult to access, should have a paint system to provide greater longevity. Piping near grade, which is very accessible for repainting, might have a lesser paint system. Guard rail and wheel-stops, which will experience abrasion and scratches, might best be repainted every few years using a lesser paint system.

 

5.2       All equipment, vessels, tanks, piping and structures are to be shop painted to the maximum extend. Areas of field welding are to be shop prepared for painting, and then masked. At the completion of erection, the field weld areas are to be properly cleaned and painted. Shop painting is to be maximized, as the quality is better and cost lower than field painting.

 

5.2.1   Where the extensive field welding is necessary, the materials might best be primer painted in the shop, and then finish painted at the completion of construction. Examples are large field-built storage tanks, and field-built cold boxes. The field painting will then be uniform, with good appearance. Inorganic zinc is often used as a pre-construction weldable primer paint.

 

 

5.3       Bulk Distribution Equipment (both cryogenic and bulk gas) shall be painted with a paint system that provides good durability and appearance, to a greater level than for fixed assets. This system might not necessitate the use of a zinc-rich primer because of higher grade of paint materials used, and the higher level of maintenance generally given to trucks and trailers (rolling stock).

 

5.4       Equipment Requiring Insulation for Thermal Protection:  Whether insulated equipment is painted or not depends on particular service and other conditions. These conditions are detailed in 3EQ68001.

 

5.5       Structural Steel

 

5.5.1   Galvanizing normally provides better corrosion protection at lower cost than paint. The advantage of galvanizing over paint depends on the corrosivity of the environment, the desired longevity, the weight and size of the items, and the availability of galvanizing service. Galvanizing has distinct advantage for items which must sustain abrasion, such as bar grating and flooring. These conditions are detailed in 3EQ68001, Section 8.5.

 

 


 

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