Service Support

Confirm

Precautions for using the head

Please proceed with the assembly of the head and shell in the following sequence, ensuring both simplicity and accuracy in the welding process, thereby contributing to improved efficiency.

Connection between the head and the container cylinder

Please proceed with the assembly of the head and shell in the following sequence, ensuring both simplicity and accuracy in the welding process, thereby contributing to improved efficiency.

01. Please measure the outer perimeter of the head. If the cylinder has been completed in advance, please contact us to inquire about the predetermined outer perimeter dimensions.

02. Please divide the outer perimeter of the head into four equal parts and mark the cylinder and head accordingly.

03. Perform the tack welding in the sequence shown in the diagram below. The customer is requested to select the tacking points based on the diameter and plate thickness.

04. After completion of the tack welding, proceed with the welding process.

　　

 

Please pay attention to the protection of the stainless steel head surface.

S30408 (06Cr19Ni10) and 304 (18-8) stainless steels, being metastable austenitic stainless steels, undergo the precipitation of chromium carbides when heated within the temperature range of 450°C to 850°C, resulting from the combination of carbon and chromium within the steel. Due to the significant reduction in chromium content surrounding the chromium carbides, a chromium-depletion zone is formed, making it susceptible to corrosion. This phenomenon is particularly prone to occur in regions adjacent to both sides of the weld bead during welding, as well as in hot-formed heads. 

The primary stresses generated in pressure vessels under operational conditions encompass those arising from internal pressure, welding residual stresses, and residual stresses resulting from the forming process of the heads. The superposition of these three stresses causes the maximum tensile stress to occur at the girth joint connecting the head and the cylinder, rendering this area susceptible to stress corrosion cracking along both sides of the girth joint. Surface scratches, welding slags, spatters, incomplete cleaning, and the use of thermal insulation materials containing chloride ions may cause surface pitting corrosion and induce stress corrosion due to improper surface protection. 

To prevent corrosion, it is essential to select appropriate materials, reduce the carbon content in S30408 (06Cr19Ni10) and 304 materials, and prioritize the protection of stainless steel head surfaces. 

 

Please pay attention when using stainless steel heads.

After the head and the cylinder are installed and welded, it is crucial to promptly clean the weld seam, heat-affected zone, and surrounding areas of welding slag, spatters, and contaminants. Furthermore, a penetrant testing (PT) test and surface pickling should be performed.

Prevent the surface of stainless steel heads from being bumped or scratched.

Prevent direct contact with carbon steel to avoid contamination by iron ions.

Not stored in the open air to prevent exposure to rain.

The structural design should prevent excessive restraint stress and avoid forced assembly welding. Strictly control the alignment tolerance and edge angle.

The chloride ion content in the water for the hydrostatic test must not exceed 25 mg/L, and the equipment must be promptly dried after the test.

In situations requiring thermal insulation, insulation materials that do not contain chloride ions should be utilized.

The acid pickling of stainless steel must not employ reducing acids such as hydrochloric acid.

Strictly adhere to the compatibility of the medium as stipulated in the 'Capacity Regulations'.

Jiuzhou Head

Previous

General knowledge of heads

Acceptance standard for head products

Next

Previous

General knowledge of heads

Next

Acceptance standard for head products

Technology Center

Share

Return to List