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Acceptance standard for head products

When customers have specific requirements for the surface of the head, those requirements shall be followed.

Acceptance criteria

Clearance in sectional form

　　

 

Clearance in sectional form:

Check with a clearance template to ensure that the convexity does not exceed 1.25% Di.

The concavity must not exceed 0.625% Di.

Straight edge, inclination, fold, total depth (height) tolerance:

The straight edge section of the head shall be free from longitudinal folds.

The tolerance for the height of the head’s straight edge section, as well as the inclination of its inner and outer sides, is as follows:

(Not including the thickening of the straight side section) 

　　

 

Diameter Straight edge height Inclination Total depth (height) tolerance
DN ≤ 2000 h=25 Outside: inside 1.5: 1.0 (-0.2～ 0.6)%DN
DN ＞ 2000 h=40 Outside: inside 2.5: 1.5
Other Negotiation agreement

Roundness tolerance

1. Measure four internal diameters equally spaced along the straight edge section, and use the difference between the maximum and minimum measured values as the roundness tolerance. 

2. The roundness tolerance shall not exceed 0.5% DN and not be greater than 25 mm.

3. When δs/DN is less than 0.005 and δs is less than 12 mm, the roundness tolerance should not exceed 0.8% DN and not be greater than 25 mm.

Groove angle, dimensional tolerance, and roughness of groove surfac

Project Tolerance
Groove angle ± 2.5°
blunt mouth width ± 1mm
Roughness of groove surface  
There shall be no cracks, delamination, inclusions and other defects.

Tolerance of outer perimeter and tolerance of inner diamete

Nominal diameter Thickness of steel Inner diameter tolerance Outer circumference tolerance
DN ＜ 600 2 ≤ δs < 4 ± 1.5 ±4
600 ≤ DN < 1000 4 ≤ δs < 6 ± 2 ±6
δs ≥ 6 ± 3 -3～9
2 ≤ δs < 4 ± 2 ±6
4 ≤ δs < 6 ± 2 ±6
δs ≥ 6 ± 3 -3～9
DN ≥ 1000 All ± 3 -3～9

Note: Generally, when Di ≥1000 and δs <10 mm, the tolerance of outer perimeter shall prevail. The tolerance of inner diameter or outer perimeter can be determined through negotiation between supply and requisitioning parties

Notes:

1. Standard length of outer perimeter = (inner diameter + nominal thickness × 2) × π (3.1416)

2. In the case of inner diameter tolerance, measure four diameters equally spaced along the straight edge section and average them.

Surface quality

The measured minimum thickness at the weld seam must not be less than the minimum guaranteed thickness of the head. Additionally, the welded surface must not be recessed more than 0.5 mm below the surface of the base material. 

During step-by-step stamping and forming, check for annular hoop marks using a template, ensuring that the gap does not exceed 1.5 mm. 

Material surface pitting must be ground to a depth of no more than 5% δs and no more than 2 mm. Otherwise, repair welding is required.

The depth of the surface material pattern on the head shall not exceed 0.2 mm. When the ground surface area of the head exceeds 20%, the entire head should be subjected to overall surface finishing. 

When customers have specific requirements for the surface of the head, those requirements shall be followed. 

Jiuzhou Head

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Characteristics of cold-formed heads

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