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Precautions for Ordering Heads

1. Basic items: shape, diameter (inner & outer), thickness, height of the straight edge, material, groove style, amount, etc.
2. Standards: GB/T25198, GB150, ASME VIII-1, PED, etc.
3. Applications: container type, storage temperature, pressure, storage materials, etc.
4. Material selection: customers can designate the sources of raw materials
5. Processing requirements for raw materials: re-inspection, UT inspection, intergranular corrosion test, steel supply state, surface processing style, etc.
6. Thickness of plate: plate feeding thickness, mix allowable plate thickness, etc.
7. Welding: welding position, test plate welding, weld line polishing
8. Non-destructive testing: standards, approaches (radiography test, ultrasonic test, magnetic test, penetration test), testing part, qualification level, etc.
9. Heat treatment: types (SR, N, SHT), test plate, etc.
10. Tolerance: outer circumference, roundness, etc.
11. Marking: marks (content), embossing seals (location and content), etc.
12. Inspection: domestic inspection, ASME, PED, etc.
13. Certificate reports: number of copies, delivery method, etc.
14. Package: filming, liner, carrier, fixing devices, etc.
15. Delivery: reasonable delivery date and warehousing period
16. Transport: clients can pick the cargo themselves or let us send the products (discharging place, time and contact person)
17. Head acceptance: acceptance criteria, time limit, and credentials, etc.
18. Others: drawings of heads and detailed requirements

Diagram of vessel heads and grooves

Notes:
1. Vo=outer groove, Vi=inner groove, I=flat groove, F=remaining dimension, R=blunt edge dimension
2. For other types of grooves, please contact us for inquiry

 

Types and parameters of heads

Notes:
1. Vo=outer groove, Vi=inner groove, I=flat groove, F=remaining dimension, R=blunt edge dimension
2. For other types of grooves please contact us for inquiry
3. Those heads with special dimensions are identified with 'D'

Head Forming Techniques

1. Cold pressing
Under room temperature, the pressing machine utilizes stamping dies to exert pressure upon the plates, which will then be formed into workpieces with the specific shape and dimension we want. After cold stamping treatment, the heads will own accurate dimension, high consistency, and good quality, and are suitable to be put into mass production. In cold stamping, fuels are unnecessary, reducing its impact to the environment, and the vessel heads to the min.

2. Cold spinning
Cold spinning refers to a plate forming technique, featuring a large save on the costs of stamping molds. By spinning the plates, the spinning machine transfers the points of application from some local points to a whole place surface. Simultaneously a certain pressure is given to the metal plate to make it deform and flow at a specific direction. The metal materials we use here must have the properties of plastic deformation and fluidity, since cold spinning is a combination of both plastic deformation and flow deformation. Except flanged-only heads, head products generally have to undergo a pre-shaping process before cold spinning. This technique is suitable for manufacturing non-standard head products.

3. Hot spinning
As a plate forming technique, hot spinning means shape the plates with spinning and heating treatment at the same time. It shows little applications in processing heads, but is ideal for producing non-standard pressure vessel heads with large thickness. Comparing with hot stamping, hot spinning treatment is superior in dealing with the diversified head diameter.

4. Hot pressing
Hot pressing technique is based on the principle that the plates are easy to be shaped as their thermoplasticity improved, applicable in processing high-strength steels and producing thick heads.
Disadvantages of hot pressing: firstly, the fuels used for heating plates will do harm to environment; next, a second heat treatment is necessary to restore and improve the plates' properties, because the plates are shaped unevenly under a heating state and the stainless steel may become fragile during cooling; finally, it may be difficult to control the tank head dimension since the expansion and contraction of heads is to a large extent determined by environment factors in the hot pressing process.

5. Segment Processing
Segment technique is generally used for cold processing. The heating methods are varied according to different materials. When it comes to processing products manufactured by stamping or spinning equipment, a segment processing is suggested. Basing on the shapes of heads for pressure containers, we have to additionally customize the molds, which will cost a long processing period. So, we choose segment technique only under some special circumstances.

Technical Parameters
Processing technique cold forming hot forming
diameter thickness (δ ) diameter thickness (δ)
Stamping 6600t hydraulic press Φ1550~ Φ3200 2~28 Φ1500~Φ2600 ≤240
3000t hydraulic press Φ650~Φ1800 2~28 Φ650~Φ1800 ≤240
680t hydraulic press Φ89~Φ600 2~16 Φ89~Φ600 ≤30
4500t hydraulic press - - Φ1000~Φ5700 ≤240
Spinning 10m cold spinning machine Φ2600~Φ10000 8~40 - -
4m cold spinning machine Φ1700~Φ4000 3~24 - -
3m cold spinning machine Φ750~Φ3000 3~12 - -
4.5m hot spinning machine Φ1700~Φ4500 - Φ1700~Φ4500 16~80
Dishing 2000t door-frame pressing machine unlimited ≤70 - -
1000t door-frame pressing machine unlimited ≤30 - -
2200t dishing press ΦΦ ≤80 - -
800t dishing press ΦΦ ≤50 - -
Common Manufacturing Standards

1. GB/T25198-2010 (China) for heads for pressure vessels
a. This regulation provides a standard for manufacturing, inspecting and accepting the tank heads made from steel, Titanium, copper, nickel and nickel alloys, as well as the common types and basic parameters of heads.
b. It is suitable for hemispherical head, elliptical head, torspherical head, spherical head, flanged only head, and conical head.
c. For other heads for common vessels and pressure equipment, this regulation is also applicable.

2. GB150 (China) for pressure vessels
Scope of application: all of the pressure vessel heads not included in the GB/T25198 standards

3. ASME VII-1 (America) for boilers and pressure vessels
Scope of application: heads manufactured basing on the ASME standards

4. JISB8247 (Japan) for heads for pressure vessel
Scope of application: heads produced according to the Japanese standards

5. AS1210 (Australia) for pressure vessels
Scope of application: heads produced according to the Australian standards

6. PED 97/23/EC (EU) for pressure equipment
a. This is a compulsory regulation formulated by EU upon the safety problems of pressure equipment.
b. Pressure Equipment Directive PED 97/2 3/EC is a compulsory regulation. Any equipment regardless of their pressure or volume, as long as their pressure exceeds 0.5bar, they have to be complied with the PED standards, such as fire extinguishers, pressure gauges, valves, safety valves, air cabinets, tower tanks, piping, fittings, pressure fittings, safety accessories and assemblies, steam equipment, and fluid delivery equipment, etc.

7. Difference between PED and ASME
a. PED refers to safety certificate, while ASME is standard factory certificate; this is the largest difference between the 2 items.
b. It is worth mentioning that, in PED certificate, the basic safety requirements are compulsory, but the technique standards are not the same. Unless users have raised their demands, manufacturers have access to choose to comply with any technique standards. This is quite different form Chinese compulsory standards for the head products.

Stamping Range and Min Head Thickness
  • 1. Shape of vessel heads: EHA.THA;
    Applicable materials: stainless steel (S.S)

  • 2. Shape of vessel heads: EHA.THA;
    Applicable materials: low-alloy steel (LA.S / Q345R, 16MnDR)

  • 3. Shape of vessel heads: EHA.THA;
    Applicable materials: carbon steel (C.S / Q235B)

Notes:
1. Data marked in blue shows the min thickness of EHA, and in red is the min thickness of THA. For other processing techniques and materials not include in these tables, please contact us for inquiry.
2. The min thickness listed in the tables is limited to the steel plates we have specially ordered from steel suppliers.
3. Outsourcing materials and materials provided by clients have to be additionally discussed according to their actual negative deviation.

Head Spinning Range

Spinning Range of Heads

The 1st table:
Shape of vessel head: EHA.THA;
applicable materials: stainless steel (S.S)

The 2nd table:
Shape of vessel head: EHA.THA;
applicable materials: carbon steel (C.S / Q235B), low-alloy steel (LA.S / Q345R, 16MnDR)

Notes:
A negotiated settlement is needed for heads whose thickness exceeds 40 or whose diameter is over 6500


Min Plate Thickness For Spinning

The 1st table:
Shape of vessel head: EHA.THA;
applicable materials: stainless steel (S.S)

The 2nd table:
Shape of vessel head: EHA.THA;
applicable materials: low-alloy steels (LA.S / Q345R, 16MnDR)

Notes:
The data marked in blue is limited to torishperical head