General knowledge of heads-Yixing Jiuzhou Head Forging Co., Ltd.

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General knowledge of heads

Heads are indispensable and critical components in pressure vessel equipment across various industries, ranging from petrochemicals and atomic energy to food and pharmaceuticals.

Purpose of heads

01. Heads are indispensable and critical components in pressure vessel equipment across various industries, ranging from petrochemicals and atomic energy to food and pharmaceuticals.

02. The heads, serving as the end cap of a pressure vessel, are the primary pressure-bearing component of the vessel.

03. The quality of the head has a direct impact on the pressure vessel’s long-term safety and reliability.

The importance of head quality

The importance of head shapes

Section shape of head	Curvature of the central part of the head	Necessary head plate thickness in design	Design plate thickness of the head when the plate thickness of the cylinder is 20mm
Hemispherical (HH)	R = d× 0.5	1/2 of the thickness of the cylinder plate	10mm
2:1 elliptic (EH)	R = D× 0.9 (approximation)	Same thickness as cylinder plate	20mm
10% dish head (DHB)	R=D	Thickness of cylinder plate × 1.54	31mm
Flat cover (flat plate)	R = infinite	8 times the thickness of the cylinder plate	160mm

Requirements for head shape

JB/T4746 head standard:

The shape of the head must be checked with a full template.

Shape tolerance: convex not more than 1.25%Di, concave not more than 0.625%Di.

The inner radius of the transition section shall not be less than the value specified in the drawing.

Spherical body: curvature affects head thickness

Transition section: reduce the peak stress of the connection between the spherical surface and the cylinder

Straight edge: avoid the superposition of the peak stress of the transition section and the welding stress of the cylinder group pair

Head processing methods

Method of construction	Hot stamping	cold stamping	cold spinning	slice method
Main process	Preheating stamping	Stamping	drum spinning	Suppression group pair
Molding equipment	heat treatment furnace Press (die set)	Press (die set)	drum press Spinning machine	Press (pad die) heat treatment furnace
workpiece temperature	Preheating	Normal temperature	Normal temperature	Normal temperature/preheating
Suitable material	high strength steel ultra-high strength steel	Stainless steel carbon steel	Stainless steel carbon steel	Unlimited
Suitable specifications	Standard	Standard	sheet thin Larger diameter	Plate thickness Large diameter
Characteristics of construction method	① Slightly rough surface ② Difficult to control size ③ Impact on the environment	① Excellent surface quality ② Same size ③ Batch manufacturing is good	① Surface indentation ② Size can be controlled ③ Die cost saving	① On-site pairing ② Long processing cycle

Cold working vs. Hot working

Characteristics of cold working	Characteristics of hot working
1. Without heating, there will be no material deterioration, especially suitable for stainless steel head processing.	Due to heating, material deterioration will occur, resulting in corrosion resistance of stainless steel head decreased, not suitable for stainless steel head processing.
2. Without heating, there will be no dimensional change caused by cooling shrinkage, the shape is regular, the size is accurate and the consistency is good	Heat forming, resulting in thermal expansion of the mold and head cooling shrinkage, the size is difficult to control and poor consistency.
3. Without heating, the surface of the head after forming maintains the smooth surface of the original material, and the appearance is beautiful.	Due to heating, the surface oxide scale of the head after forming is serious and difficult to remove.
4. No need for fuel, less energy consumption.	It requires fuel and consumes valuable resources.
5. No heating, no harmful gas and smoke, to avoid environmental pollution and global warming, consistent with China's national policy.	Due to the heating of a large number of harmful gases, pollution of the environment, resulting in public hazards, contrary to China's national policy.