Head profile · HHA

Hemispherical heads (HHA) for pressure and cryogenic service

A half-sphere profile with a straight flange and crown height D/2, formed to drawing for demanding vessel and cylinder applications.

Profile and application

A hemispherical head uses a half-sphere profile with crown height D/2. It offers high pressure capability for a given wall thickness, and is used where that geometry and the available vessel length suit the design. The drawing governs the straight flange, edge preparation and any openings.

Outside diameter: Ø300–3000 mm
Wall thickness: 2–16 mm
Reference form: GB/T 25198 · ASME VIII Div.1 UG-32(e) form
Typical use: High-pressure vessels, LNG service and cryogenic Dewar flasks

Hemispherical work can involve stainless steel and aluminium for cryogenic and LNG equipment as well as carbon steel for heavier vessels. We confirm the material grade, forming route and inspection requirements before quoting, because the same nominal diameter can need different tooling and handling as the wall thickness changes.

HHA cross-section. Final height, straight flange and edge form follow the approved drawing.

Specification at a glance

Code	Profile	Reference form	Outside diameter	Wall thickness	Typical use
HHA	Hemispherical head (HHA)	GB/T 25198 · ASME VIII Div.1 UG-32(e) form	Ø300–3000 mm	2–16 mm	High-pressure vessels, LNG service and cryogenic Dewar flasks

The published diameter is the equipment range, not a record that every size has already run. A new diameter or profile starts with a tooling check and, where required, a dimensioned first article for approval. See the full head-type comparison.

Common applications

Pressure equipment

Accumulators, separators and vessels using a hemispherical end.

LNG and gas cylinders

Formed ends for vehicle cylinders and gas-handling equipment.

Cryogenic equipment

Stainless and aluminium heads for Dewar flasks and cold service.

Materials and finishes

Family	Grades	Typical use
Carbon steel	Q235B, Q345B, SA-36, SA-414G (Q345R on request)	Storage tanks, receivers, general fabrication
Stainless steel	201, 304/2B, 304/BA, 30408 (304L and 316L on request)	Solar and hot-water cylinders, food, pharma, chemical
Aluminium	5083-O and other 5xxx grades	LNG vehicle cylinders, Dewar flasks, cryogenic service
Finishes	2B, BA, pickled, polished — necking zone Ra ≤ 0.4 µm	Where appearance or cleanliness matters

Grades outside the listed families can be reviewed on request. The material certificate supplied with the batch is tied to the heat number.

What to send for a quotation

Finished drawing, size list or sample photograph
Outside diameter, overall height and straight flange
Material grade and required surface finish
Openings, necks, bosses or lifting features with positions
Quantity, inspection requirement and delivery port

If some dimensions are still open, send the application and current sketch. We will list what has to be fixed before a price or tooling decision can be made.

Documentation and inspection

Dimensional report with the agreed measured features
Material certificate tied to the heat number
Radiographic, ultrasonic or magnetic particle testing on request
Third-party inspection welcomed for the agreed scope

Send the RFQ

Questions buyers ask first

Why choose a hemispherical head?

The half-sphere profile gives high pressure capability for its wall thickness and a smooth transition into a cylindrical shell. The trade-off is greater overall height and more surface area than a shallower dished profile.

Can the head be supplied with a straight flange?

Yes. The straight flange length, edge bevel and weld preparation are made to drawing. Please state the finished overall height and the minimum straight length your fabrication fixture needs.

Do you form aluminium hemispherical heads?

Aluminium grades such as 5083-O are available for the appropriate application. The exact grade, temper, diameter and forming route must be confirmed before quotation because material condition affects tooling and spring-back.

What inspection can be provided?

Dimensional reports and material certificates are routine. Radiographic, ultrasonic and magnetic particle testing can be carried out in-house, with third-party inspection welcomed when the project requires it.

Compare other head profiles

2:1 elliptical head (EHA)

The standard vessel profile with crown height D/4. Pressed in carbon steel, stainless steel and aluminium.

Torispherical dished head (THA)

Crown and knuckle radii to your drawing, from thin stainless end caps to heavier low-pressure tank heads.

Conical head or transition (CHA)

Conical bottoms and transitions to your apex angle, knuckle radius and straight flange, with or without openings.

Flat head or tank bottom (FHA)

Flat plates with a formed straight flange for welding, including openings and edge preparation to drawing.

Request a quote

Send the HHA geometry, material grade and inspection requirements for review.

Open the RFQ form [email protected]

Quotes usually go out within one working day. Drawings stay confidential.