Head profile · THA

Torispherical dished heads (THA), formed to drawing

A dished head with a defined crown radius and knuckle radius, from thin stainless end caps through to heavier low-pressure tank heads.

Profile and application

Torispherical heads, also called dished heads or THA heads, are specified by a crown radius and a knuckle radius. A common form is approximately R = D and r = 0.1D, but the drawing governs. We confirm both radii, the straight flange and the edge form before quoting.

Outside diameter: Ø203–1500 mm
Wall thickness: 0.6–12 mm
Reference form: GB/T 25198 · DIN 28011 form
Typical use: Solar water heaters, heat-pump cylinders and low-pressure tanks

This profile covers a wide thickness span, from thin solar and water-heater end caps to heavier low-pressure tank heads. The achievable range depends on diameter, material and forming method. A size that falls outside the common tooling is handled as a first article rather than assumed to be a repeat part.

THA 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
THA	Torispherical dished head (THA)	GB/T 25198 · DIN 28011 form	Ø203–1500 mm	0.6–12 mm	Solar water heaters, heat-pump cylinders and low-pressure tanks

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

Solar and hot-water tanks

Inner and outer heads for cylinders, including necked openings.

Heat-pump cylinders

Repeatable stainless and coated end caps for volume assembly.

Low-pressure process tanks

Dished heads and bottoms for storage and process equipment.

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

What radii should I specify for a torispherical head?

State the crown radius, knuckle radius, outside diameter, straight flange and finished height. If your drawing follows DIN 28011 or GB/T 25198, name the standard and revision so the profile is not left to interpretation.

Can THA heads include necked openings?

Yes. Openings and necks can be pressed or cut to drawing, including multi-stage necking where the connection requires a controlled inside profile. Send the opening diameter, position, height and finish requirement.

Can I use a thin THA head for a water-heater cylinder?

Yes, the line covers thin stainless and coated end caps. The exact minimum thickness depends on diameter, profile, material and the forming method, so we confirm it against the part drawing rather than publish one global minimum.

Do you provide sample parts before volume production?

A dimensioned first article can be supplied for new profiles and sizes. This lets your welding fixture, surface finish and inspection requirements be checked before the batch is released.

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.

Hemispherical head (HHA)

Half-sphere profile with crown height D/2 for high-pressure, LNG and cryogenic equipment.

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 crown radius, knuckle radius and finished dimensions for a THA head quotation.

Open the RFQ form [email protected]

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