Boiler heads – find manufacturers and suppliers

Boiler heads are curved or elliptically shaped, usually metal end pieces of pressure vessels, pipelines or tanks that seal the cylindrical part of the vessel pressure-tight and safely dissipate the forces generated inside into the vessel wall.

They form the end faces and ensure that the pressure inside is safely absorbed and dissipated. They are a central element in pressure vessel and tank construction technology.

Below you will find how they work, typical shapes, the manufacture and materials of boiler heads, their use, the advantages of the curved shape and the applicable standards:

How boiler heads work:

The curved shape distributes mechanical stresses favorably and reduces wall thickness and weight compared to flat lids.
The main task of a boiler head is to:

1. To absorb compressive forces:
   Internal pressure generates tensile stresses on the vessel bottom. A curved shape distributes these stresses more evenly than a flat surface.
2. Ensure dimensional stability:
   Bottoms prevent the container from deforming or bulging under pressure.
3. Enable connections and transitions:
   Inlets and outlets, nozzles or dome covers are often fitted to bases.
4. Flow control:
   In pipelines or apparatus, heads influence the flow conditions of the medium.

In short, the shape is crucial to ensure that the component is stable, safe and durable at a defined pressure.

Typical shapes of boiler heads:

There are various designs that are selected depending on the operating conditions:

1. Dished ends:
   Flatter domed heads with a larger radius of curvature in the dome and a short cylindrical shell rim. Very common as they are relatively easy to manufacture and offer good strength.
2. Torispherical heads:
   Have a greater calotte height and are more curved than dished ends. This makes them particularly pressure-resistant with the same wall thickness.
3. Flat bottoms:
   Inexpensive to manufacture, but only suitable for low pressures. Often reinforced with ribs or thicker walls.
4. Conical heads:
   Are used to reduce the container cross-section over a length - for example in hoppers or silos.
5. Segment bases (segment hoods):
   Consist of several curved segments that are welded together, often for large diameters.
6. Hemispherical heads:
   Ideal for very high pressures because the spherical shape distributes the load optimally. However, they are expensive to manufacture.

Manufacture and materials of boiler heads:

Boiler heads are usually made from sheet steel by hot or cold forming, e.g. by pressing, rolling or deep drawing. For larger diameters, heads are welded together from segments.

Typical materials are:

1. Unalloyed structural steels for moderate pressures and temperatures.
2. Pressure vessel steels with specified toughness and weldability.
3. Stainless steel (austenitic or ferritic) for corrosion resistance.
4. Special alloys, e.g. nickel alloys for aggressive media or high temperatures.

The choice of material depends on pressure, temperature, corrosion requirements and approvals, e.g. Pressure Equipment Directive.

Use of boiler heads:

Boiler heads are used wherever cylindrical vessels or pipelines need to be sealed - especially for pressure vessels and systems with operating pressure:

1. Pressure vessels in chemical and process engineering:
For reactors, storage tanks, columns.

2. Boiler systems:
Steam boilers, hot water storage tanks.

3. Heat exchangers:
Tube bundle closures and pressure jackets.

4. Tanks and silos:
For liquids, gases or bulk materials.

5. Pipeline closures:
Blind caps or end pieces under pressure.

6. Autoclaves and sterilizers:
Closed, pressure-tight ends.

7. Pharmaceutical and food technology:
Hygienically designed containers with polished bottoms for easy cleaning.

Advantages of the curved shape of boiler heads:

• High pressure resistance: domed shapes reduce localized stress peaks.
• Material savings: Lower wall thicknesses possible than with flat lids.
• Resistant to deformation: Safe against bulging under pressure.
• Flow-optimized: Promotes media movement, prevents deposits.
• Good weldability to cylinder walls: Can be welded precisely to the tank shell.

Standards for boiler heads:

Boiler heads are subject to strict standards, e.g.:

• EN 13445 pressurized equipment, unfired pressure vessels
• AD 2000 German regulations
• ASME VIII American standard
• DIN 28011 dished ends
• DIN 28013 Basket bottom

The standards specify shapes, dimensions, manufacturing tolerances and calculation methods for wall thicknesses.

Boiler heads are indispensable components in pressure vessel and plant construction. Their curved shape ensures optimum force distribution and enables safe and efficient pressure absorption with reduced wall thickness. They are used in many industries - from chemicals to energy to food technology - wherever media must be safely contained under pressure.

Here you will find an overview of the most important criteria to look out for when purchasing boiler heads:

The right choice of shape, material and manufacturing quality of boiler heads is crucial for the safety, service life and cost-effectiveness of systems.

• The very first question: Which regulations apply to the pressure vessel for the manufacture of which the vessel heads are required?
• In Europe, the Pressure Equipment Directive PED and EN 13445 or AD 2000 are usually decisive.
• International projects may require ASME Section VIII.
• The heads must be manufactured and certified in accordance with the required standards, e.g. DIN 28011 for dished heads.
• Purchasing should always clarify the exact standard and calculation basis in the project and specify it in the order.
• Exact dimensions are crucial for welding assembly and pressure calculation.
• Order specifications must clearly define the radius, diameter, spherical cap height, transition radius and, if applicable, cylinder base.
• Incorrect or unclear specifications lead to fitting problems or cost-intensive reworking.
• Production drawings or 3D models should therefore be coordinated, especially for special dimensions.
• The material determines the suitability for the medium, pressure and temperature:
• Unalloyed structural steels for standard pressure vessels.
• Pressure vessel steels with specified impact strength.
• Stainless steel for corrosive media or hygienic applications.
• Special materials such as duplex or nickel-based alloys for extreme requirements.
• Compliance with standard tolerances is crucial for accuracy of fit and compressive strength.
• Clean, burr-free edges and surfaces are important for weldability.
• Check the wall thicknesses - sub-tolerances can jeopardize the pressure approval.
• Check whether hot or cold forming is desired or permitted. Cold-formed heads may require annealing.
• It is advisable to choose suppliers with proven experience and tested processes.
• Surface quality is often a relevant requirement for stainless steel heads.
• In the food or pharmaceutical industry, a defined roughness, e.g. Ra < 0.8 µm, applies.
• Weldability is of central importance:
• The material of the boiler bottom must match the rest of the container material.
• Heat-affected zones must not lead to brittle fractures.
• Suppliers should guarantee weldable production, e.g. no unacceptable work hardening and clean edges.
• Required heat treatments, e.g. stress relief annealing, should be clearly specified.
• Tests and certificates are important for these safety-critical components.
• Therefore, clarify in the inquiry which tests are included in the scope of delivery.
• Delivery times and logistics play a non-negligible role in purchasing. Bear in mind that:
• Boiler bases in standard sizes are often available at short notice.
• Special dimensions or special materials often have long delivery times.
• Transportation must be carried out carefully, e.g. protection against warping, scratches and contamination.
• When buying, consider both price and economy:
• Cheap suppliers often save on material quality, certification or manufacturing tolerances.
• Reworking or refusal to test during acceptance can be very expensive.
• High-quality materials and clean production prevent subsequent damage and downtime.
• For projects with acceptance tests such as TÜV, Notified Body, it is important that the supplier knows and supports the procedure.

The quality, safety and cost-effectiveness of the entire tank is crucial when purchasing boiler heads. Conformity to standards, material quality, dimensional accuracy and clean production are essential. A good purchase therefore not only pays attention to the price, but also ensures that the base perfectly matches the tank design, the operating conditions and the legal requirements.

Boiler heads can be purchased from various suppliers. You will find comprehensive information on manufacturers and suppliers of Boiler heads around the world on Exportpages.