Heating & Cooling Stainless Steel Tanks: All Methods Explained

Half-Pipe Coil – High-Pressure Heating for Stainless Steel Tanks

The half-pipe coil is one of the most efficient methods for heating and cooling stainless steel tanks under high pressure. It is welded directly onto the vessel wall and is particularly suited for processes involving high temperatures and pressures.

A half-pipe coil is characterised by a clearly recognisable half-shell pipe segment that is welded in tight spirals around the outer wall of the vessel. The resulting channel between the pipe and the vessel wall serves as the flow path for the heat transfer medium — typically thermal oil, saturated steam or hot water. This type of temperature control is suitable for both liquid and vapour-phase media and, depending on the design, can also be configured for extremely high temperatures and pressure ratings.

• Pressure resistance: Due to the small cross-sectional area of the half-pipe, the medium can be circulated at very high pressure (up to over 40 bar) — significantly more than with a double jacket.
• High temperatures: Thermal oil heating via half-pipe coils achieves process temperatures of 200 °C and above, making them ideal for reactors and distillation systems.
• Targeted zone heating: The coil can be divided into several independent zones (e.g. upper and lower half) to achieve different temperature ranges.
• Wall reinforcement: The welded-on half-pipe coil simultaneously reinforces the vessel wall mechanically — an additional advantage under vacuum or pressure loads.
• Variants: Slightly modified designs include the rectangular half-pipe coil, which has a somewhat flatter and more angular profile.

Typical applications: Chemical reactors, distillation columns, vessels with vacuum operation, high-temperature processes in the pharmaceutical and chemical industries.

Half-pipe coil on a brand-new stainless steel reactor from Behälter KG

Thermoplate / Pillow Plate – Full-Surface Heat Exchange Without Dead Zones

Thermoplates (also known as pillow plates or dimple jackets) provide near-full-surface heat transfer and eliminate dead zones on the vessel wall. They combine high efficiency with a hygienically advantageous, smooth surface.

With this technique, a thin stainless steel sheet is welded onto the outer shell of the vessel. The cavity is then irreversibly inflated by high pressure, deforming the thin thermoplate sheet into its characteristic, rounded pillow-like shape. This creates a pillow-shaped channel system through which the heat transfer medium flows.

• Full-surface heat transfer: Unlike the half-pipe coil, a thermoplate shell has no untempered gaps. The larger exchange surface results in slightly better heat transfer.
• Low dead volume: The pattern, protruding only a few millimetres in rounded contours, requires significantly less heating or cooling medium than half-pipe coils, which typically protrude 50–80 mm. This enables rapid temperature changes and low energy consumption during start-up.
• Hygienic design: The smooth outer surface without gaps or corners facilitates cleaning and meets GMP requirements.
• Flexible geometry: Thermoplates can be adapted to different vessel shapes — cylindrical, conical or as bottom heating.
• Dimple plates: A slightly different variant are so-called dimple plates, where the thin stainless steel sheet is pre-pressed into a corrugated structure before being welded on. The somewhat different appearance offers lower pressure resistance, but is sufficient for temperature control with liquid media.

Thermoplate (protected brand name) and pillow plate (technical term) are commonly used synonymously.

Typical applications: Food and beverage industry, pharmaceuticals, dairy processing, breweries, cosmetics industry — wherever hygienic surfaces and uniform temperature control are critical.

Thermoplate shell on a Behälter KG SDE-Flexmix

Internal Heating Coil – Cost-Effective Solution for Jacketed Vessels

The internal heating coil (full-pipe coil) is a simple and cost-effective method for heating or cooling directly inside the vessel. It is particularly suited for non-critical media where direct contact between the heating pipe and the product is acceptable.

The full-pipe coil is visually similar to the half-pipe coil, but the windings are designed as a complete tube. To ensure heat transfer to the medium inside the vessel, the full-pipe coil is typically installed inside the vessel. This is therefore referred to as direct temperature control, as there is direct contact with the medium — unlike the half-pipe coil, which only acts indirectly through the vessel wall.

• Direct heat contact: Since the heating pipe is fully immersed in the product, heat transfer is particularly efficient — no vessel wall as an additional resistance.
• Simple construction: Full-pipe coils are inexpensive to manufacture, as minimal welding work is required on the vessel itself. The tubular geometry is also extremely pressure-resistant.
• Retrofittable: The full-pipe coil can easily be retrofitted, replaced or repaired in existing vessels.
• Cleaning limitations: The coil inside the vessel creates potential dead zones during cleaning of the vessel interior.
• Contamination risk: In the event of a leak in the full-pipe coil, there is a risk of contaminating the stored medium with the heat transfer fluid.

Typical applications: Storage tanks, vessels for vegetable oils, simple heating and temperature-holding processes, basic chemical operations without hygienic requirements.

Internal full-pipe coil in a tank for vegetable oils

Double Jacket (Heating Jacket) – The Classic Heating & Cooling Mantle

The double jacket is the classic and most widely used method for temperature control in stainless steel tanks. It surrounds the vessel as a second shell and enables uniform heating or cooling across the entire jacket surface.

A jacketed vessel consists of two concentric stainless steel shells: the inner product vessel and an outer shell that forms an annular cavity. In the context of vessel temperature control, the double jacket is understood as a second shell around the product-contacting vessel wall. It may enclose only the bottom dish or extend around the entire cylinder of the vessel shell. The heat transfer medium flows through this cavity — steam, hot water, cooling water or glycol-water mixtures.

Design and function

The heating jacket (also called cooling jacket in cooling applications) is welded as a second shell around the cylindrical section and often also around the vessel bottom. For temperature control, this jacket is filled with heating/cooling medium and, thanks to the largest possible exchange surface, provides very good heat transfer.

• Uniform temperature distribution: The double jacket encloses the vessel over a large area and ensures homogeneous heat distribution across the entire jacket surface.
• No internal fittings: Since the heating system is located entirely outside the product space, the vessel interior remains clear — ideal for CIP cleaning and hygienic processes.
• Versatile: Suitable for both heating and cooling. By switching the medium, the same vessel can fulfil both functions.
• Pressure limitation: Conventional double jackets generally have lower pressure resistance compared to other tempering shells — at higher pressures, half-pipe coils are preferred.
• Higher dead volume: The large jacket cavity holds a relatively large volume of heat transfer fluid, resulting in longer heat-up times and higher energy consumption during start-up.
• Special variant — trickle ring: In the dairy industry, a pressureless double jacket is often used in combination with a trickle ring, through which the jacket space is sprinkled with ice water to cool the product space.

Typical applications: Mixing tanks, blending vessels, heated storage tanks, fermentation vessels, vessels in the food, pharmaceutical and cosmetics industries.

Design of a jacketed shell in the lower cylindrical area

Immersion Heaters & Tube Bundle – Easy Retrofit Heating

Immersion heaters and tube bundle heat exchangers are compact, often retrofittable heating solutions that are installed directly inside the vessel. They are particularly suited for existing plants without a dedicated heating system.

Often mounted on the side of the vessel cylinder, the tube bundle heating element protrudes into the vessel interior. The tube bundle itself can ensure heat transfer through circulating thermal oil or hot water, for example. Alternatively, there are also electric immersion heaters that are heated directly by electricity.

• Quick retrofit: This type of temperature control can often be retrofitted into an existing tank with manageable effort.
• Large heat transfer surface: The many parallel tubes create a large exchange surface in a compact space.
• Localised heat source: The heating output is concentrated around the heating elements — in large vessels without an agitator, this can lead to uneven temperature distribution.
• Cleaning effort: A disadvantage is the increased difficulty of cleaning the product space due to the tube bundle.
• Control: Temperature can be precisely controlled via thermostats or PID controllers.

Typical applications: Retrofit vessel heating, heating of storage tanks, melting tanks, heating in existing plants without a double jacket.

Side-inserted tube bundle heating element in a melting tank

Electric Heating (Heat Cable / Heating Mat) – Up to 300 °C

Heat cables and heating mats are a flexible, retrofittable solution for electric heating of stainless steel tanks. They are mounted externally on the vessel wall and are particularly suited for temperature maintenance, frost protection and high-temperature applications.

Electric heating can be achieved by heat cables wound around the vessel shell. On large outdoor storage tanks or tank containers, such heat cables are often used for frost protection in winter, or for relatively precise temperature maintenance.

However, this type of heating is also suitable for high-temperature applications: the vessel shell is enclosed by a heating jacket in which heat cables are densely integrated. The jacket simultaneously serves as insulation. These heating jackets can be individually customised and ensure operating temperatures above 300 °C.

• Easy installation: No modifications to the vessel itself required — the heating elements are attached externally.
• Flexible geometry: Heating jackets can be individually adapted to all requirements — cylindrical, conical, dished.
• Temperature range: Depending on the design, operating temperatures above 300 °C are achievable.
• Zone control: Multiple independent heating zones with dedicated temperature sensors are possible.
• Energy consumption: Due to very high energy consumption, heating jackets are only advisable for small batch sizes (e.g. pilot-scale vessels, transport containers, small melting tanks).

Typical applications: Frost protection on outdoor tanks, temperature maintenance of pipelines and vessels, heating of silos and IBC containers, high-temperature process heat for small batches.

Silicone heating jacket for a Behälter KG SDE-Flexmix

Indirect Electric Heating via Heat Transfer Fluid

Indirect electric heating combines the simplicity of electric heating with the uniform heat distribution of a double jacket. An electrically heated heat transfer medium in the jacket cavity transfers heat gently to the product.

This type of temperature control features a double jacket in which one or more electric tube bundle heating elements are integrated. The double jacket, filled with thermal oil, is heated by the heating elements and transfers this heat to the product space. The jacket operates without pressure.

• Uniform temperature control: The heat transfer medium ensures the entire jacket surface is heated uniformly — no local hot spots as with direct electric heating.
• Independent of external infrastructure: No steam boiler, no cooling water supply required — only an electrical connection. Ideal for locations without central utilities.
• Simple control: Temperature can be precisely and reproducibly controlled via thermostat or PID controller.
• Pressureless operation: Since the heat transfer medium is not under pressure, inspection obligations under the Pressure Equipment Directive do not apply to the jacket.
• Limited cooling capacity: This system is primarily designed for heating and temperature maintenance. Active cooling requires additional equipment (e.g. a heat exchanger in the oil circuit).

Typical applications: Mobile vessels, plants at locations without steam supply, temperature-controlled mixing tanks in laboratories and pilot plants, bitumen and wax vessels.

Comparison: Pros and Cons of All Heating Methods

The following table summarises the key properties of the presented heating and cooling systems and facilitates the selection of the appropriate method for your process.

Which Heating Method Is Right for Your Process?

The optimal heating or cooling method depends on several factors: process temperature, pressure requirements, hygiene requirements, available infrastructure and whether it is a new build or a retrofit.