How a T75 cryogenic tank container is built

Double-wall construction

The inner vessel operates at low temperature and directly contacts the product. An outer shell forms the insulation space and protects the inner system from the environment.

Inner vessel supports must carry mechanical loads while limiting heat transfer, making them part of both structural and thermal calculations.

Why a vacuum is needed

Heat is transferred by conduction, convection and radiation. Reduced pressure in the interwall space significantly limits heat transfer through gas. Special insulation solutions reduce radiative heat exchange.

System performance depends on outer shell leak-tightness, preparation of the interwall space and the absence of significant thermal bridges.

Heat ingress and pressure

Heat ingress cannot be eliminated entirely. As heat enters, some product evaporates, linking the thermal performance of the design to pressure changes inside the inner vessel.

When assessing a cryogenic tank, it is therefore important to consider both capacity and the product retention characteristics specified in its design documentation.

How GOST 34233.1 defines the strength calculation approach

Pressure vessel calculations cover more than a single operating state. GOST 34233.1-2017 requires foreseeable conditions during operation, testing, transport and installation, as well as load combinations that may affect strength and stability.

Design temperature is used to select allowable stresses and assess thermal effects. For cryogenic equipment, material selection must also account for minimum metal temperature: low-temperature performance must be confirmed to prevent brittle fracture.

Working pressure and design pressure are different concepts. Design pressure is specified for strength calculations and is generally no lower than working pressure. Hydrostatic pressure, external loads and proof-test conditions are also considered.

Valves and monitoring devices

A cryogenic system includes shut-off, protective and monitoring devices rated for the relevant temperature range. Their exact arrangement depends on the application and design.

Materials, seals and component layout are especially important because conventional room-temperature solutions are not always suitable for cryogenic conditions.

Manufacturing and inspecting a welded vessel

GOST 34347-2017 sets requirements for welded steel vessels and apparatus, covering materials, manufacture, inspection, testing and acceptance. For cryogenic vessels within its scope, calculated thickness alone does not establish quality: material traceability and controlled welding are required.

The standard provides for visual and dimensional inspection of accessible weld areas and, for butt joints determining vessel strength, mechanical testing of test joints to the specified extent. The NDT and testing programme depends on the design, material and regulatory category.

For a portable cryogenic tank, these requirements apply alongside rules for transportable pressure equipment and T75 requirements. Stationary industrial vessel requirements cannot be applied to a transport tank without checking their scope.

Sespel’s industrial experience

Sespel’s cryogenic range includes T75 tank containers. The C75D43RS has a capacity of 43,300 litres, a working pressure of 1.0 MPa and an inner vessel wall temperature range of −196 to +20 °C.

This example illustrates the connection between low-temperature medium requirements, inner vessel strength and effective insulation. The specific configuration and permitted cargoes are defined in the selected model’s documentation.

Why insulation condition matters in service

Deteriorating insulation increases heat ingress and changes system behaviour. Technical condition is therefore assessed using the manufacturer’s prescribed procedures and diagnostic indicators.

Work on the inner vessel, vacuum space and safety valves is specialised maintenance performed in accordance with approved technical documentation.

Diagnostics must distinguish the structural condition of the inner vessel from the condition of its insulation. A vessel may remain leak-tight while vacuum degradation increases heat ingress and pressure rise. Conversely, good insulation cannot compensate for defective welds or valves.

Selection considerations

Selection considers product type, required useful capacity, temperature conditions, logistics cycle duration, mass and multimodal transport requirements. These parameters are assessed together.