What is the difference between a food coupling and a standard water coupling?

There is no single coupling system in use throughout Europe. The choice often depends on the country, the sector and the existing installation you are connecting to:

• Cam and groove couplings (camlock): quick to connect and disconnect using levers and widely used on tank equipment.
• Tanker couplings (TW): also commonly referred to as Elaflex couplings, with designations such as MK and VK in sizes of 2, 3 and 4 inches (VK 50, VK 80 and VK 100). The prevailing standard, particularly in Germany.
• Guillemin couplings: bayonet couplings used mainly in France.
• Storz couplings: bayonet couplings for water and the standard used by fire brigades, among others. As they are usually made of aluminium, they are not intended for chemicals. Also see the water couplings.
• Flange couplings: two flanges joined with bolts and nuts. This connection cannot open unintentionally and is therefore widely used on bunker hoses and chemical hoses, where safety and pressure are paramount.

If you are connecting to existing equipment, that connection usually determines the system. SCHIEMA advises on the coupling that suits your medium, pressure and installation, and assembles the complete hose assembly.

You need a dry disconnect coupling when not a single drop of product or any vapour may escape on disconnection, because it is harmful to people or the environment. This applies, for example, when loading and unloading tank trucks and tank containers and on pipelines in the (petro)chemical industry.

A dry disconnect coupling consists of a male part, the tank unit (on the tank or pipeline), and a female part, the hose unit (on the hose). Both parts contain check valves. When connecting and rotating, the valves open to create a free passage; when disconnecting, they close completely again so that nothing leaks out.

Well-known systems include TODO-MATIC and Mann Tek. Various brands work on the same principle and are in many cases interchangeable; do check this for each version. Where several products are loaded or unloaded side by side, dry disconnect couplings can be fitted with selectivity coding. This prevents, for example, a diesel hose from being connected to a kerosene connection.

For loading and unloading tank trucks, dry disconnect couplings, tanker couplings (TW) and cam and groove couplings (camlock) are mainly used. For products that must not leak or release vapour, a dry disconnect coupling is the safest choice: on disconnection, the check valves on both sides close immediately.

The difference from a regular flange coupling lies in speed and shut-off. A flange connection is fitted with bolts and nuts and is highly reliable under pressure, but it is not designed for frequent, quick connection and disconnection. A dry disconnect coupling is made precisely for frequent coupling without product loss.

Many companies also work with a dedicated hose: a hose used exclusively for one product, so that no residues of other products end up in it. Combined with an additional product valve on the coupling, this creates a very safe solution.