Fixed couplings are used for the reliable connection of hoses. The exact areas of application, their function, and the different sizes are summarized in this article.
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What is a Fixed Coupling?
It is a mechanical connecting element used to quickly, securely, and tightly connect hoses or other flexible lines to connections, fittings, or to each other. They are designed to create a reliable and often pressure-resistant connection that can be released again if necessary. In general, fixed couplings are intended for permanent or semi-permanent use on a device or hose – in contrast to loose couplings, which can be used more flexibly.
What Are Fixed Couplings Used for?
Fixed couplings are used in areas where quick, secure, and tight connections of hose lines to fixed installations or other hose elements are required. Typical areas of application include:
Industry
For the transport of liquids, gases, or granules in production processes, cooling systems, or during plant maintenance.
Firefighting and Disaster Relief
Here, fixed couplings, especially Storz couplings, are the standard for connecting fire hoses to hydrants, pumps, or nozzles. Quick handling is crucial in emergency situations.
Agriculture
For connecting irrigation systems, slurry transporters, or other agricultural machinery that works with liquid media.
Construction
For draining wastewater, transporting concrete, or other building materials using pumps and hoses.
Temporary Installations
Wherever flexible lines need to be temporarily integrated into a system, such as with mobile heating or cooling units.
The main purpose is always to ensure a reliable and leak-free connection that can withstand pressure and can be quickly released when necessary.
How Does a Fixed Coupling Work?
The function of a fixed coupling can be illustrated by the widely used Storz coupling system, which is designed as a bayonet lock. A Storz coupling consists of two identical coupling halves. Each half is equipped with two opposing claws (lugs) that are directed inwards. To connect the couplings, proceed as follows:
- Interlocking: The two coupling halves are brought together so that the claws of one half fit into the recesses of the other half.
- Rotation: One of the coupling halves (or both simultaneously) is then rotated by about a quarter turn. The claws engage behind the corresponding counterparts of the other half.
- Locking: The rotation firmly hooks the claws into each other. An integrated sealing ring (often made of NBR rubber) is compressed in the process, creating a tight and pressure-resistant connection.
The connection is released by an opposite rotation. This principle allows for a quick and tool-free connection that remains secure even under pressure.
Why Are Fixed Couplings Needed in Connection with Mobile Heating?
In the context of mobile heating systems, fixed couplings play a crucial role in the quick and flexible connection of heating hoses to the central heating unit. Mobile heating is used when the regular heating system fails, during renovation work, for screed drying, or at temporary events that require an external heat source.
The advantages of using fixed couplings (especially Storz couplings) with mobile heating are manifold:
Quick Operational Readiness
The bayonet lock of the Storz couplings allows for quick connection and disconnection of the heating hoses. This is important to react quickly in the event of a heating failure and to restore the heat supply.
High Operational Safety
The couplings ensure a tight and pressure-resistant connection that functions reliably even at the pressures and temperatures common in the heating circuit. This prevents leaks.
Standardization and Compatibility
Storz couplings are an established standard, which ensures compatibility between various mobile central heating units, hose types, and adapters. This simplifies the logistics and setup of temporary heating solutions.
Robust Construction
Fixed couplings for mobile heating are usually made of durable materials such as aluminum.
Typically, mobile central heating units are equipped with corresponding fixed coupling connections, to which the heating hoses with the matching counterparts are then connected. This allows for flexible routing of the heating lines over larger distances and quick adaptation to different on-site conditions.
What Different Fixed Couplings and Sizes Are Available?
There are various types of fixed couplings for specific applications, but the Storz coupling is the most widespread form in Germany and many other countries – especially in the area of firefighting and industrial applications, including mobile heating systems. The sizes of the Storz couplings are standardized and are defined by letters or the lug spacing (distance between the claws).
Sizes of Fixed Couplings
| Size | Lug Spacing (mm) | Typical Nominal Diameter (Inch) | Area of Application (Examples) |
|---|---|---|---|
| A | 133 | 4 | Large pumps, suction connections, mobile central heating units |
| B | 89 | 3 | Fire hoses (B-hoses), larger industrial pumps, mobile central heating units |
| C | 66 | 2 | Fire hoses (C-hoses), smaller industrial pumps, mobile central heating units |
| D | 31 | 1 | Smaller hoses, e.g., hand pumps, garden hoses |
In addition to the common Storz fixed couplings with internal or external threads, there are also special variants such as fixed couplings with blank caps for closing connections or those with an integrated non-return valve for specific requirements.
Material Composition of Fixed Couplings
Fixed couplings are generally made of robust materials such as aluminum (often forged) to ensure longevity and resistance to pressure and external influences. The seals are usually made of NBR (Nitrile Butadiene Rubber), a material that has good resistance to oils, greases, and many chemicals and covers a wide temperature range.
Sources:
Telle.de. PDF. Armaturen und Schlauchleitungen Storz Saug- und Druckkupplungen.