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Compression joints
In order to transport or haul oil and fat in pipes, pipe systems, plastic pipes and hose lines as for example our plastic pipe PA12HL or high pressure hose 840 bar, compression joints are needed to combine and connect these different pipes and hoses in a way that these are characterized by a high impermeability and pressure resistance.
To achieve this, innovative designs known as compression joints are assembled. In all areas, for example the adoption of central lubrication in a construction machine, an agricultural machine or a utility vehicle, as well as when installing or running industrial facilities as for example wind energy facilities, the beverage industry or the paper industry, everywhere compression joints are needed.
The utilisation of compression joints when realising and installing central lubrication is one of its central applications.
Compression joints for ordinary use are on offer designed in steel 1.0718, 1.0402, carbon 20 or 45 (surface galvanized free from chromium 6 each) among others.
A compression joint of high-grade steel (material 1.4301 and 1.4571 respectively) in turn is a suitable component to be used in food processing, beverage industry, as well as in the field of ports and other damp areas.
Reason for this is that high-grade steel is a material which is neutral as well as chemically stable in a notable way.
In order to ensure an adequate specification, quality and economization when installing and applying compression joints, their production is liable to a separate quality certification according to EN ISO 8434 as well as DIN standard 2353.
Basically, a compression joint is composed of a socket with 24° cone, a connecting nut according to DIN 3870 and a compression ring according to DIN 3861 design A or DIN 3861 design B.
The socket out of the compression joints has an incorporated screw-in thread in different sizes as well as an external screw thread with inner diameter W with 24° cone.
The connecting nut is fitted with a screw thread as well, these screw threads are available in different sizes depending on design and pipe diameter.
The compression rings themselves are fitted with a 24° cone as well, so that the huge demands on impermeability are met with.
The diversified application of compression joints in lubrication technology, central lubrication, hydraulic and pneumatic systems is made possible due to the availability of initially three typical designs of threaded connections in standardized industrial production.
Compression joints are divided into the designs LL, L and S.
These different designs are classified according to their capacitance regarding pressure conditions.
| Design | External diameter of pipe | Nominal pressure / Operating pressure |
| LL (very light) | 4-8 | 100 |
| L (light) |
6-15 18-22 28-42 |
250 160 100 |
| S (heavy) |
6-14 16-25 30-38 |
630 400 250 |
In this context the following customary rule has to be applied with these specifications regarding the operating pressure: The bursting pressure (that is the explosion limit) of compression joints is considerably higher - depending on design and pipe diameter it is 3 - 4 times higher than this operating pressure.
So in addition to the very light design LL with an operating pressure of up to 100 bar at most, there is as well design L up to 100 and 250 bar respectively and the as heavy labelled design S for compression joints with a pressure impermeability of up to 250 and 600 bar respectively.
Due to the high pressure resistance of design LL and a small construction at the same time, these compression joints have established themselves in the area of central lubrication.
The models of compression joints differ in view of a great number of combinations being possible. In addition to standard compression joints as model as straight line and as 90° angle screwed insert, other models are assembled as well.
Other fittings in the production category of compression joints are the models labelled as bulkhead connector, conical hose fitting, reducer connector and swinging screw connection. Moreover, the back-pressure valve is widely-used.
As regards the many producers who have included compression joints in their production range, variable series are to be discerned. The separate series of compression joints feature deviations in material, size and type of screw connection. Thus compression joints in steel or high-grade steel can be applied.
An additional detail when applying compression joints is a sleeve. This is the technical requirement that the compression joint can be assembled with certain synthetic hoses and pipes. However, in this case the cross-section of the pipes becomes smaller, because the sleeve takes up additional space.
In order to give the steel compression joints a long durability, reliable usage properties and a dependable functional efficiency, the producers apply a galvanic coating in the free from chromium 6 (C6F) or zinc nickel (ZNNI) version to the surface.
Compression joints used in central lubrication facilitate the technical and manual workings essentially due to their design and devise those workings to be economical and efficient. To grant this, modern compression joints have the advantage of a system which is easy to assemble.
Compression joints may be assembled in different operating cycles and represent the mostly used solution for screw connections. The pipe or hose is maintained by the compression joint in a compressed connection.
Connections with compression joints are mostly found with synthetic pipes, metal pipes and hose systems.
The optimal solution for the connection of different pipes and hoses are compression joints. The connection is maintained by positioning and screwing the connecting nut tightly, which leads to a condensed compression ring.
Within the wide range of screw connections, compression joints rank among the technical solutions which are the most resilient and serviceably designed if they are integrated in central lubrication or hydraulic systems.
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