Compression couplings are a type of fitting and allow quick and high-quality installation of the pipeline without the use of welding or threaded connections. The use of this type of couplings gives a high tightness of the assembly, while maintaining the ability to disassemble it if necessary.
Device and construction
The compression compression coupling includes the following structural elements:
- collet - a central body having threads on both sides;
- external crimping nuts;
- sealing cuffs;
- thrust rings.
Couplings
Compression couplings are divided into:
- Depending on the material from which the couplings are made: brass, bronze, steel (with anti-corrosion coating), plastic. Plastic fittings are most often made of low pressure polyethylene (HDPE). Polypropylene products are also found. PND coupling is used for working with plastic pipes.
- By configuration: straight and angular (rotary).
- By appointment: connecting; transitional (for connecting elements of different diameters or different types of pipes); couplings for sanitary fittings.
Coupling selection
When selecting a compression coupling, they are primarily oriented to the conditions of its operation. So, metal fittings are used for heating systems, for the hot water supply system, as well as for communications located in the light. For nodes and systems located in basements and underground, PND couplings are used, since they are not subject to corrosion.
In addition, when choosing a sleeve, it is desirable to select the material corresponding to the material of the connected pipe. Although it is permissible to connect polyethylene pipes with polypropylene couplings.
Mounting Features
Installation of pipelines using this type of couplings is quite simple. To carry it out, in addition to the connected pipes and the fittings themselves, two adjustable wrenches of the appropriate size will be required. Their size should correspond to the diameter of the mounted compression couplings.
Installation procedure for couplings and adapters:
- Cut the required length of the workpiece, at the ends of which carefully strip the burrs, both outside and inside.
- At the end of the pipe, put the compression sleeve elements in the following order: crimp nut, o-ring, thrust ring.
- Attach to the collet and tighten the crimping nut by hand. At this point, it is important to ensure that the nut does not warp. It should clamp the crimp and o-ring, forming a tight connection.
- Tighten the connection with a wrench. In order to avoid damage to the fitting, as a rule, tighten the nut with one key, and fix the collet with the other.
Experienced craftsmen do not completely disassemble the coupling, but only slightly unscrew the compression nut, insert the workpiece with some effort and tighten the nut back. Due to the applied force when installing the workpiece in the coupling, the joint is tight.
Advantages and disadvantages
The main advantages of using compression couplings in comparison with welded and threaded joints:
- quick and easy assembly of nodes;
- tightness and reliability;
- durability - service life over 20 years;
- the formation of detachable connections (with each assembly of the same connection only seals are replaced);
- a variety of fitting configurations.
The main disadvantages that limit the scope of compression couplings are:
- The maximum diameter of the fittings is 110 mm.
- Use in systems with a pressure not exceeding 1.6 MPa.
- For PND couplings and polyethylene couplings, there is such a disadvantage as low resistance to ultraviolet radiation. This limits their use in places where direct sunlight penetrates. Also, such materials have low heat resistance.