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Sarplast offers several types of joining solutions. The most commonly used type of joint is the Bell and Spigot which offers several advantages over the other methods. This joint is one of the main characteristics of the dual helix filament winding process. The bell is obtained during pipe production and is an integral part of the pipe itself. The spigot is machined on the other end and is part of the pipe too.

The main advantages of this type of joint are:

  • The hydraulic sealing is performed by means of two elastomeric O-rings installed in parallel grooves machined on the spigot. By inserting a nipple through the bell and between the O-rings, one can test the joint immediately after assembly. This sealing test gives high reliability to the installation and reduces to almost nil the possibilities of leakage during the final pressure test

  • By inserting a locking key into a groove through a bell opening, the joint transfers the axial stresses along the pipes and resists longitudinal forces. With this joining system one can avoid the use of bulky and expensive thrust or anchor blocks

  • The installation is very easy and quick and does not require skilled personnel

  • The joint stiffness is higher than the pipe stiffness. This guarantees a very stable joint practically without any deformation that can be used at very high pressures


DN Design Pressure (bar)
25 to 500 mm Up to 30
550 to 1200 mm Up to 20
1300 to 3000 mm Up to 16
Note: Higher pressures can be supplied on request
Bell and Spigot with double O-rings and locking key


Other types of joints offered by Sarplast are:

Mechanical Coupling joint
Mechanically coupled joints typically seal on the OD of plain end pipes through the use of sealing gaskets. Most of the commonly available mechanical couplers can be used to join our pipes.

Butt and Strap joint
This permanent joint provides continuity in both hoop and axial directions and consists of impregnated glass, mats and tissues laminated according to specified width and thickness. The laminated joint requires special designs, trained and skilled personnel and controlled conditions during the lamination operation.

Flanged joint
GRP flanges are available to meet drilling standards according to ANSI, DIN, BS, UNI, etc. Fixed flanges and stub end with steel loose flanges are available.


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Gruppo Sarplast S.r.l. - Via Rosignanina, 32 - 56040 Santa Luce - Pisa - Italia