New and very demanding requirements towards water supply, sewerage, gas supply systems or telecommunication grids resulted in intensive research works on polyethylene (PE) to improve its properties, particularly its resistance to crack propagation. This, in turn, contributed to a development of a new type of pipes, which ensure an appropriate degree of protection, long durability and service life. New raw materials and new PE piping solutions meet current market demand and contributed to the launch of more cost-effective installation technologies.

Why structured pipes?

• Higher protection 
• Increased safety 
• Longer durability 
• Higher resistance to extreme mechanical loads 
• Can be installed by means of various technologies 
• Lower investment costs 
• Shorter investment period

Single-layer pipes

• Piping installed according to international standards on a sand or fine gravel bed
• Avoid damages of the pipe surface such as notches, cuts, grooves (possible source of crack propagation) 
• Longer installation time and higher costs

Structured pipes

• Cost-effective installation in a trench without any sand bed 
• Significantly higher resistance to point loads, scratches, notches, which results in higher resistance to crack propagation 
• Applicable in trenchless technologies without any risk to damage the pipe 
• Longer installation time and higher costs

1. Scratches or notches on the outer surface of the pipe that occurred before installation (due to incorrect storage or transportation) or during the assembly (a common rule – a pipe that outer surface is damaged to more than 10% of the wall thickness should not be installed for safety reasons)
2. Point loads – direct exposure of the outer surface of a pipe to a hard (sharp) object (e.g. a stone) creates additional stressed within the pipe wall. Over time a crack occurs in the opposite wall as a result of concurrent emergence of stresses caused by the internal pressure and by the object. The crack will the propagate.

Gamrat Plastics Works introduced two types of two-layer polyethylene pipes: MULTIGAM and TWINGAM. The MULTIGAM pipes may be also offered with a steel strip inserted between the inner pipe and the protective pipe. This strip enable easy field monitoring of the pipeline and detection of any discontinuities thereof.

The MULTIGAM and TWINGAM pipes are designed for water supply systems, pressure, vacuum-pressure and gravity sewerage systems and as protecting tubes. The MULTIGAM and TWINGAM piping systems may be installed in the ground without any need for bed preparation, using traditional methods and narrow trenches. The MULTIGAM and TWINGAM pipes may also be used for construction and refurbishment of the systems by means of a trenchless method.

Joining individual pipe sections is done by:

• thermal butt welding, 
• electric resistance welding 
• in the form of a mechanical connection: socket joints, flanged joints for polyethylene pipes

The TWINGAM and MULTIGAM pipes are designed to transport water and sewage under pressure and temperature of up to 20°C. If the pipes are used to transport water of more than 20°C (up to 40°C) the allowable working pressure is calculated using the formula: PFA = fT x fA x PN, where the pressure reduction factor is taken from the table:

 The TWINGAM and MULTIGAM pipes may also be used as protecting tubes for power cables, telecommunication lines and other ones, both indoors and outdoors.

According to the Hygiene Attestation No. HK/W/0179/01/2009 issued by the Public Institute of Health in Warsaw (PZH), the TWINGAM pipes and fittings meet the hygienic criteria and may be used in systems and networks transporting drinking water.

Constructional differences of PE pipes:

The difference between MULTIGAM and TWINGAM is that the latter is made of two layers of polyethylene bound molecularly to each other. This type of bonds is not present in case of MULTIGAM pipes, the layers are made of PE80 or PE100 depending on the intended use. In case of TWINGAM pipes both layers are made of PE100 polyethylene, however, the outer layer is made of PE100 RC – plastic resistant to crack propagation. GAMRAT SA uses PE 100 RC of high resistance to a slow growth of cracks and point loads.

The physical properties of the polyethylene used for TWINGAM pipes should be conforming to the PN EN-12202-1:2004 and PN-EN 13244-1:2004 standards.

Dimensions and tolerances

The dimensions and tolerances of the TWINGAM pipes should be conforming to the PN-EN 12201-2:2004 or PN-EN 13244-2:2004 standard. In case of MULTIGAM pipes these geometrical requirements refer to the internal pipe. The thickness of the outer layer of MULTIGAM pipes depends on the intended use and agreements between the Manufacturer and the Customer bur it cannot be lower than specified in the table below: 

- Range: Ã˜90 – 450 mm
- Material PE80 or PE100
- SDR 11, SDR 17

Double-layer pipes for water supply SDR 11, Ã˜180-800, PE 100/PE100RC

Double-layer pipes for water supply SDR 17, Ã˜180-800, PE 100/PE100RC