Pipework of unplasticized polyvinyl chloride (PVC-U) on ships, with solvent-cement joints - Use, application, installation

Thermal Expansion Compensation Design

Expansion Calculation Requirements

The thermal expansion coefficient of PVC-U pipe is 0.08 mm/m·K, which is much greater than that of metal pipes. Length change calculations must consider:

• The pipe wall temperature (ambient temperature) at installation
• The minimum and maximum expected pipe wall temperatures during system operation

Length change calculation formula: ΔL = α × L × ΔT
Where: ΔL - length change (mm); α - thermal expansion coefficient (0.08 mm/m·K); L - pipe length (m); ΔT - temperature difference (K)

Compensation measures

An expansion bend or compensator must be provided between the two fixed points. These can be expansion bends, telescopic compensators, or bellows compensators. During installation, the compensator must be adjusted so that its operating range accommodates length changes caused by operation and ambient temperature.

Because plastic pipes are highly deformable under stress, compensators with minimal deformation must be used. Brackets (guide brackets) must be installed before and after the compensator to prevent lateral buckling.

Tightness Testing Requirements

Pressure Pipe Testing

Pressure testing should be performed at least 24 hours after the last bonding pass. For safety reasons, pressure testing should be performed using an incompressible medium (such as water). The pipe should be pressure-tested for one hour at 1.3 times the permissible working pressure, taking into account the pipe's pressure rating.

Non-Pressure Pipe Testing

Non-Pressure Pipes (gravity drainage systems) must be pressure-tested in accordance with DIN EN ISO 15749-2. The test pressure should be equivalent to the static pressure head at the highest drain connection in the system. Drain piping for vacuum systems should be tested in accordance with DIN EN ISO 15749-3.

Implementation Recommendations and Precautions

Installation Environment Control

The ambient temperature during bonding must be greater than 5°C, and heating should be used if necessary to prevent frost or condensation. Adhesives and cleaning agents contain volatile solvents that are flammable and explosive. Closed spaces must be well ventilated and open flames, sparks, and static electricity are strictly prohibited.

Pipeline protection requirements

Installed PVC-U pipes must not be painted with paints containing solvents or paints that are corrosive to PVC. Pipeline components must be protected from mechanical loads, external heat influences, and direct UV radiation, for example by wrapping or using protective coatings suitable for plastics.

Special working conditions

When the ambient temperature is around 0°C, avoid performing any correction work on metal parts near PVC-U pipes. When the operating ambient temperature is 0°C, insulation or heating measures should be provided to prevent the pipes from rupturing due to freezing.

Analysis of Standard Technology Evolution

Compared to the 1991 edition, DIN 86015:2018 has undergone significant updates on multiple technical levels:

• Optimized sewage piping system design requirements to meet the sewage treatment needs of modern ships
• Refined pipe end pretreatment processes to improve the reliability of adhesive connections
• Improved calculation methods for pipe clamp spacing to account for the effects of different temperatures and medium densities
• Supplementary provisions for expansion compensation devices to ensure thermal stress relief in piping systems
• Strengthening pipeline protection requirements to extend pipeline service life

These updates reflect the latest developments in ship piping technology, and in particular, provide more detailed technical guidance on the application of plastic pipes in the special environments of ships.