BS 5308-2

BS 5308-2 standard for Instrumentation cables, Specification for PVC insulated cables.

Overview

BS 5308 Part 2 specifies the requirements and dimensions for PVC-insulated instrumentation cables. These cables are designed primarily for the chemical and petrochemical industries and include options for screens, single-wire armour, or lead sheath with single-wire armour for additional protection. The cables are used to connect electrical instrument circuits and facilitate communications in demanding industrial environments. Although BS 5308 Part 2 has been withdrawn, manufacturers like Tratos can produce cables that adhere to the designs previously specified in the withdrawn standard.

Key Specifications

The cables are insulated with high-quality PVC material, ensuring durability and flexibility under various environmental conditions. They are suitable for operation at voltages up to 300 V r.m.s. core to earth and 500 V r.m.s. core to core. These cables are not intended for direct connection to low-impedance sources, such as public mains electricity supplies.

The conductors are made from plain annealed copper wire for optimal conductivity and mechanical performance. Two insulated conductors are twisted uniformly together to form a pair. For two-pair cables, if unscreened, the four cores are laid in quad formation around a central dummy. Unscreened pairs are colour-coded for identification, while screened pairs are identified using either coloured insulation or a numbered polyester film.

Protective armour options include a single layer of galvanised steel wire or a lead sheath with single-wire armour, providing enhanced mechanical strength and resistance to environmental factors. The outer sheath of the cables is made from a durable PVC material, which provides excellent resistance to moisture and chemicals.

Applications

These cables are primarily used in the chemical and petrochemical industries due to their robust insulation and protective design. While BS 5308 Part 1 focuses on polyethylene-insulated cables for the petroleum industry, BS 5308 Part 2 provides a complementary solution for environments requiring PVC insulation. These cables are not suitable for coal mining applications (Group I), but they may be used in Group II intrinsically safe systems, provided that relevant safety guidelines are followed.