wooden sleepers for railway track
1982 Edition

IS 10394 specifies the timber species suitable for wooden sleepers but does not list them in the main clauses provided. Commonly accepted species include Sal (Shorea robusta), known for its high durability and resistance to decay and termites; Teak (Tectona grandis), prized for strength but costlier; Eucalyptus, which requires proper treatment and has moderate durability; Deodar (Cedrus deodara), a naturally durable softwood; and other hardwoods such as Acacia, Neem, or Chir pine when suitably preservative treated. The timber chosen must exhibit strength, durability, and resistance to biological degradation, with mandatory preservative treatments like creosote applied. For exact species and treatment details, refer to the annexures and relevant timber standards within IS 10394.

IS 10394 outlines acceptable defects and their extents for wooden sleepers in Clause 7.1 and Table 4. For Class I and special sleepers, centre-heart defects are allowed within specific depth and location limits, such as a centre-heart depth of 10-13 cm on one end face within 5 cm (broad gauge) or 4 cm (metre/narrow gauge) from the broad face edge. Decay is permitted up to 1 cm depth near the rail seat and 2 cm elsewhere, provided it is chisellable to sound wood; exceeding these results in rejection. Borer holes are allowed in unlimited numbers, provided they are not located on or beneath the rail seat. Ruptured ends are not permitted. Sapwood surface limits vary depending on the sleeper region, with maximum percentages specified for under rail seat and other areas. Cracks and splits have defined maximum lengths and widths, with more stringent limits on spike lines and heart splits. Shakes such as cup shakes are allowed within specified arc lengths and depths. Grain slope must not exceed 1 in 15 on the broad face. Class II sleepers have slightly relaxed limits. These criteria ensure sleeper integrity and performance.

According to IS 10394, preservative treatment is mandatory for all sleepers containing sapwood and for species not marked with an asterisk in Appendix A, which indicates natural durability. Naturally durable hardwoods marked with an asterisk require no preservative treatment if only heartwood is used. Special sleepers must receive Class I level treatment to maximize durability. The preservatives and application methods must comply with the relevant IS standards and are intended to protect the sleepers from decay and insect attack. Additionally, steel clamps used with sleepers must be dipped in hot boiled linseed oil as per IS:77-1976 after inspection and before packing to prevent corrosion. The detailed Code of Practice for preservative treatment of railway wooden sleepers is in preparation, and manufacturers should refer to Appendix A for precise species and treatment guidance.

IS 10394 requires that inspection of wooden sleepers be conducted at least two months after the conversion process, ensuring the wood is adequately seasoned and not in a green state. The inspecting officer must examine all faces of each sleeper thoroughly using any means necessary to confirm conformity with the standard's specifications. Sleepers are then marked distinctly as either passed or rejected based on inspection outcomes. While the code does not explicitly specify sampling sizes, inspections are typically performed on all sleepers or statistically representative samples for quality assurance. This process ensures sleepers meet dimensional tolerances, surface condition criteria, wood quality standards, and preservation treatment requirements before deployment.

The Composite Sleeper Index (CSI) defined in IS 10394 is a numerical indicator representing the combined strength and hardness characteristics of timber species used for railway sleepers. It is computed by integrating key mechanical properties such as compressive strength parallel to grain, bending strength, and hardness, using a formula provided in Appendix C. The calculation employs CGS units and assigns weights to each property to produce a single index value. CSI values for various timber species are tabulated in Appendix A, and minimum recommended CSI thresholds for different track positions are specified in Appendix B. This index aids engineers and manufacturers in selecting timber species that meet requisite strength and durability standards for sleepers, ensuring safe and reliable railway infrastructure.