Deep Screening of Ballast-
(1) General –
(a) It is essential that track is well drained for which screening of ballast should be carried out periodically as described. Due to presence of bad formation, ballast attrition, excessive rain fall and dropping of ashes and ore, ballast gets choked up and track drainage is impaired. In such situations, it becomes necessary to screen the entire ballast right up to the formation level /sub-ballast level. Further through screening restores the resiliency and elasticity of the ballast bed, resulting in improved running quality of track. Such screening is called “Deep screening”, as distinguished from the shallow screening, which is done, during overhauling.
(b) Deep screening should be carried out in the following situations by providing full ballast cushion:
(1) Prior to complete track renewal.
(2) Prior to through sleeper renewal.
(3) Where the caking of ballast has resulted in unsatisfactory riding.
(4) Before converting existing track, fish plated or SWR into LWR or CWR; or before introduction of machine maintenance, unless the ballast was screened in recent past.
(5) The entire track must be deep screened atleast once in ten years.
(c) The need for intermediate screening between track renewals may be decided by the Chief Engineer depending on the local conditions.
