Level 3 work instruction
NR/L3/TEL/30077
Specification for the Maintenance of Cable Distribution Frames and Location Cases (formerly NR/L2/TEL/30077 and NR/WI/TEL/30077)
Issue 3, September 2011
Maintenance and inspection regime for telecoms cable distribution frames (MDF, IDF), distribution cases, location cases and FTN trackside equipment housings (TEHs): defines Type A and Type B services by earth-fault risk to signalling circuits, a 5-yearly termination inspection where Type A circuits or hostile sites exist, a check at every planned visit, and a yearly TEH external and internal service.
Clause map — what each clause deals with
| 1 | Purpose | Why frames, distribution cases and location cases holding telecoms equipment or terminations are inspected: longer life and catching failures before they affect service |
| 2 | Scope | Covers everyone maintaining NR telecoms distribution frames and location cases, including FTN housings; minor defects should be put right during the visit |
| 3 | Definitions | Defines FTN, IDF, MDF, TEH and the split into Type A (non-diverse signalling at risk from cable earth faults, with exceptions) and Type B services |
| 4 | Responsibilities | Protect working and safety-critical circuits from disturbance, report defects to fault control and record corrective actions on the work return |
| Appendix A | Maintenance of Distribution Frames and Location Cabinets | Service A (default 5 yearly, only with Type A circuits or hostile, maritime, corrosion-prone or UV-exposed cases) checks terminations; Service B each visit checks access, locks, 660V, jumpers, records |
| Appendix B | Maintenance of TEHs | Yearly service for FTN trackside equipment housings: site security, intruder alarm call-in, case fixing, corrosion, seals, earthing/bonds, labels, locks, moisture, heater, cable entry, jumpers, desiccant, cleaning, vents |