Network Rail Design Process |Correlation|Correlation waiver

Network Rail Design Process |Correlation|Correlation waiver

Network Rail Design Process

Source Records

* Source Records are the documents necessary for producing any design.

* The source record should show the state of the current infrastructure.

* It may be in the form of CAD files, Data files, or Negatives(NR/L2/SIG/11201/Mod-A8).

* There should be one “Master Record” which is on white paper with an appropriate endorsement/stamping. It is to be used to verify the source record.

Identification of Source Records

* After Remit is received, study of the project documents such as Scheme plans, OPS etc.

* Finalize the design requirements.

* Identify the source records required for the job. They are to be used as the base for developing altered / new designs.

* Source records may include existing Designs of Locations / Relay Rooms / REBs, Control Tables etc.

* Availability of Source Records is an essential requirement not only for the production of detailed designs but also for recovery of existing installations.

Procurement of Source Records

* After proper  identification of records, they are listed.

* It is important for the designer to identify the full requirement of documents at the time of placing the indent to avoid delay in receipt of documents in time.

* For Network Rail, NRG (National Records Group) is the custodian of all the records.

* There is QF901 form for Request for handover the soure records. Nowadays QF9000 form is

used as an alternative to QF901 ,QF910(Request for prints and images of source records) & QF918 version control and drawning no. request).

* The Project Manager/Document Controller ,U.K. collects the source records from NRG and forwards them to lucknow office. Records thus received from the U.K. are to be supported by  proper Transmittals verified by the CDC.



* It is the process of verifying the accuracy of source records with reference to the installation at site.

* Correlation is required, not only to tally the site conditions with the records received, but also to ensure that these records are adequate for maintenance and for fault localization/rectification.

* Correlation is a mandatory requirement before commencement of any design process.

Reasons for miss-match between records and site installations

* There may be inadequate management of records at the time of original installation works.

* Alterations to wiring or replacement/changes to equipment carried out at site but not reflected in the master records.

* Proposed works of alterations or new works installed but not commissioned.

Scope of Correlation

* The Project shall specify the scope of records to be correlated with reference to geographical area, functional elements etc and get agreed by Network Rail.

* Where design alterations are involved, the scope of correlation, as detailed in the Design Specifications should be reviewed with the Tester in charge (if appointed).

* As a minimum, this document shall include all the signaling equipments which are likely to be affected by the proposed alterations.

* During the correlation process, the testers should check all control equipments, and labeling ,equipment racks, cable terminations, and apparatus cases. Signals, points and track circuit bondings need to be checked. Checking of wiring should include counting and visual examination. Any equipment or wiring found existing but not  found in the record should be identified.

Request for Correlation

* Copies of the relevant source records of latest version are to be made available for correlation purpose. They are to be marked ”Correlation copy”.

* If proper source records are not available, they may be created from the available records by a competent person and got correlated.

* Circuit diagrams when issued for correlation should be provided with appropriate analysis sheets.  If these sheets are not available, they shall be created at the discretion of Network Rail.

Correlation update

Source records shall be updated after the quality check and disposal of the discrepancies, so the records will reflect the actuals at site.

Correlation process at site

* The complete diagram should be correlated wherever possible, as given in the scope.

* Analysis sheets will be confined to the functions concerned. External equipments if any shown on the sheets may be excluded from correlation.

* All discrepancies noted by the tester shall be recorded on the sheets with proper check markings (Rt/E/C/11723).

* The discrepancies noticed are to be independently checked for correctness and also for clerical errors.

* Error log sheets are filled in by the person carrying out the correlation.

* The existing maintenance records should also be corrected temporarily as per the correlation results. The resultant temporary maintenance copy shall be replaced with the final record copy in time.


* Source records received from NRG are to be subjected to correlation, except where correlation waiver is sought.

* Designs are to be carried out only on updated source records, unless otherwise exempted supported by a waiver. .

* As per provisions in the Standards, the Project should have scope of correlation agreed by the network Rail.

* Correlation  waiver is to be obtained wherever it is decided to correlate only the affected circuits

Correlation waiver

Network Rail may grant correlation waiver under the following circumstances:

* It is possible to verify that the records are accurate to the testing records of installation and an auditable process is in place to ensure that any subsequent amendments have been fully documented.

* Adequate records do not exist and the cost of creation would be disproportionate to the risks involved.

* A full correlation check may need such disconnection of wiring or disturbance of fragile wiring / equipment that it is assessed as introducing greater risk to the safety of railway than would arise from not completing a full correlation.

* A waiver may be full, where the installation is to be abolished in the near future.

* It can be a partial waiver for “correlation of affected sheets only” where the proposed alterations cover a small portion of a sheet.

* The Network Rail may ask for a full correlation where the installation has not been correlated for many years, or where the life expectancy is long.

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