Hullavington Ground Frame

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Origin

Provided 25/6/67 released from Hullavington SB then re-controlled onto Swindon Panel.

Release Interlocking Note

Written by Chris Bellett.

Swindon Panel Release No.462 Annetts Release Pattern Key A

Situation as described from the signalling records as at November 2002.

The GF had a trailing connection into the Up Main Reversible line and was protected by Swindon Panel signals SN133; SN135; SN733 (Route A) in the Up direction and SN164 (Route B) and SN764 (Route B) in the Down direction (with the latter two signals being located at Wootton Bassett West). There are two other signals in the Down direction between Wootton Bassett West and the GF, SN774R and SN774RR but the aspects of these signals were not affected by the GF in any way (i.e. they were not replaced to their most restrictive aspects by the loss of the GF normal detection).

The GF had ‘shut inside’ facilities and the siding connections were worked by a two lever ground frame. Lever No.1 was the release lever (released by the Annetts Key) and works the FPL in the Up Main. Lever No.2 worked the points in the Up Main (trailing to Up movements) and the trap points in the siding. Note: There is reference in the record drawings of this GF being renewed at some point in time and shows Lever No.1 as the points and Lever No.2 as the Release/FPL. The points were detected normal only and there were no shunting signals and hence Swindon Panel slots.

The Swindon Panel end GF release was standard.

The GF was required to be locked and detected normal in the URs of the protecting signals. The GF was route locked in the Down direction until track circuit LN was clear. The GF was locked in the UP direction until track circuit LN, LO, and LP track circuits were clear OR LN track circuit was occupied and a short track circuit LO(1) just clear of the Up Main trailing points had been occupied for 60 seconds (this track circuit is approximately 50m long). This allowed a train to leave part of its consist on the Up Main clear of the GF and pull forward and shunt into/out of the sidings before finally backing up to the divided portion and then heading away along the Up Main. This is standard control for an intermediate section GF. Note: Due the Up main being reversible it was also possible (technically) to shunt back from the GF towards signal SN774 at the end of the reversible section in the Down direction (e.g. by a light locomotive).

The panel route lights were conventional and there was no delay in the lighting of the route lights caused by lack of detection on the GF in either direction (the routes would not be able to be set across the GF anyway).

It should be noted that all of the above named controls still exist in Hullavington Interlocking, only the physical GF and points having been removed. GF Normal detection is maintained in the interlocking by false feed.

Alterations

The pointwork at the siding-end of the connection was rationalised in 1976:

Removal

The ground frame was shown as being recovered in July 1993: