West Expansion Ductwork

The West Expansion Ductwork is the collective designation for the western branch of the Splenic Ductwork, comprising some eleven kilometres of Melancholy-Conductive Aggregate 7 (MCA-7) conduit running from the junction at Sigma-37,642-Alpha westward through the lower flank of Spiral 14 West Quadrant and terminating at the Splenic Swamp. It is maintained by the Guild of Engineers under the general authority of Concordance 412 and is distinguished from the parent system chiefly by its behaviour under load: where the central trunk conducts Black bile at a steady pressure, the West Expansion Ductwork is permitted, and in some seasons obliged, to lengthen.

Design and the expansion allowance

The ductwork was laid during the reconstruction following the Expansion of the Lower Axial Stacks, when the drainage of the western quadrants was found to be inadequate to the volume of synthesized bile arriving from the production nodes. The Engineers' solution was to specify MCA-7 segments with an unusually wide joint allowance — 41 millimetres at each coupling, against the 12 millimetres standard elsewhere — so that the line might accommodate thermal and dimensional variation without fracture.

That allowance was very quickly overtaken by events. The western conduit passes through deposits subject to Silent Expansion, and the ductwork has responded by extending where the masonry around it has not. Survey parties of the Guild of Formal Cartographers have recorded cumulative lengthening of the branch of between four and nine metres per annum, absorbed almost entirely at the joint seals. The Guild of Engineers has declined to describe this as growth, preferring the term "accommodation," and the distinction is maintained in every maintenance return filed since.

The winter of the third recension

The branch's reputation was made in the winter of the third recension of the Expansion Protocols, when the line extended by thirty-one metres in a single season and carried a section of its own inspection walkway with it. The walkway, which had been fixed to the conduit wall at 2.4-metre intervals, was drawn out into the adjacent floor and thereafter administered, after some dispute, as a corridor of that floor.

A complaint was entered by the then-Keeper of the West Spiral, one Alder Vey, who had been obliged to issue keys for a corridor he had not commissioned and could not number. His memorial to the Concordance held that the Engineers should be answerable for any structure their ductwork produced, "whether pipe, bracket, or floor, since the floor in this instance is demonstrably a pipe." Memorial of Alder Vey, 9 The Engineers' reply, filed eleven days later, consented to the principle but not the numbering, and the corridor remains unnumbered to this day. It is marked on the quadrant plans only by a dotted line and the word "emergent."

Governance and the contradiction of the annexes

Responsibility for the branch is set out in Concordance 412, which assigns its maintenance to the Guild of Engineers and its temperature to Annex G. The two provisions have never sat comfortably together. Annex G specifies a surface temperature of 31 degrees Celsius along the whole western run; the Engineers' standing return of Floor 3,118 records that the westernmost 400 metres have not fallen below 44 degrees in living memory and cannot be brought lower without shutting down the Splenic Swamp feed.

Two readings of the annex circulate. The first, advanced by the Engineers and supported by a marginal gloss in the Register of Thermal Anomalies, holds that Annex G prescribes the temperature of the catalogue entry for the ductwork — that is, that the figure of 31 degrees is the value to be recorded, not the value to be attained. The second, favoured by the Bureau of Weights and Measures and most of the Librarians who have written on the question, holds that the annex means what it says and that the Engineers are simply in breach. No formal resolution has ever been sought, and the practical consequence is that every thermal survey of the western branch is filed twice: once as measurement and once as amendment.

Interaction with other works

Because the ductwork is both fixed and lengthening, its relations with neighbouring works are settled case by case. The Thorne Bracket, designed to anchor conduit at a fixed span, is prohibited along the West Expansion run by a standing instruction of the Engineers on the grounds that a bracket which cannot slide will eventually be somewhere else. Where the Cartographers' surveys require temporary modification of the line, permits are sought from the Guild of Engineers in the ordinary way, though since the West Stack Brief the Guild has taken to granting them only for sections it has measured within the preceding five months.

The branch is not to be confused with the West Lightwell, which lies above it and shares only a name direction; nor with the West Spiral 44, whose disputes with the Engineers concern drainage and not conduit. The junction at Sigma-37,642-Alpha where the branch begins is itself of some interest, being the only point in the system where flow may be divided by the maintenance crews without written instruction.

Current standing

The West Expansion Ductwork remains in service and remains longer each year than the year before. The Guild of Engineers inspects it twice annually, in the ordinary way. Visiting parties are asked not to rest equipment against the joint seals.