Handling specifications beyond a quota item's largest step (over the top band): no proportional extrapolation - a four-step ladder of volume-note wording first, analogous items next, supplementary quota last

Topic Positioning

Where quota items band by specification (transformer capacity, pipe diameter, foundation angle etc.) and the actual specification exceeds the largest band: is it "conversion" or "gap", and may coefficients be borrowed by ratio. The general route across railway, power, building and municipal quota systems.

Core Conclusions

1. Characterisation: over the top band is a "quota gap", not a "quota conversion". Conversion stands only on express quota wording (strength grades converted per the mix tables, machine-shift additions for thin layers split, dry / wet mortar interchange, coefficients stated in volume notes). Beyond the largest step no band exists in the quota - an uncovered case no coefficient can fix.

2. Prohibited: no linear extrapolation by specification ratio. Never scale a "within 10000 kVA" item by capacity ratio onto larger units, nor multiply a DN1000 item by 1.2 as DN1200. Such "unsupported borrowing / unsupported coefficients" audit straight into over- and mis-application.

3. The correct order (four steps):

1. Check the volume / chapter notes first; express wording governs. Three forms:
   • Execute under another volume (discipline). DB11/T 2382-2024 clause 6.10.26, original: "pipes over 400 mm nominal diameter in cooling-tower connections, and the copper pipes between multi-split outdoor and indoor units, execute under the industrial piping items."
   • Stated coefficients beyond stated conditions. TB/T 10832-2024 Volume 11, volume notes, chapter 3, item 7, original: "the concrete-bedding items for drainage pipes are compiled on the 120-degree base of the standard drawings; a 90-degree base multiplies the consumption by 0.8; a 180-degree base multiplies items below d600 by 1.2 and d600 and above by 1.57."
   • Execute under same-class items for other types / bands (with type-conversion factors). DB11/T 2382-2024 clause 6.4.9, original: "arc-suppression coils, oil-immersed reactors, rectifier transformers, autotransformers and on-load tap-changing transformers install under the corresponding oil-immersed power transformer items; amorphous-core transformers likewise, with labour and plant preferably x 0.70." And clause 6.4.7: "transformer installation sets items by type and capacity band; quantities by design-shown count."
2. Take the band within - never extrapolate. Where steps read "within X capacity / diameter", a specification inside takes that band (the smallest band not below the actual); beyond the top band, no band exists.
3. Borrow analogous-process items (across volumes or sectors / regions), listing the basis and taking on-costs per the borrowed volume. DL/T 5468-2013 clause 4.1.4 item 2, original: "where the quota (index) lacks an item, prefer quotas (indices) of similar construction process; where nothing similar exists, compile a supplementary quota (index) from the construction-drawing budgets or final accounts of comparable works; where no reference exists, compile one from the project's technical conditions."
4. With nothing analogous, compile a supplementary quota (unit-rate build-up schedule) and obtain approval / file:
   • GB/T 51095-2015 clause 5.3.12, original: "when compiling construction-drawing budgets, items missing from the budget quota shall be covered by supplementary unit-rate build-up schedules compiled under the quota's principles and methods." (No index method at budget stage; the schedule must support labour / material / plant analysis and all-in rate analysis.)
   • DL/T 5468-2013 clause 4.1.4 item 3, original: "supplementary quotas (indices) shall comply with the current quota administration rules and be used only after approval by the power engineering quota authority."
   • TB 10801-2024 clause 2.4.3, original: "for works the current quotas do not cover or fit but the project urgently needs, the investor shall organise supplementary unit-price analyses per the work's process requirements and file them with the sector standard authority." (Railway files, no prior approval.) Clauses 2.4.1: "design estimates shall use the railway quotas"; 2.4.2: "passenger station buildings, complexes, canopies and footbridges may use the provincial local quotas of the project location, with their labour / material / plant prices and on-cost quotas applied in step."
   • Beijing document [2021] No. 11 gap-item mechanism: missing pricing-basis items are supplemented by the employer per the compilation principles / basis / rules, reported to the municipal cost authority per the current supplementary-item procedure; approved items are used once within the declared scope; the Budget Consumption Standard adjusts dynamically as the "four news" technologies mature.

4. Two typical scenes

• Transformer capacity over the top: first confirm "truly over?" - same voltage class or type may already cover it. Railway Volume 9 (traction power) 110 kV transformer items run to 75000 kVA, HY-1222 to HY-1228, banded at 20000 / 25000 / 31500 / 40000 / 50000 / 63000 / 75000 kVA. Where only the voltage class or type differs (large, dry-type, autotransformer, rectifier, on-load tap-changing), execute the matching class or the volume note's "execute under XX items" - never add coefficients onto a low band. Truly over the top: compile a supplementary unit-price analysis - cranes by actual tonnage, oil filtering / drying by actual oil volume, commissioning under the system items; the equipment proper is charged separately, and heavy-haul mobilisation and preliminaries of oversize parts list separately per the approved method statement, never inside the transformer installation item.
• Pipe diameter over the top: check the volume notes for reassignment (DB11/T 2382-2024 clause 6.10.26: cooling-tower piping over 400 mm goes to industrial piping). Railway water and drainage outdoor laying items exclude pipe and fitting material costs - quantities bracketed; budgets add the material costs per the design's size, material and bracketed quantities; over-band pipes follow the volume notes, failing which steps 3-4 (borrow or supplement).

Applicability Boundaries

• First confirm "truly over?": the same voltage class / type / process may be covered, or the volume note may already say "execute under XX" - that is "application", not "gap", and application always comes first.
• Never confuse "conversion" with "gap": what the quota already comprehends (pressure testing, disinfection and flushing of laid water mains; water for drainage closure tests; indoor pressure testing and flushing) adjusts nothing however the site differs; a gap is never fixed by coefficients.
• Borrowing another volume's quota must carry that volume's on-cost regime (borrow which volume, take on-costs with it) and state the basis in the compiling notes - otherwise the review finds unsupported borrowing.
• Approval routes differ by sector / region (power: prior approval; railway: filing; local approved supplementary items often once-only within the declared scope) - never transplant across sectors; the supplementary-item procedure and bill supplementary items are different things.
• This card is method; bands, coefficients and codes follow the project's current quota text and its latest edition.

Further Reading

• TB 10801-2024 Measures for Compiling Design Estimates of Railway Capital Construction Projects, section 2.4 "adoption of quotas" (2.4.1 to 2.4.3)
• TB/T 10832-2024 Railway Works Budget Quota Manual, Volume 11 water and drainage, volume notes chapter 3 "outdoor pipe laying" (indoor / outdoor boundary, bracketed material costs, bedding-angle coefficients, pipe jacking and directional drilling) and the annex "items whose main materials are outside the base price"
• TB/T 10830-2024 Volume 9 traction power supply, chapters 1 and 2 section 12 "transformers" (110 kV, HY-1222 to HY-1228)
• DL/T 5468-2013 Guidelines for Compiling Construction-Drawing Budgets of Power Transmission and Transformation Works, clause 4.1.4
• GB/T 51095-2015 Code for Construction Cost Consultation, clause 5.3.12 (supplementary unit-rate build-up schedules)
• DB11/T 2382-2024 Construction Works Consumption Quota Standard, clauses 6.4.7 to 6.4.9 (transformers) and 6.10.24 to 6.10.32 (indoor piping)
• Beijing document [2021] No. 11 (the gap-item supplementing mechanism of the Budget Consumption Standard)