Quota attribution of piping in heat-exchange (thermal substation) station houses: three-way split among process piping, water/heating, and HVAC, plus indoor/outdoor boundaries and pressure tiering

Topic Positioning

This card resolves quota attribution for piping inside heat-exchange (thermal substation) stations, boiler rooms, and pump houses: by which trade caliber to list each piping type, where station-internal meets external (indoor/outdoor), and how pressure classes tier. The thermal substation (heat exchange, mixing, distribution, absorption-heat-pump stations) is defined in CJJ/T 34-2022 Clause 2.0.13: facilities converting heating medium type, changing parameters, and distributing, controlling, and metering heat supplied to users.

Core Conclusions

1. Master caliber: no single volume; split by medium/function.

1. In-station thermal process piping (primary/secondary, condensate, unit piping) -> process piping by pressure tier: low = nominal P <= 1.6 MPa; medium = 1.6 < P <= 10 MPa (TB/T 10833-2024 Vol. 12, Chapter 7 notes). Local acceptance matches — "process piping, valves, and flanges in thermal and booster stations execute Chapter 7" (DB13(J)/T 8060-2019 Clause 8.1.7).
2. In-station heating, water, drainage, and sanitary equipment -> water/heating: "construction and acceptance ... per GB 50242" (CJJ 28-2014 Clause 6.1.1).
3. In-station refrigeration piping and air ducts -> HVAC: "per GB 50243" (CJJ 28-2014 Clause 6.1.4).

2. Boundaries (decide attribution).

1. Station piping by inner wall face: "boiler rooms, pump houses, and the like are bounded by the inner wall face" (DB11/T 638-2016 Table C.5.1 note 1); "station-type piping applies to stations and general industrial-plant-type (boiler rooms, pump houses, softening rooms, workshops) piping" (C.5.3 note 1).
2. Railway (TB/T 10831-2024 Vol. 10, Chapter 3 notes): piping quotas compiled at low pressure; medium/high executes Vol. 12; boundaries — water at the entrance meter or junction pit, or 1.50 m outside the building face if direct; drainage at the first manhole or septic tank outside; network and process piping at the first valve pit outside or the building face; booster-pump rooms in high-rises bounded by the pump-room outer wall.
3. Railway Vol. 12 (Chapter 7): indoor/outdoor split at the building face or entrance manhole — inside = indoor piping.
4. General installation (GB/T 50856-2024 K.9.1): water at 1.5 m outside the building face (at entrance valves where provided); drainage at the first manhole; heating at 1.5 m outside (or entrance valve; with outdoor entrance assemblies at the circulation tee); gas: underground entries at the first indoor valve, above-ground at the first tee outside the wall.

3. Companion and error-prone rules.

1. Pressure red line: primary-side parameters > 1.6 MPa must take medium-pressure tiers, never low.
2. Supports separate: low/medium indoor piping sub-items for DN > 50 exclude supports — add per Chapter 1 "equipment supports" (TB/T 10833-2024 Chapter 7).
3. Flange sub-items compiled per "pair"; single flanges: consumption x 0.5 (same source).
4. Vol. 10 piping work content (unless noted) includes: pipes and joints installed, flush/test, DN25 pipe clips and hooks, steel bends (excluding expansion joints), cast/plastic drainage clips, hangers and vent caps, labor of wall/floor sleeve flashing; indoor trench earthwork and bases execute the civil chapter; indoor cast-iron water/drainage includes joint labor but not the joints themselves; wall/floor steel sleeves use outdoor steel pipe (welded) sub-items; threaded/flanged valve sub-items suit all such valves, replaceable when design differs.
5. Station companions (DB11/T 638-2016 C.5.3): removal of station pipes, accessories, and appliances not covered — list per water/heating; chases/holes, supports, insulation and covering per auxiliary works; rust and painting (except touch-up) per Appendix A; trench and manhole earthwork, bedding, bases, masonry, plastering, cover slabs, backfill, haulage, pavement, pipe thrust blocks per Appendix A.
6. Fitting listing differences: industrial (process) fittings, flanges, valves are usually separate items; water/heating pipes often include fittings in pipe items — check chapter notes to avoid duplication or omission.

Applicable Boundaries

• Applies to quota attribution, estimates/budgets, and listing of piping in heat/thermal substation, booster, boiler, pump, and softening rooms.
• Networks outside station walls are municipal heating — out of scope; ordinary stand-alone building water/heating (no station process nature) follows normal building installation.
• Boundary wording differs slightly by system (railway Vol. 10 water at entrance meter/junction pit vs general installation 1.5 m) — lock the project's quota/standard system first and follow its volume/chapter notes; CJJ 28-2014 points to acceptance-standard attribution, while listing follows the corresponding trade sub-items. Sub-items, coefficients, and work contents per the project's current quota and supporting documents.

Further Reading

• TB/T 10831-2024 Vol. 10, Chapter 3 building-services notes (water/drainage/fire piping; threaded and flanged valves; fixtures, tanks, fire-department connections)
• TB/T 10833-2024 Vol. 12, Chapter 7 process piping (components, derusting/coating, anti-corrosion, insulation, covering; rust grades micro/light/medium/heavy)
• CJJ 28-2014 Code for Construction and Acceptance of Urban Heating Networks, Clauses 6.1.1, 6.1.4
• DB13(J)/T 8060-2019 Acceptance Standard for Installation of Urban Heating Pipes and Equipment, Clause 8.1.7
• DB11/T 638-2016 Measurement Code for Building Repair Works, Appendix C Table C.5.1 (station piping, code 930501), notes C.5.3
• GB/T 50856-2024 Appendix K, K.9.1 (boundaries)
• CJJ/T 34-2022 Code for Design of Urban Heating Networks, Clause 2.0.13 (term)