+---
+title: Steam and Condensate Piping
+category: Mechanical / Piping & Pumps
+toc_depth: 3
+description: >
+ When to use: Steam supply and condensate return distribution piping for institutional, campus, healthcare, industrial, and central-plant facilities, above-grade and underground, from the boiler outlet connections to the inlet flanges of terminal equipment (heat exchangers, unit heaters, steam coils, and process loads). Covers low-pressure (0-15 psig), medium-pressure (15-100 psig), and high-pressure (100-300 psig) service, including pipe materials and joining by pressure class, expansion compensation, drip legs and steam traps, condensate receivers and pumps, pressure-reducing stations, flash tanks, valves, system insulation requirements, slope, and hydrostatic testing.
+
+ Not intended for: Boiler pressure vessels, trim, and combustion controls (see [[sync/boilers]]); closed-loop hydronic hot-water piping below 250°F and 160 psig (see [[sync/hydronic-piping]]); steam-to-water heat exchangers themselves (see [[sync/heat-exchangers]]); pipe hangers, spring supports, and seismic bracing (see [[sync/hangers-and-supports]]); insulation material selection and thickness application (see [[sync/mechanical-insulation]]); condensate-pump specification detail (see [[sync/hvac-pumps]]); domestic water piping (see [[sync/domestic-water-piping]]); fuel-gas piping to the boiler train (see [[sync/natural-gas-piping]]); and high-temperature hot water or process steam above 300°F / 300 psig governed by ASME B31.3.
+---
+
+# Scope {toc}
+
+## This specification covers steam supply and condensate return distribution piping systems for institutional, campus, healthcare, industrial, and central-plant facilities, addressing three pressure classes: low-pressure steam (0-15 psig), medium-pressure steam (15-100 psig), and high-pressure steam (100-300 psig). Coverage includes above-grade and underground steam supply mains and branches, condensate return mains and drip legs, expansion compensation, drip pockets and steam traps, condensate receivers and pumps, pressure-reducing and pressure-regulating stations, strainers, isolation and check valves, safety relief valves, flash tanks, system insulation requirements, high-temperature pipe supports, slope, and commissioning hydrostatic testing. The system boundary begins at the high-pressure or low-pressure boiler outlet connection and ends at the inlet flange of the terminal equipment served, including heat exchangers, unit heaters, steam coils, and process loads. {note}
+
+## The pressure class is the governing decision for this standard: it determines the applicable design code, the pipe material and schedule, the joining method, the valve and flange ratings, and the welder qualification requirements. Low-pressure building-services steam at or below 15 psig is governed by ASME B31.9; steam above 15 psig is power piping governed by ASME B31.1, which imposes more stringent material, examination, and welder-qualification requirements. {note}
+
+## This standard applies to all project scales, from a single-building low-pressure heating plant to a multi-building campus distribution system. {note}
+
+## The pressure class of each system shall be established by the Engineer of Record and indicated on the drawings before pipe material and code basis are selected.
+
+## Steam piping above 15 psig steam shall be designed, fabricated, examined, and tested in accordance with ASME B31.1.
+
+## Low-pressure steam piping at or below 15 psig steam shall be designed, fabricated, and tested in accordance with ASME B31.9.
+
+## The boiler external piping for a power boiler shall comply with ASME B31.1 and the boiler-external-piping jurisdictional boundary defined therein.
+
+## The Contractor shall coordinate steam and condensate piping with the boilers ([[sync/boilers]]), heat exchangers ([[sync/heat-exchangers]]), pipe supports ([[sync/hangers-and-supports]]), insulation ([[sync/mechanical-insulation]]), condensate pumps ([[sync/hvac-pumps]]), water treatment ([[sync/hvac-water-treatment]]), and the building automation system ([[sync/building-automation-system]]).
+
+# Referenced Standards {toc}
+
+## Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
+## Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
+| Standard | Title |
+|----------|-------|
+| ASME B31.1 | Power Piping (primary code for steam above 15 psig and boiler external piping) |
+| ASME B31.9 | Building Services Piping (low-pressure steam at or below 15 psig) |
+| ASME BPVC Section IX | Welding, Brazing, and Fusing Qualifications |
+| ASME B16.9 | Factory-Made Wrought Buttwelding Fittings |
+| ASME B16.11 | Forged Fittings, Socket-Welding and Threaded |
+| ASME B16.34 | Valves - Flanged, Threaded, and Welding End |
+| ASME B16.5 | Pipe Flanges and Flanged Fittings NPS 1/2 through NPS 24 |
+| ASTM A106/A106M | Seamless Carbon Steel Pipe for High-Temperature Service |
+| ASTM A53/A53M | Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and Seamless |
+| ASTM A234/A234M | Piping Fittings of Wrought Carbon Steel and Alloy Steel for Moderate and High Temperature Service |
+| ASTM C547 | Mineral Fiber Pipe Insulation |
+| ASTM C533 | Calcium Silicate Block and Pipe Thermal Insulation |
+| ANSI/ASHRAE/IES 90.1 | Energy Standard for Buildings Except Low-Rise Residential Buildings (Tables 6.8.3-1 and 6.8.3-2) |
+| NFPA 70 | National Electrical Code (NEC) |
+| IMC | International Mechanical Code, adopted edition |
+
+# Submittals {toc}
+
+## Action Submittals {toc}
+
+### The Contractor shall submit the following for the Engineer's review and approval prior to procurement and fabrication.
+
+- Pipe and fitting material data for each pressure class, including ASTM specification, grade, schedule or wall thickness, and manufacturing method (seamless or ERW)
+- Valve data for each valve type and service, including ASME B16.34 pressure-temperature rating, body and trim materials, end connections, and pressure class
+- Flange data, including ASME B16.5 class, facing, and gasket material for the operating temperature
+- Welding procedure specifications (WPS), procedure qualification records (PQR), and welder performance qualification records (WPQ) per ASME BPVC Section IX for all pressure-containing welds
+- Steam trap schedule listing each trap by service (drip, equipment, end-of-main), type (inverted-bucket, float-and-thermostatic, thermodynamic), pressure rating, orifice or capacity, and connection size
+- Pressure-reducing valve (PRV) station data, including reducing-valve type and capacity, single- or two-stage configuration, strainer, downstream safety relief valve set pressure and capacity, bypass, and gauges
+- Condensate receiver and pump set data, including receiver volume, pump type and arrangement (simplex or duplex), capacity, head, motor horsepower, and electrical characteristics
+- Flash tank data, including ASME pressure-vessel rating, dimensions, vent and outlet connections, and relief device
+- Expansion compensation data: expansion loop dimensions and anchor/guide locations, or expansion joint type, cycle rating, movement rating, and manufacturer's installation requirements
+- Pipe support details for high-temperature service, including insulated supports, anchors, guides, and any variable- or constant-spring supports, coordinated with [[sync/hangers-and-supports]]
+- Insulation system data by service: operating temperature range, insulation material (mineral fiber, calcium silicate, cellular glass), minimum thickness per ASHRAE 90.1 Table 6.8.3-1, and jacket type
+- Hydrostatic (or pneumatic) test plan, including test medium, test pressure, hold duration, and the boundaries of each test section
+
+```datasheet
+label: Action Submittals Required
+type: checkbox
+options:
+ - "Pipe and fitting material data by pressure class"
+ - "Valve data with B16.34 pressure-temperature ratings"
+ - "Flange data (B16.5 class and facing)"
+ - "WPS / PQR / WPQ welder qualification (Section IX)"
+ - "Steam trap schedule by service and type"
+ - "PRV station data with downstream relief valve"
+ - "Condensate receiver and pump set data"
+ - "Flash tank data (ASME-stamped)"
+ - "Expansion compensation calculations and details"
+ - "High-temperature pipe support details"
+ - "Insulation system data by service"
+ - "Hydrostatic / pneumatic test plan"
+default: "Pipe and fitting material data by pressure class"
+```
+
+### Fabrication and procurement shall not proceed until action submittals have been reviewed and returned.
+
+## Closeout Submittals {toc}
+
+### At substantial completion, the Contractor shall provide the following before the system is accepted.
+
+- As-built drawings showing pipe routing, valve and trap locations, anchor and guide locations, and pressure class of each section
+- Welding records for each pressure-containing weld, including the welder identification, WPS used, and examination results
+- Hydrostatic (or pneumatic) test report for each section, recording test pressure, hold time, and acceptance
+- Steam trap survey at startup confirming each trap discharges condensate and holds steam
+- PRV station setting record listing the as-set reduced pressure and downstream relief valve set pressure for each station
+- Condensate pump set startup report, including alternator operation, float-switch settings, and alarm verification
+- Operation and maintenance manuals for traps, PRV stations, condensate pumps, and flash tanks
+- Insulation completion record confirming valves, strainers, PRV stations, and trap stations are insulated
+
+```datasheet
+label: Closeout Submittals Required
+type: checkbox
+options:
+ - "As-built drawings with pressure class indicated"
+ - "Welding records and examination results"
+ - "Hydrostatic / pneumatic test reports"
+ - "Steam trap startup survey"
+ - "PRV station setting record"
+ - "Condensate pump set startup report"
+ - "O&M manuals"
+ - "Insulation completion record"
+default: "As-built drawings with pressure class indicated"
+```
+
+## Informational Submittals {toc}
+
+### The Contractor shall submit the following for information.
+
+- Mill test reports (MTRs) for pipe and fittings used in medium- and high-pressure service
+- Manufacturer's installation instructions for expansion joints, PRV stations, and steam traps
+- Condensate quality and treatment provisions where condensate is returned for boiler make-up, including conductivity monitoring and chemical-injection arrangement, coordinated with [[sync/hvac-water-treatment]]
+
+```datasheet
+label: Informational Submittals Required
+type: checkbox
+options:
+ - "Mill test reports for pipe and fittings"
+ - "Manufacturer installation instructions"
+ - "Condensate quality and treatment provisions"
+default: "Mill test reports for pipe and fittings"
+```
+
+# Quality Assurance {toc}
+
+## Welder and Procedure Qualification {toc}
+
+### Steam piping welds are pressure-containing and the leading cause of in-service failure when unqualified; documented qualification is therefore mandatory, not a formality. {note}
+
+### All pressure-containing welds shall be made in accordance with a welding procedure specification (WPS) qualified per ASME BPVC Section IX.
+
+### Each WPS shall be supported by a procedure qualification record (PQR) demonstrating the mechanical properties of a test weld.
+
+### Each welder and welding operator shall hold a current welder performance qualification (WPQ) for the process, position, and material covered by the work.
+
+### Qualification records shall be available at the project site for review before welding begins and shall remain available for the duration of the work.
+
+### A weld made by an unqualified welder, or under an unqualified procedure, shall be cut out and replaced at no cost to the Owner.
+
+## Examination {toc}
+
+### Welds shall be examined to the extent and by the methods required by the governing code for the pressure class. {note}
+
+### Welds on systems governed by ASME B31.1 shall be visually examined, with radiographic or other volumetric examination performed to the percentage required by B31.1 for the design conditions.
+
+### Welds on low-pressure systems governed by ASME B31.9 shall be visually examined in accordance with B31.9.
+
+### Defects revealed by examination shall be repaired and re-examined by the same method before the system is pressure-tested.
+
+## Code Compliance {toc}
+
+### Applying ASME B31.9 to a system that operates above 15 psig is a code violation; the building-services code does not impose the welder qualification and examination that power piping requires. {note}
+
+### Where the operating pressure of any portion of the system exceeds 15 psig steam, that portion shall be designed, fabricated, examined, and tested to ASME B31.1.
+
+### Pipe wall thickness for medium- and high-pressure service shall be verified against the pressure design rules of ASME B31.1 for the design pressure and temperature.
+
+# Environmental and Service Conditions {toc}
+
+## Design Pressure and Temperature {toc}
+
+### The design pressure and design temperature define the code basis, the pipe schedule, and the valve and flange ratings, and shall be fixed before material selection. {note}
+
+### The design pressure shall be not less than the maximum operating pressure at the point of use, including the maximum setting of any upstream pressure-reducing or relief device.
+
+### The design temperature shall be the saturation temperature corresponding to the design pressure unless superheat is present, in which case the maximum operating temperature shall govern.
+
+```datasheet
+label: System Pressure Class
+type: radio
+options:
+ - "Low-pressure steam (0-15 psig) - ASME B31.9"
+ - "Medium-pressure steam (15-100 psig) - ASME B31.1"
+ - "High-pressure steam (100-300 psig) - ASME B31.1"
+default: "Medium-pressure steam (15-100 psig) - ASME B31.1"
+```
+
+```datasheet
+label: Design Pressure
+type: range
+unit: psig
+min: 5
+max: 300
+step: 5
+default: 50
+```
+
+```datasheet
+label: Design Temperature
+type: range
+unit: °F
+min: 215
+max: 425
+step: 5
+default: 300
+```
+
+## Slope {toc}
+
+### Steam mains and condensate return lines must drain by gravity to their drip and collection points; insufficient slope leaves condensate standing in the main, which is then carried into the pipe as a slug on the next pressure change. {note}
+
+### Steam supply mains shall slope a minimum of 1/4 in. per 10 ft (1:480) in the direction of steam flow.
+
+### Condensate gravity return lines shall slope a minimum of 1/4 in. per 10 ft toward the receiver or collection point.
+
+### Where a steam main must rise in the direction of flow, the main shall be dripped at the base of the rise and the slope reversed so condensate drains back to a trapped low point.
+
+## Velocity Limits {toc}
+
+### Excessive steam velocity erodes fittings, increases pressure drop, and entrains condensate; the following limits are design targets for sizing. {note}
+
+### Steam supply mains shall be sized for a maximum design velocity of 8,000 fpm.
+
+### Steam branch lines shall be sized for a maximum design velocity of 6,000 fpm.
+
+### Two-phase condensate return lines shall be sized for a maximum velocity of 4,500 fpm, accounting for flash steam volume and not condensate mass flow alone.
+
+# Pipe, Fittings, and Joining {toc}
+
+## Pipe Material by Pressure Class {toc}
+
+### ERW A53 pipe is acceptable for low-pressure building-services steam but is not suitable for the temperatures and pressures of medium- and high-pressure service, where seamless A106 Grade B is required. {note}
+
+### Low-pressure steam (0-15 psig) pipe shall be ASTM A53 Grade B black steel, electric-resistance-welded or seamless.
+
+### Medium-pressure steam (15-100 psig) pipe shall be ASTM A106 Grade B seamless carbon steel.
+
+### High-pressure steam (100-300 psig) pipe shall be ASTM A106 Grade B seamless carbon steel.
+
+### Condensate return piping for pressurized return above 30 psig shall be Schedule 80 steel; gravity return piping shall be not less than Schedule 40.
+
+```datasheet
+label: Pipe Material
+type: select
+options:
+ - "ASTM A53 Gr. B black steel (low-pressure)"
+ - "ASTM A106 Gr. B seamless (medium/high-pressure)"
+default: "ASTM A106 Gr. B seamless (medium/high-pressure)"
+```
+
+## Pipe Schedule {toc}
+
+### The schedule must be matched to the pressure class and verified against the code pressure-design rules; the defaults below are the 80% case and do not relieve the engineer of the wall-thickness calculation for high-pressure service. {note}
+
+### Low-pressure steam piping 2 in. and smaller shall be Schedule 40, joined by thread or flange.
+
+### Low-pressure steam piping larger than 2 in. shall be Schedule 40, joined by butt-weld.
+
+### Medium-pressure steam piping shall be Schedule 80 in all sizes.
+
+### High-pressure steam piping 2 in. and smaller shall be Schedule 160.
+
+### High-pressure steam piping larger than 2 in. shall be Schedule 80, with wall thickness verified by ASME B31.1 stress calculation.
+
+```datasheet
+label: Pipe Schedule (steam supply)
+type: select
+options:
+ - "Schedule 40 (low-pressure)"
+ - "Schedule 80 (medium-pressure / high-pressure > 2 in.)"
+ - "Schedule 160 (high-pressure ≤ 2 in.)"
+default: "Schedule 80 (medium-pressure / high-pressure > 2 in.)"
+```
+
+## Fittings {toc}
+
+### Fitting type follows the joining method, which in turn follows the pressure class and size; mismatched fittings are a common source of leaks and pressure-rating shortfalls. {note}
+
+### Butt-weld fittings for medium- and high-pressure steam shall conform to ASME B16.9 and ASTM A234 Grade WPB.
+
+### Socket-weld and threaded fittings for small-bore steam shall conform to ASME B16.11.
+
+### Fittings shall match or exceed the pressure rating and material grade of the connected pipe.
+
+## Joining Method {toc}
+
+### The joining method is selected by pressure class and pipe size: welded joints for medium and high pressure, with threaded joints permitted only on low-pressure small-bore lines. {note}
+
+### Medium- and high-pressure steam piping larger than 2 in. shall be butt-welded.
+
+### Medium- and high-pressure steam piping 2 in. and smaller shall be socket-welded.
+
+### Threaded joints shall be used only on low-pressure steam piping 2 in. and smaller.
+
+### Connections to equipment, valves, and removable components shall be flanged.
+
+```datasheet
+label: Joining Method (mains > 2 in.)
+type: radio
+options:
+ - "Butt-weld (medium/high pressure)"
+ - "Socket-weld (medium/high pressure ≤ 2 in.)"
+ - "Threaded (low pressure ≤ 2 in. only)"
+ - "Flanged (equipment connections)"
+default: "Butt-weld (medium/high pressure)"
+```
+
+## Flanges {toc}
+
+### Flange class must be rated for both the design pressure and the design temperature; carbon-steel ratings derate with temperature, so a flange that passes a pressure check at ambient may be under-rated at the operating temperature. {note}
+
+### Flanges shall conform to ASME B16.5 and shall be rated for the design pressure and temperature of the connected service.
+
+### Class 150 flanges may be used where the design conditions fall within the carbon-steel Class 150 rating at the design temperature.
+
+### Class 300 flanges shall be used for systems above 150 psig or above 400°F.
+
+```datasheet
+label: Flange Class
+type: radio
+options:
+ - "Class 150 (campus steam within rating)"
+ - "Class 300 (above 150 psig or above 400°F)"
+ - "Class 600 (high-pressure service)"
+default: "Class 150 (campus steam within rating)"
+```
+
+# Steam Traps and Drip Legs {toc}
+
+## Drip Legs {toc}
+
+### A drip leg is a vertical collecting pocket at the bottom of a steam main that lets gravity pull condensate out of the fast-moving steam so a trap can discharge it; without drip legs at low points and ahead of equipment, condensate accumulates and is driven through the pipe as a destructive slug on startup. {note}
+
+### Drip legs shall be provided at all low points, at the base of risers, ahead of each pressure-reducing station, ahead of each isolation valve that may close against trapped condensate, and at the end of each steam main.
+
+### Drip leg depth shall be a minimum of 12 in. below the centerline of the steam main.
+
+### Drip legs on mains 4 in. and smaller shall be full size of the main.
+
+### Drip legs on mains larger than 4 in. shall be a minimum of half the main size, but not less than 4 in.
+
+### Each drip leg shall be fitted with a steam trap and a strainer upstream of the trap.
+
+```datasheet
+label: Drip Leg Depth Below Main Centerline
+type: range
+unit: in
+min: 12
+max: 28
+step: 2
+default: 18
+```
+
+## Steam Trap Selection {toc}
+
+### Trap type is selected by service: drip service on the mains, continuous high-volume discharge at equipment, and compact drip service on high-pressure lines each favor a different trap mechanism. {note}
+
+### Inverted-bucket traps shall be used for drip service on steam mains.
+
+### Float-and-thermostatic (F&T) traps shall be used on heat exchanger and unit heater condensate where discharge is continuous and high-volume.
+
+### Thermodynamic disc traps shall be used for compact drip service on high-pressure lines.
+
+### Each trap shall be selected for the differential pressure across it at the design condition and for the condensate load it serves, with a safety factor applied per the manufacturer's sizing method.
+
+```datasheet
+label: Steam Trap Type - Main Drip Service
+type: radio
+options:
+ - "Inverted-bucket"
+ - "Thermodynamic disc"
+ - "Float-and-thermostatic (F&T)"
+default: "Inverted-bucket"
+```
+
+```datasheet
+label: Steam Trap Type - Equipment Condensate
+type: radio
+options:
+ - "Float-and-thermostatic (F&T)"
+ - "Inverted-bucket"
+default: "Float-and-thermostatic (F&T)"
+```
+
+```datasheet
+label: Trap Maximum Operating Pressure
+type: range
+unit: psig
+min: 15
+max: 300
+step: 5
+default: 50
+```
+
+## Trap Station Arrangement {toc}
+
+### A trap station that can be isolated, cleaned, and tested without shutting the system is the difference between a trap that is maintained and one that fails open and wastes steam indefinitely. {note}
+
+### Each trap station shall include an upstream strainer, isolation valves upstream and downstream, a test or inspection means, and a union or flange for trap removal.
+
+### A check valve shall be provided downstream of each trap discharging into a common return where back-flow from other traps is possible.
+
+# Condensate Return {toc}
+
+## Return Configuration {toc}
+
+### Condensate returns by gravity where the layout and back-pressure permit; where it does not, a receiver and pump set lift the condensate back to the boiler plant. {note}
+
+### Gravity return shall be used where the condensate can drain to the receiver or boiler without lift and against the system back-pressure.
+
+### A pumped return with a condensate receiver and a duplex condensate pump set shall be used where gravity return is not feasible.
+
+```datasheet
+label: Condensate Return Configuration
+type: radio
+options:
+ - "Gravity return"
+ - "Pumped return (receiver + duplex pump set)"
+default: "Pumped return (receiver + duplex pump set)"
+```
+
+## Condensate Receiver and Pump Set {toc}
+
+### A duplex pump set with an alternator keeps condensate moving when one pump fails and is standard for any return that cannot tolerate an outage; the receiver volume must buffer the condensate load between pump cycles. {note}
+
+### The condensate pump set shall be duplex.
+
+### The pump set shall include an automatic alternator that alternates the lead and lag pumps and starts the lag pump on high level.
+
+### The receiver shall be sized to hold not less than one minute of the connected condensate load at the receiver.
+
+### Pump and motor electrical characteristics shall be coordinated with the electrical scope before installation.
+
+### Float-switch and alarm wiring shall be confirmed to be in the project electrical scope before installation.
+
+### Condensate pump controls frequently fall into a coordination gap between mechanical and electrical scopes; confirm scope boundaries explicitly during design. {note}
+
+### The pump set shall be furnished with a high-level alarm contact for connection to the building automation system ([[sync/building-automation-system]]).
+
+```datasheet
+label: Condensate Pump Arrangement
+type: radio
+options:
+ - "Duplex (lead/lag with alternator)"
+ - "Simplex"
+default: "Duplex (lead/lag with alternator)"
+```
+
+```datasheet
+label: Condensate Receiver Material
+type: select
+options:
+ - "Cast iron"
+ - "Fabricated steel"
+ - "Stainless steel"
+default: "Cast iron"
+```
+
+```datasheet
+label: Condensate Pump Motor Horsepower
+type: range
+unit: hp
+min: 1
+max: 20
+step: 1
+default: 3
+drawing_ref: true
+```
+
+## Flash Tanks {toc}
+
+### When high-pressure condensate is released into a lower-pressure return, part of it flashes to steam; discharging that mixture directly into a low-pressure header without a flash tank produces violent water hammer in the header. {note}
+
+### A flash tank shall be provided where high-pressure condensate above approximately 30 psig discharges into a low-pressure condensate header.
+
+### The flash tank shall be an ASME-stamped pressure vessel sized to separate the flash steam from the condensate at the flash pressure.
+
+### Flash steam shall be vented or recovered to a low-pressure use, and the residual condensate shall drain to the return through a trap.
+
+```datasheet
+label: Flash Tank Provided
+type: radio
+options:
+ - "Yes - high-pressure condensate to low-pressure return"
+ - "No - single-pressure return"
+default: "No - single-pressure return"
+```
+
+# Pressure-Reducing Stations {toc}
+
+## Station Arrangement {toc}
+
+### A pressure-reducing valve (PRV) station drops steam from a distribution pressure to a use pressure; it is a small assembly, not a single valve, because it needs a clean inlet, a means to maintain service during PRV maintenance, and overpressure protection on the reduced side. {note}
+
+### A PRV station shall include an upstream strainer, an upstream isolation valve, the pressure-reducing valve, a downstream isolation valve, a bypass with a globe valve, and inlet and outlet pressure gauges.
+
+### A drip leg with a trap shall be provided upstream of the station to remove condensate before the reducing valve.
+
+### Single-stage reduction shall be used where the pressure ratio across the station is within the reducing valve's recommended single-stage range.
+
+### Two-stage reduction shall be used where the pressure ratio exceeds the single-stage range or where close downstream pressure control is required.
+
+```datasheet
+label: PRV Station Configuration
+type: radio
+options:
+ - "Single-stage"
+ - "Two-stage"
+default: "Single-stage"
+```
+
+```datasheet
+label: PRV Reduced (Downstream) Pressure
+type: range
+unit: psig
+min: 5
+max: 100
+step: 5
+default: 15
+drawing_ref: true
+```
+
+## Downstream Relief {toc}
+
+### A reducing valve can fail open and pass full upstream pressure to the low-pressure side; ASME B31.1 and the IMC therefore require a relief valve downstream of every reducing station, sized to pass the full PRV capacity. {note}
+
+### A safety relief valve shall be provided downstream of every pressure-reducing station.
+
+### The downstream relief valve shall be set at or below the maximum allowable working pressure of the downstream piping and equipment.
+
+### The relief valve shall be sized to relieve the full capacity that the reducing valve can pass with its seat fully open at the inlet design pressure.
+
+# Valves and Strainers {toc}
+
+## Isolation Valves {toc}
+
+### Isolation valves must carry the pressure-temperature rating of the service, which for steam means a B16.34 rating verified at the design temperature, not just the design pressure. {note}
+
+### Isolation valves shall conform to ASME B16.34 and shall be rated for the design pressure and temperature of the service.
+
+### Gate or ball valves shall be used for isolation service where full-bore shutoff is required.
+
+### Globe valves shall be used where throttling or bypass control is required.
+
+### Valve end connections shall match the piping joining method for the service.
+
+```datasheet
+label: Isolation Valve Type
+type: radio
+options:
+ - "Gate"
+ - "Ball"
+ - "Globe (throttling/bypass)"
+default: "Gate"
+```
+
+## Check Valves {toc}
+
+### Check valves prevent reverse flow into condensate pumps and back-flow between traps discharging into a common return. {note}
+
+### Check valves shall be provided on the discharge of each condensate pump and where required to prevent back-flow in common return headers.
+
+### Check valves shall be rated for the pressure and temperature of the service and selected for the flow direction and orientation of the installation.
+
+## Strainers {toc}
+
+### A strainer ahead of each trap, control valve, and reducing valve keeps scale and weld slag out of close-clearance seats, which are otherwise wire-drawn and fail open. {note}
+
+### A strainer shall be installed upstream of each steam trap, pressure-reducing valve, and control valve.
+
+### Strainer screens in steam service shall be stainless steel with a perforation or mesh suited to the protected device.
+
+# Expansion Compensation {toc}
+
+## General {toc}
+
+### Steam pipe grows roughly 3/4 in. per 100 ft at 100 psig; unrelieved thermal growth cracks flanges, shears bolts, and pulls supports loose, so every run must be analyzed and compensated. {note}
+
+### Thermal expansion of each pipe run shall be calculated for the temperature change from installation to operating temperature.
+
+### Expansion compensation shall be provided by expansion loops, bellows expansion joints, or slip-type expansion joints, with anchors and guides arranged to direct the movement.
+
+### Expansion loops shall be the preferred method of compensation where space permits, as they require no moving seals.
+
+```datasheet
+label: Expansion Compensation Method
+type: radio
+options:
+ - "Expansion loops"
+ - "Bellows expansion joints"
+ - "Slip-type expansion joints"
+default: "Expansion loops"
+```
+
+## Expansion Joints {toc}
+
+### Where a loop will not fit, an expansion joint is used, but a joint has a finite cycle life and movement rating and must be sized to the actual analyzed movement, not a nominal value. {note}
+
+### Expansion joints shall be selected and rated by engineering analysis for the calculated movement and the design number of thermal cycles.
+
+### Anchors and guides shall be provided at the spacing required by the joint manufacturer to keep the movement axial and within the joint's rating.
+
+## Anchors and Guides {toc}
+
+### Anchors fix the pipe at intended points so expansion is directed into the loop or joint rather than into equipment; guides keep the pipe aligned between anchors. {note}
+
+### Main anchors shall be provided at the points required to direct thermal movement into the compensation devices, coordinated with [[sync/hangers-and-supports]].
+
+### Pipe guides shall be provided on each side of expansion joints and along long runs at the spacing required to prevent buckling and to keep movement axial.
+
+# Insulation Requirements {toc}
+
+## General {toc}
+
+### This standard specifies the insulation requirements by service - operating temperature, minimum thickness, and jacket - and delegates material specification and field application detail to [[sync/mechanical-insulation]]. {note}
+
+### Steam and condensate piping shall be insulated to not less than the minimum thickness required by ASHRAE 90.1 Table 6.8.3-1 for the service operating temperature.
+
+### Insulation material shall be selected for the surface operating temperature of the service.
+
+```datasheet
+label: Insulation Material
+type: radio
+options:
+ - "Mineral fiber (up to ~850°F)"
+ - "Calcium silicate (high temperature, above ~400°F surface)"
+ - "Cellular glass"
+default: "Mineral fiber (up to ~850°F)"
+```
+
+```datasheet
+label: Steam Main Insulation Thickness
+type: range
+unit: in
+min: 1.5
+max: 4
+step: 0.5
+default: 3
+```
+
+## Material by Temperature {toc}
+
+### Fiberglass has a continuous service limit near 850°F; on the hottest high-pressure mains the surface temperature exceeds the practical limit and calcium silicate or cellular glass is required instead. {note}
+
+### Mineral fiber insulation conforming to ASTM C547 shall be used for steam and condensate lines within its service temperature limit.
+
+### Calcium silicate insulation conforming to ASTM C533 shall be used on steam mains operating above approximately 400°F surface temperature, where mineral fiber is inadequate.
+
+## Insulation of Fittings and Accessories {toc}
+
+### Valves, strainers, PRV stations, and trap stations are the largest single source of heat loss and the primary burn hazard in a steam system; leaving them bare or only partly insulated wastes steam and creates a safety hazard. {note}
+
+### Valves, strainers, flanges, pressure-reducing stations, and steam trap stations shall be insulated.
+
+### Insulation at these components shall be furnished with removable, reusable insulation covers where the component requires periodic access for maintenance.
+
+```datasheet
+label: Removable Insulation Covers at Valves and Stations
+type: radio
+options:
+ - "Required at all valves, strainers, traps, and PRV stations"
+ - "Required at PRV and trap stations only"
+default: "Required at all valves, strainers, traps, and PRV stations"
+```
+
+# Routing and Underground Distribution {toc}
+
+## General Routing {toc}
+
+### The routing decision - above-grade, direct-buried, or walk-through tunnel - drives the entire insulation and protection approach and is set by the campus layout and the locations shown on the drawings. {note}
+
+### Above-grade steam piping shall be insulated and provided with a weatherproof metal jacket where exposed to weather.
+
+### Underground steam piping shall be a factory pre-insulated, direct-buried conduit system with a continuous steel or HDPE outer casing and a drainable, dryable air space or foam carrier insulation.
+
+### Routing, building entries, manholes, and anchor locations shall be as shown on the drawings. [[drawing: steam distribution routing plan]]
+
+```datasheet
+label: Distribution Routing
+type: radio
+options:
+ - "Above-grade (insulated, metal jacket)"
+ - "Underground direct-buried (pre-insulated conduit)"
+ - "Walk-through tunnel"
+default: "Above-grade (insulated, metal jacket)"
+```
+
+## Underground Pre-Insulated Systems {toc}
+
+### A buried steam line that takes on water fails fast through corrosion of the carrier pipe; the conduit system must keep the carrier dry and be testable for leaks before backfill. {note}
+
+### The pre-insulated conduit system shall be furnished by a single manufacturer as a complete system, including straights, fittings, anchors, and field joint closures.
+
+### The outer casing shall be tested for leak-tightness in accordance with the manufacturer's requirements before backfill.
+
+### Drainage and venting provisions of the conduit air space, where furnished, shall be installed in accordance with the manufacturer's requirements.
+
+# Pipe Supports {toc}
+
+## High-Temperature Support {toc}
+
+### Steam piping needs supports designed for high temperature and thermal movement; ordinary clevis hangers at insulation crush points cause corrosion under insulation and thermal bridging, so insulated supports are used at hot lines. {note}
+
+### Pipe supports shall be coordinated with [[sync/hangers-and-supports]] and shall be suitable for the operating temperature and the thermal movement of the run.
+
+### Insulated pipe supports (shoes or saddles with insulating inserts) shall be used at support points on insulated hot piping to prevent thermal bridging and corrosion under insulation.
+
+### Variable-spring or constant-spring supports shall be provided at heavy fittings and at points of significant vertical thermal movement where rigid supports would impose unacceptable load changes.
+
+# Testing {toc}
+
+## Hydrostatic Test {toc}
+
+### A hydrostatic test proves the joints before the system carries steam; it is performed at a pressure above the design pressure and held long enough to find leaks. {note}
+
+### The system shall be hydrostatically tested at 1.5 times the design pressure, but not less than 100 psig, in accordance with ASME B31.1.
+
+### The test pressure shall be held for a minimum of 10 minutes, and longer as required to complete the examination.
+
+### The system shall show no leakage and no drop in pressure attributable to leakage during the hold.
+
+### Strainers, traps, and pressure-sensitive components that could be damaged by the test pressure shall be isolated or removed during the test.
+
+```datasheet
+label: Hydrostatic Test Pressure Basis
+type: radio
+options:
+ - "1.5 x design pressure (minimum 100 psig)"
+ - "Per ASME B31.1 for the design conditions"
+default: "1.5 x design pressure (minimum 100 psig)"
+```
+
+```datasheet
+label: Test Hold Duration
+type: range
+unit: min
+min: 10
+max: 60
+step: 5
+default: 30
+```
+
+## Pneumatic Test {toc}
+
+### Where a hydrostatic test cannot be done - for example where the system cannot be drained or freezing is a risk - a pneumatic test at a lower multiplier is permitted, with the added precautions that stored gas pressure requires. {note}
+
+### A pneumatic test shall be used only where hydrostatic testing is not feasible and shall be performed at 1.1 times the design pressure in accordance with ASME B31.1.
+
+### A pneumatic test shall be conducted with the safety precautions required for stored-energy testing, including a preliminary low-pressure check and exclusion of personnel from the test area.
+
+## Startup and Trap Verification {toc}
+
+### Bringing a steam system up requires warming the pipe slowly and draining condensate as it forms; a fast startup against a cold, condensate-filled main is the classic water-hammer event. {note}
+
+### The system shall be warmed up gradually at startup, draining condensate through the drip legs and traps as the piping comes up to temperature.
+
+### Each steam trap shall be verified at startup to discharge condensate and to hold steam, and any trap found blowing steam or failing to discharge shall be repaired or replaced.
+
+# Installation {toc}
+
+## General {toc}
+
+### Field practice on steam piping is unforgiving: a missed drip leg, a back-pitched run, or an unrelieved expansion turns into water hammer or a cracked joint in service. {note}
+
+### Piping shall be installed to the slopes, drip-leg locations, anchor and guide locations, and pressure class shown on the drawings and specified herein.
+
+### Eccentric reducers shall be installed flat-on-bottom on horizontal steam mains so condensate is not trapped at the reduction.
+
+### Branch connections from a steam main shall be taken from the top of the main so condensate is not carried into the branch.
+
+### Dirt pockets and drip legs shall be installed so they can be cleaned and so the trap can be removed without cutting the pipe.
+
+## Cleaning {toc}
+
+### New steam piping carries weld slag, scale, and oil that will lodge in trap and valve seats; the system is blown down and strainers are cleaned before it is placed in service. {note}
+
+### The system shall be blown down or flushed to remove construction debris before traps and control valves are placed in service.
+
+### Strainer screens shall be removed, cleaned, and reinstalled after initial operation and again as directed during the startup period.
+
+# Delivery, Storage, and Handling {toc}
+
+## Protection {toc}
+
+### Pipe ends and pre-insulated conduit sections take on dirt and water if left open in the yard; corrosion and wet insulation that start in storage are carried into the finished system. {note}
+
+### Pipe and fittings shall be stored off the ground, with end caps or plugs left in place until the pipe is installed.
+
+### Pre-insulated conduit sections shall be stored to keep the insulation dry and shall not be installed if the insulation has become wet.
+
+### Valves, traps, and PRV components shall be stored in their original packaging, protected from dirt and weather, until installation.
+
+# Warranty {toc}
+
+## Warranty {toc}
+
+### The Contractor shall warrant the steam and condensate piping system against defects in materials and workmanship for a period of not less than one year from the date of substantial completion.
+
+### Manufactured components, including steam traps, condensate pumps, PRV stations, and expansion joints, shall carry the manufacturer's standard warranty, which shall be transferred to the Owner.
+
+### Defects in welds, joints, or components discovered within the warranty period shall be repaired or replaced at no cost to the Owner, including restoration of insulation disturbed by the repair.
+
+# Spare Parts {toc}
+
+## Spare Parts {toc}
+
+### Steam traps and strainer screens are the routine wear items; a small on-hand stock keeps a failed trap from being left blowing steam while a replacement is procured. {note}
+
+### The Contractor shall furnish spare steam trap internals or complete spare traps for each trap type and size used, in the quantity scheduled.
+
+### The Contractor shall furnish spare strainer screens for each strainer type and size used.
+
+### The Contractor shall furnish spare gaskets for each flange size used at removable connections.
+
+```datasheet
+label: Spare Steam Traps Furnished (per type/size)
+type: range
+unit: ea
+min: 0
+max: 5
+step: 1
+default: 1
+```