23 52 33 Water Tube Boilers edited.pdf

06-01-25

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SECTION 23 52 33

WATER TUBE BOILERS

PART 1 - GENERAL

1.1 DESCRIPTION

A. This section specifies packaged water tube boiler with trim

(accessories), dual fuel (natural gas and fuel oil) burner, fuel trains, and flue gas economizer.

B. A complete listing of common acronyms and abbreviations are included in Section 23 05 10, COMMON WORK RESULTS FOR BOILER PLANT AND STEAM

GENERATION.

1.2 RELATED WORK

A. Section 01 00 00, GENERAL REQUIREMENTS.

B. Section 01 33 23, SHOP DRAWINGS, PRODUCT DATA, AND SAMPLES.

C. Section 01 81 13, SUSTAINABLE CONSTRUCTION REQUIREMENTS.

D. Section 01 91 00, GENERAL COMMISSIONING REQUIREMENTS.

E. Section 23 05 10, COMMON WORK RESULTS FOR BOILER PLANT AND STEAM

GENERATION.

F. Section 23 21 11, BOILER PLANT PIPING SYSTEMS.

G. Section 26 05 33, RACEWAY and BOXES for ELECTRICAL SYSTEMS.

1.3 SUBMITTALS

A. Submittals, including number of required copies, shall be submitted in accordance with Section 01 33 23, SHOP DRAWINGS, PRODUCT DATA, AND

SAMPLES.

B. Information and material submitted under this section shall be marked

“SUBMITTED UNDER SECTION 23 52 33, WATER TUBE BOILERS”, with applicable paragraph identification.

C. Manufacturer's Literature and Data including: Full item description and optional features and accessories. Include dimensions, weights, materials, applications, standard compliance, model numbers, size, and capacity.

D. Burner and Fuel Trains:

1. Catalog data and drawings showing construction of burner parts and assembly of complete system.

2. Drawings, with dimensions, showing burner overall size and mounting on the boiler.

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3. Catalog data and outline drawings of forced draft fan, flue gas recirculation ductwork (if provided), dampers, motors and sound attenuators on fan intake or discharge.

4. Drawings showing assembly of throat refractory into furnace refractory wall.

5. Type and temperature rating of throat refractory.

6. Drawings and catalog data on all equipment in igniter (pilot) train, main fuel trains, atomizing media train. Include data on pressure and temperature ratings, flow vs. pressure drop, performance characteristics, and inspection agency approvals. Complete data on oil atomization air compressor systems with sound attenuators.

7. ASTM number and schedule numbers on all piping.

8. Type and pressure ratings of pipe fittings.

9. Burner flow and pressure data:

a. Main burner fuel and atomizing media pressures and flows at maximum required firing rate.

b. Igniter (pilot) fuel flow and burner pressure.

c. Natural gas main fuel pressure at outlet of burner-mounted pressure regulator.

d. Igniter fuel pressures (natural gas and LP gas) at outlet of burner-mounted pressure regulators.

e. Forced draft fan static pressure, power, and air flow at maximum firing rate. Amount of flue gas recirculation.

10. Full load efficiency and power factor of all motors.

11. Predicted sound level at maximum firing rate.

12. Weight of burner assembly.

13. Drawings showing location and arrangement of drive units and jackshaft system (if provided) for controlling fuel and air flow.

14. Weight of burner assembly.

15. Steps required to change from one fuel source to another.

E. Burner Management (Flame Safeguard) Control System: Refer to Section 23

09 11, INSTRUMENTATION AND CONTROL FOR BOILER PLANT.

F. ASME “P” Forms, Manufacturer’s Data Report, on boiler and economizer construction.

G. Pretest Data: Boiler, Burner, Controls: As required by Part 3.

H. Final Test Report: Boiler, Burner, Controls: As required by Part 3.

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I. Complete operating and maintenance manuals including wiring diagrams, technical data sheets, information for ordering replacement parts, and troubleshooting guide:

1. Include complete list indicating all components of the systems.

2. Include complete diagrams of the internal wiring for each item of equipment.

3. Diagrams shall have their terminals identified to facilitate installation, operation and maintenance.

J. Completed System Readiness Checklist provided by the Commissioning Agent and completed by the contractor, signed by a qualified technician and dated on the date of completion, in accordance with the requirements of Section 23 08 00, COMMISSIONING OF HVAC SYSTEMS.

K. Submit training plans and instructor qualifications in accordance with the requirements of Section 23 08 00, COMMISSIONING OF HVAC SYSTEMS.

1.4 QUALITY ASSURANCE

A. Coordinate all new and existing equipment and conditions. This includes, but is not limited to boiler, boiler trim, burner, fuel trains, gas pressure regulators and available gas pressure, fuel oil header back pressure regulator on house oil pump set and available fuel oil pressure, burner control system, combustion control system, economizer (if provided), breeching and stacks.

B. Regardless of fuel input rating, the equipment, installation and operation shall conform to NFPA 85. Where conflicts exist between NFPA

85 and this specification, this specification will govern.

1.5 AS-BUILT DOCUMENTATION

A. Submit manufacturer’s literature and data updated to include submittal review comments and any equipment substitutions.

B. Submit operation and maintenance data updated to include submittal review comments, VA approved substitutions and construction revisions shall be in electronic version on CD or DVD. All aspects of system operation and maintenance procedures, including applicable piping isometrics, wiring diagrams of all circuits, a written description of system design, control logic, and sequence of operation shall be included in the operation and maintenance manual. The operations and maintenance manual shall include troubleshooting techniques and procedures for emergency situations. Notes on all special systems or devices shall be included. A List of recommended spare parts

(manufacturer, model number, and quantity) shall be furnished.

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Information explaining any special knowledge or tools the owner will be required to employ shall be inserted into the As-Built documentation.

C. The installing contractor shall maintain as-built drawings of each completed phase for verification; and shall provide the complete set at the time of final systems certification testing. Should the installing contractor engage the testing company to provide as-built or any portion thereof, it shall not be deemed a conflict of interest or breach of the ‘third party testing company’ requirement. Provide record drawings as follows:

1. Red-lined, hand-marked drawings are to be provided, with one paper copy and a scanned PDF version of the hand-marked drawings provided on CD or DVD.

D. The as-built drawings shall indicate the location and type of all lockout/tagout points for all energy sources for all equipment and pumps to include breaker location and numbers, valve tag numbers, etc.

Coordinate lockout/tagout procedures and practices with local VA requirements.

E. Certification documentation shall be provided to COR 21 working days prior to submitting the request for final inspection. The documentation shall include all test results, the names of individuals performing work for the testing agency on this project, detailed procedures followed for all tests, and provide documentation/certification that all results of tests were within limits specified. Test results shall contain written sequence of test procedure with written test results annotated at each step along with the expected outcome or setpoint. The results shall include all readings, including but not limited to data on device (make, model and performance characteristics), normal pressures, switch ranges, trip points, amp readings, and calibration data to include equipment serial numbers or individual identifications, etc.

1.6 PROJECT CONDITIONS

A. Fuels to be Fired, Main Burner: Natural gas and No. 2 fuel oil.

B. Igniter (Pilot) Fuels: Natural Gas and LP gas (propane).

C. Natural Gas: High heating value is reported as 37.3 MJ/cubic meter (1,000 Btu/cubic foot) at gas company base pressure and temperature.

Pressure provided to the inlet of the boiler-mounted regulators will be

105 kPa (15 psig) as maintained by the main gas regulator station.

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D. Fuel Oil: Will be furnished under Government contract. House pumping system is designed to provide 840 kPa (120 psig) nominal to the fuel train entrance on each burner fuel train. Pressure will vary in accordance with characteristics of backpressure regulator on house oil pump set. Refer to Section 23 50 11, BOILER PLANT MECHANICAL EQUIPMENT.

Oil grade (No. 2) refers to ASTM D396.

E. Low Pressure Air Atomizing Burners: Each burner must include a dedicated air compressor system furnished by burner manufacturer.

F. Oil Atomizing Media:

1. Steam Atomizing Burners: Steam pressure range at inlet to atomizing train 840 to 700 kPa (120 to 100 psig). When plant is cold (steam not available), compressed air (0.8 standard cubic meters per minute at 550 kPa) (30 SCFM at 80 psig) is available (from plant compressor) as an alternate for starting any boiler and continuously operating it at a required steam output of 13 percent of full load.

2. Low Pressure Air Atomizing Burners: Each burner must include a dedicated air compressor system furnished by burner manufacturer.

G. LP Gas (Propane): Furnish and Install to the Government for igniter

(pilot) fuel by a local supplier. Regulators at tank areas will be set at 34 kPa (5 psig). Serves as igniter fuel when there is an interruption to the natural gas supply.

PART 2 - PRODUCTS

2.1 D-TYPE WATER TUBE BOILER

A. Factory-assembled, packaged water tube, industrial-class, high pressure steam boiler. Two drum, "D-type" furnace tube configuration, two pass.

Designed for natural gas and fuel oil firing.

B. Service: Designed to continuously receive feedwater at 100 degrees C (212 degrees F) and generate steam at pressures and quantities shown.

C. Performance:

1. Steam output quantity, refer to drawings.

2. Steam output quality, 99 percent minimum at all steam flow rates.

Based on water quality in boiler of 3500-ppm maximum total solids, 15-ppm maximum suspended solids, 700-ppm maximum alkalinity.

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3. Minimum Efficiency at Required Maximum Output:

a. Natural Gas Fuel (37.3 MJ/cubic meter) (1000 Btu/cubic foot): 78 percent at 15 percent excess air or 80 percent at 5 percent excess air.

b. Fuel Oil (ASTM D396 Grade 2, 4, 5, or 6): 83 percent at 15 percent excess air or 81.5 percent at 5 percent excess air.

D. Boiler Heating Surface and Furnace Volume:

1. Heating Surface Area: Provide surface area necessary to obtain required performance, however surface area shall not be less than shown on the drawings. Heating surface is defined as flat projected tube surface, including fins, in combustion space, whether or not covered by refractory, plus outside (gas side) circumferential area of all convection tubes.

2. Furnace (Combustion) Volume: Heat release at full load shall not exceed 827,000 watts per cubic meter (80,000 Btu/h per cubic foot).

Combustion volume limits shall not extend beyond first plane of entry into convection tubes. Screen tubes, when used, shall be considered the first plane of entry. Steady constant direct contact or impingement of the flame on any surface is prohibited.

E. Minimum Design Pressure: Shall equal the ASME-stamped maximum allowable working pressure of 1380 kPa (200 psig). Purpose of high design pressure is to provide additional corrosion allowance and additional safety margin to perform safety device testing.

F. Construction:

1. Codes: Comply with ASME Boiler and Pressure Vessel Code, Sections I, II, VII, and IX.

2. No element of the boiler or accessories shall be overstressed, displaced, or have cracks, broken welds, or excessive deflection.

All vertical elements of the boiler and accessories shall be plumb, and all horizontal elements shall be level.

3. Base Frame: Design for mounting on flat concrete base. All elements shall be level and square. Provide attachments for anchorage to concrete foundation.

4. Provide lifting lugs and jacking pads.

5. Drums:

a. Steam drum shall be minimum 900 mm (36 inch) diameter. Bottom drum shall be minimum 600 mm (24 inch) diameter. Equip steam drum

23 52 33 - 7 with elliptical side-hinged manway on each end. Equip bottom drum with non-hinged elliptical manways at each end. Equip all manways with properly fitted forged steel yokes, bolts, nuts, and non-asbestos gaskets. Manway covers shall have bolt slots forged integral with covers. Provide access to all manways clear of piping, valves.

b. All tube holes shall be grooved and sized for 50 mm (2 inch) tubes and shall be radial and properly located to permit proper alignment of tubes. Swaged tubes with reduced drum openings are prohibited.

c. Intermediate header for water wall or convection tubes are prohibited.

6. Drum Piping Connections:

a. Flanged, except threaded are permitted for pipe size less than 65 mm (2-1/2 inches).

b. Steam nozzle shall be 2070 kPa (300 psig) ANSI flanged. Design nozzle and drum assembly to withstand forces and moments imposed by connected piping. Studding nozzle is prohibited.

c. Locate boiler manual steam vent to permit access to gate valve from platform located above boiler.

d. Locate safety valve outlets to permit straight run of vents through roof and to permit valve handle access from platform located above boiler.

e. Separate connections for water column and auxiliary low water cutoff.

f. Connections for boiler feedwater, chemical admission, combined continuous blow down and water sampling. Locate as shown on the drawings.

g. Bottom drum blowoff.

h. Water level sensor connections (for incoming feedwater control).

i. Pressure gauge and pressure switch connections.

j. Two 50 mm (2 inch) piping connections on rear head of bottom drum for steam heater for keeping boiler warm in standby mode. Also, connection for temperature sensor for temperature control valve.

7. Drum Internals:

a. Steam purification equipment, including dry pan separators, plate-type baffles, and other devices as necessary, to meet steam

23 52 33 - 8 quality requirements and provide proper water levels in the boiler steam drum.

b. Boiler feedwater admission system to properly distribute feedwater.

c. Chemical feed piping to permit infusion of mixture of water treatment compounds along entire length of drum by continuous feed system.

d. Continuous blowdown and water sampling system as combined unit designed to collect water along entire length of drum.

e. Bottom drum blowoff system to properly collect sediment from bottom drum and to permit complete collection of sediment and drainage.

f. Steam heating pipes in bottom drum to keep boiler warm on standby. Cap for future connections of steam supply and condensate return.

g. Drum internal fittings shall be provided, securely mounted and easily removable for boiler internal access for inspections and cleaning.

8. Tubes:

a. ASTM A178/178M Grade A, seamless or electric resistance welded, outside diameter 50 mm (2 inch) or greater. Uniform internal area, not swaged at drum connections, bend radii permitting turbine cleaning by mechanical tube cleaner.

b. Arrange convection tubes in alternate narrow and wide rows to permit tube removal without removing adjacent tubes.

c. Front furnace tubes (if provided) shall be completely clear of burner throat and bullring and arranged to permit maintenance of front wall refractory system without tube removal.

d. Provide rear water wall tubes covering a minimum of 80 percent of the rear wall area. Arrange tubes to permit unobstructed view through observation ports in the rear wall and to permit maintenance of rear wall refractory without removing tubes.

e. Tubes separating the furnace from the convection area shall have continuous fins welded to each side of the tubes and to each other to form a pressure-tight membrane wall to prevent flue gas bypass of the furnace and convection spaces.

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9. Refractory:

a. Refractory quality and temperature characteristics shall be suitable for long-term service at the maximum operating conditions and shall be the boiler manufacturer’s experience-proven selection. Incorporate refractory systems in the front and rear walls, and seal interface between combustion and convection areas. Repair and replacement of refractory shall be possible without alteration to pressure parts of boiler.

b. Front and Rear Walls: Construct of shiplap firebrick arranged to permit expansion and contraction. Do not use castable refractory except to seal locations where bricks cannot be used. Provide bullring constructed of firebrick to protect burner throat refractory from forces generated within front wall. Provide expansion joint between bullring and burner throat. Incorporate openings in rear wall for observation ports, and for access to furnace as specified under paragraph, CASING, SETTING AND

INSULATION. Access opening shall include a removable refractory plug.

10. Casing, Setting and Insulation:

a. Provide double wall casing system with insulation between the walls. Inner casing can be a welded finned-tube inner wall. The inner casing or welded fin tube construction shall be sealed to prevent the combustion gases from coming in contact with the outer casing.

b. Design casing at the combustion gas outlet to receive approved stack or breeching transition section as shown. Refer to plans for details of gas outlet arrangement.

c. Provide furnace access door located near the furnace floor. Use of burner throat as access is prohibited. Equip furnace access door opening with refractory, backed up by insulation and airtight cover system.

d. Provide three 50 mm (2 inch) diameter observation ports in rear wall of furnace located to permit observation of each sidewall of furnace and full area of burner throat and bullring. Furnish each port with clear and tinted interchangeable glass; gas tight sliding metal closure between glass and furnace, forced air-cooling.

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e. Provide convection space inspection openings sealed with caps removable for inspection.

f. Insulation shall be manufacturer's proven standard materials and methods. No part of the external casing (except for areas within one foot of a casing penetration) shall reach a temperature exceeding 30 degrees C (86 degrees F) above ambient. Field-repair hot spots exceeding requirements.

g. Provide water wash troughs and drains (piped to accessible point) on both sides of lower drum to allow cleaning of exterior of convection tubes.

G. Factory Inspection and Tests:

1. Pressure Vessel Inspection and Certification: Inspect and certify the completed boiler assembly in accordance with the requirements of the ASME BPVC Section I. Submit four copies of completed ASME Form

P-3 for each boiler.

2. Inner Casing Pressure Test: Perform test after erection of the boiler pressure parts and inner casing. Seal boiler openings air-tight and pressurize the furnace and convection area to 2.5 kPa (10 inches of water) minimum. Check all welded joints with soap solution. Seal all leaks by rewelding. The inner casing shall be assumed to be tight when it holds pressure for 10 minutes with a loss not exceeding 10 percent. Test shall be certified by manufacturer and may be witnessed by a government representative.

H. Finish: Provide surface preparation, heat resistant prime and two finish coats using standard color of boiler manufacturer.

2.2 BOILER TRIM (ACCESSORIES)

A. Conform to ASME BPVC Section I. Refer to Section 23 09 11, INSTRUMENTATION AND CONTROL FOR BOILER PLANT, for operation of water level and steam pressure controls.

B. Steam Safety Valves:

1. Provide two or three on each boiler. Capacities certified by

National Board of Boiler and Pressure Vessel Inspectors (NBBI).

2. Type: Angle pattern, flanged or threaded inlet, flanged or threaded side outlet, lifting lever, cast-steel bodies, stainless steel trim, dual control rings, and lapped seats.

3. Settings and Adjustments: Factory set, sealed, and stamped on nameplate. Set pressures as shown. Lowest set pressure shall not exceed normal operating pressure by more than 207 kPa (30 psig).

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Provide 34 kPa (5 psig) difference in setting between each of the valves.

C. Steam Pressure Gauge:

1. Construction:

a. Case: Surface-mounting, bottom or back connection, threaded ring, blowout disc in rear.

b. Dial: 200 mm (8 inch) minimum diameter, non-corrosive, black markings on white background.

c. Measuring Element: Bourdon tube designed for steam service.

d. Movement: Stainless steel, rotary.

e. Pointer: Micrometer adjustable, black color.

f. Window: Laminated safety glass, or plastic.

2. Accuracy: Full span, 1/2 percent.

3. Range: 0 to 1200 kPa (0 to 160 psig).

4. Installation: Stop valve, steel piping, valved blowdown, siphon, union at gauge, valved connection for inspector's gauge. Mount gauge on sheet metal panel affixed to front of boiler. Use spacers between panel and gauge to permit operation of blow-out disc.

D. Water Level Safety and Operating Controls and Indicators:

1. Provide high and low water warning alarms, primary and auxiliary low water burner cutoffs, automatic electronic modulating feedwater level control system, gauge glass.

a. High and low water warning alarms shall operate bell and separate high and low water level indicating lights on boiler control panel and shall not shut down the burner.

b. Primary and auxiliary low water burner cutoff devices shall be in two separate water columns, piped individually to the boiler water spaces. One device shall be float-type, the other device shall be conductivity probes. Primary and auxiliary cutoffs shall require separate manual reset. Non-latching shunt switches shall allow blowdown of water columns without shutting down the burner.

c. Water level set points for all devices shall be as recommended by boiler manufacturer.

d. Water level control system shall maintain the water level within limits established by boiler manufacturer for normal water level with no tripping of high and low-level alarms with instantaneous load swings of 25 percent of boiler capacity. Feedwater pump will operate continuously.

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e. Refer to Section 23 09 11, INSTRUMENTATION AND CONTROL FOR BOILER

PLANT for detailed operation of all indication, monitoring, alarm, and control devices.

2. Water Column Unit with Water Level Controller, Gauge Glass, Water Level Sensor for Primary Low Water Cutoff:

a. Float-type electric or electronic modulating water level control device and primary low water cutoff. As an option to the float type device, electronic self-checking magnetostrictive or capacitance devices may be provided.

b. Height of water column and gauge glass shall be sufficient to show water level in the gauge glass at least 15 mm (1/2 inches) above high-water alarm set point and at least 15 mm (1/2 inches) below auxiliary low water cutoff set point.

c. Control system shall automatically modulate an electric feedwater flow control valve. Feedwater pump will operate continuously.

d. Gauge Glass - Prismatic: Single or double (offset) tilted or vertical prismatic tempered borosilicate reflex units of sufficient length to include all low water cutoff points and high-water alarm point without discontinuity. Provide gauge illuminator, mounted vertically, designed to direct light at gauge only. Locate in front of gauge. Do not block view of gauge from personnel standing 1800 mm (6 feet) in front of burner.

Provide chain-operated 1/4 turn gauge valves. Extend chains to within 1800 mm (6 feet) of the floor.

3. Auxiliary Water Column with Water Level Sensors for High and Low-

Level Alarms and Auxiliary Low Water Cutoff:

a. Conductivity probe type high and low-level alarm sensors and auxiliary low water cutoff sensor.

b. UL listed, factory-built probe and chamber unit mounted externally from the boiler.

c. Stainless steel conductivity probes and grounding probe. Virgin

Teflon insulation.

4. Water columns shall be rated for 1380 kPa (200 psig) minimum saturated steam and have boiler and drain connections.

5. Water Column Piping to Boiler and to Drains: ASTM A106/A106M, Grade

B, seamless or ERW piping, Schedule 80 threaded. Fittings shall be

300 lb. forged steel. All changes in direction shall be with

23 52 33 - 13 crosses, no ells. Provide valved drain piping connected to the lowest part of each of the water columns.

6. Electrical: Provide circuit breakers, transformers, all devices for complete control system. All control electronics and relays shall be in waterproof NEMA 4 panels.

7. Modulating Feedwater Control Valve:

a. Characterized rotary or sliding gate valve. Operated by electric drive unit actuator with top mount integrated digital positioner.

Equal-percent valve flow characteristics. Modified linear valve flow characteristics shall be utilized when digital positioner is furnished.

b. Performance: Refer to schedules on the drawings for pressure, temperature, and flow requirements. If not shown on the drawings, the valve shall be designed for maximum flow rate of 125 percent of the maximum boiler steam output with 69 kPa (10 psig) pressure drop, maximum inlet pressure of 2070 kPa (300 psig), maximum temperature of 138 degrees C (280 degrees F). Shut-off seat leakage less than 0.0001 percent of valve CV.

c. Rotary Valve: Three-piece carbon steel body, 316 stainless steel ball and stem, Polyfil seat, TFE coated stainless steel seal, 2070 kPa (300 psig) 138 degrees C (280 degrees F) minimum ratings. Flanged ends or wafer type for pipe sizes over 50 mm (2 inches), threaded ends for pipe sizes 50 mm (2 inches) and less.

d. Sliding Gate Valve: Stainless steel body, head section, actuator springs valve stem and fixed disc. Tribaloy (STN2) self-aligning sliding disc. Carbon filled PTFE packing. Minimum ratings 2070 kPa (300 psig), 138 degrees C (280 degrees F).

e. Sound Levels: Conform to Section 23 05 51, NOISE AND VIBRATION

CONTROL FOR BOILER PLANT.

f. Electric Drive Unit for Rotary Valve: Shall have sufficient power to operate valve under all operating conditions. All parts of linkage between drive unit and valve shall be free-working, securely attached, and shall not distort under all operating conditions.

E. Low Water Cutoff Shunt Switches: Provide two separate non-latching pushbutton controls, one to short-circuit probe-type primary low water cutoff and the second to short-circuit the auxiliary low water cutoff

23 52 33 - 14 when each is blown down. Locate pushbuttons within reach of drain valves for cutoffs.

F. High Steam Pressure Cutouts:

1. Provide two UL listed, FM approved units with different set points.

Unit with lowest set point shall be the high-pressure limit switch

(manual reset); unit with highest set point shall be the high-high pressure limit switch (manual reset).

2. Bellows or bourdon tube actuated sealed snap-acting switch with adjustable set point and switch position indicator.

3. The high-pressure limit switch (manual Reset) unit shall have an adjustable differential pressure or dead-band, so the reset pressure is an adjustable set point and switch position indicator.

4. Adjustable differential pressure.

5. Construction:

a. UL listed.

b. Design for 1380 kPa (200 psig) minimum emergency pressure.

c. Switch position indicator visible without removing cover.

d. Set pressure range: To 150 percent of required set pressure.

e. Provide set point indicators with graduated scales for set point and differential pressure that are visible without removing cover.

6. Mounting: Pipe directly to boiler steam drum or to water column.

There shall be no valves between cutouts and steam drum. Provide siphons at each switch to protect bellows from high temperature.

7. Set Points:

a. High pressure limit switch (manual Reset) Unit: Refer to boiler schedule shown on the drawings. If not shown, set at 34 kPa (5 psig) below the set pressure of the high- high pressure limit

(manual reset) unit.

b. High pressure limit switch (manual Reset) Unit: reset point shall be by 80 percent of the normal operating pressure of the boiler.

(The pressure the boiler must drop to before the unit can be reset)

c. High-High pressure limit switch (Manual Reset) Unit: 34 kPa (5 psig) below lowest safety valve set pressure. Subtractive differential not to exceed 69 kPa (10 psig).

8. Refer to Section 23 09 11, INSTRUMENTATION AND CONTROL FOR BOILER PLANT for the operation of the cutouts.

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2.3 BURNER AND FUEL TRAINS

A. Burner Type: Combination natural gas and fuel oil, packaged, forced draft, single burner, modulating firing, register type on D-type boilers, and variable speed forced draft fan. Interrupted igniter

(pilot), electrically ignited, natural gas and propane. Design for low excess air operation. Design burner for low NOx emissions. Burner shall be tested by the boiler manufacturer.

1. Gas Burner: Ring type with multiple ports and spuds, or spud type.

2. Oil Burner: Gun type, inside mix, steam or low pressure air atomizing.

3. Igniter (Pilot): Interrupted, electrically ignited, natural and LP

(propane) gas.

4. Burner changeover from one fuel to another shall not require any disassembly and reassembly of any part of the burner or fuel train.

Fuel oil guns shall be a permanent part of the burner or shall easily slide into place in the burner.

B. Service:

1. Continuous long-term operation at all firing rates on each fuel listed under PROJECT CONDITIONS in Part 1. Design the entire burner and fuel train system for application to the specific boiler furnished and for service at the available fuel pressures and heating values.

2. Operate at all loads on any one fuel without any manual changes to burners, fuel trains or fuel pressures, atomizing media trains or pressures.

3. Igniter (Pilot) Fuels: Normal fuel will be natural gas. Propane will be used if there is an interruption in natural gas service.

C. Performance:

1. Igniter (pilot) flame on natural gas and propane shall form close to the point of ignition and shall be stable. Ignite both the gas and oil burner with single igniter.

2. Main flame on gas and oil fuels shall ignite at lowest firing rate.

3. Main flame characteristics at all firing rates:

a. Flame retained within 150 mm (6 inches) of diffuser.

b. Flame stable with no blowoff from the burner or flashback into the burner. No pulsations.

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c. Throat refractory shall be sufficiently heated to provide stable flame on gas firing.

d. No deposits of unburned fuel or carbon at any location.

e. No carryover of flame beyond the end of the first pass (furnace).

f. Flame impingement on furnace tubes or refractory is prohibited.

4. Main Burner Operation:

a. Minimum turndown gas - 10:1, oil - 8:1.

b. Utilize full travel of fuel control valve characterization cams

(if cam type valve is utilized).

c. Operate at all loads on any one fuel without any manual changes to burners, fuel or atomizing media trains or pressures, air train.

d. “Omitted”

e. Excess Air in Flue Gases (Low Excess Air Burners) with Oxygen Trim at Null Position:

Boiler Steam Output Percent of Maximum Required Capacity

Percent Excess Air Allowable Range

Below 20 10 minimum

20 to 39 5 to 15

40 to 100 5 to 10

f. Performance at any load point shall be repeatable after increasing or decreasing the firing rate. Repeatability plus or minus 2 percent excess air, at 20 percent and higher boiler loading except excess air must remain within ranges specified above.

5. Oxygen trim control set at maximum position shall not blow out the fire at any load point. At minimum position, the combustion shall not go below stoichiometric.

6. Oil Atomization: If plant is cold (no steam available), and if steam-atomizing burners are provided, light-off shall be with compressed air atomization media supplied by house compressor.

Boiler shall operate with combustion controls on "manual" and continuously generate at least 13 percent of the maximum rated steam flow with input compressed air at 550 kPa (80 psig) and a maximum of

0.8 standard cubic meters per minute (30 SCFM). Each burner must

23 52 33 - 17 include a dedicated air compressor system furnished by the burner manufacturer.

7. Noise and Vibration: Refer to Section 23 05 51, NOISE AND VIBRATION

CONTROL FOR BOILER PLANT for requirements on forced draft fan and oil atomization system. Burners shall operate without pulsation.

8. Flue Gas Emissions Limits:

a. Carbon Monoxide: Shall not exceed 200 ppm.

b. Smoke: On natural gas and No. 2 oil shall not be visible and shall not exceed No. 1 on the Bacharach smoke scale.

c. NOx: ____ ppm maximum, corrected to 3 percent oxygen, dry basis on natural gas and low nitrogen No. 2 fuel oil

D. Burner Design, Construction and Arrangement:

1. Burner Access (Main Burner and Igniter): Arrange fuel trains, controls, and other devices so that they do not interfere with the removal and replacement of burner parts.

2. Arrangement of Fuel Trains: All devices shall be accessible for maintenance or replacement without removal of other devices. Do not mount any piping or devices within 600 mm (2 feet) of boiler side and top casings unless the casing can be removed without removal of gas train components. Do not attach any piping or devices to boiler casings.

3. Coatings: Provide surface preparation, heat resistant prime and two finish coats using standard color of boiler manufacturer.

4. Combustion Air System and Flue Gas Recirculation (FGR) System (if provided):

a. Air flow rates controlled by forced draft fan inlet or outlet dampers and variable speed drive.

b. Symmetrical, balanced distribution of combustion air into the burner.

c. Provide induced type FGR system if FGR is necessary to achieve specified NOx limits. All FGR ductwork shall comply with Section

23 51 00, BREECHINGS, CHIMNEYS, AND STACKS.

d. Forced Draft Fan: Airfoil or backwardly inclined wheel, electric motor driven. Design for required excess air and for static pressure that is based on losses from fan inlet to stack or chimney outlet, including economizer (if provided), at jobsite altitude. Fan shall have no resonant frequencies at all operating speeds.

23 52 33 - 18

e. Motor: TEFC or open drip proof, non-overloading under all fan operating conditions, design for 40 degrees C (104 degrees F) ambient, premium efficiency type. Motors for variable speed service shall be rated inverter-ready. Refer to Section 23 05 10, COMMON WORK RESULTS FOR BOILER PLANT AND STEAM GENERATION.

f. Damper: Design to provide accurate control of excess air with minimum hysteresis. On variable speed systems, the damper shall operate across all firing rates.

g. Motor Starter Panel: Provide motor starter and variable speed drive mounted in NEMA 4 enclosure, readily accessible. Refer to

Section 23 05 10, COMMON WORK RESULTS FOR BOILER PLANT AND STEAM

GENERATION. Refer to Section 23 09 11, INSTRUMENTATION AND

CONTROL FOR BOILER PLANT, for burner management system motor power interlocks.

h. Sound Attenuators: Provide attenuators on forced draft air intakes to reduce sound levels to allowable limits. Refer to

Section 23 05 51, NOISE AND VIBRATION CONTROL FOR BOILER PLANT.

5. Provide front and rear viewport, with one clear and one tinted replaceable interchangeable glass. Locate to permit view of main and igniter flames.

6. Burner Throat: Refractory tile, shaped to promote proper combustion, arranged with provisions for expansion and contraction and rated by the refractory manufacturer for the maximum service conditions.

7. Electrical Conduit: Provide liquid-tight flexible metal conduit with sealing fittings for all power and control services to fuel trains and burners. Flexible metal conduit must be limited to 900 mm (3 feet) in length unless additional length is required for door or burner swing. Refer to Section 26 05 33, RACEWAY AND BOXES FOR

ELECTRICAL SYSTEMS.

E. Natural Gas Main Fuel Valve and Piping Train:

1. Arrangement: Comply with typical arrangement in NFPA 85, Annex A, as modified by the following description: Starting at the entrance to the train, the devices are, in sequence: plug valve, filter, pressure gauge, pressure regulator, valved connection to pilot burner fuel train, flow meter (if required), pressure gauge, low pressure switch, two automatic safety shut off valves, valved leak

23 52 33 - 19 test, high pressure switch, fuel flow control valve, plug valve, pressure gauge, burner. Provide tee connection for vent between the automatic safety shut off valves. Vent line shall include valved leak test connection, automatic vent valve, valved leak test connection, lockable plug valve, vent thru roof. High and low-pressure switches shall be located to sense the constant pressure controlled by the burner pressure regulator and not the variable burner pressure.

2. Filter: Replaceable fiberglass or cellulose cartridge, 10 micron or smaller particle retention. Static pressure capability two times the maximum lock-up pressure of nearest upstream pressure regulator.

Maximum pressure loss at high fire 1.3 kPa (5 inches WG). Provide vent with cock for relieving pressure in filter.

3. Pressure Regulator:

a. Type: Single seated, diaphragm-operated, designed for natural gas service. Controlled pressure shall be sensed downstream of main valve. Valve may be self-operated or pilot-operated as necessary to comply with performance requirements.

b. Service: Provide precisely controlled downstream pressure in fuel train, with upstream pressure as shown or specified. Inlet and outlet emergency pressure rating shall be at least twice the lock-up pressure of the nearest upstream pressure regulator.

Purpose of high-performance regulator is to provide more accurate flow control and thus greater burner efficiency and to allow set points of high and low gas pressure switches to be closer to the normal operating pressure.

c. Performance: Coordinate with burner requirements. Lock-up pressure shall not exceed 1.5 times regulated pressure.

Coordinate speed of response with opening and closing time of automatic safety shut-off valves so that controlled pressure will be maintained during the opening and closing of the safety shut-off valves. The outlet pressure droop from low fire to high fire shall not exceed 5 percent of the set pressure.

d. Construction, Main Valve: Cast-iron body, replaceable plug and seat.

e. Manufacturer: Fisher (match existing – field verify)

23 52 33 - 20

4. Automatic Safety Shut-Off Valves:

a. Type: Motorized-opening, spring closing, controlled by burner control system. Two valves required.

b. Service: Provide open-shut control of fuel flow to burner. Valves shall shut bubble tight and be suitable for operation with upstream pressure of two times the highest pressure at entrance to boiler-mounted regulators.

c. Performance: Timed opening of six seconds or less to safely and smoothly ignite main flame, and close within one second.

d. Construction: Valves 65 mm (2-1/2 inches) and greater, flanged ends; valves 50 mm (2 inches) and less threaded ends; position indicator showing open and shut, visible from front or side of boiler. Aluminum seating surfaces are prohibited. Proof of closure interlock switch on each valve. Proof of closure electrical circuit shall include non-latching push button interrupter for testing the circuit. Valved leak test fittings before and after each valve.

e. Approval: FM approved, UL listed for burner service.

f. Manufacturer: Maxon (match existing – field verify)

g. Proof of Closure Test: Provide non-latching push button control in the proof of closure circuit to interrupt the circuit for testing.

5. Automatic Vent Valve:

a. Type: Motorized or solenoid closing, spring opening, full port, controlled by burner control system.

b. Service: Provide open-shut control of vent line that is connected between the two-safety shut-off valves. Valves shall shut bubble-tight and be suitable for operation with upstream pressure of two times the highest pressure at entrance to boiler-mounted regulators. Valve shall be open whenever safety shut-off valves are closed.

c. Approval: UL listed for burner service.

6. Vent System Manual Plug Valve for Leak Tests: Located on vent line on outlet side of automatic vent valve. Provide locking device and lock wrench to lock valve to open position. Provide cylinder padlock keyed to VA Engineering key. Provide valved leak test connections between automatic vent valve and plug valve and ahead of the automatic vent valve.

23 52 33 - 21

7. Pressure Switches: Refer to the paragraph, BURNER MANAGEMENT (FLAME

SAFEGUARD CONTROL) SYSTEM WITH SAFETY INTERLOCKS AND ACCESSORIES in

Section 23 09 11, INSTRUMENTATION AND CONTROL FOR BOILER PLANT.

8. Fuel Flow Control Valve:

a. Type: Throttling, controlled by combustion control system (Refer to Section 23 09 11, INSTRUMENTATION AND CONTROL FOR BOILER

PLANT). Valve with adjustable characterization cam required on single point positioning control systems.

b. Performance and Service: Control fuel flow in exact proportion to combustion airflow over the entire firing range of the burner.

Static pressure rating shall exceed the lockup pressure of the boiler-mounted regulator.

c. Construction: If provided, characterization cam shall be shaped by at least twelve adjustment screws.

9. Pressure Gauges, Flow Meter: Refer to Section 23 09 11, INSTRUMENTATION AND CONTROL FOR BOILER PLANT.

F. Fuel Oil Valve and Piping Train:

1. Arrangement: Comply with typical arrangement in NFPA 85, Annex A, as modified by the following description. Starting at the entrance to the train, the devices are, in order: manual shut off valve, filter, pressure gauge, pressure regulator (if required by burner furnished), low pressure switch, high pressure switch, meter (if specified), oil flow control valve, valved drain, automatic safety shut off valve, valved leak test, automatic safety shut off valve, valved leak test, manual shut off valve, pressure gauge, burner.

2. Filter: Permanent edge-type elements, cleanable by rotation of a handle without interruption of flow. Filter element spacing 0.1 mm

(0.004 inch). Pressure rating shall exceed upstream safety relief valve set pressure plus accumulation. Maximum pressure loss 21 kPa

(3 psig) at high fire. Provide plugged drain. Temperature rating 121 degrees C (250 degrees F) on heated oil service.

3. Automatic Safety Shut-Off Valves:

a. Type: Motorized-opening, spring closing, controlled by burner control system. Two 2-way valves required on No. 2 oil service;

one 3-way and one 2-way required on heated oil service or by burner design.

b. Service: Provide open-shut control of fuel flow to burner. Valves shall shut bubble-tight and be suitable for operation with

23 52 33 - 22 upstream pressure exceeding upstream safety relief valve set pressure plus accumulation. Temperature rating 121 degrees C (250 degrees F) on heated oil service.

c. Performance: Timed opening of eight seconds or less to safely and smoothly ignite oil burner, one-second closure.

d. Construction: Threaded ends, valve position indicator visible from front or side of boiler. Proof of closure interlock switch on each valve. Provide non-latching push button switch in proof of closure circuit to interrupt circuit for testing.

e. Approval: FM approved, UL listed for burner service.

f. Provide 10 mm (3/8 inch) relief valve on piping between safety shut-off valves, 1380 kPa (200 psig) rating, tight shut-off. Set pressure lower than pressure rating of safety shut-off valves.

Provide valved leak-test connections between the two-safety shut off valves and after the second safety shut off valve.

4. Pressure Switches: Refer to the paragraph, BURNER MANAGEMENT (FLAME

SAFEGUARD CONTROL) SYSTEM WITH SAFETY INTERLOCKS AND ACCESSORIES in

Section 23 09 11, INSTRUMENTATION AND CONTROL FOR BOILER PLANT. Set points shall be as required by the burner manufacturer. If there are no requirements, the set points shall be within 50 percent of the controlled pressure.

5. Fuel Flow Control Valve:

a. Type: Throttling, controlled by combustion control system (Refer to Section 23 09 11, INSTRUMENTATION AND CONTROL FOR BOILER

PLANT). Valve with adjustable characterization cam required for single point positioning control systems.

b. Performance and Service: Control fuel flow in exact proportion to combustion airflow over the entire firing range of the burner.

Pressure rating shall exceed oil pump safety relief valve pressure setting plus accumulation.

c. Construction: If provided, characterization cam shall be shaped by at least twelve adjustment screws.

d. Option: Burner manufacturer's standard fuel flow control system may be utilized for single point positioning systems if it has an adjustable characterization feature equal to the flow control valve specified.

23 52 33 - 23

6. Oil Guns and Nozzles: On steam atomizing systems, provide two special nozzles if necessary for cold start on compressed air atomization. Provide special guns if nozzles do not fit guns furnished for steam atomizing nozzles.

7. Provide oil pump arranged and piped to provide automatic drainage of oil gun when burner is shut down manually. Not required when oil gun is less than 600 mm (2 feet) long.

8. Pressure Gauges, Thermometers, Flow Meter: Refer to Section 23 09

11, INSTRUMENTATION AND CONTROL FOR BOILER PLANT.

9. Boiler/Burner-Mounted Oil Pump and Relief Valve: Do not provide.

House pumps are provided that include relief valves.

G. Steam Atomizing Valve and Piping Train (with Compressed Air for Cold

Start):

1. Steam/Air Selection: Provide flexible hose to permit selection of steam or compressed air. Refer to Section 23 21 11, BOILER PLANT

PIPING SYSTEMS. Hose connections shall be within 1800 mm (6 feet) of the floor. Permanent interconnection of steam and compressed air piping is prohibited.

2. Differential Pressure Control Valve:

a. Type: Spring loaded, diaphragm-actuated, controlled by oil pressure at burner.

b. Service: Provide control of steam or air pressure to the oil burner. Base valve size on steam and air pressure available at valve inlet. Valve body shall be rated for 1380 kPa (200 psig) steam pressure.

c. Performance: As required by burner.

d. Construction: Cast-steel body, stainless steel trim, double stainless-steel diaphragms with vented space between to separate oil and steam or air.

3. Pressure Switches: Refer to paragraph, BURNER MANAGEMENT (FLAME SAFEGUARD CONTROL) SYSTEM WITH SAFETY INTERLOCKS AND ACCESSORIES in

Section 23 09 11, INSTRUMENTATION AND CONTROL FOR BOILER PLANT.

4. Shut-Off Valve:

a. Type: Motorized or solenoid opening, spring closing, controlled by burner control system.

b. Service: Provide open-shut control of atomizing media flow to burner. If solenoid valve requires a minimum differential

23 52 33 - 24 pressure for operation, coordinate pressure requirements with available pressures. Valve body shall be rated for 1034 kPa (150 psig) steam, dead-end shut-off.

c. Approval: UL listed.

H. Low Pressure Air Atomizing System:

1. Complete system for each burner, furnished by burner manufacturer, including compressor and drive, air filter, low pressure switches

(2) and all piping systems. Where compressor is driven by separate motor and coupling drive system, provide all equipment including motor, coupling, compressors, starter, wiring and protection.

2. Motor: Premium efficiency type. Refer to the Section 23 05 10, COMMON WORK RESULTS FOR BOILER PLANT AND STEAM GENERATION.

3. Motor Controls: Provide motor starter in NEMA 4 enclosure. Refer to

Section 23 05 10, COMMON WORK RESULTS FOR BOILER PLANT AND STEAM

GENERATION. Refer to Section 23 09 11, INSTRUMENTATION AND CONTROL

FOR BOILER PLANT, for burner management control interlock proving power supply to motor.

4. Sound Attenuators: Provide compressor enclosure, air intake silencer, or other means to reduce sound levels to those required.

Refer to the Section 23 05 51, NOISE AND VIBRATION CONTROL FOR

BOILER PLANT.

5. Pressure Gauges and Pressure Switches: Refer to Section 23 09 11, INSTRUMENTATION AND CONTROL FOR BOILER PLANT.

I. Igniter (Pilot) Fuel Valve and Piping Train, Burner and Ignition System:

1. Arrangement: Comply with typical arrangement in NFPA 85, Annex A, as modified by the following description: Arrange the system to allow selection of either natural gas or propane for the ignition fuel.

Provide separate piping with plug valve, pressure gauge, filter, and pressure regulator for natural gas and for propane. Connect to the main burner natural gas service downstream of the main burner pressure regulator. Join the natural gas and propane services by means of a three-way plug valve. Continue with one pipeline including a low-pressure switch, pressure gauge, automatic safety shut off valve, automatic vent, automatic safety shut off valve, igniter.

2. Filters: Replaceable elements, five micron or smaller particle retention. Static pressure capability two times the maximum lockup

23 52 33 - 25 pressure of nearest upstream pressure regulator. Maximum pressure loss, at full flow, 1.3 kPa (5 inches WG). Provide unions for filter removal.

3. Pressure Regulators:

a. Type: Single-seated, diaphragm-operated. Provide separate regulators for natural gas service and for LP gas service. (Refer to the schematic diagrams shown on the drawings).

b. Service: Provide controlled pressure in igniter train as required by igniter, with upstream pressures as shown or specified. Inlet and outlet emergency pressure rating shall be at least twice the lockup pressure of the nearest upstream pressure regulator. As an alternate to the outlet emergency pressure rating, provide internal relief valve vented to outside set at pressure that will avoid overpressure on regulator outlet that could damage the regulator.

c. Performance: Lockup pressure shall not exceed 1.5 times the regulated pressure.

d. Construction: LP gas regulator must be designed for 861 kPa (125 psig) maximum pressure.

4. Automatic Safety Shut-Off and Vent Valves:

a. Type: Solenoid-type, two normally closed shut-off valves and one normally-open vent valve, arranged as shown, controlled by the burner control system. Provide threaded leak-test ports with threaded plugs on each shut-off valve body.

b. Service: Provide open-shut control of fuel flow to igniter and vent between shut-off valves. Design for 138 kPa (20 psig) differential at shut-off.

c. Approval: Safety shut-off valves UL listed, FM approved for burner service. Vent valves UL listed for burner service.

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