1、05-11 23 52 39 - 1 SECTION 23 52 39 FIRE-TUBE BOILERS SPEC WRITER NOTES: 1. Delete between /-/ if not applicable to project. Also delete any other item or paragraph not applicable in the section and renumber the paragraph. Deleted paragraphs should be labeled “omitted”. 2. References to pressure are
2、 gage pressure unless otherwise noted. 3. Contract drawings must include (as applicable) the VA National CAD Standards listed below: SD235239-01 Fire Tube Boiler SD235239-02 Access Platform Arrangement For Fire Tube Boiler SD235239-03 Natural Gas and Liquefied Petroleum Gas Burner and Igniter Fuel S
3、tandard Piping Diagram SD235239-04 No. 2, 5 unit with highest set point shall be manual reset. 2. Bellows actuated sealed snap-acting switch or mercury switch with adjustable set point and adjustable differential pressure (automatic reset unit); switch position indicator. 3. Rated for 1375 kPa (200
4、psi) minimum emergency pressure. 4. Set pressure range: To 150 percent of required set pressure. 5. Provide indicators with graduated scales for set point and differential pressure. 6. Mounting: Connect to water column piping. There shall be no valves between cutoff and boiler shell. Provide siphons
5、 at each switch to protect bellows from high temperature. 7. Set Points: a. Automatic Reset Unit: Refer to boiler schedule shown on the drawings. If not shown, set at 35 kPa (5 psi) below the set pressure of the manual reset unit. b. Manual Reset Unit: 35 kPa (5 psi) below lowest safety valve set pr
6、essure. Subtractive differential not to exceed 70 kPa (10 psi). 8. Refer to Section 23 09 11, INSTRUMENTATION and CONTROL FOR BOILER PLANT for the operation of the cutouts. 2.3 BURNER AND FUEL TRAINS: SPEC WRITER NOTE: Delete low NOx requirements unless required by air emissions authorities. Provide
7、d by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-05-11 23 52 39 - 15 A. Burner Type: Combination natural gas and fuel oil, packaged, forced draft, modulating firing /, variable speed forced draft fan/. / Design for low NOx emissions. / 1. Gas Burner: Ring ty
8、pe with multiple ports or spuds. 2. Oil Burner: Gun type, inside mix, low pressure air atomizing. 3. Igniter (Pilot): Interrupted, electrically ignited, natural gas and propane. B. Service: 1. Continuous operation at all firing rates on each fuel listed under Article, PROJECT CONDITIONS of Part 1. D
9、esign the entire burner and fuel train system for application to the specific boiler furnished and for service at the available fuel pressures. 2. Igniter (Pilot) Fuels: Normal fuel will be natural gas. Propane will be used if there is an interruption in natural gas service. 3. Main Fuels: After boi
10、lers are accepted for operation, choice of fuels will be based on cost and availability. 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
11、 oil fuels shall ignite at lowest firing rate. 3. Main flame characteristics at all firing rates: a. Flame retained at the burner. b. Flame stable with no blowoff from the burner or flashback into the burner. No pulsations. c. No deposits of unburned fuel or carbon at any location. d. No carryover o
12、f flame beyond the end of the first pass (furnace tube). 4. Operation: a. Minimum turndown / 10/1 / 8/1 /. b. Operate at all loads on any one fuel without any manual changes to burners, fuel trains or fuel pressures, atomizing media trains or pressures. c. Excess Air in Flue Gases with Oxygen Trim a
13、t Null Position: Boiler Steam Output, Percent of Maximum Percent Excess Air Allowable Range Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-05-11 23 52 39 - 16 Required Capacity Below 25 15 minimum 25 39 15 35 40 100 15 25 d. Performance at any load
14、point shall be repeatable after increasing or decreasing the firing rate. Repeatability plus or minus five percent excess air, at 25 percent and higher boiler loading except excess air must remain within ranges specified above. SPEC WRITER NOTE: Oxygen trim control should be specified on boilers tha
15、t have parallel positioning combustion controls. /e. 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./ f. Noise and Vibration: Refer to Section 23 05 51, NOISE and VIBRATION CONTROL FOR B
16、OILER PLANT for requirements on forced draft fan and oil atomization system. Burners shall operate without pulsation. SPEC WRITER NOTE: Engineer must review local emissions rules and revise the following paragraphs as necessary. 5. Flue Gas Emissions Limits: a. Carbon Monoxide: Shall not exceed 200
17、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. SPEC WRITER NOTE: Delete NOx requirements except where required by local air emissions authorities. Insert local NOx emissions limits if applicable. If local emissions rules expr
18、ess the requirement in a different way, revise the subparagraph to conform. c. NOx: _ ppm maximum, corrected to 3 percent oxygen, dry basis on natural gas /and low nitrogen No. 2 fuel oil/. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-05-11 23 52
19、39 - 17 D. Construction: 1. Burner Access (Main Burner and Igniter): Arrange fuel valve and piping trains, controls and other devices so that they do not interfere with the removal and replacement of burner parts. 2. Arrangement of Fuel Valve and Piping Trains: All devices shall be accessible for ma
20、intenance or replacement without removal of other devices. Do not attach any piping or devices to boiler casings. 3. Coatings: Provide surface preparation, heat resistant prime and finish coats using standard color of boiler manufacturer. Refer to Section 09 91 00, PAINTING. 4. Combustion Air System
21、 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 flue gas recirculation (FGR) system if FGR is
22、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
23、inlet to stack or chimney outlet, including economizer (if provided), at jobsite altitude. Fan shall have no resonant frequencies at all operating speeds. e. Motor: TEFC or open drip proof, non-overloading under all fan operating conditions, design for 40 C ambient, premium efficiency type. Motors f
24、or variable speed service shall be rated inverter-ready. Refer to Section 23 05 11, COMMON WORK RESULTS FOR HVAC and STEAM GENERATION. f. Damper: Design to provide accurate control of excess air with minimum hysteresis. On variable speed systems, the damper shall control only at lower firing rates.
25、g. Motor Starter Panel: Provide motor starter /and variable speed drive/ mounted in NEMA 4 enclosure, readily accessible. Refer to Section 23 05 11, COMMON WORK RESULTS FOR HVAC and STEAM GENERATION. Refer to Section 23 09 11, INSTRUMENTATION and Provided by IHSNot for ResaleNo reproduction or netwo
26、rking permitted without license from IHS-,-,-05-11 23 52 39 - 18 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 VIBRA
27、TION CONTROL FOR BOILER PLANT. 5. Provide 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 ra
28、ted 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. Refer to Section 26 05 33, RACEWAY and BOXES FOR ELECTRICAL SYSTEMS. 8. Facto
29、ry Testing: Mount burner and controls on boiler at factory and fire-test at all load points. SPEC WRITER NOTE: Delete any fuel valve and piping trains not required. Determine if the natural gas supplier has any special requirements that must be incorporated in the main or igniter fuel trains. E. Nat
30、ural Gas Main Fuel 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 gage, pressure regulator, valved connection to pilot burner fuel
31、train, flow meter (if required), pressure gage, low pressure switch, two automatic safety shut off valves, valved leak test, high pressure switch, fuel flow control valve, plug valve, pressure gage, burner. Provide tee connection for vent between the automatic safety shut off valves. Vent line shall
32、 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: Re
33、placeable fiberglass or cellulose cartridge, 10 micron or smaller particle retention. Static pressure capability two times the Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-05-11 23 52 39 - 19 maximum lock-up pressure of nearest upstream pressure r
34、egulator. Maximum pressure loss at high fire 1.3 kPa (5 inches water column). Provide vent with cock for relieving pressure in filter. 3. Pressure Regulator: a. Single seated, diaphragm-operated, designed for natural gas service. Controlled pressure shall be sensed downstream of main valve. Valve ma
35、y be self-operated or pilot-operated as necessary to comply with performance requirements. b. Service: Provide precisely controlled downstream pressure in fuel train, as required by burner and fuel trains furnished, with upstream pressure as shown or specified. Inlet and outlet emergency pressure ra
36、ting shall be at least twice the lock-up pressure of the nearest upstream pressure regulator. c. Performance: Maximum outlet pressure droop 5 percent of the set pressure over the burner firing range. Maximum lock-up pressure 1.5 times regulated pressure. Speed of response to opening of automatic saf
37、ety shut off valves shall be sufficient to allow set pressure of low pressure switch to be within 20% of the normal operating pressure with no nuisance burner trips. d Construction, Main Valve: Cast iron body, replaceable plug and seat. Downstream pressure-sensing line. 4. Automatic Safety Shut-Off
38、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 entranc
39、e to boiler-mounted regulators. SPEC WRITER NOTE: Valves with longer opening times often do not allow the main burner to ignite within the specified (and code required) 10 seconds trial for main flame. c. Performance: Timed opening of six seconds or less to safely and smoothly ignite main flame, and
40、 close within one second. d. Construction: Valves 65 mm (2-1/2 inches) and larger, flanged ends; valves 50 mm (2 inches) and below threaded ends; position indicator showing open and shut, visible from front or side of boiler. Aluminum seating surfaces not permitted. Closed position Provided by IHSNo
41、t for ResaleNo reproduction or networking permitted without license from IHS-,-,-05-11 23 52 39 - 20 interlock switch on each valve. Valved leak test fittings before and after each valve. e. Approval: FM approved, UL listed for burner service. SPEC WRITER NOTE: VA safety device testing program has r
42、evealed problems with auto safety shut off valves other than Maxon. Problems included proof of closure switches, and pressure pulses upon closure that affect the high gas pressure switches. f. Proof of Closure Test: Provide non-latching push button controls in the proof of closure circuit to complet
43、e the circuit when the valves are open and interrupt the circuit when the valves are closed. 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 t
44、he 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.
45、 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 a
46、nd plug valve and ahead of the automatic vent valve. 7. Pressure Switches: Refer to the article on burner management system in Section 23 09 11, INSTRUMENTATION CONTROL FOR BOILER PLANT. Switch settings must be within 20% of the controlled pressure. High pressure switches shall have lockable service
47、 isolating valves and valved connections for pressurizing the switches and testing the set and trip points. 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). Provided by IHSNot for Resal
48、eNo reproduction or networking permitted without license from IHS-,-,-05-11 23 52 39 - 21 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
49、regulator. c. Valve Requirement for Single Point Positioning Jackshaft Control Systems: Valve shall have adjustable characterization cam shaped by at least twelve adjustment screws. 9. Pressure Gages, Flow Meter: Refer to Section 23 09 11, INSTRUMENTATION AND CONTROL FOR BOILER PLANT. F. Fuel Oil Train: 1. Arrangement: Comply with typical arrangement in NFPA 8
