OPERATION AND MAINTENANCE MANUAL. PowerFlex he

Transcription

1 OPERATION AND MAINTENANCE MANUAL PowerFlex he

2 Index A. Introduction... 1 B. Warranty... 2 C. Description and features of your unit General description Flue gas circuits strategy Boiler circulation pattern Boiler flexibility Boiler Enclosure... 3 D. Performance... 3 E. Initial Start up Boil out procedure Refractory curing procedure... 5 F. Operation Water volume safeguard Low water cut off controls (L.W.C.O.) Fuel firing safeguard Modulating burner control Interlock switches Cold start up Start up procedure... 7 F. Shut down & Storage Shut down procedure Standby Protection Wet Storage Dry Storage... 9 G. Inspection, maintenance and testing requirements Daily tasks Weekly tasks Monthly tasks Annual tasks Safety or relief valves Pressure gauge

3 7. Thermometer H. Water treatment I. Cleaning Fireside cleaning Water side cleaning

4 A. Introduction The following notes on boiler operation are of a general nature, prepared to acquaint operators with the basic operation and care of the boiler unit. More specific and detailed information regarding operation and maintenance of boiler components and auxiliary equipment supplied at this particular installation can be found in the various section of this manual and in the attached technical and maintenance documents supplied for the components installed on your boiler. Because of the different codes, regulations and specifications applicable in North America, many safety devices and controls vary from one installation to another. This manual illustrates only the standard components. The design and basic components of this boiler have been conceived to provide normal service and continued operation. It is the operator's responsibility to properly maintain it under normal operating conditions. Page 1

5 B. Warranty WARNING : For these warranties to be considered valid and in function, the start up report must be sent back to Novatherm following the original start up. Novatherm warrants that its products will be free from any defects in material and workmanship which became apparent under normal use, and of which the Buyer gives written notice to Novatherm within a period of 12 months from the date of start up or 18 months from the date of shipment or offer to ship, whichever occurs first. Novatherm shall repair or shall replace any parts which are found to be defective in design, workmanship or material, provided said equipment is operated by the purchaser in accordance with generally approved practice and in accordance with the conditions of service, if any, herein specified. The Manufacturer or his authorized representative must be given the opportunity to inspect the product alleged to be defective and the installation or use thereof. Buyer is responsible for all shipping charges of the defective parts back to the manufacturer for inspection, when required and/or shipping of the new or repaired parts to the location. No labour warranty is included against any expense for removal or reinstallation of the defective part. As for the OEM equipment supplied mounted or not with the boiler, Novatherm purchases only the best equipment obtainable and it is guaranteed to the extent of the original manufacturer s warranty. The sole judgement of the said manufacturers shall determine the extent of allowance for, or replacement of any such parts claimed defective. No labour warranty is included against any expense for removal, fixing or reinstallation of any OEM equipment. This warranty does not cover damages due to improper product installation or negligence on the part of the Buyer, or loss or damage that occurred during transport to the Buyer. This warranty could be voided if Buyer repairs, modifies or replaces any parts of the boiler or modifies the operating conditions for which the boiler was designed, without Novatherm s prior written consent. No other warranty shall be implied from the manufacture, sale, furnishing or erection of any of the said equipment to be furnished herein or it use, except as may be otherwise specifically provided herein. This warranty does not cover any damage or defect directly or indirectly, or wholly or party, attributable to accident or the misuse, abuse or neglect of the products. Novatherm shall not be liable for any injury, loss or damage direct or consequential arising out of the inability to use the product, loss of anticipated profits, loss by reason of plant shutdown, non operation or increased expense of operation of other equipment, or other consequential loss or damage of any nature. Page 2

6 C. Description and features of your unit 1. General description The boiler unit is a water tube boiler connecting an upper and lower drums by a bundle of bent tubes. The tubes are installed tangent to each other and are bent to form the furnace and the passes directing flue gas towards the boiler exit. The tubes arrangement provides a symmetrical design and insures a balance flow of circulating water. 2. Flue gas circuits strategy Depending on the unit model and the capacity of the boiler, flue gas circulation can make from 5 to 9 passes through the boiler. This design maximizes the heat transfer capability and optimizes the gas draft losses. 3. Boiler circulation pattern The return water (cold) enters at the back end of the lower drum (collector) and exits (hot) at the front end of the upper drum (collector). Fluid will go up and down in three circulation passes, through fixed diverting baffles are mounted inside the drums (collectors). 4. Boiler flexibility By design, this boiler is flexible and the tubes can expand without constraint. Rapid start up is possible and thermal shock risks are almost none existing. 5. Boiler Enclosure The boiler inner casing is made of 11 gauge steel and 2 thick 1,900 o F ceramic insulation. The boiler combustion chamber floor and ends are insulated with 1,900 o F ceramic fibreboard insulation. Front and rear walls are protected with 2,700 o F high temperature castable refractory. The boiler outer casing consists in 20 gauge corrugated aluminum panels. A 2 in. air space between the inner casing and outer casing provides further insulation to ensure cool jacket surface and to minimize heat loss. The outer casing can be removed in sections and has a hard enamel paint finish. D. Performance All heat generating equipment are designed for a specific purpose. When supplied with fluid at the specified inlet temperature and pressure, the boiler is designed to transfer a definite quantity of heat to the fluid and maintain a defined discharge temperature. Operating conditions, exceeding the design limitations will shorten the life of the boiler and components parts With a new boiler, the temperature of the gas leaving the boiler, and the draft loss trough the boiler will normally be constant for a given rating and percent excess air. This illustrates the desirability of keeping Page 3

7 accurate records for performance from the start of operation. When the equipment is new, a standard will be set up, the deviation from which will serve as a measure of satisfactory operation and as an indicator of an undesirable condition. Steps may then be taken to determine and correct the cause for the discrepancy, and often avoid the development of serious difficulties. Records should be kept in a form that facilitates comparison of similar operating conditions. The amount of fuel consumed is either measured or estimated. The means employed will depend upon the nature of the fuel and the equipment available for measuring. An analysis of a representative fuel sample should be obtained periodically. This will determine the calorific value. The fuel analysis may also serve to determine the causes of a decline in efficiency. The temperature and analysis of gases leaving the boiler can indicate if the combustion is complete and effective. Combustion should be completed before the gases leave the furnace section. The best percentage of excess air to use depends upon the nature of the fuel, the burner characteristics and other factors such as NOx and CO levels permitted. The presence of CO in flue gas indicates incomplete combustion. A gas analyser should be provided to determine the percentage of CO, CO2 and O2 at startup or whenever the burner is adjusted. We have provided enough heating surface to obtain the lowest possible exit gas temperature and maximize boiler efficiency, depending on the model and capacity, the gas temperature will be: 50 F to 150 F above return temperature But the exit gas temperature must not drop below the flue gas acid or vapor dew point and the gas should not be in contact with metal at a temperature below those dew points, which are: Natural gas Acid Dew Point is from 130 F to 170 F due to sulphur in the gas (1.1 to 11.3ppm) Water vapor dew point is 135 F depending on excess air Fuel oil Acid dew point is from 150 to 250 F depending on sulphur in fuel Water vapor point is from 110 to 115 F At this temperature, moisture in the flue gas condenses and produces high concentration of acid ions on the metal surface. As a reference, the condensate ph at dry out for natural gas is in the order of 3.8. Care should be taken when a boiler is started from cold. Refer to the cold start up article in this manual. The piping and controls must be arranged to ensure that water circulation is constant through out the boiler. A flow switch, installed on the return piping, must be installed to prevent the burner from operating if the flow is inferior to the minimum required (generally set to 90% of nominal flow) For maximum boiler life, we recommend that the water in a steel boiler be maintained at all times during operation above 150 o F, preferably 160 o F if possible, to prevent corrosion through condensation of flue gases, The injection of cold water into a hot boiler will also produce thermal shocks and create undue stresses, which tend to produce tube failure. A differential not exceeding 80 o F is recommended Page 4

8 E. Initial Start up 1. Boil out procedure The first thing to do before putting a new boiler into service is to clean the boiler and the system. Oil, grease or foreign matter must be removed from the piping and the boiler heating surfaces of any new installation. To boil out a new boiler, the following procedure can be useful if the services of a water treatment specialist are not available. For every 200 litres (50 gallons) of water, use one pound of tri sodium phosphate and one pound of caustic soda. Dissolve in warm water, avoiding contact with skin or clothing. Remove safety or relief valves. Install a pipe in the opening for filling and overflow. Close all other valves. Fill boiler with clean water up to middle of upper drum. Add the cleaning solution and fill to the top. Fire intermittently, at low fire, to maintain water at boiling point for 5 hours, introducing a small amount of fresh water which will permit the overflow to carry off impurities. Increase overflow until water clears. Stop burner and drain boiler completely. Open manhole in the upper drum and the inspection plug in the lower drum. Wash with a water hose. Inspect surfaces. Repeat boil out procedure if necessary. On steam systems the condensate should be checked for impurities and wasted until found satisfactory. 2. Refractory curing procedure The refractories used in the construction of your boiler have been chosen in regard of best insulation properties and lifetime. They however need some special attention on the first start up. In order to avoid unwanted thermal stress in refractories, this start up schedule must be followed. Adjust burner on Low fire for the first 8 hours. Hour 1: Hour 2: Hour 3: Hour 4: Hour 5 to 8: Fire for 5 minutes, stop for 10 minutes alternatively. Fire for 5 minutes, stop for 5 minutes. Fire for 10 minutes, stop for 5 minutes. Fire for 15 minutes, stop for 5 minutes. Continue Low fire After 8 hours, progressively increase temperature to full fire. Curing process should not be interrupted. Curing process can be done during boil out. Page 5

9 F. Operation Your boiler has been designed, manufactured and tested in accordance with the requirements of section I of the ASME Boiler and Pressure Vessel code. The objective of these requirements is to afford protection of life and property and to provide margin for deterioration in service so as to give a reasonably long and safe period of usefulness. The prime consideration for all operation is the safety of people and equipment. The two most dangerous conditions remain the same today as throughout the history of steam generation: the loss of water and the explosive mixture of fuel and air. Those concerns are addressed by the following controls: 1. Water volume safeguard With a hot water heater, the piping and controls must be arranged to ensure that water circulation is constant through out the boiler. The flow switch installed on the return piping will prevent the burner from operating in the flow is inferior to the minimum required. 2. Low water cut off controls (L.W.C.O.) If the water drops to a dangerous level, the burner will be turned off. A probe installed on the upper drum (collector) is wired to the L.W.C.O. relay that trigger the burner shut down process. 3. Fuel firing safeguard The main function of the burner integrated control is to prevent the formation of an explosive mixture of fuel and air in any portion of the boiler during any phase of operation, including start up and shutdown. Therefore this mixture should never be allowed to exist except inside the combustion chamber at the burner, and then only when the burner is lighted. All safety system of this type, are designed with the following functions: a pre firing purge of the furnace proofing of the appropriate permissive for firing the ignition fuel proofing of the appropriate permissive, including ignition permissive, for the main flame continuous monitoring of firing conditions and other key operating parameters emergency shutdown procedure of the firing equipment when required a post firing purge of the boiler If any odour of gas or oil is noticed, shut off the boiler and check for source of order. Leaking lines, stuck valves and defective lighting devices should be investigated. 4. Modulating burner control In addition to the safety functions supplied by your microprocessor based integrated burner controls, the water temperature is controlled by modulating the burner firing. A temperature proportional Page 6

10 control acts on a modulating motor to vary both the fuel valve and the air damper position in order to increase fire on temperature drop, and reduce fire on temperature rise. Temperature controls are set to cut burner circuit if operating control setting is exceeded and reach high limits. 5. Interlock switches Air pressure switch in the burner air plenum will stop the burner if air pressure gets too low preventing an explosion hazard when not enough air is delivered to the furnace when fuel is still flowing. A high pressure switch in the fuel supply line will stop the burner if the fuel pressure gets too high. If excessive gas flows to the furnace, the burner could fill the furnace with a hazardous combustible mixture. A low pressure switch in the fuel supply line will stop the burner if the fuel pressure gets too low. If pressure falls too low, the burner could go out and continue to fill the furnace with a hazardous combustible mixture. 6. Cold start up When cold water is introduced into a boiler, condensation will occur if the bulk of the gas stream or gas in contact with metal surface are below the acid or vapor dew point. When starting a cold boiler, the low fire must be used intermittently to warm up slowly. 7. Start up procedure Before starting up a boiler, make sure that everything is in proper working condition. Check to be sure you have done the following: 1. Inspect all electrical, fuel, water and vent connections. 2. Inspect the waterside. See that manhole and handhold covers are securely installed and inspect the pressure section of the boiler. 3. Inspect the fireside. Be sure there are no foreign matters left inside and there is no trace of fuel, oil, gas or fumes. 4. Check the safety valve for correct setting and installation. 5. Check the main stop valve. Be sure it is closed. 6. Verify supply of fuel and voltage. 7. Fill the boiler with water. 8. Open the top try cock (steam boiler) or relief valve (steam and water boiler) to vent the air from the boiler during warm up period. 9. Verify the burner and the limit controls settings. 10. Test the flame safeguard control to be certain of its operation. 11. Start the circulating pump 12. Start the boiler (refer to the burner section for operation and sequence). 13. The boiler can now be put in automatic mode. Page 7

11 F. Shut down & Storage 1. Shut down procedure When taking a boiler off the line, do the following: 1. Gradually reduce load and set the fuel control system to low fire position. 2. Following manufacturer's recommendations shut down the burner. The unit is to be post purged with the fan for at least 5 minutes and then allowed to cool on natural draft. This will prevent the refractory from cooling too rapidly and possibly flaking the surface. 3. A cooling rate exceeding 100 F per hour to 150 F per hour by excessive opening of vents should be avoided to limit risks of cracking in the refractory 4. Vents can be fully opened when the pressure drops to 15 to 20 psig. 6. The boiler can be drained only after the water temperature drops below 200 F 7. When the pressure gauge indicates 1 to 2 psig, open the relief valve from forming. 2. Standby Protection Many boilers used for heating or seasonal loads or for standby service may have extended periods of non use. Special attention must be given to these, so that neither waterside nor fireside surfaces are allowed to deteriorate from corrosion. Corrosion can be more serious during this down time than when the boiler is actually in service. The key factors responsible for corrosion are water, oxygen, and ph. Elimination of either moisture or oxygen will prevent appreciable corrosion. Two types of storage systems are widely used; these are wet and dry storage methods. 3. Wet Storage 1. As the boiler is being shut down and as the pressure subsides, but before steaming stops, add chemicals to the boiler to scavenge oxygen and to control ph, per the recommendations of your water treatment specialist. 2. When the boiler pressure gauge indicates about 10 psig, completely flood the system with deaerated treated water with the drum vent open. Close the drum vent after it begins to overflow. The steam stop valve should already be closed. Water should be added through the feed pump until 10 psig is maintained as indicated by the drum pressure gauge. Close the feedwater valves. 3. Observe the steam drum pressure gauge and maintain pressure. If pressure builds, it may be due to leaking feedwater valves, which may not be properly seated. A pressure loss (after the boiler is cool) indicates leakage, so check all fittings and valves for leakage. 4. Frequent water samples should be taken and analyzed by your water treatment specialist. If the analysis indicates a need for additional chemicals, the level in the boiler steam drum should be lowered to normal level and chemicals added. The boiler should be then be steamed to circulate the solution, and the process of wet storage repeated as previously described. 5. Close all gas side access doors. Isolate the system to prevent cold air from reaching the heating surface. Periodic inspections of the external surfaces of the pressure parts should be made to guard against condensation and subsequent corrosion. 6. During storage, steps should be taken to protect the exterior components from the possibility of rust or corrosion. These parts should be protected from moisture and condensation. Page 8

12 7. Electrical equipment should likewise be protected. Keeping the control circuit energized may prevent condensation from forming in the control cabinet. 4. Dry Storage When the unit will be idle for a considerable length of time and can be put back on line after a short preparation period, the dry storage method is recommended. 1. The unit should be cooled down and then completely drained. Make sure that no pockets of water remain in the drum, piping, water column, etc. Open all vents to assure complete drainage. 2. Open all the manways and thoroughly wash the water side surfaces to remove any sludge deposits. Mechanically clean residual particulate from the gas side metal surfaces and inspect the system thoroughly. 3. Dry the system thoroughly. If an air hose is used, be sure condensate from the air tank is not blown into the tubes and that the air is oil free. 4. Place flat wooden trays of moisture absorbent, such as quick lime or silica gel, inside the drums to absorb any moisture that will be trapped when the unit is closed up. The trays should be placed on supports to allow air to circulate under them. For recommendations on quantity of moisture absorbent, your water treatment specialist should be contacted. The trays should not be more than 3/4 full of the dry absorbent to prevent overflow of the corrosive liquid that has been absorbed. 5. After the entire system is dried the boiler system should be pressurized with nitrogen to approximately 5 psig though the drum vent. Close the steam outlet, drain valves, and feedwater block valves. Ensure that the system has been purged completely before pressurizing. 6. Close all the openings to prevent water, steam or air leakage into the unit. Leave open the code required drain valve between the process steam stop valves to prevent back leakage of condensate from any downstream header that may be pressurized. 7. Isolate the boiler to prevent moisture from reaching the heating surface. 8. Keep the boiler room dry and well ventilated to reduce possible surface corrosion. 9. If it is suspected that moisture cold have been absorbed by the refractory, follow the recommended refractory dry out procedure. Page 9

13 G. Inspection, maintenance and testing requirements An inspection schedule listing the procedures should be established. It is recommended that boiler room log be maintained, recording daily, weekly, monthly, and yearly maintenance activities. Even though a boiler operates in an automatic or semi automatic mode, the electrical and mechanical devices controlling the boiler require systematic and periodic maintenance. Alertness in recognizing unusual noises, improper gauge readings, leaks, signs of overheating, etc.., can make the operator aware of developing malfunction and react to prevent excessive repairs or unexpected downtime. Any leak even minor in piping connections, its accessories if neglected can become serious. This applies to water gauge glass, water level control, valve packing, and gaskets. The following are suggested maintenance schedules 1. Daily tasks 1. Test low water cutoff, check water level and gauge glass 2. Check pressure gauges and thermometers 3. Check burner operation (fuel pressure, flame appearance) 2. Weekly tasks 1. Test flame safeguard and check pilot 2. Check burner operation 3. Check high limit control 4. Check fuel supply line for leaks 5. Check all piping for leaks repair 6. Inspect boiler circulation pump pack/lubricate as required 3. Monthly tasks 1. Full check on low water cut off 2. Check safety valve 3. Full check on all boiler controls 4. Inspect complete boiler feed water system 4. Annual tasks Insurance regulation or local laws may require a periodic inspection of the pressure vessel by an Authorized Inspector. Use this major inspection to do the following: 1. Check condition of refractory for damage or cracking. Patch and repair as required. 2. Inspect and test the pressure relief valves in accordance with supplier s recommendations 3. Inspect and clean the flue gas side of the boiler 4. Inspect and clean the water side of the boiler if necessary 5. Perform any major repairs or replacements that may be required. Page 10

14 5. Safety or relief valves Safety or relief valves supplied with boilers have been selected to meet ASME code requirements and have been set to the pressure specified. Replace only with identical valves. Only the valve manufacturer is authorized to vary the settings. Discharge piping must be made per A.S.M.E. code. When a safety valve will not close but continues to leak at the pressure lower than that for which it is set, try to free it by operating the lift levers. If this fails to stop the leak, the valve must be replaced. 6. Pressure gauge For steam or hot water boilers, a pressure gauge is supplied. The only maintenance work necessary is regular cleaning of the window and recalibration. Gauge cocks should always be opened and closed slowly to avoid pressure shocks to the gauge. 7. Thermometer The thermometer supplied with hot water boilers must be installed (top outlet) so as to read the boiler water temperature. As optional equipment, a stack thermometer may be supplied and should be installed in the stack to read the temperature of the gases leaving the boiler. Check the thermometer daily for break and clean if necessary. Calibrate regularly. H. Water treatment Practical experience has shown that even though hot water boilers generally operate on closed systems, water losses and entrance of air may lead to pitting, corrosion and formation of sludge or scale. It is therefore essential to obtain suitable water treatment recommendations from specialist and to apply them rigidly. A water meter is recommended in order to determine the amount of makeup water used. Page 11

15 I. Cleaning 1. Fireside cleaning Flu gas temperature is the best indication of the condition of the boiler heating surfaces. When a stack thermometer is used, its reading will indicate when the fireside of the boiler needs cleaning. Soot acts as an insulator; any accumulation increases the gas temperature at the boiler outlet and reduces both transfer and efficiency. As a general rule, the radiation zone should not accumulate substantial deposits because of the high temperature in that particular area. If required, however, cleaning can be achieved from the rear access door, which has been designed to provide access to the radiation zone of the boiler. Abnormal operation of the burner may cause soot to accumulate in the convection area. The entire outer casings and inner casings can be easily removed and replaced for inspection and maintenance of tubes and cleaning. Since the bent tubes are spaced close to each other, it is recommended that a spray or brush be used to clean the convection tubes. Removal of soot and other deposits can be done as follows: 1. Remove the outer casings on both sides and rear and place them in a clean area. 2. Remove the rear manway cover. 3. Unbolt and remove top inner casing. 4. Boiler passes can now be brush cleaned and vacuumed from the rear of the boiler. 5. Reinstall rear inner casing. Seal and bolt top only. 6. Remove inner casing. This will expose the inner cover pass seal. Remove inner cover pass seal and insulation. 7. Passes can now be cleaned and vacuumed from the sides of the boiler. 8. The first pass (combustion area) can now be brushed and vacuumed through the rear manway of the boiler. 9. After cleaning the boiler, reinstall the inner cover pass seals. Be sure covers are well sealed and secured. 10. Reinstall inner side casings. Be sure the refractory rope seals are in place for a gas tight boiler. 11. Reinstall all nuts and bolts (clean up area). 12. Replace the outer casings with clean hands. 13. Inspect tube surfaces for signs of overheating (bulging, blackened surfaces, etc..) 2. Water side cleaning 1. Remove all manway and handhole covers 2. Open all bottom blowdown and drain valves. 3. Inspect the interior of drums and review with your water treatment specialist any suspected accumulation of sludge, scale or metal surface discoloration. 4. Use a hand scraper to remove accumulated sludge and scale and vacuum them out. 5. If permissible, hose the inside of the boiler with clean water under high pressure. Page 12

16 6. Clean metal surfaces where cover plate bears against shell plate or ring. 7. Use new gasket with graphite paste, center cover plate and tight bolt firmly. Page 13