1、Recommended Practice for theOperation, Maintenance and Testingof Firebox Flame ArrestorsAPI RECOMMENDED PRACTICE 12NSECOND EDITION, NOVEMBER 1, 1994REAFFIRMED: APRIL 2008Recommended Practice for theOperation, Maintenance and Testingof Firebox Flame ArrestorsExploration and Production DepartmentAPI R
2、ECOMMENDED PRACTICE 12NSECOND EDITION, NOVEMBER 1, 1994REAFFIRMED: APRIL 2008SPECIAL NOTES API publications necessarily address problems of a general nature. With respect to par- ticular circumstances, local, state, and federal laws and regulations should be reviewed. . API is not undertaking to mee
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14、ts do in fact conform to the applicabJe API standard. Copyright Q 1994 American Petroleum Institute API RP*L2N 94 m 0732290 0539142 B13 W CONTENTS Page SCOPE . DEFINITIONS THEORY . OPERATION . MAINTENANCE AND INSPECTION . TESTING Figures 1-Equipment for Testing . 2-Testing Flame Arrestor Element 1 1
15、 1 2 2 5 17 21 iii API RP*l2N 74 m 0732270 0539143 75T m FOREWORD The bar notations identify parts of this standard that have been changed from the previ- This standard shall become effective on the date printed on the cover but may be used ous API edition. voluntarilyfrom the date of distribution.
16、Recommended Practice for the Operation, Maintenance and Testing of Firebox Flame Arrestors 1 Scope 1.1 This recommended practice should be considered in the installation, maintenance and testing of firebox flame ar- restors installed on the air intake of oilfield production equipment. Flame arrestor
17、s are commonly used on indirect heaters, emulsion treaters, glycol reconcentrators and other equipment used to heat fluids in production operations. These flame arrestors are designed to prevent flashback through the arrestor in the event that combustible fluids in the atmosphere should be drawn int
18、o the heater through the air intake and come in contact with the main burner or pilot flames. 1.2 This recommended practice is limited to gas fired, nat- ural draft burner systems with continuously burning pilots. Flame arrestors for oil fired burners or burner systems using forced draft or induced
19、draft are outside the coverage of this recommended practice. Also excluded from coverage of this recommended practice are burner systems in which a spark produced by the system could cause an internal explosion such as with a spark ignition device. 1.3 Equipment known as line arrestors, tank arresto
20、rs, spark arrestors, or stack arrestors are outside the coverage of this recommended practice. 1.4 Some of the recommended practices for field testing after installation may not be applicable to equipment located in confined areas. The user may modify these recommended practices as required to satis
21、fy his own specific needs. 2 Definitions 2.1 access opening: An opening which allows communi- cation to the interior of the flame arrestor housing making the mixer, pilot, burner, etc., accessible. This opening is nor- mally closed by a flat plug or plate 3“ to 4“ in diameter, se- curely attached to
22、 the housing and tightly sealed against the opening. 2.2 breeching: An extension of the firetube outside of the vessel which is being heated. The arrestor breeching serves as the attachment for the flame arrestor and surrounds the mechanical devices such as mixer, igniter, etc. 2.3 mixer, pilot, bur
23、ner: Mechanical devices located in the arrestor housing and breeching which mix the fuel and air and control burning and flame position. 2.4 combustion: The chemical reaction of rapid oxidation which is accompanied by the emission of light and heat-the flame. Combustion begins when the temperature o
24、f the ig- nitable substance reaches its apparent ignition temperature. This process will be self-sustaining as long as the heat re- leased in combustion maintains the temperature within the flammable range of the ignitable substance. 2.5 firebox: The firebox is also called the firetube. It is the en
25、closure where the fuel is burned, and is submerged in the fluid to be heated. The most common configuration is one or more U-tubes. The fire is propagated in one end and exhausts into a stack on the other end. 2.6 flame arrestor: A device which prevents the propaga- tion of flame from an enclosed ar
26、ea which contains the burner. If the area outside the enclosure were to contain an ignitable mixture, flashback would thus be prevented. The flame arrestor must be able to accomplish this without stop- ping the communication of air between the two areas. 2.7 flame arrestor element (flame cell): A de
27、vice which is mounted in a housing that serves as the combustion air in- take. Its function is to prevent propagation of the flame from the firebox to the outside atmosphere. Sustained exposure to direct flame impingement may render the element inopera- tive. 2.8 flame arrestor housing: An enclosure
28、 which contains the flame arrestor element and may contain mechanical devices such as mixer, air controller, etc. It bolts to the breeching. 2.9 manufacturer: The assembler or supplier of complete flame arrestor units. 2.10 stack: A vertical pipe on the exhaust end of the fire- tube which exhausts t
29、he products of combustion and creates draft through the firetube. 2.1 1 user: The owner or operator of the vessel containing the flame arrestor. 2.12 vessel: An enclosure containing fluid that is being heated. 3 Theory 3.1 Flame arrestor elements used on oilfield production equipment are designed to
30、 extinguish a flame caused by the ignition of combustible gas or vapor which has entered the firebox from the atmosphere surrounding the unit and has come in contact with the pilot or main burner flame, and thus prevent passage of the flame to the atmosphere. The flame arrestor is designed to remove
31、 heat faster than the heat may be generated by the combustion process. By maintaining a temperature lower than the ignition temperature of the ig- nitable substance, combustion is extinguished. 3.2 When a flammable mixture burns in a tubular enclo- sure, some of the heat of combustion is absorbed by
32、 the sur- 1 API RP*L2N 94 W 0732290 0539145 522 W API RECOMMENDED PRACTICE 12N rounding walls. If the enclosure is of sufficiently small diam- eter, enough heat will be absorbed to prevent propagation of the flame. Therefore, the smaller the tube and the greater the coefficient of heat conductivity
33、of the material from which the tube is made, the greater will be the dissipation of heat from the system. Aluminum is often used to form the ele- ment due to its corrosion resistance and heat transfer proper- ties, although other materials such as stainless steel may be used. It is acknowledged that
34、 designs other than banks of parallel tubular enclosures could conceivably be used for ar- restor elements. Placement of the element within the housing may be in either the horizontal or the vertical plane and is a matter of design choice. 3.3 The previous discussion points out the need to prop- erl
35、y space the arrestor away from the flame. Should the dis- tance be too short, the cooling effect of the arrestor may be offset by the heat of the flame. This might render the arrestor inoperative even if the element were intact and undistorted. 4 Operation 4.1 Proper operation is of critical importa
36、nce in ensuring that the benefits of a properly designed firebox flame arrestor are realized. 4.2 The area immediately surrounding the firebox flame arrestor should be readily accessible and free of obstacles, such as piping or vessels, which would prevent unrestricted movement of personnel in the e
37、vent of an emergency. The immediate area should be free of potential hazards such as relief valve outlets, instruments bleeding combustibles, or open drains, and should have adequate ventilation. 4.3 Before any firebox flame arrestor is put into operation, a visual inspection should be made to ensur
38、e that all fittings, gaskets, and bolts are in place. Personnel knowledgeable with gas firing accessories should confirm that there are ad- equate valves, regulators, and accessories for proper opera- tion, and that these are installed correctly. According to the manufacturers recommendation the pro
39、per location of the aidgas mixer, burner tip and pilot assembly should be veri- fied. All automatic controls and devices should be inspected and actuated periodically to be sure they are operational and that they are properly set. 4.4 The burner should be put into operation according to the followin
40、g recommended steps: a. Make sure the atmosphere is suitable for open flame. The use of a portable combustible gas indicator is recommended. b. Close all gas supply valves for the main burner and pilot. c. Drain fuel gas scrubbers if so equipped. d. Check for an adequate fluid level above the firetu
41、be. En- sure that the firebox and stack are clear and free of foreign debris. e. Open the lighting port of the firebox. Do not stand di- rectly in front of the firetube or the lighting port. Stand to the side, and up-wind, if possible, of the lighting port and end plate of the firetube. Under no cir
42、cumstances should an indi- vidual crawl underneath a heater to light a pilot. f. Determine if combustible gas is present. If a combustible gas indicator is available, check for combustibles in the pilot area and also down the firetube. If combustibles are indi- cated, recheck positive closing on the
43、 valves, wait for the firetube to ventilate, and retest for combustible gases. If a portable combustible gas indicator is not available, then ad- equate purge time, with all gas supply valves closed, must be allowed before trying to light the burner system. When a sat- isfactory gas check has been s
44、ecured, proceed to light the pilot. g. The torch should be premeasured to reach precisely to the pilot. Light the torch using diesel fuel or kerosene. The torch should be of such material that debris will not be left in the firebox after lighting. CAUTION: Do not use gasoline or any other volatile f
45、uel. Pass the torch in front of the opening to check for possible flashback. (If flashback occurs, start over at Step a.) Insert the torch, placing it next to the pilot. Leave the torch in position and slowly open the pilot valve until the pilot ignition is heard. CAUTION: If the pilot does not ligh
46、t in a reasonable period of time, close the pilot valve and begin at Step f. CAUTION: Do not place the torch on the ground as hydro- carbons may be present. 4.5 The flame should be centered in the firetube. The burner should be regulated for continuous firing when possi- ble. The aidgas mixture shou
47、ld be set to provide proper burning quality and to prevent hazardous firetube carbon de- posits. This may require that the system be shut down, ad- justed, and re-lit several times if the adjustments cannot be made without opening the arrestor housing. Remove the torch and extinguish. 5 Maintenance
48、and Inspection 5.1 To maintain proper operation, the flame arrestor should be installed in a sturdy housing which is normally bolted to the firebox entrance. A gasket should be placed be- tween the firebox entrance and the housing to ensure a proper seal. The housing is designed to hold the flame ar
49、- restor element, gas lines, mixer, pilot, and other accessories required for burner operation. Inspection, maintenance, and care of this equipment helps ensure that the equipment oper- ates as intended. 5.2 A flame arrestor element is designed to form air paths of carefully controlled size, configuration and length. Any- thing which changes the size, configuration or length of the air passages may affect arrestor performance. Any air path from the exterior into the firetube which does not pass di- API RP+L2N 74 m 0732270 0537346 4b9 m RECOMMENDED PRACTICE FOR THE OPERATION, MAINTE
