SECTION 2 APPLICATION FUNDAMENTALS
ENVIRONMENTAL CONDITIONS IN NEC CLASS I HAZARDOUS LOCATIONS Section II covers a great number of illustrations which can be applied directly to a hazardous area under consideration to establish the degree and extent of the hazard in the location. The various illustrations are documented in tables and represent a number of cases which normally will exist in petrochemical and chemical plants and related industries for Class I flammable products. The degree and extent of hazard shown in the illustrations are developed on the basis of four specific conditions, as follows: (1) An open or closed source of hazard (2) A heavier- or lighter-than-air flammable product (3) A source of hazard in an indoor or outdoor location (4) A location sufficiently or insufficiently ventilated. The above conditions allow a number of different combinations which are compiled in Table 2-1. Each combination of conditions in Table 2-1 is shown in bold letters and is identified by a code letter. Each code letter represents a specific condition under which a source of hazard can operate. For example, code letter "A" in Table 2-1 represents a condition in which a closed source of hazard handling a heavierthan-air flammable product is located in an indoor location which is sufficiently ventilated. The code letter and each combination of conditions are shown in the Tables 2-2. There are eleven Tables 2-2. Table 2-1. Eleven Different Combinations of Major Conditions A. CLOSED sources of hazard with HEAVIER-than-air gases or vapors in SUFFICIENTLY ventilated INDOOR locations. B. CLOSED sources of hazard with HEAVIER-than-air gases or vapors in INSUFFICIENTLY ventilated INDOOR locations. C. CLOSED sources of hazard with HEAVIER-than-air gases or vapors in SUFFICIENTLY ventilated OUTDOOR locations. D. OPEN sources of hazard with HEAVIER-than-air gases or vapors in SUFFICIENTLY ventilated INDOOR locations. E. OPEN sources of hazard with HEAVIER-than-air gases or vapors in INSUFFICIENTLY ventilated INDOOR locations. F. OPEN sources of hazard with HEAVIER-than-air gases or vapors in SUFFICIENTLY ventilated OUTDOOR locations. G. CLOSED sources of hazard with LIGHTER-than-air gases or vapors in SUFFICIENTLY ventilated INDOOR locations. (continued)
Table 2-1. (continued) H. CLOSED sources of hazard with LIGHTER-than-air gases or vapors in INSUFFICIENTLY ventilated INDOOR locations. I. CLOSED sources of hazard with LIGHTER-than-air gases or vapors in SUFFICIENTLY ventilated OUTDOOR locations. J. CLOSED or OPEN sources of hazard with HEAVIER- or LIGHTER-than-air gases or vapors in SUFFICIENTLY or INSUFFICIENTLY ventilated locations K. CLOSED sources of hazard with HEAVIER-than-air gases or vapors in SUFFICIENTLY or INSUFFICIENTLY ventilated locations. Each Table 2-2 has three vertical columns indicating the following specific features under which a source of hazard will operate. (1) Type of location (2) Size of source of hazard (3) System pressure or density. Each of the three features in combination with the four specific conditions in the title block of Table 2-2 will result in a great number of different cases. These cases are represented by a number of illustrations and are grouped under the same code letter as in Table 2-2. The cases are primarily related to Class I flammable products although some cases will also cover Class II and Class III flammable products. The illustrations are identified as follows. In the top of the illustration, the vapor density of the flammable product is identified as heavier- or lighter-thanair and whether the source of hazard has an open or closed operating mode. At the bottom of the illustration the type of source of hazard is identified and whether the hazardous location for the source of hazard is sufficiently or insufficiently ventilated. Specific environmental conditions and the degree and extent of the hazard are also shown in the illustrations. If the source of hazard in the illustrations is shown in an enclosed location, the location is considered indoors. If the source of hazard is shown in a nonenclosed location, the location is considered outdoors. If the location in the illustration is shown with a roof opening or mechanical fan, it must be understood that the location is sufficiently ventilated. If the location is nonenclosed it must also be understood that the location is sufficiently ventilated by natural ventilation. If the enclosed location is shown without a roof opening or mechanical fan, it is understood that the location is insufficiently ventilated. "Sufficiently ventilated location" means a ventilation system that is satisfactory and in compliance with the ventilation requirements as explained in Chapter 6 of Section I. For mechanical ventilation to operate in a building satisfactorily, its proper
location must be determined on the basis of the actual location of doors, windows, louvers and similar openings and this may require that the mechanical ventilation be placed in the wall or in the roof of the building opposite and as far as possible from these openings. Bear in mind that the mechanical ventilation or vent as shown in the roof or wall of buildings in the illustrations does not intend to indicate its actual location. These buildings merely indicate the presence of sufficient ventilation. Actual locations for mechanical ventilation can be found in Chapter 6 of Section I. To assure that mechanical ventilation provides sufficient ventilation, it is necessary that the ventilation is capable of diluting a flammable gas or vapor in the air to safe concentrations as explained in Chapter 6 of Section I. Sometimes it is necessary to provide the mechanical ventilation with a safeguard. For example, a location adjacent to or within a hazardous area which is required to be classified nonhazardous, could be considered unsafe if not provided with a suitable safeguard even when there is ventilation which is capable of diluting the flammable gas or vapor in the air to safe concentrations. These requirements are also explained in Chapter 6 of Section I. All specific data shown in bold letters in the title block of Tables 2-2 are related to the source of hazard. To establish what illustrations in Section II should be used for a particular hazardous location under consideration, start with Table 2-1. From Table 2-1, determine the four basic requirements under which the source of hazard must operate, such as: 1) Is the system operating mode open or closed? 2) Is the flammable product heavier- or lighter-than-air? 3) Is the source of hazard located indoors or outdoors? and 4) Is the location sufficiently or insufficiently ventilated? For example, assume that the four basic requirements for the source of hazard reads as follows: (1) System operating mode = Closed (2) Vapor density = Heavier-than-air (3) Location = Indoors (4) Ventilation = Insufficient To establish into which category this condition falls, refer to Table 2-1 and find this combination under a code letter. For the above example the combination is covered by code letter "B." Next, refer to Tables 2-2 and find the table with this same code letter. (In this case, Table 2-2J does not apply.) Establish in Table 2-2B the appropriate figure number for the applicable illustration by establishing the three specific requirements for the location of the source of hazard. For this example, assume the following three specific requirements: (1) Type of location = Pump station
(2) Size of the source of hazard = Large (3) System pressure = High The applicable illustration which matched the above requirements in Table 2-2B is narrowed down to one particular illustration which is number B-5. Bear in mind that when the ambient or process temperature for the flammable product is below flashpoint, the location need not be classified. When the temperature is equal or exceeding the flashpoint of the flammable product, then of course, the location is considered hazardous and classification of the location is necessary. Next, consider another example which is not directly related to the source of hazard, but is a control room located adjacent to a hazardous area. To determine the classification for the control room, it is necessary to first determine the type of area the control room will be located in. Follow the preceding steps to determine the four basic requirements: (1) System operating mode = Closed (2) Vapor density = Lighter-than-air (3) Location = Indoors (4) Ventilation = Insufficient Select the applicable code letter from Table 2-1 which in this case is letter "H"o In this case, size of the source of hazard and system pressure is irrelevant. Next, refer to Table 2-2H and determine the applicable figure number. In Table 2-2H there are four control rooms listed: Figures H-3, H-4, H-5 and H-6. As shown in the illustrations, three control rooms are located adjacent to a Div. 1 location, Fig. H-4, H-5 and H-6, and one control room, in Fig. H-3, is above a Div. 1 area. To establish which illustration will apply, consider the following three items: (1) Type of location under consideration = Control room (2) Location of control room = Adjacent to Div. 1 area (3) Access to the adjacent hazardous area? = No Since the control room is located adjacent to a hazardous area, Fig. H-3 does not apply and the fact that the control room has no access to a hazardous area means that only one illustration will apply: Fig. H-4. As shown in Fig. H-4, the control room is non hazardous without being ventilated. A brief explanation of each individual illustration is given in the following pages. Each explanation includes answers to questions which have led to the classification and extent of the hazard for the location involved.
TABLE 2-2 A CLOSED SOURCES HAZARD WITH HEAVIER THAN AIR GASES OR VAPORS IN SUFFICIENTLY VENTILATED INDOOR LOCATIONS FIG. NO. TYPE LOCATION SIZE SOURCE HAZARD SYSTEM PRESSURE OR DENSITY A-1 PUMPHOUSE 0-51 HP AS INDICATED IN FIG. A-1 A-2 PUMPHOUSE 60-201 HP AS INDICATED IN FIG. A-2 A-3 PUMPHOUSE 201 HP AND UP LOW/MOD. A-4 PUMPHOUSE 201 HP AND UP A-5 STORE HOUSE SMALLAND LARGE LOW A-6 STORAGE CONTAINERS MINI OR SMALL - A-7 PIPING SYSTEM LARGEAND MINI MODERATE A-8 PIPING SYSTEM MINI MODERATE
TABLE 2-2 B CLOSED SOURCES HAZARD WITH HEAVIER THAN AIR GASES OR VAPORS IN INSUFFICIENTLY VENTILATED INDOOR LOCATIONS FIG. NO. TYPE LOCATION SIZE SOURCE HAZARD SYSTEM PRESSURE OR DENSITY B-1 PROCESS PLANT LARGE MODERATE B-2 PROCESS PLANT LARGE LOW/MODERATE B-3 PUMPHOUSE 0-51 HP 60-201 HP AS INDICATED IN FIG. B-3 B-4 PUMPHOUSE 0-51 HP 60-201 HP AS INDICATED IN FIG. B-4 B-5 PUMPHOUSE 201 HPANDUP MODERATE B-5 PUMPHOUSE 201 HP AND UP B-6 PUMPHOUSE 201 HPANDUP AS INDICATED IN FIG. B-6
TABLE 2-2 C CLOSED SOURCES HAZARD WITH HEAVIER THAN AIR GASES OR VAPORS IN SUFFICIENTLY VENTILATED OUTDOOR LOCATIONS FIG. NO. TYPE LOCATION SIZE SOURCE HAZARD SYSTEM PRESSURE OR DENSITY C-1 PROCESS PLANT LARGE MODERATE C-2 PROCESS PLANT LARGE C-3 PUMP WELL SMALL LOW C-4 PUMP STATION 0-51 HP LOW/MOD. C-4 PUMP STATION 0-51 HP C-5 PUMP STATION 60-201 HP LOW/MOD. OR C-6 PUMP STATION 201 HP AND UP LOW/MOD. C-6 PUMP STATION 201 HPANDUP C-7 STORAGE TANK SMALL LOW C-8 PITS ANY SIZE ANY PRESSURE
TABLE 2-2 C (CONT.) CLOSED SOURCES HAZARD WITH HEAVIER THAN AIR GASES OR VAPORS IN SUFFICIENTLY VENTILATED OUTDOOR LOCATIONS FIG. NO. TYPE LOCATION SIZE SOURCE HAZARD SYSTEM PRESSURE OR DENSITY C-9 VALVE A SMALL LOW, MODERATE AND C-10 * PUMP STATION ANY SIZE MODERATE C-11 * PUMP STATION SMALL MODERATE AND C-12 MARINE TERMINAL MODERATE - C-13 CONTROL ROOM m LARGE C-14 CONTROL ROOM X LARGE * = PERMANENTIGNITIONSOURCE: C-10 EARLYIGNITION C-11 REMOTE IGNITION H = NOT VENTILATED; NO ACCESS TO HAZARDOUS AREA. x = VENTILATED + SAFEGUARD; ACCESSTOHAZARDOUSAREA. A = REGULARLY OPERATED OR WORKED ON.
TABLE 2-2 D OPEN SOURCES HAZARD WITH HEAVIER THAN AIR GASES OR VAPORS IN SUFFICIENTLY VENTILATED INDOOR LOCATIONS FIG. NO. TYPE LOCATION SIZE SOURCE HAZARD SYSTEM PRESSURE OR DENSITY D-1 DRUM FILLING SMALL LOW D-2 PROCESS EQUIPMENT A O SMALL LOWOR D-3 FUME HOOD ENCLOSURE MINI LOW O = PROVIDED WITH FUME HOOD = FLOOR SPACE IS FOR INDIVIDUAL DRUMS. TABLE 2-2 E (SAME AS TABLE 2-2 D, EXCEPT INSUFFICIENTLY VENTILATED) E-1 DISPENSING AREA SMALL LOW E-2 PROCESS PLANT - LOWOR MODERATE TABLE 2-2 F (SAME AS TABLE 2-2 D, EXCEPT OUTDOOR LOCATION) F-1 OPEN TANK SMALL LOW F-2 STORAGETANK SMALL LOW F-3 STORAGETANK SMALL LOW F-4 IMPOUNDING BASIN MINI VERY LOW F-5 CONTROL ROOM LARGE H NOT VENTILATED; NO ACCESS TO HAZARDOUS AREA. NONE
TABLE 2-2 G CLOSED SOURCES HAZARD WITH LIGHTER THAN AIR GASES OR VAPORS IN SUFFICIENTLY VENTILATED INDOOR LOCATIONS FIG. NO. TYPE LOCATION SIZE SOURCE HAZARD SYSTEM PRESSURE OR DENSITY G-1 COMPRESSOR STATION 60-201 HP VD BELOW 0.75 G-2 CONTROL ROOM 60-201 HP VD BELOW 0.75 G-3 STORAGE AND PROCESS AREA MINI VD BELOW 0.75
TABLE 2-2 H CLOSED SOURCES HAZARD WITH LIGHTER THAN AIR GASES OR VAPORS IN INSUFFICIENTLY VENTILATED INDOOR LOCATIONS FIG. NO. TYPE LOCATION SIZE SOURCE HAZARD SYSTEM PRESSURE OR DENSITY H-1 COMPRESSOR STATION 60-201 HP LOW/MOD. H-2 COMPRESSOR STATION 60-201 HP H-3 CONTROL ROOM # 60 HP AND UP ANY PRESSURE H-4 CONTROL ROOM 60 HP AND UP ANY PRESSURE H-5 CONTROL ROOM A 60 HP AND UP H-6 CONTROL ROOM 60 HP AND UP LOW/MOD. X H-7 COMPRESSOR STATION SMALL LOW/MOD./ NOT VENTILATED; NO ACCESS TO HAZARDOUS AREA. VENTILATED; ACCESS TO HAZARDOUS AREA. VENTILATED + SAFEGUARD; ACCESS TO HAZARDOUS AREA. VENTILATED + SAFEGUARD.
TABLE 2-2 I CLOSED SOURCES HAZARD WITH LIGHTER THAN AIR GASES OR VAPORS IN SUFFICIENTLY VENTILATED OUTDOOR LOCATIONS FIG. NO. TYPE LOCATION SIZE SOURCE HAZARD SYSTEM PRESSURE OR DENSITY 1-1 COMPRESSOR STATION 0-51 HP 1-1 COMPRESSOR STATION 60-201 HP LOW/MOD./ I-2 COMPRESSOR STATION 0-51 HP LOW/MOD. I-2 COMPRESSOR STATION 0-51 HP I-3 HYDROGEN GAS STORAGE MINI - I-4 COMPRESSOR STATION 0-51 HP LOW/MOD. I-5 CONTROL ROOM El ANY SIZE VD BELOW 0.75 NOT VENTILATED; BELOW HAZARDOUS AREA. VD = < 0.75
TABLE 2-2 J CLOSED OR OPEN SOURCES HAZARD WITH HEAVIER OR LIGHTER THAN AIR GASES OR VAPORS IN SUFFICIENTLY OR INSUFFICIENTLY VENTILATED LOCATIONS FIG. NO. TYPE LOCATION SIZE SOURCE HAZARD SYSTEM PRESSURE OR DENSITY J-1A PIT ANY SIZE - J-1B PIT ANY SIZE - J-2 LOADING/ UNLOADING - SEETABLE FIG. J-2 J-3A/B PUMPHOUSE ANY SIZE - J-3C PUMPHOUSE ANY SIZE - J-4 SAFE DISTANCES FOR GAS FILLED CYLINDERS MINI - J-5 ACCESSTOA DIV. 2 HAZARDOUS BOUNDARY LARGE - J-6 PIPING SYSTEM MINI LOW, MOD. OR J-7 BRUSHING AND NON BRUSHINGAIR MINI MODERATE J-8 PROCESS PLANT SMALLOR LARGE LOW, MOD. OR J-9 SAFE DISTANCES PROCESS PLANT SMALL LOW, MOD. OR J-10 LOW AND INTEGRITY SEAL FITTINGS MINI LOW, MOD. OR J-11 SAFE DISTANCES FOR H2 GAS MINI MODERATE OR TABLE 2-2 K CLOSED SOURCES HAZARD WITH HEAVIER THAN AIR GASES OR VAPORS IN SUFFICIENTLY OR INSUFFICIENTLY VENTILATED LOCATIONS K-1 PIPING SYSTEM SEE FIG. K-1 SEE FIG. K-1 K-2 PIPING SYSTEM SEE FIG. K-2 SEE FIG. K-2
2.1 GENERAL REQUIREMENTS FOR GROUP A Group A represents closed sources of hazard that contain "Class I flammable products" with heavier-than-air gases or vapors located indoors that are sufficiently ventilated and which are classified in accordance with the information in Section I. Figure A-I 0 The major requirements for classifying the location as shown in Fig. A-I are as follows: Items pertaining to the degree of danger: Bl - type of product = flammable liquid Cl - system operating mode = closed Dl - location with/without source of hazard = with D2 - above or below grade = above D3 - how is location considered = indoors D4 - no. vapor tight walls of location = 3 D5 - type of location = pumphouse El - type of ventilation = exhaust E3 - amount of ventilation = sufficient Fl - how isflammablegas/vapor released = occasional Items pertaining to the extent of danger: Al - type of source of hazard = pump A2 - size of source of hazard = small B5 - flammability class = I B6 - vapor density = heavier-than-air C5 - system pressure = moderate D6 - floor space occupied = 50% F5 - pump driver and size = 50 hp A sufficiently ventilated pump station which contains small sources of hazard may be classified Div. 2 for 50% or 100%. The choice between both types of classifications is a function of the magnitude of the explosion danger. This magnitude of explosion danger is expressed in a probability factor which, as explained in Section J of Chapter 3, is below 10 or 10 and above. If the probability factor is less than 10, the explosion danger is considered small and the pump station should be classified for 50%. If the probability factor is 10 or more, the explosion danger is considered large and requires a 100% classification. As explained in Section J of Chapter 3, the probability factor is expressed in PU value and depends on four major conditions: 1) pump size, 2) floor space
CLOSED SYSTEM HEAVIER THAN AIR VAPORS EXHAUST FAN PIERCED WALL CLASSIFICATION THIS LOCATION = 50% (ITEM "A") FLOOR SPACE OCCUPIED CLASS 1 DIV. 1 CLASS 1 DIV. 2 UNCLASSIFIED X = WILL EXTEND BEYOND BUILDING OPENING. ITEM NO. FLOOR SPACE OCCUPIED IN PERCENT SYSTEM PRESSURE INPSI EXTENT DANGER AREA, FEET CLASSIFICATION LOCATION IN PERCENT EXPLOSION PROBABILITY FACTOR PU A 50 LOW/MOD. OR 25 50 3/5/8 B 75 LOW/MOD. 25 O 50 4/7 C 100 LOW/MOD. 50 5/9 D 75 25 100 11 E 100 O MAY BE LESS THAN 25 FT FOR LOW AND MOD. IF PUMP IS AIR BRUSHED 25 100 x 14 FIG. A-1. PUMPHOUSE WITH SMALL PUMPS (0-51 HP) HANDLING CLASS I FLAMMABLE LIQUID (SUFFICIENTLY VENTILATED LOCATION)
occupied, 3) pressure in the system and 4) whether flammable vapors could accumulate in the pump station when there is a pump failure. Since the pump station in Fig A-I is sufficiently ventilated, accumulation of flammable vapors is not an issue. Based on the information given in the table above, the probability factor for the pump station in Fig A-I is determined as follows: a Floor space occupied = 50% = 2 PU b System pressure = moderate = 2 PU c Quantity of release = small = 1 PU The probability factor for the above conditions is axb + c or 2x2 + 1 = 5 PU. Since the probability factor is 5 PU, the classification of the pump station in Fig. A-I needs to be 50% Div. 2. The boundary dimensions for pumps rated 50 Hp and below, operating at moderate system pressure shall be 5 V, 25 Ho and 3 Hi as shown in Fig. A-I. In view of this dimension and the fact that the floor space is for 50% occupied, no additional danger zone is necessary. The classification and extent of hazard for the pump station is in compliance with the following: Figure A-2. Table Item Figure Item 1-3 8 1-3 F 1-4A 1 The major requirements for classifying the location as shown in Fig. A-2 are as follows: Items pertaining to the degree of danger: Bl - type of product = flammable liquid Cl - system operating mode = closed Dl - location with/without source of hazard = with D2 - above or below grade = above D3 - how is location considered = indoors D4 - no. vapor tight walls of location = 3 D5 - type of location = pumphouse El - type of ventilation = exhaust E3 - amount of ventilation = sufficient Fl - how isflammablegas/vapor released = occasional Items pertaining to the extent of danger: Al - type of source of hazard = pump (continued)
Figure A-2. (continued) Items pertaining to the extent of danger: A2 - size of source of hazard = small B5 - flammability class = I B6 - vapor density = heavier-than-air C5 - system pressure = high D6 - floor space occupied = 50% F5 - pump driver and size = 60 Hp A sufficiently ventilated pump station which contains small sources of hazard may be classified Div. 2 for 50% or 100%. The choice between both types of classifications is a function of the magnitude of the explosion danger. This magnitude of explosion danger is expressed in a probability factor which, as explained in Section J of Chapter 3, is below 10 or 10 and above. If the probability factor is less than 10, the explosion danger is considered small and the pump station should be classified for 50%. If the probability factor is 10 or more, the explosion danger is considered large and requires a 100% classification. As explained in Section J of Chapter 3, the probability factor is expressed in PU value and depends on four major conditions: 1) pump size, 2) floor space occupied, 3) pressure in the system and 4) whether flammable vapors could accumulate in the pump station when there is a pump failure. Since the pump station in Fig A-2 is sufficiently ventilated, accumulation of flammable vapors is not an issue. Based on the information given in the table above, the probability factor for the pump station in Fig A-2 is determined as follows: a Floor space occupied = 50% = 2 PU b System pressure = high = 3 PU c Quantity of release = large = 3 PU The probability factor for the above conditions is axb + c or 2x3 + 3 = 9 PU. Since the probability factor is 9 PU, the classification of the pump station in Fig. A-2 needs to be 50% Div. 2. The boundary dimensions for pumps ranging from 60 Hp and up, operating at high system pressure shall be 5 V, 50 Ho and 3 Hi as shown in Fig. A-2. In view of this dimension and the fact that the floor space is for 50% occupied, an additional danger zone is necessary. The classification and extent of hazard for the pump station is in compliance with the following:
CLOSED SYSTEM HEAVIER THAN AIR VAPORS EXHAUST FAN PIERCED WALL CLASSIFICATION THIS LOCATION = 50% (ITEM T) FLOOR SPACE OCCUPIED CLASS 1 DIV. 1 CLASS 1 DIV. 2 UNCLASSIFIED X = WILL EXTEND BEYOND BUILDING OPENING. ITEM NO. FLOOR SPACE OCCUPIED IN PERCENT SYSTEM PRESSURE INPSI EXTENT DANGER AREA, FEET CLASSIFICATION LOCATION IN PERCENT EXPLOSION PROBABILITY FACTOR PU F 50 LOW/MOD. 25 50 4/6 G 75 LOW/MOD. 25 50 5/8 H 100 LOW/MOD. 25 X 50 6/10 I 50 50 50 9 J 75 OR 100 50 X 100 12/15 FIG. A-2. PUMPHOUSE WITH SMALL PUMPS (60-201 HP) HANDLING CLASS I FLAMMABLE LIQUID (SUFFICIENTLY VENTILATED LOCATION)
Figure A-3. Table Item Figure Item 1-3 8 1-3 H 1^A 2 1-9 I The major requirements for classifying the location as shown in Fig. A-3 are as follows: Items pertaining to the degree of danger: Bl - type of product = flammable liquid Cl - system operating mode = closed Dl - location with/without source of hazard = with D2 - above or below grade = above D3 - how is location considered = indoors D4 - no. vapor tight walls of location = 4 D5 - type of location = pumphouse El - type of ventilation = exhaust E3 - amount of ventilation = sufficient Fl - how isflammablegas/vapor released = occasional Items pertaining to the extent of danger: Al - type of source of hazard = pumps A2 - size of source of hazard = large B5 - flammability class = I B6 - vapor density = heavier-than-air C5 - system pressure = low to moderate F5 - pump driver and size = Elect, motor, 201 hp and up The basis for entirely classifying the pump station is the large size of the source of hazard. The reason for classifying the pump station Div. 2 is the presence of sufficient ventilation. The extent of the Div. 2 area shall be 50 feet horizontal because of items A2, Bl, B5, B6 and C5. Since the Div. 2 classification extends to the perimeter of the pump station, an additional danger zone of 10 feet wide is required at any opening of the pump station such as a door opening, nonbolted windows, louvers for inlet air or any other openings which may release flammable gases or vapors to the outdoors under ventilation failure. In addition to the 10 feet wide additional danger zone, the horizontal boundary must extend to its full length beyond any opening of the pump station if the boundary extends to the outdoors. The additional danger zone and the boundary outdoors also may be classified Div. 2.
CLOSED SYSTEM HEAVIER THAN AIR VAPORS EXHAUST FAN AIR PENETRATION VAPORTIGHT WALL SOURCE HAZARD AIR LOUVRES PIT 201 HP AND UP CLASS 1 DIV. 1 CLASS 1 DIV. 2 UNCLASSIFIED FIG. A-3. PUMPHOUSE WITH MAIN PUMPS HANDLING FLAMMABLE LIQUID AT LOW OR MODERATE PRESSURE (SUFFICIENTLY VENTILATED LOCATION)
The classification and extent of hazard for the pump station is in compliance with the following: Figure A-4. Table Item Figure Item 1-3 8 1-3 I 1-4A 3 1-8 C The major requirements for classifying the location as shown in Fig. A-4 are as follows: Items pertaining to the degree of danger: Bl - type of product = highly-volatile liquid Cl - system operating mode = closed Dl - location with/without source of hazard = with D2 - above or below grade = above D3 - how is location considered = indoors D4 - no. vapor tight walls of location = 3 D5 - type of location = pumphouse El - type of ventilation = exhaust E3 - amount of ventilation = sufficient Fl - how isflammablegas/vapor released = occasional Items pertaining to the extent of danger: Al - type of source of hazard = pumps A2 - size of source of hazard = large B5 - flammability class = I B6 - vapor density = heavier-than-air C5 - system pressure = high F5 - pump driver and size = Elect, motor, 201 hp and up The basis for entirely classifying the pump station in Fig. A-4 is the large size of the source of hazard. The reason for classifying the pumpstation Div. 2 is the presence of sufficient ventilation. The extent of the Div. 2 area shall be 100 feet horizontal because of items A2, Bl, B5, B6 and C5. Since the Div. 2 classification extends to the perimeter of the pump station, an additional danger zone of 10 feet wide is required at any opening of the pump station such as a door opening, nonbolted windows, louvers for inlet air or any other opening which may release flammable gases or vapors to the outdoors under ventilation failure. In addition to the 10 feet wide additional danger zone, the horizontal boundary must extend to its full length beyond any opening of the pump station
CLOSED SYSTEM HEAVIER THAN AIR VAPORS EXHAUST FAN SOURCE HAZARD: VAPORTIGHT WALL AIR PENETRATION 201 HP AND UP PIT CLASS 1 DIV. 1 CLASS 1 DIV. 2 UNCLASSIFIED FIG. A-4. PUMPHOUSE WITH MAIN PUMPS HANDLING VOLATILE LIQUID AT PRESSURE (SUFFICIENTLY VENTILATED LOCATION)
if the boundary extends to the outdoors. The additional danger zone and the boundary outdoors may also be classified Div. 2. The classification and extent of hazard for the pump station is in compliance with the following: Figure A-5. Table Item Figure Item 1-3 8 1-3 J 1-4A 4 1-8 C The major requirements for classifying the location as shown in Fig. A-5 are as follows: Items pertaining to the degree of danger: Bl - type of product = flammable liquid Cl - system operating mode = closed Cl - equipment regularly worked on = no C5 - system pressure = low Dl - location with/without source of hazard = with D2 - above or below grade = above and below D3 - how is location considered = indoors D4 - no. vapor tight walls of location = 2 D5 - type of location = liquid warehouse El - type of ventilation = natural or electric Fl - how isflammablegas/vapor released = accidently Items pertaining to the extent of danger: Al - type of source of hazard = drums, containers A2 - size of source of hazard = small B5 - flammability class = I, II, and III B6 - vapor density = heavier- and lighterthan-air The liquid warehouse shown in Fig. A-5 is a separate building for storing flammable liquid. Liquid warehouses may store Class I, II, and III flammable liquids, if the containers and portable tanks meet DOT regulations and/or ANSI and ASTM standards. However, Class IA flammable liquids may not be stored in portable tanks (660 gal. max.) without automatic fire fighting facilities and Class I liquid is prohibited in the basement. Class II and III liquids may be stored in a basement if this basement is provided with an automatic sprinkler system and other fire fighting facilities. Suitable fire extinguishers and or hose lines shall be installed throughout the building. Dispensing of Class I and II liquid is not permitted unless the dispensing area is cut off from the storage area and suitably
CLOSED SYSTEM HEAVIER THAN AIR VAPORS GRAVITY OR ELECTRIC FAN STOREHOUSE VEHICLE SUITABLE CONTAINERS FILLED WITH VOLATILE LIQUID SUITABLE VESSELS FILLED WITH VOLATILE LIQUID CLASS 1 DIV. 1 CLASS 1 DIV. 2 UNCLASSIFIED FlG. A-5. DETACHED LIQUID WAREHOUSE (ADEQUATELY VENTILATED LOCATION)
ventilated. The liquid warehouse need not be classified provided flammable liquid is stored in metal containers meeting DOT regulations or in nonbreakable plastic containers meeting the requirements of ANSI and ASTM standards as follows: (1) Metal drums of 60 gal. maximum for Class I, II and III liquid. (2) Approved metal portable tanks of 660 gal. maximum for all classes except Class IA unless protected by fire fighting facilities. (3) Approved plastic containers of 1 gal. for Class IA and 5 gal. for Class IB, IC, II and III. (4) Approved polyethylene containers of 1 gal. for Class IA, 5 gal. for Class IB and IC and 60 gal. for Class II and III. (5) Ventilation may be provided, either by means of a gravity fan or electric exhaust fan. For Class I liquid and/or Class II and III liquid with temperatures above flashpoint dilution of flammable gases or vapors shall be the same as for storage rooms inside a building. (Refer to Fig. A-6.) An arcing device within 3 feet of any container containing flammable liquid shall be provided with an enclosure suitable for a Div. 1 location. The classification and extent of hazard for the warehouse is in compliance with Table 1-4, Subtable A item 5. Figure A-6. The enclosed room in Figure A-6 is a room without external walls inside a building for storing flammable liquid. a. Classified Nonhazardous The enclosed room may be classified nonhazardous if used only for storage of Class II and III flammable liquids in: (1) metal DOT type containers of 60 gal. maximum (2) metal nondot type containers of 5 gal. maximum (3) glass containers of 1 gal for Class II and 5 gal for Class III (4) approved plastic containers of 5 gal. maximum (5) safety cans of 5 gal maximum (6) polyethylene DOT type containers of 60 gal maximum (7) approved portable metal tanks of 660 gal. maximum. (continued)
CLOSED SYSTEM HEAVIER THAN AIR VAPORS UNPROTECTED STORAGE ROOM NOT OVER 500 SQ. FT. GRAVITY OR MECHANICAL FAN CLASS IA CLASS IB LIMITED TO 22 CONTAINERS 60 GAL EACH DOT SPEC. DRUMS AND CONTAINERS CLASS 1 DIV 1 CLASS 1 DIV 2 UNCLASSIFIED UNCLASSIFIED WHEN CLASS Il AND III LIQUID IS STORED IN SUITABLE AND NON BREAKABLE CONTAINERS OR IF TEMPERATURE IS BELOW FLASHPOINT. VENTILATION REQUIRED ONLY IF LIQUID IS DISPENSED OR F CLASS AND m L Q(j D IS STORED IN NON SUITABLE AND/OR BREAKABLE CONTAINERS. FIG. A-6. STORAGE ROOM FOR FLAMMABLE LIQUID INSIDE A BUILDING, VENTILATED
b. Classified Div. 2 The storage room must be classified Div. 2 if the room stores Class I flammable liquids in: (1) metal DOT type containers of 60 gal maximum (2) metal non DOT type containers of 1 gal. for Class IA and 5 gal. for Class IB and IC (3) glass containers of 1 pt. for Class IA, 1 qt. for Class IB and 1 gal. for Class IC (Class IA and CLass IB liquids may be stored in glass containers of not more than 1 gal. capacity if the required liquid purity would be affected by storage in metal containers.) (4) approved plastic containers of 1 gal. for Class IA and 5 gal. for Class IB and IC (5) safety cans of 2 gal. for Class IA and 5 gal. for Class IB and IC (6) polyethylene DOT type containers of 1 gal. for Class IA and 5 gal. for Class IB and IC (7) approved portable tanks of 660 gal. maximum for all classes except for Class IA unless provided with sprinkler system. Storage rooms are classified non hazardous if Class II and III liquid is stored in suitable, non breakable containers, or in non suitable and breakable containers with location sufficiently ventilated, or if the temperature is below flashpoint. Exhaust air shall be provided from one or two points located on one side of the wall, with an air inlet on the opposite wall. The location of the room air outlet is dependent on the vapor density of the flammable product. c. Storage in the Basement The storage of Class I flammable liquid is prohibited. The storage of Class II and III liquid is permitted if the basement is provided with automatic sprinkler systems and other fire protection facilities. The classification and extent of hazard for the storage area is in compliance with Table 1-4A, Subtable item 6. Figure A-7. The major requirements for classifying the location as shown in Figure A-7 are as follows: Items pertaining to the degree of danger: Bl - type of product = flammable liquid (continued)
CLOSED SYSTEM HEAVIER THAN AIR VAPORS LARGE SOURCES HAZARD 1O 1 RAD. 1O 1 RAD. 3' RAD. MINI SOURCE HAZARD PIPING SYSTEM FLANGE VALVE FITTING AND METER CLASS 1 DIV. 1 CLASS 1 DIV. 2 UNCLASSIFIED ENTIRE INDOOR LOCATION IS CLASSIFIED DIV. 2 F OPERATING AT PRESSURE. FIG. A-7. PIPING SYSTEM WITH SCREWED FITTINGS, BOLTED FLANGES, VALVES AND METERS, OPERATING AT MODERATE PRESSURE. (SUFFICIENTLY VENTILATED LOCATION)
Figure A-7: (continued) Cl - system operating mode = closed C2 - equipment regularly worked on = no Dl - location with/without source of hazard = with D2 - above or below grade = above D3 - how is location considered = indoors D4 - no. vapor tight walls of location = 4 D6 - floor space occupied = not more than 50% El - type of ventilation = exhaust fan E3 - amount of ventilation = sufficient Fl - how is flammable gas/vapor released = occasional Items pertaining to the extent of danger: Al - type of source of hazard = piping system A2 - size of source of hazard = large B5 - flammability class = I B6 - vapor density = heavier-than-air C5 - system pressure = moderate The location in Fig. A-7 contains a piping system with a number of large sources of hazard. Each individual component of the piping system is allowed to be classified Div. 2 because of: 1) its closed operating mode, item Cl; 2) the occasional release of flammable vapors in case the components should break down, item Fl; and 3) because of the sufficient ventilation in the location, items El and E3. The extent of the Div. 2 area shall be as follows. Since the individual components of the piping system are large, item A2, and are operating at moderate pressure, item C5, and not more than 50% floor space is occupied, item D6, the extent of the danger zone shall be 10 feet vertical and 25 feet horizontal, 18" high as shown in Fig. A-7. If the piping system is operating at high pressure or if more than 50% of the floor space is occupied, the entire location must be classified Div. 2. The classification and extent of hazard for the location is in compliance with Table 1-4A, item 7 and with Fig. K-I. Figure A-8. The major requirements for classifying the location as shown in Fig. A-8 are as follows: Items pertaining to the degree of danger: Bl - type of product = flammable liquid (continued)
Cl - system operating mode = closed C2 - equipment regularly worked on = no Dl - location with/without source of hazard = with D2 - above or below grade = above D3 - how is location considered = indoors D4 - no. vapor tight walls of location = 4 D6 - floor space occupied = not more than 50% El - type of ventilation = exhaust fan E3 - amount of ventilation = sufficient Fl - how is flammable gas/vapor released = occasional Items pertaining to the extent of danger: Al - type of source of hazard = piping system A2 - size of source of hazard = mini B5 - flammability class = I B6 - vapor density = heavier-than-air C5 - system pressure = moderate The location in Fig. A-8 contains a piping system with a number of mini sources of hazard. Each individual component of the piping system is allowed to be classified Div. 2 because of: 1) its closed operating mode, item Cl; 2) the occasional release of flammable vapors in case the components should break down, item Fl; and 3) because of the sufficient ventilation in the location, items El and E3. The extent of the Div. 2 area shall be as follows. Since the individual components of the piping system are of the mini type, item A2, and are operating at moderate pressure, item C5, and not more than 50% of the floor space is occupied, item D6, the extent of the danger zone shall be 3 feet horizontal and 3 feet vertical. If the distance between the source of hazard and the floor is 3 feet or slightly over 3 feet the danger zone shall be extended all the way to the floor as shown in Fig. A-8. If the piping system is operating at high pressure and does not occupy more than 50% of the floor space, the extent of the Div. 2 area shall be 5Ra, 15 Ho, 18" High. If the piping system is operating at high pressure and occupying more than 50% floor space, the entire location must be classified Div. 2. The location does not have to be classified if the probability factor is 5 or less and the mini sources of hazard are well maintained. The classification and extent of hazard for the location is in compliance with Table 1-4A, item 8 and with Fig. K-I.
CLOSED SYSTEM HEAVIER THAN AIR VAPORS MINI SOURCES HAZARD PIPING SYSTEM FLANGE VALVE FITTING AND METER CLASS 1 DIV. 1 CLASS 1 DIV. 2 UNCLASSIFIED ENTIRE INDOOR LOCATION IS CLASSIFIED DIV. 2 IF OPERATING AT PRESSURE AND MORE THAN 50% FLOOR SPACE IS OCCUPIED. FIG. A-8. PIPING SYSTEM WITH SCREWED FITTINGS, BOLTED FLANGES, VALVES AND METERS, OPERATING AT MODERATE PRESSURE. (SUFFICIENTLY VENTILATED LOCATION)