2.9 GENERAL REQUIREMENTS FOR GROUP I

Transcription

1 2.9 GENERAL REQUIREMENTS FOR GROUP I Group I represents closed sources of hazard that contain Class I flammable products with lighter-than-air gases or vapors located outdoors that are sufficiently ventilated and which are classified in accordance with the information in Section I. Figure 1-1. The major requirements for classifying the location as shown in Fig. 1-1 are as follows: Items pertaining to the degree of danger: Bl - type of product = flammable gas Cl - system operating mode = closed Dl - location with/without source of hazard = with D2 - above or below grade = above D3 - how is location considered = outdoors D5 - type of location = compressor station El - type of ventilation = natural 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 = compressor B6 - vapor density = lighter-than-air F5 - pump driver and size = as indicated in Fig. 1-1 Figure 1-1 represents a gas compressor located outdoors pumping flammable gas. Since the gas compressor is located outdoors, item D3, the location is considered sufficiently ventilated by natural ventilation, items El and E3. Because the gas compressor has a closed system and is located outdoors, the location for the gas compressor can be classified Div. 2. Since the flammable material in the gas compressor is lighter than air, the extent of the hazard horizontally need only be 15 feet for compressors rated up to 51 Hp, operating at high pressure and 25 feet for compressors rated between 50 and 201 Hp, operating at low or moderate pressure. The classification and extent of hazard for the location is in compliance with the following: Table Item Figure Item For low or moderate pressure ,3 1-2 A,C For high pressure ,2,4 1-2 B,C

2 CLOSED SYSTEM LIGHTER THAN AIR VAPORS SOURCE OF HAZARD CLASS 1 DIV. 1 CLASS 1 DIV. 2 UNCLASSIFIED X = 15 FEET FOR HIGH PRESSURE (UP TO 51 HP) x = & ^pqr ^MODERATE QR HIGH PRESSURE OR COMPRESSED LIQUIFIED FLAMMABLE GASES (60 HP-201 HP) FIG COMPRESSOR STATION HANDLING FLAMMABLE GASES OUTDOORS

3 Figure 1-2. The major requirements for classifying the location as shown in Fig. 1-2 are as follows: Items pertaining to the degree of danger: Bl - type of product = flammable gas Cl - system operating mode = closed Dl - location with/without source of hazard = with D2 - above or below grade = above D3 - how is location considered = outdoors D5 - type of location = compressor station El - type of ventilation = natural E3 - amount of ventilation = sufficient Fl - how isflammablegas/vapor released = occasional Items pertaining to the extent of danger: Al - type of source of hazard = compressor B6 - vapor density = lighter than air F5 - pump driver and size = as indicated in Fig. 1-2 Figure 1-2 represents a gas compressor located outdoors pumping flammable gas. Since the gas compressor is located outdoors, item D3, the location is considered sufficiently ventilated by natural ventilation, items El and E3. Because the gas compressor has a closed system and is located outdoors, the location for the gas compressor can be classified Div. 2. Since the flammable material in the gas compressor is lighter than air, the extent of the hazard horizontally need only be 10 feet for compressors rated up to 51 Hp, operating at low and moderate pressure, and 15 feet for compressors rated up to 51 Hp operating at high pressure. The classification and extent of hazard for the location is in compliance with the following: Table Item Figure Item For low or moderate pressure A For high pressure B Figure 1-3. Figure 1-3 represents an outdoor storage area for storing more than 400 CF of hydrogen gas. (CF = cubic feet of gas at psia and 7O 0 F.) The general safety requirement for hydrogen gas is to maintain a minimum safe clearance of 15 or 25 feet around the storage cylinders. The 25 feet clearance is required if ventilating air is obstructed.

4 CLOSED SYSTEM LIGHTER THAN AIR VAPORS SOURCE OF HAZARD CLASS 1 DIV. 1 CLASS 1 DIV. 2 UNCLASS.FIED X = 10 FEET FOR LOW AND MODERATE PRESSURE (UP TO 51 HP) x = ^ ^ FQR ^ pressure QR COMPRESSED LIQUIFIED FLAMMABLE GASES (UP TO 51 HP) FIG COMPRESSOR STATION HANDLING FLAMMABLE GASES OUTDOORS

5 CLOSED SYSTEM LIGHTER THAN AIR VAPORS riao CLASSI>DIV q,nivi ' 1 CLASS I, DIV. 2 UNCLASSIFIED X = 15 ft. WITH UNOBSTRUCTED NATURALAIRFLOW X = 25 ft. WITH OBSTRUCTED AIR FLOW FIG STORAGE CYLINDERS FOR GASEOUS HYDROGEN LOCATED OUTDOORS

6 Electrical equipment may be of the general purpose type if they are located outside the 15 or 25 feet boundary. Within the 15 or 25 feet boundary the electrical equipment is required to be suitable for a Class I, Div. 2 location. The storage cylinders for the hydrogen gas are not to be considered the actual source of hazard. Valves, screwed fittings, and gauges are normally the actual source of hazard. As an additional safety precaution, storage cylinders for hydrogen gas shall not be located underneath power lines or below piping systems containing flammable and combustible liquids. Where flammable and combustible liquids are involved a minimum horizontal safe distance of 25 feet must be maintained between the two. The classification and extent of hazard for the location is in compliance with the following: Figure 1-4. Table Item The major requirements for classifying the location as shown in Fig. 1-4 are as follows: Items pertaining to the degree of danger: A2 - size of source of hazard = small Bl - type of product = flammable gas Cl - system operating mode = closed Dl - location with/without source of hazard = with D2 - above or below grade = above D3 - how is location considered = outdoors D4 - number of vapor-tight walls of location = none, except upper part D5 - type of location = compressor station El - type of ventilation = natural E3 - amount of ventilation = sufficient Fl - how isflammablegas/vapor released = occasional Items pertaining to the extent of danger: Al - type of source of hazard = compressor B6 - vapor density = lighter-than-air C5 - system pressure = low or moderate F5 - pump driver and size = electric, 0-51 Hp F7 - probability factor = 5 Pu Figure 1-4 represents a shelter for gas compressors operating at low or moderate pressure. Since the shelter virtually has no walls it is considered an outdoor location, item D3. When the gas compressor breaks down, flammable

7 CLOSED SYSTEM LIGHTER THAN AIR VAPORS VAPOR TIGHT WALL!SOURCE OF HAZARD ROOF SUPPORT CLASS 1 DlV. 1 FLOORSPACEOCCUPIED =50% = 2 PU CLASS 1DlV 2 SYSTEMPRESSURE = MODERATE = 2 PU GAS RELEASE = SMALL = 1 PU UNCLASSIFIED TOTAL PROBABILITY FACTOR = 5 PU FIG. I-4. COMPRESSOR STATION WITHOUT WALLS HANDLING FLAMMABLE GAS AT LOW OR MODERATE PRESSURE (SUFFICIENTLY VENTILATED GAS STATION)

8 gases will escape from the gas compressor and since the gases are lighter than air, item B6, the gas will rise to the roof of the shelter. Because the roof of the shelter is open, no accumulation of flammable gases will occur under the roof of the shelter. Because the area under the roof is sufficiently ventilated, it may be classified Div. 2. The extent of the Div. 2 hazard above the roof shall be 15 feet horizontally and 25 feet vertically. At the source of hazard, the boundary shall also extend 15 feet horizontally. No additional danger zones are necessary since the 15 feet horizontal distance is shorter than the distance between the source of hazard and the outer perimeter of the building. Only when the location in the shelter is entirely classified is an additional danger zone required. The classification and extent of hazard for the location is in compliance with the following: Figure 1-5. Table Item The major requirements for classifying the location as shown in Fig. 1-5 are as follows: Items pertaining to the degree of danger: Bl - type of product = flammable gas Cl - system operating mode = closed Dl - control room without source of hazard = yes D3 - how is location considered = indoors D4 - number of walls of control room = 4 D5 - type of location = control room El - type of ventilation in control room = none Fl - how isflammablegas/vapor released = occasional Items pertaining to the extent of danger: Al - type of source of hazard = gas compressor B6 - vapor density = below 0.75 Figure 1-5 represents a control room located under a compressor station which is classified Div. 2. The control room in Fig. 1-5 is without ventilation and does not have to be classified. The reason for this is that the control room does not give access to a hazardous area, but most importantly the vapor density of the flammable product in the compressor station is below A vapor density of below 0.75 will cause a flammable gas in the air to rise quickly. These gases in the air, therefore, cannot enter the control room and in view of this, the control room is allowed to be classified nonhazardous without

9 ventilation. The classification and extent of hazard for the location is in compliance with the following: Table Item

10 CLOSED SYSTEM LIGHTER THAN AIR VAPORS SOURCE OF HAZARD CONTROL ROOM CLASS 1 DIV. 1 VAPOR DENSITY OF FLAMMABLE SUBSTANCE CLASS 1D,V. 2 is BELOW UNCLASSIFIED FIG. I-5. CONTROL ROOM BELOW DIV. 2 HAZARDOUS AREA (INSUFFICIENTLY VENTILATED CONTROL ROOM)

11 2.10 GENERAL REQUIREMENTS FOR GROUP J Group J represents open or closed sources of hazard that contain Class I flammable products with heavier- or lighter-than-air gases or vapors located in sufficiently or insufficiently ventilated locations and which are classified in accordance with the information in Section I. Figure J-I. Figure J-I represents two pits below finished grade located outdoors adjacent to a source of hazard. The pits must be classified as follows. If a pit is located in a hazardous area in which flammable gases or vapors released to the atmosphere have a vapor density greater than 0.75, the pit must be classified Div. 1 as shown in Fig. J-IA. The reason for this classification is that with a vapor density greater than 0.75 the gas or vapor will accumulate in the pit. The pit within the hazardous area can be classified nonhazardous if the flammable gases or vapors in the hazardous area have a vapor density below 0.75 as shown in Fig. J-IB. The reason for this classification is that airborne flammable gases or vapors with vapor densities below 0.75 will quickly rise when exposed to the open and, therefore, will not accumulate in the pit. The classification and extent of hazard for the location is in compliance with the following: Figure J-2. Table Item 1^J 1 and 2 Figure J-2 represents a loading platform for handling flammable liquid with heavier-than-air gases or vapors. A loading platform is normally part of a bulk storage plant which receives flammable and combustible liquid that is distributed to other locations by tank cars, tank vessels or pipe lines. The loading of the flammable product is either at the top or bottom of the tank car, with or without an atmospheric vent or recovery system. The degree and extent of the hazard is as indicated in columns 5 and 6 of the table in Fig. J-2. The classification and extent of hazard for the location is in compliance with: Figure J-3. Table Item 1-4J 2 Figure J-3 represents a building which is divided into two separate areas. One area is a pumphouse handling liquefied petroleum gas, and the other area is an adjacent location. Liquid petroleum gas (LP-gas) includes a material with a vapor

12 CLOSED SYSTEM HEAVIER AND LIGHTER THAN AIR VAPORS V.D. GREATER THAN 0.75 SOURCE OF HAZARD A (SEE ALSO FIG. C-8) SOURCE OF HAZARD V.D. SMALLER THAN 0.75 CIJVSS 1 DIV. 1 CLASS 1 DIV. 2 UNCLASSIFIED FIG. J-1. PITS IN OUTDOOR, DIV. 2 LOCATIONS

13 CLOSED/OPEN SYSTEM HEAVIER THAN AIR VAPORS ITEM NO. LOCATION LOADING AND UNLOADING PRESSURE CLOSEDOR OPEN WlTHOR WITHOUT ATM. VENT. WITHOR WITHOUT RECOVERYSYSTEM DEGREEANDEXTENT OFHAZARD DIV. 1 DIV. 2 1 TOP LOW CLOSED WITHOUT WITH O 3R 2 BOTTOM LOW CLOSED WITHOUT WITH O 3 V, 10 HO, 18Hl 3 TOP LOW OPEN WITH WITHOUT 3R 15V 15HO 4 TOP HIGH CLOSED WITHOUT WITH 5R 15V 15HO CLASS 1 DIV. 1 CLASS 1 DIV. 2 UNCLASSIFIED FIG. J-2 LOADING/UNLOADING PLATFORM, OUTDOORS FOR FLAMMABLE LIQUID

14 CLOSED SYSTEM HEAVIER THAN AIR VAPORS NON VAPOR TIGHT WALL ADJACENT ROOM VAPOR TIGHT WALL SOURCE OF HAZARD NON VAPOR TIGHT WALL ADJACENT ROOM VAPOR TIGHT WALL SOURCE OF HAZARD NON VAPOR TIGHT WALL CLASS 1 DIV. 1 SOURCE OF HAZARD CLASS 1 DIV. 2 UNCLASSIFIED FIG. J-3. PUMPHOUSE HANDLING LIQUID PETROLEUM GAS

15 pressure equivalent to that of propane that is mainly made up of the following hydrocarbons: propane, propylene, butane or butylene. For a pumphouse which is not sufficiently ventilated as shown in Fig. J-3A, the pumphouse must be classified Div. 1. For a pumphouse which is sufficiently ventilated as shown in Fig. J-3B and J-3C, the pumphouse is allowed to be classified Div. 2. Because the extent of hazard in the pumphouse reaches the open perimeter of the pumphouse, an additional danger zone of 15 feet wide must be applied at the opening of the pumphouse as shown in Fig. J-3. The location adjacent to the pumphouse does not have to be classified if the common wall between the pumphouse and the adjacent location is vapor proof and the distance between the opening of the adjacent location and the pumphouse opening is greater than 15 feet. A common wall which is not vapor tight requires that the adjacent location be classified as follows: (1) Div. 1 if the adjacent location is not sufficiently ventilated and the pumphouse is classified Div. 1 or Div. 2 (2) Also Div. 1 if the adjacent location is sufficiently ventilated and the pumphouse is classified Div. 1 (3) Div. 2 if the adjacent location is sufficiently ventilated and the pumphouse is classified Div. 2 (4) Also Div. 2 if the adjacent location is sufficiently ventilated but gives access to a Div. 2 hazardous area outdoors as a result of a distance between the opening of both locations being less than 15 feet. The classification and extent of hazard for the pumphouse and adjacent location is in compliance with the following: Figure J-4. Table Item Figure Item 1-4J 4 and A, B, and C 1-6 2, 3, 7 and 8 Figure J-4 represents minimum requirements for safe distances between containers filled with liquefied petroleum gas (LPG) and an electrical ignition source. The minimum safe distance between a container filled with LPG and an ignition source, a central air conditioning (AC) unit or window-type AC unit, is 5 feet if the container is of the DOT type. The minimum safe distance must increase to 10 feet if the DOT type containers are locally filled. The minimum safe distance should be 15 feet if the containers are of the

16 CLOSED SYSTEM HEAVIER THAN AIR VAPORS AIR INTAKE *5' MIN. *5' MIN. *5' MIN. WINDOW DOTCYLINDERS CENTRAL CRAWL A.C.UNIT FORLPG A.C. UNIT SPACE OPENING *MUST BE 10 FT. MIN. IF DOT CYLINDERS ARE FILLED LOCALLY. MUST BE 15 FT. MIN. IF NOT DOT CYLINDERS. FIG. J-4. SAFE DISTANCES BETWEEN IGNITION SOURCE AND DOT AND NONDOT CYLINDERS FILLED WITH LPG.

17 nondot type. The safe distances between containers for flammable products and electrical ignition sources is in compliance with the following: Figure J-S. Table Item 1-4J 6 Figure J-5 represents a 2-wall building with sources of hazard and two 4-wall spaces without sources of hazard. The two 4-wall spaces are marked "A" and "B" and are located within the hazardous boundary of the sources of hazard in the 2-wall building. The access opening of space "A" is located at grade level and the opening of space "B" gives access to an elevated boardwalk located above the hazardous boundary. The hazardous boundary from the sources of hazard extends to the outdoors horizontally to left and right as shown in Fig. J-5. Both boundaries are classified Div. 2. Since the door opening of space "A" gives direct access to the hazardous boundary space "A" must be classified Div. 2 although it may be sufficiently ventilated. The door opening of space "B" is above the hazardous boundary. Space "B" which gives access to the boardwalk need not be classified if the distance between the bottom of its access opening and the finished grade is twice the height of the 18" high hazardous boundary. Space "B" is not considered safe if the access opening is less than twice the height of the hazardous boundary. If the walls of space "A" and space "B" are not vapor tight, the horizontal distance between these walls and the perimeter of the 2-wall building shall not be smaller than twice the width of the additional danger zone. In this case, the additional danger zone is 10 feet wide and extends vertically to a height equal to the height of the 2-wall building. The horizontal distance, therefore, shall not be less than 20 feet if the walls of the spaces are not vapor tight. If the walls are vapor tight, but provided with nonbolted windows, then the horizontal distance between windows and the perimeter of the 2-wall building shall also not be smaller than twice the width of the additional danger zone. A distance smaller than twice the width of the 10 feet wide additional danger zone requires that the spaces be classified Div. 2. The 20 feet safe distance does not apply to the hazardous boundaries since the boundary is only 18" high. The classification of both enclosed spaces "A" and "B" is in compliance with the following: Table Item Figure Item 1-4J 7 and A and C 1-6 6

18 CLOSED SYSTEM HEAVIER THAN AIR VAPORS 2-WALL BUILDING ADDITIONAL DANGER ZONE, 1OFT. WIDE 4-WALL BUILDING 4-WALL BUILDING BOARDWALK HAZARDOUS BOUNDARY HAZARDOUS BOUNDARY CLASS 1 DIV. 1 CLASS 1 DIV. 2 UNCLASSIFIED BUILDING "A" SUFFICIENTLY VENTILATED MUST BE CLASSIFIED DIV. 2. BUILDING 11 B" NON-VENTILATED MAY BE CLASSIFIED NON-HAZARDOUS. FIG. J-5. ACCESS TO A DIV. 2 HAZARDOUS BOUNDARY

19 Figure J-6. Figure J-6 provides requirements for hazardous boundaries for small process areas associated with lighter-than-air Class I flammable gases. The lighter-thanair gases are processed and handled by operating personnel. The gases are transported from a single gas container, located outdoors, to the process area located indoors via a piping system which is sized not greater than 1/4" or 1/2". The components in the piping system are of the mini type and consist of a pressure reducer, valves, manifolds and gauges. The gas container is pressurized between 2,000 and 3,000 psi and its gas content is less than 400 CF. (CF = cubic feet of gas at psia and 7O 0 F.) The pressure reducer is located at the gas container outdoors and reduces the pressure in the piping system indoors to a desired lower pressure. The components in the piping system indoors are considered sources of hazard as follows: (1) valves and manifolds if they are connected to the piping system with low integrity seal connectors, (2) gauges regardless of how they are connected to the piping system. The hazardous boundary for the components are listed in Fig. J-6. The sizes of the boundaries are selected on the basis of the following requirements: 1) pressure in the piping system, 2) air brushing the sources of hazard, and 3) location of electrical equipment versus location of source of hazard. These requirements are shown in the diagram in Fig. J-6. The correct application of the diagram is to turn it 90 counter-clockwise. Since the flammable material is lighter-than-air, the air stream of the ventilating system must move upwards, i.e., from an air inlet in the wall 12" above the floor to a suction fan in the roof of the indoor location. Since only small quantities of gas can be released from each of the sources of hazard and since the gas is lighter-than-air, it is sufficient if ventilating air dilutes the gas to slightly below the LEL. If the process area is located in a relatively large room or space it is recommended that a fume hood is used above the sources of hazard. With a fume hood, ventilating air need not dilute the gas to slightly below the LEL. Since gases with vapor densities of 0.75 or less in the air will rise quickly, suction air in the fume hood need only be of sufficient quantity to accelerate the upward movement of the gas provided all ignitable gas particles in the air are caught by the fume hood. As shown in the diagram, a mini source of hazard is located between two electric devices "A" and "B." Also shown are two air flows: one which is brushing the mini source of hazard, and the other which is not. When the lighterthan-air flammable material is airborne, it will rise, it will not move in the opposite direction. If the gas is forced out by system pressure, the gas escaping

20 from underneath a source of hazard will move downwards before rising. For example, when a leak should occur underneath the source of hazard, the pressure in the system forces the gas down before it can rise. However, if the source of hazard is brushed by air, the downward movement of the gas is greatly negated by the rising air. If the pressure is low or moderate and if the rising air counteracts the downward movement of the gas and if it first reaches an electric device before reaching the source of hazard, a safety zone of 3 feet below the source of hazard is considered ample. Three feet is considered sufficient to allow the gas to move down before it is caught by the rising air. Therefore, any electric device, such as device "A" in the diagram, may be of the general purpose type if it is below the 3-feet boundary. However, if the system pressure is high, the downward movement of the gas is much greater and because of this a longer radius should be applied. The radius should be 5 feet instead of 3 feet. Also, if ventilating air is not brushing the source of hazard a radius of 5 feet must be applied. Any electric device or equipment located between 3 feet and 5 feet radius must be suitable for a Div. 2 location. Below 5 feet the electric device may be of the general purpose type. Electrical equipment within three feet of the source of hazard must be explosion proof. A much larger than 5 feet hazardous area must be applied above the source of hazard if ventilating air reaches the source of hazard first before reaching the electric device. In this case, the boundary above the source of hazard must extend at least 15 feet. Above the source of hazard the hazardous area is a cone from which the center line can be easily determined. The width of the cone, however, is not easily determined because it is a function of quantity of gas being released and the speed at which the gas rises. The greater the speed of the gas, the smaller the width of the cone required. Any electrical equipment in the cone must be suitable for a Div. 2 location and outside the cone electrical equipment can be of the general purpose type. The division between a 3 or 5 feet danger zone and a zone of a minimum of 15 feet length is called a "demarcation line." As indicated in the table, the greater the system pressure, the more conservative the area classification. When a pressure reducer is applied, a less conservative classification may be used. However, if the pressure reducer shares the same location as the components with the lower pressure, the classification should be based on the higher pressure. If the pressure reducer is not in the same location, the classification should be based on the lower pressure. The classification of the location is in compliance with the following: Table Item 1-4J 9

21 CLOSED SYSTEM LIGHTER THAN AIR GASES AIR OUTLET AlR INLET MINI SOURCE OF HAZARD WITH "LOW INTEGRITY SEAL- CONNECTORS ITEM NO. SYSTEM PROCESSURE AIR BRUSHING ELECTRIC DEVICE LOCATION ENCLOSURE RADIUS X1 X2 EXTENDED LENGTH X3 1 YES A G-P 3ft. 15ft. MIN. 2 3 LOW OR MOD NO YES A B X-P X-P 5ft. 3ft. 15ft. MIN. 15ft. MIN. 4 NO B X-P 5ft. 15ft. MIN. 5 6 HIGH YES/NO YES/NO A B X-P X-P 5ft. 5ft. 15ft. MIN. 15ft. MIN. A, B = LOCATION OF ARCING DEVICE WITH RESPECT TO LOCATION OF SOURCE OF HAZARD. G»P = GENERAL PURPOSE ENCLOSURE X-P = SUITABLE FOR DIV. 2 LOCATION FIG. J-6. PIPING SYSTEM WITH SCREWED FITTINGS, VALVE, ETC. FOR INDOOR GASEOUS SYSTEMS OF LESS THAN 400 CF.

22 Figure J-7. Figure J-7 represents two sufficiently ventilated enclosed process areas "1" and "2" in which lighter-than-air flammable gases are processed. The gases are processed via a piping system from a single container to a process tank. The gas content in the container is less than 400 CF. (CF = cubic feet of gas at 14.7 psia and 7O 0 F.) The piping system contains the following mini-type components: Pressure reducer located at the container outdoors, gauges located indoors. All components are connected to the piping system with low integrity seal connectors. (For low integrity seal connectors refer to Fig. J-IO.) Because of the low integrity seal connectors, valves and manifolds are considered sources of hazard. Gauges are considered sources of hazard by themselves. Both process areas (1) and (2) are identical except for the locations of the air inlets. In process area (1) the air inlet is located in the right building wall. As a result of the different air inlet locations, the sources of hazard in building (1) are brushed by ventilating air and in building (2) they are not. Since the vapor density of the flammable gas is below 0.75, the flammable gas does not necessarily have to be diluted to below 1/4 of the LEL. As airborne gas with a vapor density below 0.75 will rise quickly by itself, it is sufficient if ventilating air dilutes the gas to slightly below the LEL. The dilution needs not be slightly below the LEL if a fume hood is being used. In this case, ventilating air needs only be of sufficient quantity to accelerate the upward flow of the gas, provided all escaping gases are caught by the fume hood. Because the sources of hazard are of the mini-type and ventilated, each component can be provided with a small danger zone that needs only to be classified Div. 2. The radius of the danger zones shall be selected from a table in Fig. J-6. In building (1) the radius shall be 3 feet in accordance with item 1, column (4) in the table for a system pressure that is low or moderate. For building (2) the radius shall be 5 feet in accordance with item 2, column (4) in the table. In process area 1 the source of hazard is brushed by ventilating air, and in process area 2 it is not. Electrical equipment "A" in building (1) can be of the general purpose type since it is below the demarcation line and outside the 3 feet boundary. Electrical equipment "A" in building (2) is also below the demarcation line but at the boundary of the 5 feet danger zone and therefore must have an enclosure that is suitable for a Div. 2 location. Electrical equipment "B" in building (1) can be of the general purpose type since it is sufficiently away from the hazardous cone. If not, as in building 2, equipment "B" must be suitable for a Div. 2 location. In building (1) the cone is narrow as a result of air brushing the source of hazard. In building (2) the cone is wide because the source of hazard is not brushed by ventilating air and requires that the electrical equipment be suitable for a Div. 2 location. The electrical equipment "C" and "D" in both buildings may be of the general purpose type since they are far away from the hazardous cones. (Fifteen

23 CLOSED SYSTEM LIGHTER THAN AIR VAPORS EXHAUST FAN ELEC. EQUIP CONE PROCESS TANK PLATFORM DEMARCATION LINE SOURCE OF HAZ. ("NON SEAL" TYPE) AIR INLET VENTILATING AIR BRUSHING SOURCE OF HAZARD LESS THAN 400 CF CAPACITY EXHAUST FAN ELEC. EQUIP AIR INLET PLATFORM PROCESS TANK CONE DEMARCATION LINE SOURCE OF HAZ. ("NON SEAL" TYPE) VENTILATING AIR NOT BRUSHING SOURCE OF HAZARD LESS THAN 400 CF CAPACITY CLASS I, DIV. 1 CLASS I, DIV. 2 UNCLASSIFIED FIG. J-7. BRUSHING AND NON BRUSHING VENTILATING AIR

24 feet minimum without obstructions to ventilating air and 25 feet minimum with obstructions to ventilating air.) The classification of the location is in compliance with the following: Figure J-8. Table Item 1-4J 10 The major requirements for classifying the location as shown in Fig. J-8 are as follows: Items pertaining to the degree of danger: Bl - type of product = flammable gas 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 = process plant El - type of ventilation = fume hood E5 - safeguards = yes Fl - how isflammablegas/vapor released = occasionally Items pertaining to the extent of danger: A2 - size of source of hazard = small or large B5 - flammability class = I B6 - vapor density = lighter-than-air C5 - system pressure = low, moderate, or high Figure J-8 represents a process plant located indoors, handling lighter-thanair flammable gases. The building as shown in Fig. J-8 may be classified non hazardous if the source of hazard is provided with a fume hood. Since the source of hazard is closed, the area between the source of hazard and the fume hood shall be classified Div. 2. The inlet of the fume hood must be as close as possible to any point where the escape of flammable vapors may be expected. The entire exhaust duct system should operate below atmospheric pressure with the exhaust fan located in the roof. To maintain a nonhazardous environment around the source of hazard, the exhaust fan must be provided with an alarm system that operates when there is a suction fan failure. Lighter-than-air gases released by the source of hazard do not have to be diluted to below the LEL of the flammable gas. A lighter-than-air gas will rise quickly by itself when it is airborne. Ventilating air, therefore, needs only to be of sufficient quantity to accelerate the upward flow of the gas provided that all gas particles in the air are caught by the fume hood. An exhaust opening in the roof

25 CLOSED SYSTEM LIGHTER THAN AIR VAPORS FIREPROOFWALL FUME HOOD SOURCE OF HAZARD CLASS 1 DIV. 1 CLASS 1 DIV. 2 UNCLASSIFIED FIG. J-8. PROCESS EQUIPMENT PRODUCING FLAMMABLE GASES (SUFFICIENTLY VENTILATED BY FUME HOOD)

26 shall also be provided as an additional safety precaution. At the outlet of the suction fan, the degree and extent of the danger zone shall be as follows. For large, closed sources of hazard the danger zone around the outlet shall be Div. 2 with a 5-foot radius. For small, closed sources of hazard the danger zone shall have a 3-feet radius. For heavier-than-air flammable material refer to Fig. D-2. The classification of the location is in compliance with the following: Figure J-9. Table Item 1-4J 11 Figure J-9 provides safe clearances between buildings and building openings when lighter-than-air Class I flammable gases need to be released to the atmosphere. As shown in Fig. J-9 the gases are produced in a process area on the lower floor of a multi-story building "A." Removal of the gases in the process area to the outdoors is either by a fume hood connected to a wall opening or a suction fan in the wall. The flammable gases may be vented through the wall if the right wall above the process area is vapor tight. A vapor-tight wall with bolted windows is also considered vapor tight. If the right wall above the process area is not vapor tight, or if it is provided with non bolted windows or openings, the suction fan in the process area must be provided with a vertical riser that extends 7 feet above the roof of building "A". The 7-feet riser must also extend above the roof line of neighboring buildings. Without a riser the minimum horizontal distance between the suction fan in building "A" and the neighboring building "B" shall be 25 feet provided the neighboring wall is vapor tight. A much smaller clearance than 25 feet may be applied if the vapor-tight neighboring wall has a minimum fire resistance of 2 hours. If the neighboring wall is not vapor tight or if it is provided with an opening or air inlet the horizontal distance between the suction fan without a stack and the neighboring wall shall be 50 feet. The vertical distance between both roof openings in building "A" shall be 15 feet minimum and the horizontal distance between the two roof openings shall be 50 feet minimum. This horizontal distance may be smaller if the fan in "A" is a suction fan with a type "A" safeguard. Clearances are in compliance with the following subtable in Table 1-4: Figure J-IO. Table Item J 12 Piping systems used for hydrogen gas for a small process plant are generally sized 1/4" or 1/2". The components in the piping system normally consist of a

27 OPEN OR CLOSED SYSTEMS LIGHTER THAN AIR VAPORS 15 1 IF "A" IS WITH VENTILATION INTAKE 7' IF "A" IS WITHOUT VENTILATION INTAKE PRESSURE FAN IF WALL "A" IS VAPOR TIGHT SUCTION FAN PROCESS AREA SOURCE OF HAZARD PRESSURE FAN VT WALL * NOT APPLICABLE IF VT WAiI HAS A FIRE RESISTANCE RATING OF 2 HRS. A NOT APPLICABLE IF ROOF FAN IN 11 A" IS A SUCTION FAN WITH TYPE "A" SAFEGUARD. FIG. J-9. SAFE DISTANCES FOR FLAMMABLE GAS RELEASED TO THE OUTDOORS

28 pressure reducer, valves, manifolds, gauges and connectors. Figure J-IO gives an overview of the type of connectors normally used in a 1/4" or 1/2" piping system. The connectors may consist either of low-integrity or high-integrity seal connectors. For hydrogen gas low-integrity seal connectors are unreliable because they may cause leakage. Vibration and temperature fluctuation or remake of the connectors are the main reason for causing leakage. High-integrity seal connectors on the other hand are considered leak free because of their quality construction and their quality components. These seal connectors are made leak free because: 1) they are provided with metal gaskets of proper material, 2) are welded into the piping system, 3) are provided with proper workmanship (seal beads are not to rotate against the gasket) and 4) a new metal gasket is used every time the connector is loosened and retightened. Low-integrity seal connectors, therefore, are considered sources of hazard and high-integrity seals connectors are not. Gauges by themselves are also sources of hazard. They are the weakest component in the system because the pressure sensing element in the gauge is known to fail. Valves and manifolds of high quality are considered sources of hazard only if they are provided with low-integrity seal connectors or if they are systematically opened and closed at short intervals. For a piping system equipped with low-integrity seal connectors it is mandatory that sufficient ventilation be applied in accordance with the requirements of Fig. J-6. Classification of the location shall also be in compliance with Fig. J-6. Ventilation and classification of the location may be omitted if the piping system is provided only with high-integrity seal connectors welded into the piping system, and gauges in the piping system are omitted. Hydrogen gas containers and pressure reducers are normally not provided with high-integrity seal connectors. Therefore, they should be located outdoors unless sufficient ventilation is applied when they are located indoors. Indoors the piping system and components are considered leak free as long as they are provided with high-integrity seal connectors, gauges are omitted and the system is thoroughly leak tested. The classification and extent of hazard for the location is in compliance with the following: Figure J-Il. Table Item 1-4] 13 Figure J-Il covers safe clearances for air vents in connection with the possible presence of hydrogen gas in the air. Also covered in Fig. J-Il are safe clearances for public assemblies, cars and welding and cutting areas.

29 HIGH INTEGRITY AND LOW INTEGRITY SEAL CONNECTORS WELD TYPE HIGH PERFORMANCE COUPLINGS WITH METAL GASKET HELIUM LEAK RATE 4 x 1 (T 9 cc/sec HELIUM LEAK RATE 1 x 1 (T 9 cc/sec HIGH INTEGRITY SEAL CONNECTORS SINGLE FERRULE COMPRESSION FITTING DOUBLE FERRULE COMPRESSION FITTING LOW INTEGRITY SEAL CONNECTORS GAUGE CONNECTOR "AN" FLARED TUBE FITTING LOW INTEGRITY SEAL CONNECTORS FIG. J-10. 1/4" ~ 1/2" PIPE FITTINGS FOR H 2 GASES

30 Safe distances between containers filled with hydrogen gas and electric driven suction fans should not be less than 50 feet and 25 feet for welding and cutting areas and 15 feet for electrical arcing devices. As shown in Figure J-Il, there are three exhaust systems, #1, #2, and #3. A distance of 50 feet between air inlet #1 and the hydrogen gas containers must be considered unsafe because a hydrogen gas leak will be easily sucked into the building. However, if vent #3 is an air outlet, it is also unsafe during a gas leak it the vent driver breaks down. Air outlet #3 is safe only if it is provided with a type "A" safeguard. Clearances are in compliance with the following subtable of Table 1-4: Table Item J 14

31 CLOSED SYSTEM UGHTER THAN AIR VAPORS 1. AIR INLET 2. = AIR INLET 3. = AIR OUTLET H 2 CONTAINERSWITH A COMBINED CONTENT OF LESS THAN 3000 CF PUBLIC ASSEMBLY WELDING AC UNIT A = SAFE IF DISTANCE IS 50 FT. MIN. B = SAFE IF DISTANCE IS 15 FT. MIN. C = SAFE IF DISTANCE IS 25 FT. MIN. LOCATION AIR INLET 1 = SAFE LOCATION AIR INLET 2 = UNSAFE LOCATION AIR OUTLET 3 = UNSAFE UNLESS FAN IS PROVIDED WITH A TYPE "A" SAFEGUARD. FIG. J-11 SAFE DISTANCES FOR HYDROGEN GAS OUTDOORS

32 1.11 GENERAL REQUIREMENTS FOR GROUP K Group K represents closed sources of hazard that contain Class I flammable products with heavier-than-air gases or vapors located in sufficiently or insufficiently ventilated locations which are classified in accordance with the information in Section I. Figure K-I. Figure K-I represents components in a piping system for heavier-than-air flammable material operating at low, moderate, or high pressures located indoors which are either sufficiently or insufficiently ventilated. The classification and extent of the danger zone for the components in Fig. K- 1 is a function of: 1) size of the components, 2) their operating modes, 3) the pressure in the piping system, and 4) whether the location is sufficiently ventilated or not. For classification requirements for the components refer to the table in Fig. K-I. In the table in Fig. K-I there are two classifications shown, a location entirely classified and a location partially classified. Some of the partially classified locations are provided with an asterisk. This means that the location must be entirely classified if the piping system with components occupies more than 50% of the floor space. If they do occupy more than 50% of the floor space the components are considered to occupy 100% of the floor space. For example, the location for mini sources of hazard in item 3 of column (1) in Fig. K-I is marked with an asterisk. When these sources of hazard occupy more than 50% of the floor space, the location is considered 100% occupied and the asterisk indicates that it is required that the entire location be classified. As indicated in the table, the greater the system pressure, the more conservative the area classification. When a pressure reducer is applied, a less conservative classification may be used. However, if the pressure reducer shares the same location as the components with the lower pressure, the classification should be based on the higher pressure. If the pressure reducer is not in the same location the classification should be based on the lower pressure. If the flammable product is volatile or very flammable, a more conservative classification is required. To establish whether these locations require a more conservative classification, it is necessary that a severity factor of 1.0 PU be added to the probability factor which must be established for the location first. For example, if the sources of hazard in item 4, column (1) occupy more than 50% floor space, the probability factor for that location is 9 PU. An addition of a 1.0 PU severity factor makes the probability factor 10 PU. This 10 PU factor requires that the location be entirely classified Div. 2. As another example, the probability factor for item 5, column (2) is 8 PU when the location is unattended and more than 50% floor space is occupied. The addition of a 1.0 PU severity factor brings

33 the probability factor to 9 PU. In this case, where the probability factor is less than 10, the location need not be entirely classified. However, the boundary recommended for the sources of hazard in item 5, column (2) is required to be of a larger size when the flammable product is volatile or very flammable. For standard boundary sizes of 3, 5, 10 and 15 feet, increase the size to 5, 10 15, and 20 feet respectively. For volatile and very flammable products refer to the tables in the appendix. Add only a 1.0 PU severity factor if the flammable product in the location is marked with a "4" in the appendix tables. For information on how to determine a probability factor, refer to Section J in Chapter III. If the location needs to be sufficiently ventilated it is necessary to determine the suction fan location. Refer to Section D in Chapter VI for approximate locations of suction fans. Some of the locations in Fig. K-I do not require classification if the location is 1) sufficiently ventilated, 2) the process equipment well maintained, and 3) the probability factor is 5 PU or less. Locations which comply with these three conditions are marked in the table with "NC" which means "nonclassified." For example, the location in item 4, column (1) need not be classified if 1) the sources of hazard do not occupy more than 50% of the floor space, 2) the location is sufficiently ventilated, 3) the sources of hazard are well maintained, and 4) the probability factor for the above conditions is not more than 5 PU. There is a distinct difference between a nonclassified location and a nonhazardous location. A nonclassified location is a location with one or more sources of hazard but which is considered free from explosion danger because of tight inspections and maintenance procedures and sufficient ventilation. A nonhazardous location is a location free from explosion danger because it is provided with sufficient ventilation and suitable safeguards and generally without a source of hazard. Although there is a distinct difference between both locations, a location which needs no classification is in fact a nonhazardous location. Therefore, a nonclassified location can also be considered a nonhazardous location. "Well maintained" is defined as a maintenance procedure in which the probability of leakage or failure of a component in a piping system is almost nonexistent. This is normally accomplished by frequent inspections. Lack of frequent inspections requires that the location be classified. Column (1) and column (2) of item 5 in the table in Fig. K-I is marked with a *. This means that the classification shown in column (1) and column (2) of item 5 is valid only as long as the probability factor for the location does not exceed 5 PU. If the probability factor is higher than 5 PU, then the classification for the location in item 5 shall be as in item 3 of column (T) for mini sources of hazard and item 3 of column (2) for small sources of hazard. To maintain a probability factor of 5 PU, the piping system cannot carry Class IA liquid and the location

34 must be attended. The classification of the location is in compliance with the following: Figure K-2. Table Item 1-4K 1 Figure K-2 represents a piping system operating at low, moderate, or high pressure located outdoors. The classification and the extent of classification for the piping system is a function of 1) size of the source of hazard, 2) operating mode of the source of hazard, 3) vapor density of the flammable product, and 4) pressure in the system. The classification of the location is in compliance with the following: Table Item 1-4K 2

35 CLOSED SYSTEM HEAVIER THAN AIR VAPORS ITEM NO SYSTEM PRESSURE HIGH HIGH MOD. MOD. LOW LOW VENT. INDOORS NO YES NO YES NO YES CLASSIFICATION FOR INDOOR LOCATIONS MINI 6'ANDBELOW DIV. 1,5 Ra+ * DIV. 2, 7 Ra + 15 HO, 18" DIV. 2, 5 Ra + * 15 HO, 18" DIV. 1,3Ra+ * DIV. 2, 5 Ra +10 HO, 18" DIV. 2, 3 Ra NC DIV. 2, 5 Ra + 10 HO, 18" * NON HAZARDOUS IF WELL MAINTAINED SMALL BETWEEN 6" 14" DIV. 1 ENTIRE LOCATION DIV. 2 ENTIRE LOCATION DIV. 1,5Ra+ * DIV. 2, 7 Ra + 15 HO, 18" DIV. 2, 5 Ra+ * 15 HO, 18" DIV. 2, 5 Ra + 15 HO, 18" * DIV. 2, 3 Ra NC LARGE 14"ANDABOVE DIV. 1 ENTIRE LOCATION DIV. 2 ENTIRE LOCATION DIV. 1 ENTIRE LOCATION DIV. 2, 10 Ra+ * 25 HO, 18" DIV. 1,5 Ra+ * DIV. 2, 7 Ra + 25 HO, 18" DIV. 2, 3 Ra + 10 HO, 18" NC * = IF NOT OCCUPYING MORE THAN 50% FLOOR SPACE; OTHERWISE CLASSIFY ENTIRE LOCATION. NC= NON CLASSIFIED IF PROBABILITY FACTOR IS 5 OR LESS AND SOURCES OF HAZARD ARE WELL MAINTAINED AND OCCUPY NOT MORE THAN 50% FLOOR SPACE. * = FOR PROBABILITY FACTOR NOT OVER 5; FOR OVER 5 USE ITEM 3(1) AND 3(2). FIG. K-1 PIPING SYSTEM WITH SCREWED FITTINGS, FLANGES, VALVES, ETC., FOR INDOOR LOCATIONS CONTAINING FLAMMABLE LIQUID

36 CLOSED SYSTEM HEAVIER THAN AIR VAPORS ITEM NO SYSTEM PRESSURE HIGH MOD. LOW MINI 6'ANDBELOW DIV. 2, 3 Ra + 10 HO 1 18" DIV. 2, 3 Ra NON-HAZARDOUS IF WELLMAINTAINED CLASSIFICATION FOR OUTDOOR LOCATIONS SMALL BETWEEN 6" -14" DIV. 2, 5 Ra + 15 HO, 18" DIV. 2, 3 Ra + 10 HO, 18" DIV. 2, 3 Ra LARGE 14"ANDABOVE DIV. 2, 10 Ra + 25 HO, 18" DIV. 2, 5 Ra + 15 HO 1 18" DIV. 2, 3 Ra + 10 HO 1 18" FIG. K-2 PIPING SYSTEM WITH SCREWED FITTINGS, FLANGES, VALVES, ETC., FOR OUTDOOR LOCATIONS CONTAINING FLAMMABLE LIQUID