CHAPTERS THE EXTENT OF EXPLOSION DANGER FOR NEC CLASS I LOCATIONS

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1 CHAPTERS THE EXTENT F EXPLSIN DANGER FR NEC CLASS I LCATINS A. General The purpose of classifying a hazardous location is to provide an acceptable level of safety against explosion danger for personnel and equipment. This is accomplished not only by establishing the degree of explosion danger as shown in Table 1-3, but also by establishing the extent of the explosion danger, and by furnishing suitable electrical equipment in compliance with the established degree and extent of explosion danger. The determination of the degree of the explosion danger is a rather simple procedure. By applying the guidelines in Chapter 2 and in Table 1-3, the degree of danger for the hazardous location can be established without any difficulty. The determination of the extent of explosion danger, however, is far more complex and requires an in-depth understanding of the nature of the explosion danger. For example, in Item 8 of Table 1-3, a closed source of hazard is located in a sufficiently ventilated building. According to Item 8 the classification of the location must be Div. 2. The question now is; how far does the Div. 2 area extend in horizontal and vertical direction? Should it be 10, 15, 25, 50 or 100 feet, or should the entire indoor location be classified, or only partially classified Div. 2? These questions shall be addressed later on. B. The Dimensional utline of a Div. 1 and Div. 2 Zone As a general rule, the dimensional outline of a Div. 1 and a Div. 2 zone is measured from the outline of the source of hazard in horizontal and vertical directions as shown in Fig 1-4. The distance between the outline of the source of hazard and the boundary line is called the extent of danger, or simply, the boundary, or boundary distance. The vertical and horizontal distances are expressed in, respectively, "V" and "H." As shown in Fig 1-4, the distance "V" starts from the top of the source of hazard in a vertical direction. "Hi" is also a vertical distance, measured from the floor or grade. Thus, a boundary with a 5V, 25H and 3 Hi means a boundary of 5 feet vertical, 25 feet horizontal, and 3 feet high. All "V" and "H" dimensions are measured in feet. When "Hi" reads

2 18Hi, it means a vertical distance of 18 inches high. This figure is the only figure which is related to inches. All other figures are in feet. C. Quantity of Flammable Substances Versus Extent of Explosion Danger The extent of explosion danger is primarily a function of the quantity of the flammable gas or vapor released into the atmosphere. These quantities are influenced by the discharge and evaporation rates, and the rupture opening through which the flammable gas, vapor or liquid will escape. This in turn is a function of the type and size of the source of hazard, the vapor density, the flammability class of flammable products and the temperature and pressure in the system. These conditions must be considered before the extent of the explosion danger can be established. However, it is not practical to make predictions of the size of the rupture opening through which a flammable gas, vapor or liquid will escape if the source of hazard breaks down. It requires a great deal of study and analysis, making the evaluation too involved and too cumbersome. It is also not practical to determine the rate of release of the flammable gas, vapor or liquid, or the diffusion rate of the flammable gas or vapor in the air. It is far more practical to predict a quantity of flammable gas or vapor that a given size source of hazard is capable of releasing into the atmosphere, when the source of hazard should break down. It is also far more practical to establish whether a static type or dynamic type source of hazard is involved. The quantities of flammable gases or vapors released into the atmosphere are proportional to the traveling distance of the flammable gas or vapor. The greater the quantity, the longer the traveling distance. The smaller the quantity, the shorter the traveling distance. Before the flammable gas or vapor has reached its maximum traveling distance there is a point in space at which the flammable gas or vapor will reach a nonhazardous concentration. It is the distance between the source of hazard and this point that determines the extent of the explosion danger. The size of the hazardous area must not be less than this distance. A more indepth discussion on traveling distances can be found under Section G, "Transition Zones for NEC Class I Locations" in Chapter 3. The quantity of flammable gases or vapors released into the atmosphere and consequently, the traveling distance of the flammable gas or vapor, therefore, is a valid basis for determining the extent of the danger area. Large sources of hazard are normally capable of releasing large quantities of flammable gases or vapors, whereas small and mini sources of hazard are more likely to produce small quantities. To simplify the method for establishing the proper size of a hazardous area, the quantity of the flammable gas, vapor or liquid released into the atmosphere is taken as the basis for establishing the size of the hazardous area. Consequently, the size of a hazardous area is established by the

3 FINISHED GRADE SURCE F HAZARD H H SURCE F HAZARD LEGEND V = VERTICAL DISTANCE IN FEET H = HRIZNTAL DISTANCE IN FEET Hi = VERTICAL HEIGHT IN INCHES R = RADIUS IN FEET 1-4. BUNDARIES FR NEC CLASS I LCATINS

4 size of the source of hazard, and since the source of hazard is either large, small or mini, the quantity of flammable substances released to the atmosphere can only be large or small. Unfortunately, the size of the source of hazard alone cannot be relied upon completely in determining the size of the hazardous area. This is due to the fact that the quantity of the flammable gas or vapor released to the atmosphere is greatly influenced by temperature and pressure in the system, and type of source of hazard. The higher the temperature or pressure in the system, the greater the quantity released. Therefore, small sources of hazard may also produce large quantities of flammable gases or vapors when their temperature or pressure is high, and large sources of hazard may produce small quantities of flammable gases or vapors when their temperature or pressure is low. Consequently any source of hazard, regardless of its size, that is capable of releasing large quantities of flammable gases or vapors, requires large hazardous areas, whereas sources of hazard that can release only small quantities of flammable gases or vapors require small hazardous areas. The different boundary requirements with respect to the size of the source of hazard clearly indicate that the size of the source alone is not a valid guideline for determining the amount of flammable gases or vapors which the source is capable of releasing. In order to determine whether a source of hazard is capable of releasing small or large quantities of flammable gases or vapors into the atmosphere, it is necessary to take into account several additional factors which are explained in Section D of this chapter. These will affect the relationship between source of hazard size and small or large hazardous areas. It is important to understand, however, that the wording "small and large quantities of flammable gases or vapors released" as used above must not be confused with the wording, "in quantities sufficient" as described in article 500 of the NEC which reads: "Class I locations are those in which flammable gases or vapors are or may be present in the air 'in quantities sufficient 1 to produce explosive or ignitible mixtures." To eliminate confusion between the two wordings, it is important to understand the intent of the wording in the NEC. Misinterpretation of the intent of the wording in the NEC could lead to the conclusion that a flammable gas or vapor in the air is not dangerous if its quantity in the air is small. That is not so. The wording "in quantities sufficient" in the NEC is related to the explosion range of the flammable product and the wording "small or large quantities released" as explained in here to the bulk of the flammable product. A large bulk of flammable gas or vapor in the air, therefore, could be of insufficient quantity if it has not entered its explosion range. n the other hand a small bulk of flammable gas or vapor in the air will have a sufficient quantity when it has entered its explosion range. Hydrogen gas, for example, has an explosion range between 4 and 75%.

5 When the hydrogen gas in the air has a concentration of less than 4%, the NEC considers it as being of insufficient quantity to produce an explosive mixture. When the flammable gas or vapor is within its explosion range, the NEC considers it to have a concentration of sufficient quantity to produce an explosive mixture. Therefore, for a small or large quantity of flammable gas or vapor to become explosive, it is necessary that its concentration in the air be present in sufficient quantities, which is only possible when it has entered its explosion range. D. Factors Influencing Quantities of Flammable Gases or Vapors Factors that influence the quantity of a flammable gas or vapor released into the air are: 1) the type and size of the source of hazard, 2) the temperature and the pressure in the system, and 3) the flammability class of the flammable product. The larger the quantity released into the air, the greater the danger in the location. The extent of the danger is mainly dictated by the vapor density of the flammable product. The vapor density and any one or more of the factors listed above will influence the traveling distance of the flammable gas or vapor in the air and subsequently the degree and extent of the hazardous area. Sufficient ventilation is another factor which has a great impact on the traveling distance of the flammable gas or vapor and subsequently also on the extent of the hazardous area. The traveling distance is inversely proportional to air velocity. Information on traveling distances of flammable gases and vapors in the air with respect to ventilation is outlined under "Ventilation Requirements" in Chapter 6. An extremely important factor is pressure in the system. Pressure is directly related to failure or breakdown of process equipment. Pressure in the system is defined as "low," "moderate," and "high." The failure of process equipment is also a function of wear, but mainly of pressure in the system. They, then, will also have an impact on the extent and degree of the hazardous area. Higher pressure in a system requires a more conservative approach than lower system pressures. For example, mini sources of hazard such as piping systems including screwed fittings, bolted flanges, valves and meters located in a sufficiently ventilated indoor area must be classified Div. 2 if operating at moderate pressure. The extent of the Div. 2 area shall only be a circular zone of 3 feet radius around each individual component of the piping system. The reason for this classification is the presence of sufficient ventilation and because of the moderate pressure in the system. If the indoor location containing the same piping system is not sufficiently ventilated, then the location must be classified Div. 1 with a 3 feet radius and Div. 2 with a 5 feet radius, 10 feet horizontal and 18 inches high. The same indoor location without sufficient ventilation must be classified Div. 1 with a 5 foot radius and Div. 2 with a 7 foot radius, 15 feet horizontal and

6 18 inches high if the piping system is operating at high pressure. At high pressure the risk of breakdown is much greater, and the fact that there is not sufficient ventilation makes the location more dangerous. In outdoor locations the individual components of the same piping system must be provided with a Div. 2 circular zone of 3 feet radius, 10 feet horizontal, 18 inches high. The reason for this classification is that outdoor locations are allowed to have smaller hazardous boundaries. An all welded piping system without screwed fittings, bolted flanges, valves and meters operating at any pressure, on the other hand is allowed to be classified nonhazardous. This is because the breakdown of an all welded piping system is considered remote. A well-maintained mini-type piping system with screwed fittings, bolted flanges, valves and meters operating at low pressure located in sufficiently ventilated indoor areas is also allowed to be classified nonhazardous. The supporting arguments for this classification are 1) low pressure, 2) sufficient ventilation, 3) only small quantities of flammable material will be released to the atmosphere in case a component should break down, and most important, 4) the piping system is well maintained. For detailed classification requirements refer to Section II, Figs. K-I and K-2. Sources of hazard other than the mini type such as sources of hazard which are small and large are required to have a larger area size. For example, a large pump handling a Class I flammable liquid outdoors operating at high pressure will produce much larger quantities of flammable material into the air in case of breakdown or failure than a mini static type source of hazard. The supporting reasons for this case are: type, because the pump is a rotating equipment; size, because it is large; pressure, because it is high; flammable product, because it is Class I. All of these factors support the conclusion that large quantities of vapor, much larger than by mini sources of hazard, will be formed under accidental failure. Thereby, when the flammable product is heavier-than-air, the traveling distance will be long and subsequently a large hazardous area, say of 50 feet horizontal, is required. A large quantity of flammable gases or vapors is associated with boundary sizes of 50 and 100 feet. (See Figs. 1-2 and 1-3.) If the same pump should handle a Class II heavier-than-air flammable product at the same high pressure, then smaller quantities of flammable vapors are expected in the air requiring a smaller hazardous area. This means that a horizontal hazardous area of only say 25 feet maximum is needed, even though it is a large source of hazard. Justification for this is that Class II flammable products will cover smaller areas than Class I flammable products. In this example then, the flammability class of the flammable product becomes more important than the size of the pump, the high pressure and type of the equipment. The question may arise as to what impact the type of source of hazard may have on the classification of the hazardous area. The answer is that the particular kind of source of hazard will indicate how much mechanical wear may be

7 expected, which will then influence the ultimate classification of the hazardous area. If mechanical wear is nonexistent or low, then only the size of the source of hazard, the product and its pressure are relevant factors in classifying the area. But if there is continuous mechanical wear, the type of source of hazard becomes an important matter. Generally, a more conservative approach is required for a high rate of mechanical wear than for a low rate of wear. Therefore, the mechanical wear must also be taken into consideration in establishing the classification and the size of the hazardous area. When a source of hazard is frequently operated or worked on, it is subjected to greater wear and will break down sooner and will also more often release ignitable concentrations of gases or vapors to the atmosphere. This puts the closed mini source of hazard in the same category as an open source of hazard which is normally releasing flammable vapors to the atmosphere continuously. For example, if a mini source of hazard, such as a valve, is operated often or is frequently worked on, the source is considered to have a high rate of wear. In this case a circular Div. 1 zone with a 3 or 5 feet radius for the mini source of hazard would be required instead of a Div. 2 circular zone. For dynamic type sources of hazard the required size of the hazardous area is generally larger than for the static type sources of hazard even when the static type sources of hazard are larger. The reason for this is that the dynamic type source of hazard is normally subjected to a higher rate of wear and the static type is not. However, if the static type source of hazard has a greater wear, it must be provided with a Div. 1 classification because the equipment may break down more often. n the other hand, a dynamic source of hazard having the same wear does not have to have a Div. 1 classification because it may not break down as often. Process equipment, therefore, that might frequently break down requires a Div. 1 classification and process equipment that only occasionally breaks down requires a Div. 2 classification. If frequent breakdowns can be expected, the process equipment becomes comparable with an open source of hazard which is normally classified Div. 1. The process equipment of the dynamic type source of hazard which breaks down only occasionally is not comparable with an open source of hazard and therefore it can be classified Div. 2. In view of these considerations the determination of whether quantities of flammable gases or vapors released into the atmosphere, and whether their associated traveling distances are large or small, becomes more meaningful. However, whether the quantity of the flammable gas or vapor and the traveling distance is large or small, it is still necessary to determine the required dimensions of the size of the hazardous area in order to produce a safe and economical electrical installation. These dimensions must be large enough to cover the entire distances which the flammable gas or vapor must travel to reach a nonhazardous concentration. Since the dimensions of a hazardous area must cover each

8 individual traveling distance, a great number of hazardous area dimensions is needed. It is, however, impractical to provide a great number of hazardous area dimensions for each individual traveling distance. It is more practical to apply a limited number of dimensions that cover a given group of traveling distances of different lengths. Each one of these dimensions must also cover the largest possible distance a Class I flammable product will travel. Therefore, for some flammable products the size of the hazardous area for a given group of traveling distances is more than ample, and for others they may be just right. The groups of dimensions are broken down in horizontal distances of 100, 50, 25, 15, 10, 5, 3, and less than 3 feet. They are classified Div. 1 or Div. 2 depending on the situation in the location as explained above. Large sources of hazard normally require 100 and 50 feet boundaries. Small sources of hazard normally will require 25,15,10, 5 and 3 feet boundaries. Mini sources of hazard are generally in the range between 15 and 3 feet or less. The various groups of dimensions are listed in Tables 1-4 and 1-5. They are also shown in the illustration in Section II. All dimensions listed and shown are prepared for Class I flammable products. For area dimensions required for Class II flammable products refer to section "F" in this chapter. To maintain conservatism for Class II flammable products, it is best to apply the dimensions for Class I flammable products. The question as to how the Div. 2 classification should extend in Item 8 of Table 1-3 can now be answered as follows: The main ingredients shown in Item 8 of Table 1-3 are: 1) a closed operating mode, 2) an indoor location and 3) sufficient ventilation. With these 3 ingredients known, the size of the hazardous area can be obtained from item 1 through item 11 in Table 1-4. A number of items in Table 1-4 are for heavier-than-air flammable products, and others are for lighter-than-air flammable products. If it is assumed that the flammable substances in Item 8 of Table 1-3 are heavier than air, then only Item 1 of Table 1-4 will apply. The next important ingredient is to establish the size of the source of hazard and the pressure in the system. With the size of the source of hazard and the pressure in the system known, the size of the hazardous area is narrowed down more to one particular dimension. For example, say the source of hazard is of the dynamic type. If the size of the source is "small" (up to 51 HP) and the pressure in the system is "moderate," and flammable gases or vapors which might escape from the enclosed confinement are "heavier than air," the required dimensions of the Div. 2 hazardous area can be obtained from the subtables listed in column (7) of Table 1-4. nly Subtable "A" will apply and from this subtable only item 1 which reads "5V, 25Ho, 3Hi" will apply. Because of the strong relationship between the quantity of a flammable gas

9 or vapor released to the atmosphere and the temperature in the system, one method is to divide the temperature into a number of temperatures, each of which can be associated with a given quantity of flammable gases or vapors in the air. However, since only two quantities of flammable gases or vapors released to the atmosphere are considered important, "small" and "large," the temperature must also be equally divided into two ranges. ne range is a temperature "above" flash point up to and including 5 0 F. The other is a temperature "far above" flash point which is associated with a temperature of at least 5 times the flash point. However, since the temperature is in direct proportion to the system pressure, it is much simpler to use the other method which equates temperature to system pressure. System pressure is defined as low, moderate and high. Low pressure in a system is below 100 PSI. Moderate pressure is generally 100 PSI up to and including 500 PSI, and high pressure is above 500 PSI. The three pressure categories: low, moderate and high, are included in the subtables "A" through "K." Table 1-4 has 5 self-explanatory columns. Column 5 of Table 1-4 refers to the subtables marked with a letter. For example: If the system operating mode of a source of hazard is "closed" and the source of hazard is handling a "heavier"-than-air flammable product "outdoors," refer to Item 3 of Table 1-4. Col. 5 of Table 1-4 reads the associated subtable for Item 3 of Table 1-4, which for this case is subtable "C." In subtable C there are 15 different conditions. nly one of the 15 conditions will apply. The solution of the proper condition is based on the pressure in the system, the size of the source of hazard, the size of the driver if any, and the type of locations. Whether or not an additional danger zone must be applied can be found in Column 8 of each subtable. Instead of using the boundary dimensions in the subtables, the dimensions in the illustrations in Section II can be used, or the boundaries in Table 1-5 for less common sources of hazard. The illustrations in Section II will show various conditions that may reflect actual situations encountered in chemical and petrochemical industries. The illustrated boundaries in Section II can be applied for gas compressors and for conditions where Class I flammable liquid is used with either lighter or heavier than air vapors. The illustrations may also be used for actual conditions that are similar to the illustrations, or for Class II flammable liquid with the requirements explained in this chapter. E. Early and Remote Permanent Ignition Sources As explained in Section D-3 of Chapter 1, early ignition is defined as a condition in which no explosion will occur if an ignitable concentration of

10 flammable gases or vapors in the air comes in contact with a "local" ignition source, with a temperature above the ignition temperature of the flammable product. Also explained in Section D-3 is a condition in which an explosion will occur if the ignitible concentration comes in contact with a "remote ignition source" with a temperature above the ignition temperature of the flammable product. Even when the flammable material is confined in a closed system from which it can escape only if the system breaks down, the location cannot be classified Div. 2 if the above conditions exist. If a "local" or "remote" ignition source exists with a temperature above the ignition temperature of the flammable product, the location must be classified Div. 1. These types of ignition sources can be compared with conditions in which flammable gases or vapors are released into the atmosphere continuously or frequently which, as a result of this condition, require that the location be classified Div. 1. Therefore, a location containing a "local" of "remote" ignition source is also required to be classified Div. 1. The "local" ignition source is required to have a circular zone of 3 feet diameter. A Div. 2 transition zone surrounding the Div. 1 zone may be applied but is not necessarily required. When a "remote" ignition source is involved, the area between the source of hazard and the remote ignition source must be classified Div. 1. This is only true if the flammable gases or vapors in the area have not reached safe concentrations before contacting the remote ignition source. If the flammable gas or vapor has reached safe concentrations before contacting the remote permanent ignition source, then the area need not be classified Div. 1. To avoid a possible explosion as a result of a remote ignition source, it is necessary to maintain sufficient distance between the source of hazard and the remote ignition source. But first, what is sufficient distance? Sufficient distance is the proper boundary size for a hazardous location which is selected from Table 1-4 on the basis of 1) the type and size of the source of hazard, 2) the pressure in the system and 3) the flammability class and the vapor density of the flammable product. For example, if the recommended boundary size for a source of hazard is to be 25 feet long, and the actual distance between the source of hazard and remote ignition source is within the 25 feet boundary, an explosion can be expected if the flammable gas or vapor in the air comes in contact with the remote ignition source. If, on the other hand, the actual distance should be longer than 25 feet, no explosion will be expected, in which case the 25 feet area can be considered remotely hazardous. The following example will illustrate the conditions mentioned above. Consider, for example, an area with four electric motor driven pumps and one pump driven by a high pressure steam turbine as shown in Fig 1-5. All pumps are handling volatile flammable liquid. The high pressured steam turbine

11 DIV. 2 AREA DIV. 2 AREA DIV. 1 AREA DIV. 2 TRANSITINZNE LEQEND "a" = HIGHPRESSURESTEAMTURBINE P1.P2.P3 = 50 HP PERATING AT HIGH PRESSURE P4. P5 = 250 HP PERATING AT MDERATE PRESSURE 1-5. NN-ELECTRICAL PERMANENT IGNITIN SURCE

12 TABLE 1-4 SUMMARY F SPECIFIC CNDITINS INFLUENCING THE DEGREE AND EXTENT F HAZARD N. SYSTEM PERATING MDEF SURCESF HAZARD TYPE F LCATIN t LCATIN SUFFICIENTLY VENTILATED? t HEAVIERR LIGHTERTHANAIR GASESR VAPRS IDENTIFICATIN LEHERSFR SUBTABLES if- 1 CLSED INDRS YES HEAVIER A 2 CLSED INDRS N HEAVIER B 3 CLSED UTDRS YES HEAVIER ' I 4 PEN INDRS YES HEAVIER D 5 PEN INDRS N HEAVIER E 6 PEN UTDRS YES HEAVIER F 7 CLSED INDRS YES LIGHTER G 8 CLSED INDRS N LIGHTER H 9 CLSED UTDRS YES LIGHTER I * 10 PENRCLSED INDRS/UTDRS YES/N HEAVIERRLIGHTER J 11 CLSED INDRS/UTDRS YES/N HEAVIER K * = INCLUDESCNTRLRMINHAZARDUSLCATlNS. A = INCLUDES PERMANENT IGNITIN SURCES t = APPLIES T SURCES F HAZARD if- = THE DATA IN CL 1,2,3 AND 4 IS INCLUDED IN THE TITLE BLCK F THE SUBTABLE. THE DATA IN THE TITLE BLCK APPLIES NLY T THE SURCE F HAZARD UNLESS INDICATED THERWISE. EACH SUBTABLE IS IDENTIFIED BY A CAPITAL LEHER.

13 TABLE A DEGREE AND EXTENT F DANGER AREA FR CLSED SURCES F HAZARD WITH HEAVIER THAN AIR GASES R VAPRS IN SUFFICIENTLY VENTILATED INDR LCATINS N. N. TYPE SURCE F HAZARD R LCATIN SIZEF SURCE F HAZARD SIZEF PUMP DRIVER IN H.P. SYSTEM PRESSURE R DENSITY DEGREEANDEXTENTF HAZARD IN LCATIN DIV. 1 DIV. 2 ADDITINAL DANGER ZNES REFER T A-1 A-2 A-3 PUMPHUSE PUMPHUSE PUMPHUSE AND UP AS INDICATED IN A-1 AS INDICATED IN A-2 LW/MD. 5 V, 25 H, 3 Hi# 5 V, 25/50 H, 3Hi ENTIRE INDR LCATIN N t YES * YES 4 A-4 PUMPHUSE 201 AND UP HIGH 25V.50H+50H* 3 Hi R ENTIRE INDR LCATIN YES 5 A-5 STRE HUSE AND LW N 6 7 A-6 A-7 STRAGEF CNTAINERS PIPING SYSTEM MINI R MDERATE ENTIRERM * 10 V, 25 H 1 18 Hi N N 8 A-8 PIPING SYSTEM MINI MDERATE 3R * N t = WHEN 50% F FLR SPACE IS CCUPIED PER A-1. = WHEN 50, 75 AND 100% F FLR SPACE IS CCUPIED AND H = 50' PER FlG. A-2. t = FR CLASS I FLAMMABLE PRDUCTS NLY. * = DES NT HAVE T BE CLASSIFIED IF PRB. FAC. IS 5 R LESS AND WELL MAINTAINED. # = CNSERVATIVE FR LW AND MD. PRESSURE. MAY BE LESS IF PUMP IS BRUSHED BY AIR?ft = 3 Hi FR INDRS; 2 Hi FR UTDRS

14 TABLE B DEGREE AND EXTENT F DANGER AREA FR CLSED SURCES F HAZARD WITH HEAVIER THAN AIR GASES R VAPRS IN INSUFFICIENTLY VENTILATED INDR LCATINS N. N. TYPE SURCE F HAZARD R LCATIN SIZEF SURCE F HAZARD SIZE F PUMP DRIVER IN H.P. SYSTEM PRESSURE R DENSITY DEGREEANDEXTENTF HAZARD IN LCATIN DIV. 1 DIV. 2 ADDITINAL DANGER ZNES REFER T B-1 B-2 B-3 PRCESS PLANT PRCESS PLANT PUMPHUSE LW/MD. HIGH AS INDICATED IN B-3 ENTIRE INDR LCATIN ENTIRE INDR LCATIN 5 V, 25 H, 3 Hi 25 V, 50 H 1 2 Hi IF HAZARD EXTENDS BEYND BUILDING 25 V, 100 H, 2 Hi IF HAZARD EXTENDS BEYND BUILDING ENTIRE INDR LCATIN YES * YES t YES t B-4 B-5 B-5 B-6 PUMPHUSE PUMPHUSE PUMPHUSE PUMPHUSE AND UP 201 AND UP 201 AND UP AS INDICATED IN B-4 MDERATE HIGH LW * ENTIRE INDR LCATIN ENTIRE INDR LCATIN ENTIRE INDR LCATIN 5 V, 25 H, 3 Hi 25/50 H, 2 Hi IF t HAZARD EXTENDS BEYND BUILDING 50 H, 2 Hi IF t HAZARDEXTENDS BEYND BUILDING 100 H, 2 Hi IF HAZARD EXTENDS BEYND BUILDING 5 V AND 5 H BEYND DIV. 1 ZNE YES t YES t YES t N * = FR MDERATE AND HIGH SYSTEM PRESSURE SEE TABLE IN B-6. = 50 H FR HP RANGE AND HIGH PRESSURE. t = NLY IF ENTIRE BLDG. IS CLASSIFIED, R HAZARD EXTENDS T BLDG. PENING, t = 2 Hi FR HP AND UP

15 TABLE C DEGREE AND EXTENT F DANGER AREA FR CLSED SURCES F HAZARD WITH HEAVIER THAN AIR GASES R VAPRS IN SUFFICIENTLY VENTILATED UTDR LCATINS N. 1 N TYPE SURCE F HAZARD R LCATIN PRCESS PLANT SIZE F SURCE F HAZARD SIZE F PUMP DRIVER IN H.P. SYSTEM PRESSURE R DENSITY MD7HIGH DEGREEANDEXTENTF HAZARD IN LCATIN DIV. 1 DIV V H, 2 Hi ADDITINAL DANGER ZNES REFERT N 2 3 PUMPWELL LW 5 V 1 10 H 1 18 Hi N 3 4 PUMP STATIN UP T 51 LW/MD. 3 V, 10 H, 18 Hi N 4 4 PUMP STATIN UP T 51 HIGH 5 V, 15 H 1 18 Hi N 5 05 PUMP STATIN LW/MD. R HIGH 5 V, 25 H 1 2 Hi N 6 06 PUMP STATIN 201 AND UP MDERATE HIGHLYVLATILE 25 V 1 50 H 1 2 Hi N PUMP STATIN STRAGE TANKS PITS 201 AND UP MDERATE FLAMMABLE * = +50 H, 2 Hi WHEN PRESSURE HIGH AND QUANTITIES F VLATILE MATERIAL CULD BE RELEASED, t = FR HIGH AND LW PRESSURE SEE TABLE IN FIG C-6. LW 5 FT FIXED RF 10 FT FLAT RF ENTIRE LCATIN A AND C 5 V, 50 H 1 2 Hi 1FT ENTIRE LCATIN NLYWHEN VENTILATED N N N

16 TABLE C (Cont'd) DEGREE AND EXTENT F DANGER AREA FR CLSED SURCES F HAZARD WITH HEAVIER THAN AIR GASES R VAPRS IN SUFFICIENTLY VENTILATED UTDR LCATINS N. N. TYPE SURCE F HAZARD R LCATIN SIZE F SURCE F HAZARD SIZEF PUMP DRIVER IN H.P. SYSTEM PRESSURE R DENSITY DEGREEANDEXTENTF HAZARD IN LCATIN DIV. 1 DIV. 2 ADDITINAL DANGER ZNES REFERT 10 11* C-9 C-1 0 VALVE * PUMP STATIN STEAM TURBINE MD./HIGH HIGH 3R 5R 3R 5/1 0 V, 10/1 5 H, 18Hi 5 V, 25 H 1 2 Hi N N 12* C11 PUMP STATIN STEAM TURBINE MD./HIGH 3 V, 25 H 5 V, 25 H, 18Hi N 13 C-12 MARINE TERMINAL MDERATE AS INDICATED IN C-12 N C-1 3 C-1 4 CNTRL RM CNTRL RM x HIGH HIGH ' YES YES * = PERMANENT IGNITIN SURCE; C-10 EARLY IGNITIN, C-11 REMTE IGNITIN, t = REGUURLY PERATED R WRKED N, IF NT DIV. 1 = ; DIV. 2 = 3 V, 10 H, 18 Hi AND AS INDICATED IN C-9. = CLASSIFICATIN APPLIES T CNTRL RM. = NT VENTILATED; N ACCESS T HAZARDUS AREA, x = VENTILATED + SAFEGUARD; ACCESS T HAZARDUS AREA.

17 TABLE D DEGREE AND EXTENT F DANGER AREA FR PEN SURCES F HAZARD WITH HEAVIER THAN AIR GASES R VAPRS IN SUFFICIENTLY VENTILATED INDR LCATINS N. N. TYPESURCE FHAZARDR LCATIN SlZEF SURCE F HAZARD SlZEF PUMP DRIVER IN H.P. SYSTEM PRESSURE R DENSITY DEGREEANDEXTENTF HAZARD IN LCATIN DIV. 1 DIV. 2 ADDITINAL DANGER ZNES REFERT D-2 D-3 DRUM FILLING PRCESS EQUIPMENT TESTING FACILITY R MINI " LW LW LW 3R AS INDICATED IN D-2 12" R LESS 5 V 1 10 H, 18 Hi t AS INDICATED IN D-2 ENTIRE INSIDE LCATIN N N N t «FLR SPACE IS FR INDIVIDUAL DRUMS * PRVIDED WITH FUME HD. TABLE E (SAME AS TABLE D, EXCEPT INSUFFICIENTLY VENTILATED) 1 E-1 DISPENSING AREA LW 5R ENTIREAREA N 2 E-2 PRCESS PLANT LW ENTIRE INDR LCATIN RSSVJ H, 2 Hi YES

18 TABLE F DEGREE AND EXTENT F DANGER AREA FR PEN SURCES F HAZARD WITH HEAVIER THAN AIR GASES R VAPRS IN SUFFICIENTLY VENTILATED UTDR LCATINS N. N. TYPE SURCE F HAZARD R LCATIN SIZE F SURCE F HAZARD SIZE F PUMP DRIVER IN H.P. SYSTEM PRESSURE R DENSITY DEGREEANDEXTENTF HAZARD IN LCATIN DIV. 1 DIV. 2 ADDITINAL DANGER ZNES REFER T 1 F-1 PEN TANK LW 5R 3V, 25 H, 3 Hi N 2 F-2 F-3 TANK FARM LW 5R 10 V, 10 H * N 3 F-4 IMPUNDING BASIN MINI VERY LW 15 H, 18Hi N 4 F-5 CNTRL RM J NNE N t * = FR F-3 ALL THE WAY UP T THE DIKES. t = NT VENTILATED; N ACCESS T HAZARDUS AREA, f = APPLIES T LCATIN WITH SURCE F HAZARD = CLASSIFICATIN APPLIES T CNTRL RM

19 TABLE G DEGREE AND EXTENT F DANGER AREA FR CLSED SURCES F HAZARD WITH LIGHTER THAN AIR GASES R VAPRS IN SUFFICIENTLY VENTILATED INDR LCATINS N. N. TYPE SURCE F HAZARD R LCATIN SIZE F SURCE F HAZARD SIZEF PUMP DRIVER IN H.P. SYSTEM PRESSURE R DENSITY DEGREEANDEXTENTF HAZARD IN LCATIN DIV. 1 DIV. 2 ADDITINAL DANGER ZNES REFER T 1 G-1 CMPRESSR STATIN R VAPR DENSITY BELW 0.75 ENTIRE INDR LCATIN N t 2 G-2 CNTRL-RM R VAPR DENSITY BELW 0.75 YES x 3 G-3 STRAGE AND PRCESSAREA MINI VAPR DENSITY BELW 0.75 ENTIRELY R PARTIALLY N = CLASSIFICATIN APPLIED T CNTRL RM. CNTRL RM HAS ACCESS T HAZARDUS LCATIN. VENTILATIN IN CNTRL RM PRVIDED WITH TYPE "B" SAFEGUARD. t = N; BECAUSE FRCED VENTILATRED X = YES; BECAUSE NT FRCED VENTILATED

20 TABLE H DEGREE AND EXTENT F DANGER AREA FR CLSED SURCES F HAZARD WITH LIGHTER THAN AIR GASES R VAPRS IN INSUFFICIENTLY VENTILATED INDR LCATINS N. N. TYPE SURCE F HAZARD R LCATIN SIZEF SURCE F HAZARD SIZE F PUMP DRIVER IN H.P. SYSTEM PRESSURE R DENSITY DEGREEANDEXTENTF HAZARD IN LCATIN DIV. 1 DIV. 2 ADDITINAL DANGER ZNES REFER T H-1 H-2 H-3 H-4 H-5 H-6 H-7 CMPRESSR STATIN CMPRESSR STATIN CNTRL + RM CNTRL RM CNTRL RM CNTRL RM CMPRESSR STATIN * x R R R R AND ABVE 0-51 LW/MD. HIGH HIGH LW/MD. AS IN H-7 = CLASSIFICATIN APPLIES T CNTRL RM. t = APPLIES T LCATIN WITH SURCE F HAZARD. * = NT VENTILATED; N ACCESS T HAZARDUS AREA. = VENTILATED + SAFEGUARD; ACCESS T HAZARDUS AREA, x = VENTILATED; ACCESS T HAZARDUS AREA. + = VENTILATED + SAFEGUARD. ENTIRE UPPER PART ENTIRE INDR LCATIN 15 H MIN.+ UPPER PART V UP T DIV. 1 15H ENTIRE INDR * LCATIN * UPTBUILDING WALLS YES RF YES YES t YES t YES t YES t N

21 TABLE I DEGREE AND EXTENT F DANGER AREA FR CLSED SURCES F HAZARD WITH LIGHTER THAN AIR GASES R VAPRS IN SUFFICIENTLY VENTILATED UTDR LCATINS N. N. TYPE SURCE F HAZARD R LCATIN SIZE F SURCE F HAZARD SIZE F PUMP DRIVER IN H.P. SYSTEM PRESSURE R DENSITY DEGREEANDEXTENTF HAZARD IN LCATIN DIV. 1 DIV. 2 ADDITINAL DANGER ZNES REFERT CMPRESSR STATIN UP T 51 HIGH 15 V 15 H N I-2 CMPRESSR STATIN CMPRESSR STATIN UP T 51 LW/MD. R HIGH LW/MD. 25 V, 25 H 10 V 1 10 H N N 4 I-2 CMPRESSR STATIN UP T 51 HIGH 15V.15H N 5 I-3 HYDRGEN GAS STRAGE MINI 25 V, 25 H N 6 7 I-4 I-5 CMPRESSR STATIN CNTRL RM * R 0-51 LW/MD. VAPR DENSITY BELW 0.75 ENTIRE UPPER PART 15 H LWER PART N YES t - CLASSIFICATIN APPLIES T CNTRL RM. t = APPLIES T LCATIN WITH SURCE F HAZARD. * = NT VENTILATED; BELW HAZARDUS AREA; VD IS < = 15 H WHEN N BSTRUCTIN AGAINST AIR FLW.

22 TABLE J DEGREE AND EXTENT F DANGER AREA FR PEN R CLSED SURCES F HAZARD WITH HEAVIER R LIGHTER THAN AIR GASES R VAPRS IN SUFFICIENTLY R INSUFFICIENTLY VENTILATED LCATINS N. N. TYPE SURCE F HAZARD R LCATIN SIZEF SURCE F HAZARD SIZEF PUMP DRIVER IN H.P. SYSTEM PRESSURE R DENSITY DEGREEANDEXTENTF HAZARD IN LCATIN DIV. 1 DIV. 2 ADDITINAL DANGER ZNES REFER T 1 J-1A PIT ANY SIZE ENTIRE PIT t 2 J-1B PIT ANY SIZE NNHARZARDUS 3 4 J-2 J-3A LADING/ UNLADING PUMPHUSE ANY SIZE SEETABLE J-2 SEETABLE J-2 ENTIRE * LCATIN SEETABLE J-2 YES 5 J-3B PUMPHUSE ANY SIZE ENTIRE LCATIN t YES 6 7 J-4 J-5 CYLINDERS ACCESSTA DIV. 2 BUNDARY 201 HP ANDUP SAFE DISTANCE FR LP GAS AS INDICATED IN J-4 BUILDING "A" DIV. 2 YES x 8 J-5 ACCESSTA DIV. 2 BUNDARY 201 HP ANDUP BUILDING "B" N.H. YES x * = NT SUFFICIENTLY VENTILATED. t = ALS SEE C-8. t = SUFFICIENTLY VENTILATED, x = APPLIES T SURCE F HAZARD.

23 TABLE J (CNT.) DEGREE AND EXTENT F DANGER AREA FR PEN R CLSED SURCES F HAZARD WITH HEAVIER R LIGHTER THAN AIR GASES R VAPRS IN SUFFICIENTLY R INSUFFICIENTLY VENTILATED LCATINS N. N. TYPE SURCE F HAZARD R LCATIN SIZEF SURCE F HAZARD SIZEF PUMP DRIVER IN H.P. SYSTEM PRESSURE R DENSITY DEGREEANDEXTENTF HAZARD IN LCATIN DIV. 1 DIV. 2 ADDITINAL DANGER ZNES REFER T 9 J-6 PIPING SYSTEM MINI LW, MD. R HIGH SEETABLE IN J J-7 J-8 J-9 BRUSHING/ NNBRUSHING AIR PRCESS PLANT SAFE DISTANCES FR PRCESS PLANT * R LW, MD. R HIGH LW, MD. R HIGH INLET AS SHWN IN J-8 LG. 1=3 FEET LC.2 = 5FEET UTLET 3 RA R 5 RA N N J-10 J-11 LW AND HIGH INTEGRITY SEAL FITTINGS SAFE DISTANCES FR H2 GAS UTDRS MINI MINI LW, MD. R HIGH LWR HIGH SEE J-6 * FR FLAMMABLE GAS RELEASED T THE UTDRS.

24 TABLE K DEGREE AND EXTENT F DANGER AREA FR CLSED SURCES F HAZARD WITH HEAVIER THAN AIR GASES R VAPRS IN SUFFICIENTLY R INSUFFICIENTLY VENTILATED LCATINS N. N. TYPE SURCE F HAZARD R LCATIN SIZEF SURCE F HAZARD SIZE F PUMP DRIVER IN H.P. SYSTEM PRESSURE R DENSITY DEGREEANDEXTENTF HAZARD IN LCATIN DIV. 1 DIV. 2 ADDITINAL DANGER ZNES REFERT 1 2 K-1 K-2 PIPING SYSTEM PIPING SYSTEM SEE K-1 SEE K-2 SEE K-1 SEE K-2 SEETABLE IN K-1 SEETABLE IN K-2 SEETABLE IN K-1 SEETABLE IN K-2

25 TABLE 1-5 SURCES F HAZARD FR LIGHTER AND HEAVIER THAN AIR FLAMMABLE SUBSTANCES N. TYPEF SURCE F HAZARD LCATIN DEGREE AND EXTENT F HAZARD 1 AIRUTLET 1 FRCEDAIR PEN SURCE F HAZARD VD = >0.75 UTDRS DIV. 1,3' RA + DIV. 2, 2' RA BEYND, DIV. 1 EXTENDING 10 H AT FLR FRM DlV. 1 2 AIR UTLET, FRCED AIR PEN SURCE F HAZARD VD =>0.75 UTDRS DIV. 1,5' RA + DIV. 2, 5 1 RA BEYND DIV. 1 EXTENDING 25 H AT FLR FRM DIV. 1 3 AIRUTLET 1 FRCEDAIR CLSEDSURCEF HAZARD VD = >0.75 UTDRS DIV. 2, 3' RA EXTENDING 10 H AT FLR FRM 3 RA 4 AIRUTLET 1 FRCEDAIR CLSED SURCE F HAZARD VD = >0.75 UTDRS DIV. 2, 5 RA EXTENDING 25 H AT FLR FRM 5 RA 5 AIR UTLET, FRCED AIR CLSEDSURCEF HAZARD VD = <0.75 UTDRS DIV. 2, 3 RA 6 AIR UTLET, FRCED AIR CLSEDSURCEF HAZARD VD = <0.75 UTDRS DIV. 2, 5 RA 7 BLEEDERS AND DRAIN VALVES UTDRS DIV. 2, 5' RA. UTDR LCATINS ARE SUFFICIENTLY VENTILATED

26 TABLE 1-5 SURCES F HAZARD FR LIGHTER AND HEAVIER THAN AIR FLAMMABLE SUBSTANCES N. TYPEF SURCEF HAZARD LCATIN DEGREEAND EXTENT F HAZARD 8 DRAINS, PEN T CLLECT AND REMVE FLAMMABLE LIQUIDS UTDRS Dl V. 2, 18" H, 18" V ABVE GRADE DIV. 1 BELW GRADE 9 DRAINS, PEN T CLLECT AND REMVE FLAMMABLE LIQUIDS INDRS DIV. 2, 18" H, 18" V ABVE GRADE DIV. 1 BELW GRADE 10 ENGINES RUNNING N DIESEL FUEL INDRS * NN HAZARDUS 11 FLARE UTDRS NN HAZARDUS 12 FLWING WELL WITHUT CELLAR UTDRS DIV. 2, 5 RA 13 FUME HD, FAN IN WALL PEN SURCE F HAZARD VD = >0.75 UTDRS DIV. 1, 5' RA + DIV. 2, 5' RA BEYND DIV.!,EXTENDING 25' H AT FLR FRM DIV. 1 t 14 FUME HD, FAN IN WALL, PEN SURCE F HAZARD VD = >0.75 UTDRS DIV. 1, 3 1 RA + DIV. 2, 2' RA BEYND DIV. 1,EXTENDINGI 1 H AT FLR FRM DIV. 1 ' UTDR LCATINS ARE SUFFICIENTLY VENTILATED INDR LCATINS ARE NT SUFFICIENTLY VENTILATED UNLESS MARKED BY * t APPLIESTFAN

27 TABLE 1-5 (CNT.) SURCES F HAZARD FR LIGHTER AND HEAVIER THAN AIR FLAMMABLE SUBSTANCES N. TYPEF SURCEF HAZARD LCATIN DEGREEAND EXTENT F HAZARD 15 FUME HD, FAN IN WALL, CLSEDSURCEF HAZARD VD = >0.75 UTDRS DIV. 2, 5' RA EXTENDING 25' HRIZNTALLYATFLR FRMWALL t 16 FUME HD, FAN IN WALL, CLSEDSURCEF HAZARD VD = >0.75 UTDRS DIV. 2, 3' RA EXTENDING 10' HRIZNTALLYATFLR FRM WALL t 17 FUME HD, FAN IN RF, CLSEDSURCEF HAZARD VD = <0.75 UTDRS DIV. 2, 5' RA t 18 FUME HD, FAN IN RF, CLSEDSURCEF HAZARD VD = <0.75 UTDRS DIV. 2, 3' RA t 19 GAS PERATED PNEUMATIC INSTRUMENTS FR HYDR- CARBN SERVICE FLW, PRESSUREANDCNTRL UTDRS Dl V. 1,1 8" RA + DIV. 2 18" RA BEYND DIV GAS PERATED INSTRUMENTS SAME AS IN 19 INDRS * DIV. 2 ENTIRE LCATIN VENTED SAME AS IN GAS PERATED INSTRUMENTS SAME AS IN 19 INDRS DIV. 1 ENTIRE LCATIN UTDR LCATINS ARE SUFFICIENTLY VENTILATED INDR LCATINS ARE NT SUFFICIENTLY VENTILATED UNLESS MARKED BY * t APPLIESTFAN

28 TABLE 1-5 (CNT.) SURCES F HAZARD FR LIGHTER AND HEAVIER THAN AIR FLAMMABLE SUBSTANCES N. TYPEF SURCE F HAZARD LCATIN DEGREE AND EXTENT F HAZARD 22 GASLINE DISPENSING SERVICE STATIN UTDRS DIV. 2, 18" H ' H, 18" HI 23 HYDRCARBN PRESSURE VESSEL UTDRS DIV. 2, 10 RA 24 HYDRGEN GAS STRAGE CYLINDER LESS THAN 400 CF UTDRS DIV. 2, 5' RA BELW DEMARCATIN LINE, 15 FT ABVE DEMARCATIN LINE 25 HYDRGEN GAS STRAGE CYLINDERS MRE THAN 400 CF UTDRS DIV FT WITHUT BSTRUCTIN 25 FT WITH BSTRUCTIN 26 HEADER (MANIFLD) INDRS * DIV. 2 ENTIRE LCATIN 27 INJECTINWELL UTDRS DIV. 2, 5' RA 28 IMPUNDING BASIN UTDRS DIV. 2, 15' H, 18" HI UTDR LCATINS ARE SUFFICIENTLY VENTILATED INDR LCATINS ARE NT SUFFICIENTLY VENTILATED UNLESS MARKED BY *

29 TABLE 1-5 (CNT.) SURCES F HAZARD FR LIGHTER AND HEAVIER THAN AIR FLAMMABLE SUBSTANCES N. TYPE F SURCEF HAZARD LCATIN DEGREEAND EXTENT FHAZARD 29 IL WATER SEPARATR UTDRS CLASSIFICATINSAMEAS PITWITHUTMECHANICAL VENTILATIN. HEAVIER THAN AIR FLAMMABLE VAPRS UTDRS DIV. 1,ENTIREPIT 31 PITWITHMECHANICAL VENTILATIN. HEAVIER THAN AIR FLAMMABLE VAPRS UTDRS DIV. 2, ENTIRE PIT 32 PIT NT WITHIN HAZARDUS LCATIN, CNTAINING PIPING, FITTINGS, VALVES, etc. UTDRS DIV. 1,ENTIRE PIT 33 PIPING SYSTEM WITH VALVES, FLANGES, FITTINGS FR FLAMMABLE LIQUID INDRS UTDRS SEE FIG K1 AND K2 34 PRTABLE CNTAINERS FR CLASS I FLAMMABLE LIQUID IN RM WITH N EXTERNAL WALLS INDRS * DIV. 2, ENTIRE RM 35 PRESSURERELIEFVALVE. LIGHTER R HEAVIER THAN AIRVAPRS. UTDRS Dl V. 2, 10' RA UTDR LCATINS ARE SUFFICIENTLY VENTILATED INDR LCATINS ARE NT SUFFICIENTLY VENTILATED UNLESS MARKED BY *

30 TABLE 1-5 (CNT.) SURCES F HAZARD FR LIGHTER AND HEAVIER THAN AIR FLAMMABLE SUBSTANCES N. TYPEF SURCEF HAZARD LCATIN DEGREEAND EXTENT F HAZARD 36 RECEIVER FUMMABLE LIQUID UTDRS Dl V. 1,5' RA + DIV. 2, 10' RA BEYND DIV SUMP, PEN T CLLECT AND CNTAIN FLAMMABLE LIQUIDS UTDRS DIV H, 1 1 V ABVE GRADE DIV. 1 BELW GRADE 38 SUMP, PEN T CLLECTANDCNTAIN FLAMMABLE LIQUIDS INDRS DIV.!,ENTIRE LCATIN 39 STRAGETANKFR DIESEL FUEL UTDRS NN HAZARDUS 40 VENTS, ATMSPHERIC TANK VENTS R BUILDING VENTS FR HEAVIER THAN AIR PRDUCTS UTDRS DIV. 1,5' RA + DIV. 2, 5' RA BEYND DIV VENT, ATMSPHERIC HEAVIER THAN AIR VAPRS FR STRAGETANKS UTDRS DIV. 1,5' RA + DIV. 2, 5' RA BEYND DIV VENT, ATMSPHERIC HEAVIER THAN AIR VAPRS FR STRAGETANKS UTDRS DIV. 1,3' RA + DIV. 2, 2' RA BEYND DIV VENT, ATMSPHERIC HEAVIER AND LIGHTER THAN AIR VAPRS FR MINI INSTRUMENTS AND CNTRLS UTDRS Dl V. 1 18" H + DIV. 2, 18" RA BEYND DIV. 1 UTDR LCATINS ARE SUFFICIENTLY VENTILATED INDR LCATINS ARE NT SUFFICIENTLY VENTILATED UNLESS MARKED BY *

31 in Fig 1-5 has a surface temperature in excess of the ignition temperature of the flammable product and is, therefore, considered a "remote permanent ignition source." The equivalent HP rating of the steam driven pump Pl is 50 HP. Pumps Pl, P2 and P3 are small pumps operating at high pressure and driven by 50 HP electric motors. Pumps P4 and P5 are large, operating at moderate pressure and driven by electric motors of 250 HP. Determine for each individual pump the recommended boundary distance. The boundary distance is influenced by the size of the pump and the pressure in the system. Since the pumps are located in an outdoor area refer to Fig 1-2 for the required boundary distance. Select in Fig 1-2 the recommended boundary distance for the particular pump driver on the basis of size, HP rating of electric motor and pressure in the system. According to Fig 1-2B the recommended horizontal boundary distance for Pumps Pl, P2 and P3 is 15 feet, and for Pumps P4 and P5, 50 feet. Since the permanent ignition source "a" in Fig 1-5 is within the 15 and 50 feet horizontal boundary distance of Pumps Pl, P2 and P4, the area between the ignition source and Pumps Pl, P2 and P4 must be classified Div. 1. The area in opposite direction of Pump P4, also 50 feet long, is allowed to be classified Div. 2. Since the actual distance between P3 and the ignition source "a" is longer than 15 feet, the area between Pump P3 and the ignition source need not be classified Div. 1. However, since Pump P3 is within the 50 feet Div. 1 zone of Pump P4, the area between Pump P3 and the ignition source automatically becomes Div. 1. The required 50 feet horizontal boundary for Pump P5 does not reach the permanent ignition source "a." Because of this, the area surrounding Pump P5 is not required to be classified Div. 1, but must be classified Div. 2 in compliance with Item 3 of Table 1-4. (Fig C-6 in Table "C," item 7). Since Div. 1 zones normally do not directly border to a nonhazardous area, a Div. 2, 5 feet wide transition zone is required between the Div. 1 zone and the nonhazardous area. The breakdown of Pump Pl, however, could cause early ignition of the flammable vapors released. If early ignition is possible, the Div. 1 area surrounding Pump Pl does not have to be 15 feet, but should be reduced to 3 feet without a Div. 2 transition zone. F. The Extent of Explosion Danger for Class n Flammable Products As pointed out previously, the required extent of explosion danger for locations storing, handling, and/or processing Class I flammable products can be obtained directly from Tables 1-4 and 1-5. These tables may also be used for Class II flammable products. However, bear in mind that the recommended hazardous areas in these tables are prepared exclusively for Class I flammable products because of their large vapor traveling distances, and not for Class II flammable products, which

32 generally have shorter vapor traveling distances. Although the vapor traveling distances for Class II flammable products are generally shorter, it is very convenient to apply Tables 1-4 and 1-5 for Class II flammable products. Greater safety is achieved by applying the larger areas. However, the larger areas for Class II flammable products of course are not the most economical. For additional feet of area, electrical equipment needs to be adequate. If for economical reasons or any other reason, smaller hazardous areas for Class II flammable products are preferred, the following steps are to be followed to establish the proper dimensions for these Class II flammable products. First, assume that the location under consideration does not contain a Class II flammable product, but a Class I flammable product. This is necessary to obtain the required area size for the Class I product which later must be reduced to suit the Class II flammable product. Second, the actual operating temperature of the Class II flammable product must be used for the Class I product. This is necessary to obtain vapor pressure of the Class I flammable product, which must be used to determine the required area size for the Class II product. Third, find in Fig 1-6 the vapor pressure for the Class I flammable product based on a 100% flash point, and the actual operating temperature of the Class II flammable product. Fig 1-6 shows flash points, operating temperatures and vapor pressures for Class I, Class II and Class III flammable products. Class III flammable products however are not considered. Next find in Fig 1-6 the vapor pressure for the Class II flammable product at its original flashpoint. Finally, establish the inverse ratio of both vapor pressures. This ratio is a measure for the actual boundary size for the class II flammable product. For example, assume a closed source of hazard containing a Class II flammable liquid has a flashpoint of F. Assume that the operating temperature of the Class II flammable product is 20 0 F. Consider the same source of hazard, processing a Class I flammable product, also operating at a temperature of 20 0 F. Find from Table 1-4 or Table 1-5, the required horizontal boundary distance for the Class I flammable product. Say the required boundary distance is 25 feet. From Fig 1-6 find the vapor pressure for the Class I flammable product at 10 0 F flashpoint by starting at the bottom of Fig 1-6 at 10 0 F flashpoint. Go straight up until the vertical line is intersected by the 20 0 F line and read at the left border line the vapor pressure for the Class I flammable product, which is.13 atmosphere. The vapor pressure for the Class II flammable product is found in the same manner, except start in Fig 1-6 at the original flashpoint for the Class II flammable product, which is F. Go straight up until the vertical line is intersected by the 20 0 F line, and read at the left border line the vapor pressure for the class II flammable product which is atmosphere. The inverse ratio of the two vapor pressures is Multiply the 25 feet

33 CLASSI PRDUCTS CLASS Il PRDUCTS CLASS III PRDUCTS FLASHPINTS AT DEGREES F TEMPERATURE VERSUS VAPR PRESSURE FR FLAMMABLE LIQUIDS

34 boundary for the Class I flammable product by 0.27 which equals to 6.7 feet. Boundary sizes are standardized in 3, 5, 10, 15, 50 and 100 feet. Take the next higher size above 6.76 feet. The boundary size required for the Class II flammable product is then 10 feet. Since the source of hazard is closed, and if it is assumed to be in a sufficiently ventilated location, the 10 foot size needs only to be classified Div. 2. If cost of the electrical installation for the Div. 2 area is a major consideration, 10 feet is a valid size. If cost has little impact on the hazardous area, then the 25 foot size should be applied. G. Transition Zones for NEC Class I Locations As previously pointed out, the size of a hazardous area is established on the basis of the horizontal distance a flammable gas or vapor in the air must travel to reach safe concentrations. Traveling distances are established by analysis, test and experiments. The traveling distance, however, is influenced by the quantity of flammable gases or vapors released into the atmosphere. Large quantities of flammable gases or vapors released into the atmosphere have the tendency to travel long distances before reaching safe concentrations, causing the point of safe concentration to shift farther away from the point of release. Small quantities of flammable gases or vapors in the air have the tendency to travel short distances before reaching safe concentrations. This brings the point of safe concentration closer to the point of release. Traveling distances, therefore, may have different sizes before reaching safe concentrations. They may be short or long, depending on the conditions under which a flammable gas or vapor is released into the atmosphere. To apply a hazardous area safely, the size of the hazardous area must match each individual distance a flammable gas or vapor will travel to reach safe concentrations. Because of the many conditions under which a flammable product can be released into the atmosphere, a great number of hazardous area sizes are required to cover each individual traveling distance. However, too many hazardous area sizes will cause confusion and makes the application too elaborate. To simplify the application of hazardous areas, the traveling distances are divided into groups based on specific conditions, whereas each group is assigned one specific hazardous area size. This reduces the number of hazardous area sizes and simplifies the application considerably. f course the size of the hazardous area selected for a particular group must match the longest traveling distance in that group. Since each selected hazardous area will cover a number of traveling distances of different sizes, the result is that the hazardous area in some cases may be too long, and in other cases, just right. To even further simplify the application of the hazardous areas, the groups are associated with a specific quantity of flammable gases or vapors released to