536 Design of GAS-HANDLING Systems and Facilities Figure 17*24. Standard explosion-proof junction boxes and conduit fittings. (Courtesy of Crouse-H/nc/s Electrical Construction Materials, a division of Cooper Industries, Inc.) 1. Confine internal explosions to explosion-proof enclosures and con- duit systems. 2. Minimize the passage of gases, and prevent the passage of flame, through conduit or cable. 3. Prevent process gas or liquid in process piping from entering con- duit or cable systems. 4. Prevent "pressure piling." Pressure piling is a phenomenon caused by the fact that ignition in an enclosure can first pre-compress gases in a conduit or other enclosure to Electrical Systems 537 Figure 17-25. Standard sealing fittings. (Courtesy of Crouse-Hinds Electrical Construction Materials, a division of Cooper Industries, Inc.] Figure 17-26. Cutaway drawing of a property installed sealing fitting. (Courtesy of Crouse-Hinds Electrical Construction Materials, a division of Cooper Industries, Inc.] S38 Design of GAS-HANDLING Systems and Facilities which It is connected. When pre-compressed gases are then ignited in the second enclosure, pressures exceeding those for which it has been tested can be reached. Receptacles and Attachment Plugs Receptacles and attachment plugs for Class I, Division 1 and 2 areas must be approved for the area. They must provide a means of connection to the grounding conductor of a flexible cord. Typical Class I receptacles and attachment plugs are shown by Figure 17-27. Figure 17-27. Typical Class I, Division 1 and 2 receptacles and attachment plugs. (Fop, courtesy of Crouse-Hinds Electrkal Construction Atoteria/s, a division of Cooper Industries, Inc.; bottom, courtesy ofAppleton Electric Co., a division of Emerson Electric Co.) Electrical Systems 539 Seal Locations Seals must be installed in the following locations: 1. Seals are required at entries by conduit or cable to explosion-proof enclosures containing arcing or high-temperature devices in Divi- sion 1 and Division 2 locations. It is not required to seal \ 1 A in. or smaller conduits into explosion-proof enclosures in Division 1 areas housing switches, circuit breakers, fuses, relays, etc., if their cur- rent-interrupting contacts are hermetically sealed or under oil (hav- ing a 2-in. minimum immersion for power contacts and 1-in. for control contacts). 2. Seals are required where 2 in. or larger conduits enter explosion- proof enclosures containing taps, splices, or terminals in Division 1 areas (but not Division 2 areas). 3. Seals are required in conduits leaving Division 1 areas or traversing from Division 2 areas into unclassified areas, on either side of the boundary. No union, coupling, junction box, or fitting is allowed between the seal and the boundary. Metal conduits that pass com- pletely through a Division 1 or a Division 2 location without a union, coupling, junction box, or fitting within 12 in. of the Division 1-Division 2 or Division 2-unclassified boundary do not require a sealing fitting at the boundary. 4. Except for conduit or cable entries into explosion-proof enclosures containing arcing or high-temperature devices (as described in Item 1 above), cables that will leak gas through the core at a rate of less than 0.007 ft 3 /hr at 6 in. of water pressure need not be sealed if they are provided with a continuous gas/vapor-tight sheath. Cables with such a sheath that will transmit gas at or above this rate must be sealed if connected to process equipment that may cause a pressure of 6 in. of water at the cable end. 5. Cables without a continuous gas/vapor-tight sheath must be sealed at classified-unclassified area boundaries. 6. All cable terminations in Division 1 areas must be sealed. This requirement is imposed by API RP 14F, when specific cables are allowed in Division 1 areas. 7. Special sealing fittings (not yet commercially available) are required for cables and conduits connected to process connections that depend on a single seal, diaphragm, or tube to prevent process fluid 540 Design of GAS-HANDLING Systems and Facilities from entering the conduit or cable system. Single barrier devices probably are best avoided if multiple barrier devices are available. Sealing fittings must be installed as close as practicable to explosion- proof enclosures, but in no case more than 18 inches from the enclosures, Although junction boxes and other devices which materially increase the cross-sectional area of the conduit system connecting the enclosure and the seal may not be installed between an enclosure and a seal, explosion- proof unions, couplings, elbows, capped elbows, and conduit bodies such as an "L," "T," or "cross" are allowed if the conduit bodies are not larger than the trade size of the connecting conduit, A single seal may suffice for two enclosures if it is installed no more than 18 in. from either enclosure. Certain devices may be obtained which are "factory-sealed* 9 —that is, interconnecting wiring is sealed by the manufacturer where it enters/exits enclosures. These devices do not require an additional (external) seal, and often can be utilized to advantage in lessening installation time and reducing space requirements (for an external seal). These devices are tested only for internal explosions and not for exter- nal explosions pressurizing the devices from the outside. As an example, a factory-sealed push-button start/stop station connected to an explosion- proof motor starter cannot suffice as a seal for the motor starter conduit entry. A separate seal must be installed at the point of conduit entry. Cable termination fittings are available which also are approved as sealing fittings, and often incorporate a union in their design. Particularly for space-limited installations, the difference in length requirements for such dual-purpose devices, as compared to standard sealing fitting/cable terminator/union combinations, can be consequential. Seal Fittings Installation When seal fittings are installed, certain mechanical practices must be followed. The following requirements are often overlooked by both installers and inspectors: 1. Accessibility. Sealing fittings should not be installed behind walls or in other inaccessible locations. 2. Orientation. Certain fittings are designed specifically for either hori- zontal or vertical mounting; others may be installed either horizon- tally or vertically, or even at oblique angles. Electrical Systems 541 3, Approved compound. Only approved compound and damming fiber may be used. Rags or putty materials may not be used to construct dams. Some cable seals use a self-hardening putty-like material and do not require damming fiber. 4, Splices. Splices and taps may not be made in sealing fittings. Most sealing compounds are poor insulators, and electrical shorts could occur. 5. Drains. Drains or drain seals must be provided in locations neces- sary to prevent water accumulation. 6. Thickness. Completed conduit seals must have a seal which is at least as thick as the trade size of the conduit. In no case can the seal be less than %-in. thick. Specific Equipment Considerations Transformers Although transformers suitable for other industrial installations are generally suitable for producing applications, certain options may be desirable—primarily due to environmental considerations. At locations subject to harsh environmental conditions, and particularly at locations subject to washdown with high-pressure hoses, non-ventilated enclosures are desirable, if not necessary. Likewise, at locations subjected to salt water and salt-laden air, it often is desirable to specify copper windings and lead wires. Most manufacturers provide standard units with alu- minum windings and lead wires. Even if aluminum coils are used, it is almosl always desirable to require stranded copper lead wires. This will lessen corrosion and loose terminal problems when transformers are interconnected to the facility electrical system with copper conductors. If the transformers are to be installed outdoors in corrosive environments, cases should be of corrosion-resistant material (e.g., stainless steel) or be provided with an exterior coating suitable for the location. Many producing facilities are located offshore or in other environmen- tally sensitive areas. In these areas, the use of dry (versus liquid-filled) transformers will eliminate the necessity of providing curbing and other containment systems to prevent pollution. Dry transformers are normally preferred for most production facility applications. Liquid-filled trans- formers should be considered, however, for high voltage and large units (particularly over several hundred kVA). 542 Design of GAS-HANDLING Systems and Facilities Electric Motors Apart from considerations given to corrosion resistance and suitability for hazardous (classified) areas, the selection of electric motors for oil field applications is the same as the selection of electric motors for other industrial applications. One exception may be the selection of motors for areas where electric power is self-generated. Frequency and voltage vari- ations may occasionally occur at such locations. For such locations, con- sideration should be given to specifying motors which are tolerant to at least 10% voltage variations and 5% frequency variations. It is cautioned that NEMA Design B motors (normal starting torque) may not be suitable for applications requiring high starting torque such as positive displacement pumps. NEMA Design C motors should be used in this service. Most standard motors are manufactured using non-hygroscopic NEMA Class B insulation. For added protection in an offshore environment, open drip-proof or weather protected motors should be specified with a sealed insulation system. NEMA Class F insulation is also available in most motor sizes and is advisable to provide an improved service factor. A motor used in standby operation mode should be equipped with a space heater to keep the motor windings dry. In classified areas these space heaters must meet the surface temperature requirement of the spe- cific hazardous area. Lighting Systems Lighting systems are installed both to provide safety to operating per- sonnel and to allow efficient operations where natural light is insufficient. The lighting required for safety to personnel depends on the degree of the hazard requiring visual detection and the normal activity level. It typically varies from 0.5 to 5.0 footcandles. Lighting levels required for efficient operations vary from as low as 5 footcandles to as high as 100 footcan- dles, or more. Table 17-4 contains some general lighting guidelines. The first step in the design of a lighting system is the determination of the various lighting levels required for the specific areas of the facility. Typically, the majority of the fixtures are high intensity discharge (HID) fixtures and fluorescent fixtures. Certain applications may require incan- descent fixtures as well. HID fixtures include those using mercury vapor and sodium vapor lamps. Mercury vapor fixtures are usually less expensive than sodium Electrical Systems 543 Table 17-4A Minimum Recommended Levels of Illumination for Efficient Visual Tasks Minimum Lighting Level Area (Footcandles) Offices, General 50 Offices, Desk Area 70 Recreation Rooms 30 Bedrooms, General 20 Bedrooms, Individual Bunk Lights 70 Hallways, Stairways, Interior 10 Walkwavs, Stairways, Exterior 2 Baths, General 10 Baths, Mirror 50 Mess Halls 30 Galleys, General 50 Galleys, Sink & Counter Areas 100 Electrical Control Rooms 30 Storerooms, Utility Closets 5 Walk-in Freezers, Refrigerators 5 TV Rooms (lights equipped with dimmers) Off to 30 Work Shops, General 70 Work Shops, Difficult Seeing Task Areas 100 Compressor, Pump and Generator Buildings, General 30 Entrance Door Stoops 5 Open Deck Areas 5 Panel Fronts 10 Wellhead Areas 5 fixtures initially, and are readily available in most styles. However, sodi- um vapor fixtures are more efficient in the use of electricity. Because of quite poor color rendition and difficulty in safe disposal of expended lamps, low pressure sodium fixtures are less desirable than high pressure sodium fixtures and are seldom recommended for produc- tion facilities. High pressure sodium fixtures are particularly attractive for illuminating large open areas. At locations where power cost is low and where many fixtures are required due to equipment shadowing, mer- cury vapor fixtures often are preferred because of their lower initial cost, lower replacement lamp cost, and better color rendition. The low profile of fluorescent fixtures often dictates their use in areas with low headroom, such as in wellbays on offshore platforms and in 544 Design of GAS-HANDLING Systems and Facilities Table 17-4B Minimum Recommended Levels of Illumination for Safety Minimum Lighting Level Area (Footcandles) Stairways 2.0 Offices 1.0 Exterior Entrance 1.0 Compressor and Generator Rooms 5.0 Electrical Control Rooms 5.0 Open Deck Areas 0.5 Lower Catwalks 2.0 buildings with conventional ceiling heights. The relatively short life, low efficiency, and susceptibility to vibration exclude incandescent lamps from serious consideration for many applications, particularly for general area lighting. In areas free from vibration and easily accessible for main- tenance, however, incandescent fixtures may be quite acceptable. When designing lighting systems, particular attention should be given to locating fixtures where relamping can be performed safely and effi- ciently. Poles which can be laid down, as opposed to climbed, are often preferred—particularly at offshore locations. This feature offers less advantage, of course, at land locations where bucket trucks or the like can be used for relamping. In locations subject to vibration, it normally is prudent to install lighting fixtures with flexible cushion hangers or flexi- ble fixture supports (hanger couplings) to increase lamp life. Remotely mounted ballasts for HID fixtures are frequently desirable, particularly when the fixtures themselves must be installed in locations of high tem- perature and locations difficult to access for maintenance. The ceilings of large compressor and pump buildings are examples of locations where remote ballasts often are attractive. Motor Control Center The engineer providing the initial design of major facilities is faced with the decision of providing a motor control center building or individ- ual (usually rack-mounted) motor starters and corresponding branch cir- cuit protection devices. For installations using only several motors it fre- Electrical Systems 545 quently is more economical to provide individual (usually explosion- proof) motor starters and circuit protection devices. For facilities that include large numbers of motors and other electrical equipment, it normally is both more economical and more convenient to furnish a building to enclose the required motor starters and distribution panels. This building is normally referred to as a motor control center (MCC). In addition to typically allowing less expensive non-explosion- proof equipment, these buildings are frequently environmentally con- trolled (air conditioned, and possibly heated in colder climates) to reduce equipment corrosion and enhance reliability. Maintenance is more easily performed indoors than if the equipment were installed outside and main- tenance personnel were subject to extreme cold, rain, snow, or other adverse weather conditions. If air conditioning systems are designed for buildings housing electri- cal equipment, the heat generated by the electrical equipment must be considered when sizing the air conditioning equipment. Artificial heat is seldom required in all but the coldest of climates. Enclosures The selection of equipment enclosures involves consideration of envi- ronmental conditions as well as the possibility of exposure to flammable gases and vapors. The National Electrical Manufacturers Association (NEMA) provides a list of designations for enclosures that is adequate to specify many enclosure requirements. As an example, enclosures desig- nated as NEMA 7 are explosion-proof, suitable for Class I areas for the gas groups labeled. NEMA 7 enclosures may be labeled for only one group (such as Group D) or for several groups (such as Groups B, C, and D). NEMA 1 enclosures are designed to perform little other purpose than to prevent accidental personnel contact with enclosed energized compo- nents, but are suitable for most unclassified areas. NEMA 4X enclosures, watertight, and constructed of corrosion-resistant material, are often pre- ferred for outdoor non-explosion-proof applications in areas subjected to harsh environmental conditions or high pressure hose washdown. CORROSION CONSIDERATIONS Even though the electrical design details of a system may be well specified, the system will not endure or continue to provide safety to per- sonnel unless proper materials are selected and certain installation proce- [...]... turbine, 479,4 82 internal, 469 See also Engines Combustors, 479 Communications, power supply, 517 Components compressors, 28 6-307 heavy, 137 intermediate, 111, 130 -131 ,135 ,137 ,149 light, 111, 131 -1 32, 135 , 137 554 Compression engine, 470 gas, 2 Compressor buildings, 514 horsepower, determining, 27 2 -27 6 ratio, overall, 25 3 specifying, 27 0 -27 2 stages, determining, 27 2 -27 6 use, oil and gas fields, 25 4 Compressors... cylinder MAWP, 29 0 cylinder piston displacement, 308 cylinder sizing, 307-310 cylinders, 26 8 distance pieces, 29 3 -29 4 double-acting cylinders, 28 9, 307 engine-driven, 393 flash gas, 25 3, 27 6 flexibility, 310 foundation design, 319 frames, 28 7 -28 9 gas lift, 25 4, 26 2, 27 6, 27 8 general, 25 3 -28 5 heads, 461 Helical-Lobe, 26 6 -26 7 industry specifications, 320 - 321 integral units, 25 8, 25 9, 28 8 kinetic, 25 5 lubrication... lubrication, 29 9, 313- 317 natural gas, 461 offshore installations, 320 packing lubrication system, 316 packing, 29 8-300 pipe sizing, 317-319 pipeline booster use, 26 2 piston displacement, 308 piston wear bands, 29 6 pistons and piston rods, 29 6 positive-displacement, 25 5 reciprocating, 3, 25 5 -26 4 ,28 6- 326 high-speed, 25 8 -25 9 low-speed, 25 9 -26 4 process considerations, 27 6 -28 0 rod, 29 4, 310-311 rotary ,3 ,25 5 screw,... frames, 28 6 bearings, 29 6 -29 8 booster, 25 4, 27 6, 28 6 capacity control devices, 3 02 casinghead gas, 25 4 centrifugal, 3, 26 7 -27 0, 28 6 centr i fugal proces s considerations, 28 1 -28 5 centrifugal, stonewalling, 28 0 -28 1 centrifugal, surge control, 28 0 -28 1 components, 28 6-307 crankshafts, 29 4 crossheads 29 4 cylinder capacity, 307 cylinder clearance, 305-307 cylinder cooling, 3 12- 313 cylinder liners, 29 1 cylinder... screw, 25 5, 26 6 -26 7 separable units defined, 25 8 single-acting cylinders, 28 9, 307 types, 25 5 -27 0 valve unloader types, 303 valve velocity, 301-3 02 valves, 300-3 02 vane, 3, 25 5, 26 4 -26 6 vapor recovery, 20 4, 27 6 vibration, 317-319 volumetric efficiency, 308 Condensate, 3, 111 Condensate stabilization, 3, 130 -150 Condensate stabilizers cold feed, 111, 134 , 136 -137 , 149, 24 9 definition, 134 design, 137 gas-producing... hazardous areas, 461, 525 sizing, 495 standby, 494,496 TEFC, 525 turbine, 494 units, 493 German Lurgi Company, 1 72 Giycoi circulation rate, 21 1 -21 2 concentration, 20 8 -20 9 dehydration process, description, 198 -20 4 dehydration, 91,196 -22 8 /glycol heat exchanger, 20 2 reboilers, heat duty, 21 7 -21 8 reboilers, pressure, 21 0 -21 1 reboilers, temperatures, 20 9 -21 0 reconcentration systems, 20 1 reconcentration,... Processing and Manufacture) Canadian Standards Association (CSA) 178 Rexdale Boulevard Rexdale, Ontario M9W 1R3 Canada C 22. 1, Part I Canadian Electrical Code C 22. 2, No 30 Explosion-proof Enclosures for Use in Class I Hazardous Locations C 22. 2, No 14 Motors and Generators for Use in Hazardous Locations C 22. 2, No 157 Intrinsically Safe and Nonincendive Equipment for Use in Hazardous Locations C 22. 2, No 174... Locations, Class I and II, Division 2, and Class III, Divisions 1 and 2 United States Code of Federal Regulations c/o U.S Government Printing Office Washington, D.C 20 4 02 Title 29 , Occupational Safety and Health Standards, Subpart S, Part 1910 Electrical Title 30, Oil and Gas and Sulfur Operations in the Outer Part 25 0 Continental Shelf Title 33, Subchapter C, Aids to Navigation Part 67 Title 46, Shipping... 174 Furnaces, 82, 109 flow rate, relief valves, 370 gravity, 97 heating value, 4 leaks, 3 92, 393, 395 lift compressors, 25 4 permeation process, 178-179 processing plant, 149 processing processes, choice of, 24 9 -25 2 processing, definition, 24 1 processing, methods, 24 4 24 9 processing, objectives, 24 4 processing, refrigeration method, 24 6 -24 8 production facilities, 7,47, 65, 522 reservoirs, 2 sales, 3,111,151,195... 550 Design of GAS-HANDLING Systems and Facilities Std 303 Recommended Practice for Auxiliary Devices for Motors in Class I, Groups A, B, C, and D, Division 2 Locations RP 446 Recommended Practice for Emergency and Standby Power Systems for Industrial and Commercial Applications Instrument Society of America (ISA) P, O Box 122 77 Research Triangle Park, NC 27 709 S5.1 Instrumentation Symbols and Identification . positive-displacement, 25 5 bearings, 29 6 -29 8 reciprocating, 3, 25 5 -26 4 ,28 6- 326 booster, 25 4, 27 6, 28 6 high-speed, 25 8 -25 9 capacity control devices, 3 02 low-speed, 25 9 -26 4 casinghead gas, 25 4 process. compressors, 28 6-307 Casing vapor recovery heavy, 137 compressors, 25 4 intermediate, 111, 130 -131 ,135 ,137 ,149 Casinghead gas compressors, 25 4 light, 111, 131 -1 32, 135 , 137 554 Compression kinetic, . determining, 27 2 -27 6 packing lubrication system, 316 ratio, overall, 25 3 packing, 29 8-300 specifying, 27 0 -27 2 pipe sizing, 317-319 stages, determining, 27 2 -27 6 pipeline booster use, 26 2 use,