Process Engineering Equipment Handbook Episode 2 Part 6 potx

G-14 Generators; Turbogenerators FIG. G-11 Open cooling system. (Source: Alstom.) FIG. G-12 Generator assembly. (Source: Alstom.) Pilot exciter The pilot exciter is a synchronous generator with permanent magnets on the rotor. The rotor magnets are enclosed in a short-circuited aluminum ring that prevents demagnetization of the poles because of short-circuiting in the stator winding. The stator winding insulation satisfies the requirements for temperature class F (155°C). Exciter housing Openings are provided in the side walls of the housing for cooling air intake and exhaust and for service activities. Support bearing The support bearing consists of shield, bearing insulation, bearing, and shaft seals. The bearing, which consists of a bearing body with white metal lining, is insulated from the shield. The shaft seals against oil leakage from the bearing housing consist of a split seal of oil-resistant insulation material. An air extractor is connected to the bearing space to prevent oil leakage through the external seals. Internal shaft seals are provided with sealing caps and the intermediate space is connected to the blocking air from the pressure side of the fan. Generators; Turbogenerators G-15 FIG. G-13 Main exciter. (Source: Alstom.) Cooling The exciter can be provided with either an open or a closed cooling system. With an open cooling system, a housing with filter cassettes is mounted on one side of the exciter housing for the incoming cooling air. The cooling air exit is directed downward under the exciter housing. With a closed cooling system, the filter housing is replaced with supply and exhaust air channels connected to the cooler housing of the generator. Surface Treatment In its standard version, the generator is painted with a lacquer of two-component type based on ethoxylized chlorine polymer. The generator is primed inside and outside and then finished externally in a neutral blue color. The paint is resistant to corrosive, tropical, and other aggressive atmospheres. Static Excitation When the rotor winding of the generator is supplied with current from a static rectifier unit, the rotor is provided with a slipring shaft and supplied via brush gear. Slipring shaft The slipring shaft (see Figs. G-14 and G-15) consists of shaft extension, insulations, sliprings, contact screws, and terminal conductors. The shaft extension consists of a steel forging with flange for connection to the shaft of the generator rotor. The center of the shaft extension is drilled for the terminal conductors. The sliprings are manufactured of steel and have generously dimensioned contact surfaces for the carbon brushes. The spiral-machined contact surface is carefully ground and polished. This prevents current concentrations and reduces brush and slipring wear. The sliprings are shrunk on the shaft extension on a cylinder of insulating material. The radial connections from the sliprings to the terminal conductors consist of insulated contact screws through holes in the shaft extension. The terminal conductors in the slipring shaft and the rotor shaft are connected with contact screws. Brush gear The brush gear consists of a frame, insulation, brackets with brush holder, and carbon brushes. The brackets are insulated from the frame with rings of insulation material and are connected to a supply ring to which cables for the excitation current are connected. Each bracket is provided with a brush holder pocket for connection of a handle to hold two carbon brushes. The carbon brushes in the handle parts are mounted in holders of coil-spring type that give a constant brush pressure during the service life of the brush. The handle parts are insulated and the brush holders can be removed from the brush holder pockets by hand when the brushes are to be replaced. Brush replacement is thus possible during operations. Slipring housing Openings are formed in the side walls of the housing for service. These are covered with hatches provided with air filters. The opening in the end wall of the housing, G-16 Generators; Turbogenerators towards the generator, through which the slipring shaft passes, is provided with a seal. Inspection and Testing General basic inspection and testing points performed during the fabrication of the generators are included in a check plan. Each manufacturing operation is subject to extensive checking. Final tests Tests in accordance with Table G-1 constitute part of the normal testing before delivery. A type test is performed on the first machine in a manufactured series and Generators; Turbogenerators G-17 FIG. G-14 Slipring shaft end. (Source: Alstom.) its result is used as a reference for the subsequent machines of the same type. A more extensive test can be offered separately. Control and Protection Temperature monitoring A number of platinum wire resistance elements installed in different parts of the machine are used for continuous monitoring of the temperature of the parts. The connection cables of the elements are routed to junction boxes on the outside of the stator housing. The number and location of the elements are shown in the following list: G-18 Generators; Turbogenerators FIG. G-15 Slipring assembly detail. (Source: Alstom.) Number Location 6 In stator winding, between coil sides (2/phase) 2 Cooling air supply 2 Cooling air exhaust 1 Cooling air exhaust from exciter As a standard, the resistance elements have a resistance of 100 ohms at 0°C. Bearing vibration measurement Vibration transducers of seismic type for bearing vibration measurement can be delivered mounted on the bearing shields of the generator. Heating elements Heating elements are installed in both the generator and exciter unit to prevent condensation during standstill of the generator at lower temperatures. Current transformers Current transformers can be mounted on the stator terminals outside the generator casing. The transformers can be delivered in accordance with the purchaser’s requirements. Protective equipment The original equipment manufacturer recommends that the generator, as a minimum, be equipped with the following protective equipment: ᭿ Overcurrent protection ᭿ Overvoltage protection ᭿ Differential protection ᭿ Negative phase-sequence current protection ᭿ Stator earth fault protection ᭿ Rotor earth fault protection ᭿ Underexcitation protection and/or underexcitation limiter ᭿ Reverse power protection (depending on the drive machine type) Generators; Turbogenerators G-19 TABLE G-1 Normal Testing Test Type Test Routine Test Overspeed test ¥¥ Measurement of winding resistances ¥¥ Generator characteristics ¥ Measurement of generator losses (through run-down test) ¥ Bearing vibration measurement ¥ Loading point with cos j = 0 overexcited ¥ Heat run ¥ Measurement of the voltage curve form under no-load conditions ¥ Measurement of reactances ¥ Voltage test ¥¥ Measurement of insulation resistance ¥¥ Sound measurement ¥ Measurement of bearing insulation resistance ¥¥ ᭿ Overexcitation and/or overexcitation limiter ᭿ Loss-of-excitation protection; in installations where there is a risk of high overvoltages, a surge diverter is to be installed and, in certain cases, protective capacitors Operating Characteristics Operations with constant winding temperature With gas turbine operations, the principle described as follows is applied. This provides an optimum relation between the permitted power output of the generator and the power available from the turbine at varying cooling medium temperatures. In accordance with international standards, particularly for gas turbine–powered generators, the generator can be loaded so that the maximum winding temperature permitted remains the same with a cooling air supply temperature other than 40°C. The winding temperature rises permitted increase or decrease as much as the temperature of the cooling medium falls below, or exceeds, respectively, the values given previously. Synchronous compensator operation The generators are particularly suitable for synchronous compensator operation. To permit such operation, however, mechanical disconnection of turbine and generator is usually required and one of the main bearings must be provided with thrust bearings. Operation at low ambient temperatures With very low temperatures the generator can be provided with a recirculation arrangement for cooling air or water. Noise Reduction When there are special acoustic requirements, the generator can be installed in a sound-absorbing enclosure consisting of a steel frame with panels of perforated steel sheets with sound-absorbing mineral wool in-fill. The sealing against water leakage between the panels and the supporting structure consists of a self-adhesive rubber strip and silicon-rubber caulking. The roof and walls of the enclosure are provided with service openings. Base frame The stator frame of the generator is self-supporting and therefore requires no base frame to provide stiffness. If the center height is required to be higher than standard, the generator can be provided with a separate, welded, steel base frame. Grinding (see Abrasives; Some Commonly Used Specifications, Codes, Standards, and Texts) Grinding Wheels (see Abrasives) G-20 Grinding Wheels H Hazards (see Color Coding; Explosion; Some Commonly Used Specifications, Codes, Standards, and Texts) Heat Exchangers (see also Cogeneration; Regenerator; Vaporizers) A heat exchanger basically removes or adds heat to a fluid. The most common types in process plants are shell and tube exchangers. Plate types (consisting of heat- conducting fins), cascade types (single pipe bent back and forth many times), and spiral plate and extended surface types are less common. The working principle behind the heat exchanger is well illustrated in the section on condensers (see Condensers). A heat exchanger is usually custom designed for a large process plant by the overall contract designer. Builders of items such as condensers and separators generally also make related items such as heat exchangers and will have a catalog on smaller items that can be bought without a custom order. Some information on different commonly available heater types follows. Heat Pumps; Heat Pumps, Geothermal; Heating Systems with a Renewable Energy Source* Working Theory behind Geothermal Heat Pumps How earth loops work A system of high-density polyethylene pipes is buried in the ground or installed in a body of water to exchange heat between the building and earth. An antifreeze solution is circulated through the pipes by low wattage pumps. The plastic pipe wall becomes a heat exchanger between the fluid and the surrounding earth. In the heating mode the liquid in the pipe is cooler than the surrounding earth. In the cooling mode the opposite condition exists. Since heat flows from a warm area to a cooler one, heat exchange occurs under both conditions. Pond and lake loops Short polyethylene loop coils are stretched horizontally and attached to a plastic mesh to form a mat-style anchored heat exchanger. Several mats are connected together, and once in position the pipes are filled with fluid, possibly weighted, and the mats sink to the bottom. See Fig. H-1. Open loops (well systems) In areas where a good supply of clean ground water and an accessible water discharge system is available, an earth loop becomes unnecessary. Well water is pumped directly through the unit and heat is either extracted from or rejected back to the water table. See Fig. H-2. H-1 * Source: Enertran, Canada. Adapted with permission. Earth loop configurations Earth loops (Figs. H-3 and H-4) are installed in either horizontal or vertical configurations; the choice depends upon geographical location and the land area available. [This information source’s systems are sized to meet or exceed CSA Standard—M445 (sizing requirements), fulfilling the stringent energy efficiency requirements of the North American Building Codes.] Earth loop lengths are calculated using a sophisticated computer program that predicts annual loop performance, energy consumption, and operating costs. Horizontal loops. Horizontal loop designs vary from a single, in-series pipe to multipipe parallel systems. Pipes are laid in trenches 4–6 ft deep, using a backhoe or trencher, and pressure tested, and then the trench is backfilled. See Fig. H-3. Vertical loops. Vertical loops usually require less pipe than horizontal configurations. Vertical loops are connected in series or parallel or both. Drilling equipment produces small diameter holes, 75 to 300 ft deep. Two pipes are joined H-2 Heat Pumps; Heat Pumps, Geothermal; Heating Systems with a Renewable Energy Source FIG. H-1 Pond and lake loops. (Source: Enertran.) FIG. H-2 Open loops (well systems). (Source: Enertran.) [...]... tube or multiple tube combinations; lengths to 20 ft (6 m) 4 Accompanying control panels available with thyristor or contactor designs 5 Design pressures available up to 60 00 psi (4 42 kg/cm2) 6 Fluid temperatures available -29 2°F to + 120 2°F (-180°C to +65 0°F) 7 Suitable for most liquids and gases including high viscosities Heaters, Electric H-9 FIG H- 12 Pilot impedance heater in Romansville plant heats... bare tube coils of comparable area (Source: Armstrong Engineering Associates.) H-14 Heaters, Electric H-15 FIG H -27 Process- type heaters are available from 2 in (51 mm) to 48 in ( 121 9 mm) shell diameter Unit is 42 in (1 066 mm) shell diameter (Source: Armstrong Engineering Associates.) FIG H -28 Bottom bundles are sheathed element heater Liquid level of intermediate fluid is boiled by bottom bundle and... Armstrong Engineering Associates.) FIG H-41 900-kW radiant heater for liquid sodium (Source: Armstrong Engineering Associates.) Hydraulic Filters H -23 FIG H- 42 1000-kW radiant furnace Steel vertical vaporizer to heat 1000 kW, 94-in-diameter (23 88 mm), 42 ft ( 12. 8 m) overall height (Source: Armstrong Engineering Associates.) Heavy viscous materials that may be difficult to heat by conventional equipment. .. H-31 Indirect fluid electric vaporizer with controls mounted High pressure heater of corrosive fluid Fluid side 3175 psi (22 3 kg/cm2) design pressure (Source: Armstrong Engineering Associates.) FIG H- 32 Circuitry of sheathed element electric process resistance heaters (Source: Armstrong Engineering Associates.) Special attention is given to heat rejection facilities for tropic or warm zone operations to... involve H -20 Heaters, Electric FIG H- 36 Typical simple control schematic ladder diagram including a thermostat Many optional control features may also be included to suit process specific needs (Source: Armstrong Engineering Associates.) FIG H-37 Indirect fluid electric heater insulated and mounted on skid with all controls in place One of several at the same site in South America Capacity 24 kW (20 ,65 0 kcal/hr)... Armstrong Engineering Associates.) FIG H-15 Multitube longitudinal fin tube-type heater (Source: Armstrong Engineering Associates.) FIG H- 16 Three-stage single tube Inconel heater for heating viscous organic fluid (Source: Armstrong Engineering Associates.) Heaters, Electric H-11 FIG H-17 Twin single tube vapor heaters of stainless steel type 304 construction heating ethyl ether from 3 92 F (20 0°C) to 8 42 F... element electric process resistance heaters as well as circuit equations are in Fig H- 32 H- 16 Heaters, Electric FIG H -29 Large radiant furnace used to heat either fluidized bed vessel or to heat high pressure, high alloy, or high temperature fluid containing coils (Source: Armstrong Engineering Associates.) FIG H-30 Stainless steel reboiler for mixed organic acids (Source: Armstrong Engineering Associates.)... surface 2 Fins are strong enough to allow high pressure hose cleaning and user walking on heaters 3 Electric heaters are not subject to condensate freeze-up in the event of low temperatures 4 Heaters may be supplied to hold temperatures from cryogenic levels up to 120 0°F (65 0°C) 5 High turndown capacity possible due to electric heat control Not limited by steam condensing at a minimum of 21 2°F (100°C) 6. .. corrosive fluids 9 Just the tube is needed—no shell is required 10 High electrical flux density is possible 11 Handles 2- phase mixtures, liquids and solids mixed 12 Suitable for high-temperature (20 00°F/1093°C), low-temperature (- 325 °F/ -198°C), and high-pressure (up to 5000 psi/3 52 kg/cm2) operating parameters 13 Heaters operate at very low voltages so there is no safety issue 14 Flow pipes carry the... about 125 0°F (67 7°C) design operating temperature Most sizes are CSA and BASEEFA approved as well as Australian Code approved Typical shell diameters run from 1.5 in (38.1 mm) OD up to and including 48 in ( 122 0 mm) OD Shells and pressure parts are available fabricated of most pressure vessel materials (steel, stainlesses, nickel, Monel, Hastelloy, Inconel, Incoloy, etc.) Design voltages include 60 0 volts . to 20 ft (6 m) 4. Accompanying control panels available with thyristor or contactor designs 5. Design pressures available up to 60 00 psi (4 42 kg/cm 2 ) 6. Fluid temperatures available -29 2°F. possible 11. Handles 2- phase mixtures, liquids and solids mixed 12. Suitable for high-temperature (20 00°F/1093°C), low-temperature (- 325 °F/ -198°C), and high-pressure (up to 5000 psi/3 52 kg/cm 2 ) operating. ethyl ether from 3 92 F (20 0°C) to 8 42 F (450°C). (Source: Armstrong Engineering Associates.) FIG. H-18 Heavy-duty electrical resistance heating elements with welded fins. (Source: Armstrong Engineering