Process Engineering Equipment Handbook Episode 1 Part 9 potx

For condenser calculation, the OEM uses standard fouling coefficient h v for every tube material based on experience. Layout philosophy Due to the routing of the steam flow, CB condensers achieve better heat transfer values (k-values) than some other designs. In order to obtain the required condenser pressure up to 20 percent less surface area is required in comparison with some older designs. Cold end optimization This manufacturer establishes the optimum combination condenser/turbine in each case using the following parameters: ᭿ Cooling water temperature ᭿ Cooling water flow rate ᭿ Power consumption of the cooling water pump ᭿ Space conditions Type Series (see Figs. C-272 and C-273) In the interests of standardization, a type series has been developed for the CB condenser that covers the entire power range of industrial turbines and small steam and cogeneration plants. This series provides an appropriate link to the large-scale condensers made by this OEM (type series CM). Together with the option of varying the tube length it is possible to provide the optimum condenser for every requirement and plant size. Selection of Material In most cases the condenser is manufactured from material according to DIN standards. If required by the customer, materials can also be used in compliance with other standards, such as ASTM. Tube material The tube material on the steam side must satisfy the requirements of the water/steam circuit. On the water side it must meet the cooling water requirements. C-244 Condensers FIG. C-272 Schematic representation of the CB condenser-type series up to the CM series. (Source: Alstom.) Due to the manifold requirements the selection of the tube material is of great importance. The basis of every selection is a sample of the cooling water, which is analyzed by specialists. In cooperation with the end user the appropriate material is then selected. The most important criteria are: ᭿ Corrosion resistance to cooling water ᭿ Sand content of the cooling water ᭿ Cooling water velocity ᭿ Thermal conductivity of the material ᭿ Chemistry of the steam circuit ᭿ Resistance to droplet erosion The following materials are mainly employed: Brass. If the quality of the cooling water is good (river water, freshwater lakes) admiralty brass or aluminum brass is a well-proven material, an important feature being high thermal conductivity. Copper nickel alloys. If the quality of the water is poor, such as met with in ports and large rivers, CuNi alloys are preferred because they are more resistant than brass. In cooling tower operation also these alloys are of advantage as the cooling tower water is usually highly concentrated and therefore aggressive. Stainless steels. For special requirements, such as for brackish water or sea water, high-grade steels are suitable. These have the advantage that much higher water Condensers C-245 FIG. C-273 Type series of CB condenser. (Source: Alstom.) velocities are admissible; in the case of nonferrous metals the velocity is limited by waterside erosion. Titanium. This material fulfills practically all requirements. It is extremely resistant to corrosion and allows high water velocities as well as offering very good resistance to steamside droplet erosion. The price and the relatively low thermal conductivity can be compensated for, to some extent, by providing thinner tube wall thicknesses. Tubesheet In general, tubesheets are made of carbon steel with a stainless steel or titanium cladding on the cooling water side. The tubes are roller expanded into the tubesheet. Upon request, the tubes can also be welded into the tubesheet. See Figs. C-274 and C-275. The tubesheets are welded to the condenser shell, thus ensuring reliable tightness. The waterboxes are also welded to the tubesheet. If required, a flange connection can also be provided. Venting Venting the steam shell The steam shell of a condenser is under vacuum. Careful manufacture and the use of high-grade sealing materials help to reduce the amount of air inleakage to a minimum but it can never be completely eliminated. The steam shell of a condenser must therefore be permanently vented. For evacuation purposes, this OEM uses water-jet ejectors or steam-jet ejectors and, in special cases, also water ring pumps. The layout of the suction units employs concepts in compliance with the German VGB (technical association of large power C-246 Condensers FIG. C-274 Cladded tubesheet, welded to the condenser housing. (Source: Alstom.) Condensers C-247 FIG. C-275 Example of sacrificial anodes for protection of tubes and waterbox. Here the typical shape of the CB air cooler can be seen. (Source: Alstom.) FIG. C-276 Determining the air inleakage as a function of the steam flow to the condenser. (Source: Alstom.) utilities) recommendations. This is a reliable venting system for all types of loads, requiring minimum equipment and operational outlay. With improved venting characteristics, considerable savings in investment can be achieved with this OEM’s design (see Fig. C-276). Startup venting Generally the service ejectors are also used as startup ejectors for generating the necessary vacuum in the water/steam system before starting up the plant. With an end-user request, special hogging vacuum pumps can also be employed to reduce the evacuation time. For this purpose usually water ring pumps are provided, as these have a constant high flow rate over a wide pressure range. Waterbox venting For economic cooling with fresh water or sea water, the outlet waterbox must have a slight vacuum due to the geodetic requirements. This results in degassing of part of the cooling water’s dissolved air. This degassed air must be constantly removed and for this purpose single-stage water ring pumps are usually employed. Accessories Basically there are two major accessories: the sponge ball cleaning system and the steam dump device (SDD). Sponge ball cleaning system (see Fig. C-277) To a greater or lesser degree all cooling water contains dirt particles that, without countermeasures being taken, adhere to the insides of the condenser tubes thus impairing the efficiency of the heat transfer. With a continuously operated cleaning system fouling can be reduced to a minimum, the so-called standard fouling. This standard fouling also protects the tube material from erosion or corrosion. A cleaning system is also recommended for corrosion-resistant materials, such as titanium or high-grade steel. In contrast to alloys containing copper, these materials tend to biofouling, i.e., to forming layers of bacteria. This, in contrast to copper, is due to them being nontoxic to bacteria. C-248 Condensers FIG. C-277 Example of a fouled tube (without cleaning system) and a clean tube (with sponge ball cleaning system). (Source: Alstom.) Steam dump device (SDD) End users often need to bypass the turbine during the startup operation or in the event of load rejections and to route the boiler steam directly into the condenser. A component part of this bypass system is the steam dump device (SDD) into the condenser. See Figs. C-278 and C-279. With SDDs the high-energy steam is attemperated with spray water (taken downstream of condensate pumps) and introduced into the condenser via a perforated cone above the tubes. This SDD system transports the steam smoothly into the condenser. It has a low noise level. Condensers C-249 FIG. C-278 HP/LP bypass system with steam dumping into the condenser. (Source: Alstom.) FIG. C-279 Steam dump device (SDD). The high-energy steam is cooled with condensate and led into the condenser via a perforated cone above the tubes. (Source: Alstom.) Design, Manufacture Manufacturing drawings and tube patterns are raised on CAD systems, enabling direct transfer to numerically controlled tool machines. See also Figs. C-280 through C-282. Figure C-283 shows the front end (cooling water inlet and outlet) of a two-pass CB condenser in the turbine building of a power plant. The water inlet is at the bottom and the water outlet at the top. The CB condenser itself is compact and allows simple piping assembly. The space saving contributes to reducing the costs of the turbine building. Choosing a Condenser The condenser of choice should be an optimum combination of: ᭿ High thermal performance ᭿ Compact design ᭿ Optimum space utilization ᭿ Self-supporting, robust structure without additional internal supports required C-250 Condensers FIG. C-280 CB condenser during manufacture, ready for tubing. (Source: Alstom.) ᭿ Economical manufacture ᭿ Simple transport and assembly ᭿ Extremely low oxygen content in the condensate without any additional measures ᭿ Simple makeup water supply ᭿ No condensate subcooling, resulting in higher efficiency ᭿ High availability Condensers C-251 FIG. C-281 Tubesheet and support plates must be in exact alignment for tubing to be carried out correctly. (Source: Alstom.) FIG. C-282 Titanium tubes welded into the tubesheet. The weld quality achieved requires years of experience and careful attention to detail. (Source: Alstom.) C-252 Condensers FIG. C-283 CB condenser in the turbine building of a power plant. (Source: Alstom.) [...]... System(s) TABLE C -18 C-265 Conversion Factors for Translational Velocity and Acceleration 19 Multiply Value in Æ or Æ By To obtain value in Ø ft/s ft/s2 in/s in/s2 cm/s cm/s2 m/s m/s2 Ø g-sec, g g-s, g 1 ft/s ft/s2 0.0 311 0.0 010 2 0 .10 2 1 32 .16 0.002 59 0.0833 0.0328 3.28 39. 37 in/s in/s2 386 12 .0 1 0. 393 7 cm/s cm/s2 98 0 30.48 2.540 1 0.0254 0. 010 m/s m/s2 9. 80 0.3048 10 0 1 TABLE C - 19 Conversion Factors... Multiply numerical value in terms of Æ By To obtain value in terms of Ø Average value Root-meansquare (rms) value Peak-to-peak value 1 1.5 71 1. 414 0.500 Average value 0.637 1 0 .90 0 0. 318 Root-meansquare (rms) value 0.707 1. 111 1 0.354 Peak-to-peak value 2.000 3 .14 2 2.828 1 Ø Amplitude Amplitude Types of vibration transducers or probes There are three main kinds of probe that measure: ᭿ Displacement ᭿... TABLE C - 19 Conversion Factors for Rotational Velocity and Acceleration 19 rad/s rad/s2 degree/s degree/s2 rev/s rev/s2 rev/min rev/min/s Ø Multiply Value in Æ or Æ By To obtain value in Ø rad/s rad/s2 degree/s degree/s2 1 57.30 0. 017 45 1 6.283 360 rev/s rev/s2 0 .15 92 0.00278 1 rev/min rev/min/s 9. 5 49 0 .16 67 60 0 .10 47 6.00 0. 016 7 1 rigidity added by hangers For instance, although two pieces of pipe may... Copper/constantan Iron/constantan Chromel/alumel Chromel/alumel Platinum and 10 % rhodium/platinum Platinum and 13 % rhodium/platinum Platinum and 30% rhodium/platinum and 6% rhodium Platinel 18 13/platinel 15 03 Iridium/iridium 60% and rhodium 40% -300 to 750°F -300 to 16 00°F -300 to 2300°F 32 to 18 00°F 32 to 2800°F 32 to 290 0°F 10 0 to 3270°F 32 to 2372°F 2552 to 3326°F A gas turbine generally has a protective... System(s) FIG C- 295 Plots of amplitude and phase versus machine rpm clearly identify critical speeds and resonant conditions .15 FIG C- 296 Amplitude peak and phase change at 500 rpm .15 Condition Monitoring; Condition-Monitoring System(s); Engine Condition Monitoring; Engine Condition–Monitoring System(s) FIG C- 297 18 0° phase shift at 14 00 rpm with no corresponding amplitude peak .15 FIG C- 298 An amplitude... substitute for commonsense or process knowledge, having the appropriate CMS pays dividends Industry measurements have provided the following impressive figures ( 19 98 $U.S.): The case for CMS 1 From data drawn from the North American power industry: ᭿ Run-to-failure strategy cost was $18 /hp ᭿ Planned maintenance (overhaul at specified time intervals) cost was $13 /hp ᭿ Cost using a CMS was $9/ hp, indicating maintenance... phase shift .15 C-275 C-276 Condition Monitoring; Condition-Monitoring System(s); Engine Condition Monitoring; Engine Condition–Monitoring System(s) FIG C- 299 A 360° phase change corresponds to an amplitude dip at 10 00 rpm .15 ᭿ Two systems in resonance at or near the same frequency ᭿ Correcting only one cause of resonance may not solve the problem entirely In Fig C- 299 a dip is seen at 10 00 rpm together... is noted there is an amplitude peak as well as 18 0° phase change at 500 rpm in Fig C- 296 There Condition Monitoring; Condition-Monitoring System(s); Engine Condition Monitoring; Engine Condition–Monitoring System(s) C-273 FIG C- 294 Waterfall graph of increasing rpm .13 is also a 12 00 rpm peak noted but with no corresponding 18 0° phase shift The peak at 12 00 rpm is therefore unrelated to resonance condition... response and the excitation is called the phase angle Tables C -18 through C-20 and Figs C-2 89 and C- 290 list several definitions common to the field of vibration analysis C-266 Condition Monitoring; Condition-Monitoring System(s); Engine Condition Monitoring; Engine Condition–Monitoring System(s) TABLE C-20 Conversion Factors for Simple Harmonic Motion 19 Multiply numerical value in terms of Æ By To obtain value... resonance condition and could be caused by a neighboring machine In Fig C- 297 a 18 0° phase shift is noted at 14 00 rpm but without a corresponding amplitude peak Reasons could include: ᭿ The excitation force at 14 00 rpm being extremely low ᭿ A very heavily damped system ᭿ A pickup (sensor) located at the nodal point In Fig C- 298 an amplitude peak is accompanied by a 360° phase shift Reasons could include: . substitute for common- sense or process knowledge, having the appropriate CMS pays dividends. Industry measurements have provided the following impressive figures ( 19 98 $U.S.): 1. From data drawn from. 750°F Iron/constantan -300 to 16 00°F Chromel/alumel -300 to 2300°F Chromel/alumel 32 to 18 00°F Platinum and 10 % rhodium/platinum 32 to 2800°F Platinum and 13 % rhodium/platinum 32 to 290 0°F Platinum and. techniques. Vibration analysis. In the early operational years of the aviation RB 211 (on which land-based RB 211 s are based), vibration monitoring (VM) instrumentation helped avoid fan shaft locating