Turbine speed condensing turbines

A Campbell diagram is frequently used to determine the effect of multiple excitation frequencies in high-speed steam turbines. Figure 7-11 shows a Campbell diagram for a condensing steam turbine. If this partic uiar turbine operates at a speed of 8,750 rpm, the turbine blades would not be excited. But, if the turbine speed is reduced to 7,500 rpm, the turbine blades would be excited at four times running speed. If the turbine were operated at 10,000 rpm, a three-times running speed excitation would be encountered. What this means is that any vibration in the... 

Turbine ) Increasing turbine speed. Evaluate the steam level and consider adding an exhaust condenser. 

But not for long. After 15 min of operation, the turbine speed slipped back down. Once again, I had lost a lot of vacuum in the surface condenser. Once again, the vapor outlet temperature had dramatically increased. But this time, the condensate outlet temperature had also increased. What was my new problem ... 

The offending wildlife were removed. The condenser was reassembled. The motive steam was started to the turbine. Both the turbine and the air blower were running well above critical speed. We lined the flow of combustion air up to the combustion chamber. Everything was finally going my way, except for one minor problem. 

Then, steam pressure to the ejectors was adjusted to achieve the highest possible vacuum. Cooling water pump turbine speeds were increased to push the flow of cooling water to the overhead condensers. Also, condensers were backflushed (see Chapter 16). 

Five principal drivers are used for multistage centrifugal compressors. These include condensing turbines, topping turbines, electric motors, gas turbines, and steam turbines. Electric motor drives generally are used in regions where cheap power is available. Steam turbines are usually inexpensive to operate and can provide up to 18,000 rpm. Condensation turbines usually run at lower speeds of between 10,000 to 14,000 rpm, while gas turbines tend to be the most expensive to operate and usually run in the range of 5,000-6,000 rpm. 

Steam turbine, 53, 146, 282-92, 179 back pressure, 282 blade deposits, 479 condensing, 282 efficiency, 288 extraction, 282 induction-type, 282 paitial admission, 288 rating, 290 reliability, 478 selecuon variable, 275, 285 speed, 278 stage losses, 286 steam temperatures, 284 steam velocity, 288 trip and throttle valve. 479 Step unloading system, 80 Stiffness coefficients, 385 Stodola slip, 153, 155 Stonewall, 186 Straight labyrinth. seal leakage, 532... 

On this system, the turbine is speed controlled and passes steam, depending on the electrical demand. The bypass-reducing valve with integral desuperheater makes up any deficiency in the steam requirements and creates an exhaust steam pressure control. Alternatively, any surplus steam can be bypassed to a dump condenser, either water or air cooled, and returned to the boiler as clear condensate. 

In early times 70/30 brass condenser tubes failed by dezincification and Admiralty brass (70Cu-29Zn-lSn) was brought into use. This proved little better, but some time later the addition of arsenic was found to inhibit dezincification. Failures of Admiralty brass by impingement attack became a serious problem, particularly as cooling water speeds increased with the development of the steam turbine. The introduction of alloys resistant to this type of attack was a great step forward and immediately reduced the incidences of failure. 

There are two general types of steam turbines extraction and condensing. The most common turbine with which the process operator comes into contact is used to spare an electric-motor-driven centrifugal pump. The three-phase, AC motors used in the United States and South America are either 1800 or 3600 rpm. The motors used in Europe are 1500 or 3000 rpm. Small steam turbines (20 to 500 hp) used to drive centrifugal pumps, are rated for the same speed as the electric motors that are used in that particular service. 

Finally, the steam turbine s buckets can foul with hardness deposits from the steam. This reduces the turbine efficiency, and may prevent a pump from running at its rated speed. Injecting steam condensate into the steam supply can remove such deposits. 

The high-pressure steam from the separator is sent to the steam turbine under speed control, and the generated electricity is sent to the grid or to other users. The low-pressure steam is condensed by cooling it with cooling water. The flow of the cooling water is modulated by the turbine exhaust pressure controller. 

While the steam turbine has largely displaced the engine, the latter has still a distinct field. It is to be preferred where speed variation is necessary, where starting conditions are severe and for low-pressure operation of small units using saturated steam, whether condensing or non-condensing. 

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