Steam turbines valves

High-frequency, destructive vibrations. Unaffected by operating speed. Steam turbine valve vibration Rare occniTence change valve ping, seat shape, and/or increase valve gear rigidity... 

Driving units shut down by closing the main stop valve and the steam turbine regulating valves and at the same time closing the butterfly valve upstream of the expander (closing time 2-3 sec)... 

The full FCC string is synehronized using the governor eontrols on the steam turbine. Synehronization of the three-body TPG string is aeeomplished through the eontrol system and large expander valves. 

Steam turbine performance is modeled using a standard steam flow versus horsepower map and valve position versus steam flow. The turbine inlet valve(s) is positioned by the governor system to maintain constant speed (or another parameter when synchronized). 

For Main Air Blower serviee without a steam turbine in the string, the unit shall be started by first applying windage steam and then aeeelerating the train to rated speed using the eleetrie motor. After aehieving stable rated speed, the expander inlet valve will be... 

A train that generates only eleetrieity from the hot flue gas is ealled a Total Power Generation (TPG) train. A TPG train eonsists of a power reeovery expander, gear, generator, and sometimes a steam turbine (Figure 6-39). The valve arrangement for a TPG train requires speeial attention beeause the train operation and the proeess operation are independent. 

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... 

Steam Turbine - A PR valve is required on the steam inlet to any steam turbine if the maximum steam supply pressure is greater than the design pressure of the casing inlet. The PR valve should be set at the casing inlet design pressure and sized such that overpressure of the casing is prevented, under conditions of wide open steam supply and normal exhaust flow. 

Steam from the steam generator exits containment through a main steam isulaiion valve (MSrV) to drive the turbine. When most of the energy in the steam has been removed by the turbine, the steam is condensed to liquid and returned to the steam generator by the feedwater puntp. The heat removed by the condenser goes to the heat sink. 

Figure 6,1-2 is a simplified illustration of a BWR. The pressure of the moderator-cooling water at about half the pressure in a PWR forms steam as it flows upward through the core. Steam passes through a moisture separator (shown as vertical lines just above the core) exits the containment through Main Steam Isolation Valves (MSIV) drives the turbine and generates electricity. After the steam is cooled by the turbine, it is condensed, and pumped back to the reactor by the feedwater pump. 

STEAM TURBINE 9000-9099 -High Pressure Turbine 9100-9199. Intermediate Pressure Turbine 9200-9250. Lnw Pressure Turbine 9260-9269. Valves 9270-9279. Piping 9280-9289. Lube 01 I 9290-9309. Controls... 

As with the electrical load profile, it is also necessary to analyze the heat load over the daily and annual cycles. Ideally, the heat load will match the available heat from the electrical generator (however, this is rarely the case). There will be periods when supplementary output will be necessary which can be achieved by, say, supplementary firing the waste heat gases of a gas turbine, or heat output reduction is necessary by the introduction of bypass stacks. For a steam turbine installation bypass pressure-reducing valves will be necessary to supplement steam output, while a dump condenser may be needed at low-process steam demands. The nature of the electrical and heat load will obviously have significant influence in the development of the scheme and scope of equipment. 

Carryover refers to the entrainment of BW (and the contaminating solids contained in the water) into the steam. Contamination of steam from entrained water may lead to deposits in superheaters, on turbine valves, and in steam traps, valves, and flash vessels. 

An obvious method of controlling the capacity of a compressor is to vary the speed. This method is applicable to units driven by variable-speed drivers such as steam pistons, steam turbines, gas engines, diesel engines, etc. In these cases the regulator actuates the steam-admission or fuel-admission valve on the compressor driver and thus controls the speed. 

Figure 17.3 shows a steam turbine with three, rather than one, nozzles. The single, largest, left-hand valve is called the main nozzle. It handles 60 percent of the motive-steam flow. Each of the two smaller nozzles handles 20 percent of the steam. These 20 percent nozzles can be plugged off by a device sometimes called either a horsepower valve, jet valve, speed valve, star (for the handle shape) valve, or port valve. 

Figure 17.4 shows a centrifugal pump, driven by a steam turbine. The correct operating speed for the pump and turbine is that speed that puts the process-control valve in a mostly open, but still controllable, position. As we slow the turbine to force open the process-control valve, the turbine s governor valve will close. Steam flow to the turbine will decline in accordance with fan laws ... 

The control scheme shown in Fig. 17.4 is certainly quite common. But is it the best Figure 17.5 is a copy of the crude charge system in a now-defunct refinery in Port Arthur, Texas. I saw it in operation many years ago. It worked fine. The required flow of crude directly controls the governor. The turbine speed is then always at its optimum. The AP across the process-control valve is always zero, because there is no process-control valve. This design is a direct descendant of the original method of controlling the steam flow to pumps. The steam inlet valve was opened by the operator, so that the desired discharge flow was produced. 

On larger steam turbines, we have automatically, rather than manually, operated horsepower valves. The mechanism that controls the movement of the horsepower valves, is called a steam rack. If you have... 

During the evening, my operators decided to increase the combustion airflow from the blower or air compressor. This is done by opening the suction valve to the blower. Naturally, it requires more work to compress more air. But the turbine could not produce any more work or horsepower because the steam turbine s governor speed-control valve was already 100 percent open ... 

Another possibility is to open the speed or hand valve, as described in Chap. 17, Steam Turbines. This will introduce more steam into the... 

Example 7.2 is of cases with control valve throttling and pump speed control. In large systems, the value of power saved can easily overbalance the extra cost of variable speed drives, either motor or steam turbine. 

---