Steam turbine-driven pumps

Also, try to avoid running a steam turbine-driven pump as a coker Iteater cliarge pump. If the pump s steam supply comes from the same steam header, fluctuations in the steam header pressure (such as when steam is cut into a full coke drum) can cause a brief but deadly slippage in feed flow to.lhelieater. 

Frequently, a major unit shuts down when a compressor trips off. The cause may be low lube- or seal-oil pressure. The pumps providing the lube- and seal-oil pressure are typically spared (backed up). A steam turbine-driven pump is normally backed up by a motor-driven spare. The motor-driven pump should come on when the lube-oil pressure drops below a preset point. 

Many years ago, working as an outside operator during a strike (i.e., I was a scab), I noted that on some of my steam turbine-driven pumps, the level of oil in the oiler glasses rose perhaps Vito 1 inch every day. I actually thought that in some mysterious way, that lubrication oil was being produced inside the bearing housing. Of course, it was just water. 

For variable-speed pumps, such as steam turbine-driven pumps, control valves should not be used. The facility shown in Fig. 38.2 is a control scheme that is used not infrequently at older plants. It s a fine piece of technology, which has been lost with time. No control valve is used. The turbine speed is altered to directly maintain the vessel level. With the increasing use of variable-speed alternating-current motors, elimination of parasitic control valves should become more common. 

Failure of the cooling water pump is an important consideration, and the number of cooling water circulation pumps needs to be established carefully. The number of cooling water circulation pumps can be equal to the number of steam turbine-driven pumps that normally operate. 

Close-Coupled Pumps (Fig. 10-38) Pumps equipped with a built-in electric motor or sometimes steam-turbine-driven (i.e., with pump impeller and driver on the same shaft) are known as close-coupled pumps. Such units are extremely compact and are suitable for a variety of services for which standard iron and bronze materials are satisfactory. They are available in capacities up to about 450 mVh (2000 gal/min) for heads up to about 73 m (240 ft). Two-stage units in the smaller sizes are available for heads to around 150 m (500 ft). 

The lubricating oil system for a turbine is very important and is nearly always provided with a dual pumping arrangement. One pump can be driven directly off the turbine shaft and the other by separate electric motor or steam turbine. In another arrangement, one pump can be separately electric driven and the other separately steam turbine driven. Twin coolers are often provided in the dual system to... 

Gas and steam turbines rigid turbo-generator rotors rotors turbo-compressors machine-tool drives small electrical armatures turbine-driven pumps. 

Steam Turbine-Driven FW Pumps (FW Pump Turbines)... 

Close-Coupled Pumps (Fig. 10-49) Pumps equipped with a built-in electric motor or sometimes steam-turbine-driven (i.e., with pump... 

If the pump is driven by a steam turbine, the pump speed could be lower than in the design. 

It is quite important not to operate a turbine-driven pump by throttling the steam flow to the turbine. Let s assume that the operators have set the turbine speed at 3500 rpm, by adjusting the steam inlet gate valve upstream of a malfunctioning governor. Suddenly, the discharge flow-control valve cuts back, and the pump s flow decreases from 2000 to 1200 GPM. The pump speed will then increase, because fewer pounds of liquid are being pumped, and less horsepower is required to spin the pump. 

Two of the units at the Oak Creek Power Plant have full-sized steam turbine driven boiler feed pumps, along with half-sized motor driven boiler feed pumps for use at low loads and unit startup. The boiler feed pump turbines are supplied with steam from a particular turbine "bleed-point". 

Mechanical energy consumption 14.6 MW (preparation system, mills and feed-water pump are steam turbine driven)... 

Three feed water pumps are installed which are driven by steam turbines. Two pumps are used in normal operation. Each has a flow capacity of 50% of full reactor power operation and one feed water pump trip does not cause any reactor scram. 

In the Main Feedwater System, three of the pumps are steam turbine driven. The fourth pump is motor driven and is normally only used for startup and shutdown. This pump starts automatically on loss of main feedwater and reactor trip (see CESSAR-DC, Section 10.4.7.2.3.D). 

One turbine-driven emergency feedwater pump is included for each steam generator. (These are in addition to the two motor-driven emergency feedwater pumps.) In previous designs one turbine-driven pump was shared by both steam generators. 

Low-low level in 2/4 level channels in any two steam generators turbine-driven pumps... 

NUREG-1275, Vol. 10, Operating experience feedback report - Reliability of steam turbine-Driven standby pumps, October 1994. 

A loss of electrical load transient could occur from a generator trip, a turbine trip, or a loss of main condenser vacuum. Generally, the most severe transient would be caused by the loss of condenser vacuum. The main feedwater pumps in many plants are steam turbine-driven and exhaust to the main condenser. Thus, loss of condenser vacuum also could cause a loss of the main feedwater pumps. In this case the sequence of events would be similar to the loss of feedwater transient. The most severe effect of the transient, the peak pressure in the primary system, would be of about the same magnitude as in the loss of feedwater flow transient. 

The upset in Event 4 is similar to the upset in Event 1. Operator intervention can stop this runaway by starting the steam turbine driven water pumps, or adding Shortstop. While this operator action was judged to be very effective, no risk reduction credit was taken because of operator availability. The analysis shown in Table 7 led to safety integrity level 3 for SIF S-1. 

Loss of steam to the turbine for cooling water pumps may cause substantial plant relief. If all cooling water pumps are steam turbine driven, the contingency will be maximum, but this is seldom the case. In most cases, cooling water pumps are a combination of electric motor drive and steam turbine drive. The impact of other drives needs to be analyzed carefully. 

The steam balance in the plant shown in Figure 2 enables all pumps and blowers to be turbine-driven by high pressure steam from the boiler. The low pressure exhaust system is used in the reboiler of the recovery system and the condensate returns to the boiler. Although there is generally some excess power capacity in the high pressure steam for driving other equipment, eg, compressors in the carbon dioxide Hquefaction plant, all the steam produced by the boiler is condensed in the recovery system. This provides a weU-balanced plant ia which few external utiUties are required and combustion conditions can be controlled to maintain efficient operation. 

Lube oil units are typieally available in two versions the manu-faeturer s standard or in aeeordanee with API Standard 614. The major eomponents of a unit are the oil tank, auxiliary oil pump, double filter and, seleetively, one or two oil eoolers. All eomponents of the smaller units are mounted on a eommon bedplate, separated from the other eomponents. The oil ean be heated by an eleetrieal or steam-powered heating unit. The neeessary instrumentation is a standard supply item and, if requested, the switehes and motors ean be prewired. The main and auxiliary oil pumps are driven by different types of drivers (e.g., one by an eleetrie motor and the other by either a small steam turbine or by direet eonneetion to the shaft end of a major maehine easing in the turbotrain). 

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