Pumping throttled

Modern fuel management systems require extreme resistance to wear, friction and fuel, and also require dimensional stability. Bosch are using sintered polyimide from Du Pont as spacers, thrustwashers and bushings for fuel pumps, throttle adjusting motors and mono-jetronic idle control units. 

Centrifugai pump Throttling valve Flow nozzle... 

Pumping, throttled (vacuum technology) Pumping on a processing system with some conductance restriction in place to lower the actual pumping speed of the system. 

The sputter deposition system consists (in a general case) of a vacuum chamber, sputter sources, a substrate holder and a pumping system. The control panel selects the target source and substrate position and controls the sputtering power. The vacuum system contains a mechanical pump, a turbo pump, throttle valve, and chamber. The separate RF power supply is remote. It supplies the RF power needed to generate plasma in the deposition chamber. 

V ri ble Frecjuency Drives. An important energy by-product of soHd-state electronics is the relatively low cost variable speed drive. These electronic devices adjust the frequency of current to control motor speed such that a pump can be controlled direcdy to deUver the right flow without the need for a control valve and its inherent pressure drop. Eigure 11 shows that at rated load the variable speed drive uses only about 70% as much power as a standard throttle control valve system, and at half load, it uses only about 25% as much power. 

FIG. 8-85 Pressure, flow, and power for a throttling process using (1) a control valve and a constant speed pump and (2) an adjustable speed pump. 

Throttle discharge of running pump until spare can get in system. Slow down running pump if it is a turbine or variable-speed motor. 

Change process to adjust specific gravity to design value, or throttle pump to reduce horsepower requirements. This will not correct problem with some vertical turbine pumps that have a flat horsepower-required curve. 

The potential for power recovery from liquid streams exists whenever a liquid flows from a high-pressure source to one of lower pressure in such a manner that throttling to dissipate pressure occurs. Such throtthng represents a system potential for power that is the reverse of a pump—in other words, a potential for power extraction. Just as in a pump, there exists a hydraulic horsepower and a brake horsepower, except that in the recoveiy they are generated or available horsepowers. 

Increased - operating range with inlet - throttling -Speed limitation on semilean pump ... 

Process Controls If the inlet or outlet liquid to a piuTro-tnrbiue is regulated by a level controller on the hqnid-snpply vessel, a falling liquid level inside the vessel will cause this coutroUer to throttle a valve, reducing the differential pressure available to the pump-... 

FIG. 29-60 Excess head developed by lean and semilean pumps and the steam-throttle flow for a semdean-pump turbine. To convert gallons per minute to cubic meters per minute, multiply by 0.00379 to convert pounds per hour to kilograms per second, multiply by 1.260 X 10 . ... 

For ease of illustration we will consider the characteristics and behaviour of a centrifugal pump which is similar in behaviour to radial/axial flow fans and centrifugal/screw compressors. Figure 63 shows the mechanical connection of a flow valve to control the output of the pump or the discharge of the fluid through the throttle of the valve. Figure 6.39 illustrates the characteristics of the pump ... 

The system resistance increases and discharge reduces at the same rated speed This condition refers to point B, to which the earlier point A, has now shifted. The system now operates at a higher head f/j2. whereas the actual head has not increased. This condition has occurred due to higher system resistance offered by the throttle. The pump and the prime-mover efficieticy will now reduce to 73 7r from its original 8.3%. 

Figure 6.42 Discharge versus head curves of a pump at different speeds and resistances introduced by throttle...

In the third e.vample, the line terminates at 53%. This means DO NOT run this pump at less than 53% of the BEP. 53% of 4500 gpm is 2385 gpm. Because this is a firewater pump and because firemen need to throttle the nozzles on their fire hoses, then we need to install a pressure relief valve on this system with a discharge bypass line so that the pump dumps the restricted water (less than 2400 gpm) back into the suction tank or lake. If not, this firewater pump is likely to suffer bearing failure during an emergency. 

Compensates Operational Praetiees - It s a common practice in many plants to close or throttle a discharge valve with the pump running to meter the flow through the pipes. 

A - ABSORBER FD - FLASH DRUMS C - COMPRESSORS 1C - INTERCOOLED COMPRESSORS P- PUMP T - HYDRAULIC TURBINE D - DEHYDRATOR AC - AFTER COOLERS X- THROTTLE G GENERATOR... 

The leak size can be reduced by using double mechanical seals or a mechanical seal and a throttle bush, the space between the two being vented to a safe place. Major leaks may still occur, however, due to collapse of the bearing or seal. LFG pumps should therefore be fitted with emergency isolation valves (see Section 7.2.1), particularly if the temperature is low or the inventory that can leak out is high. 

Throttling of pump discharge may also be used to provide finer control and to permit operation when pump suction pressure may be inadequate for full flow operation. 

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