Pump fluids

Various heat pumping schemes have been proposed as methods for saving energy in distillation. Of these schemes, use of the column overhead vapor as the heat pumping fluid is usually the most economically attractive. This is the vapor recompression scheme shown in outline in Fig. 14.6. 

Various coupling designs are available to transmit torque from the driver, eg, electric motor, to a pump. In order to contain the pumped fluid inside the pump and prevent the pumpage from leaking, several types of sealing methods are used. A few options are described herein. 

Transfer of Momentum Deceleration of one fluid (motivating fluid) in order to transfer its momentum to a second fluid (pumped fluid) is a principle commonly used in the handhng of corrosive materials, in pumping from inaccessible depths, or for evacuation. Jets and eductors are in this categoiy. 

Positive-displacement pumps may be of either the reciprocating or the rotary type. In all positive-displacement pumps, a cavity or cavities are alternately filled and emptied of the pumped fluid by the action of the pump. 

The efficiency of an ejecdor or jet pump is low, being only a few percent. The head developed by the ejector is also low except in special types. The device has the disadvantage of diluting the fluid pumped by mixing it with the pumping fluid. In steam injectors for boiler feed and similar seiwices in which the heat of the steam is recovered, efficiency is close to 100 percent. 

Eermanent magnets for both the internal and external rotors, there is ss heat to the pumped fluid than with canned-motor pumps. Some canned-motor pumps have fully pressure-rated outer shells, which enclose the canned motor others don t. With magnetic-drive pumps, containment of leakage through the can to the outer shell can be a... 

An easy way to understand NPSHr is to call it the minimum suction pressure necessary to keep the pumped fluid in a liquid state. 

Positive di.splaeement pumps normally have some strict tolerance parts. These parts vary with the type and design of the pump. This strict tolerance controls the flow, and the pressure that these pumps can generate. When this tolerance opens or wears by just a few ten thousandths, these pumps lose almost all their efficiency and ability to function. These strict tolerance parts must be changed with a planned certain frequency, ba.sed on the abrasive nature and lubricity of the pumped fluid, to maintain the maximum efficiency of the pump. 

Permit the pump and paeking to leak generously for about 15 minutes to allow the packings to absorb the pumped fluid,. swell, seat and adjust to the stuffing box wall and the shah. 

The dual seal is good to control the environment inside the seal without diluting the pumped product. It works with re-circulated barrier fluid. It establishes a barrier between the pumped fluid and the environment (Figure 14-20). 

When liquid content of the feed is high, a condenser and a separator are needed. The liquid-to-gas ratio can be as high, so that even at reaction temperatures a liquid phase is present. The reactor still performs as a CSTR, however the response time for changes will be much longer than for vapor phase alone. Much lower RPM will be needed for liquid-phase studies (or liquid and gas phase experiments) since the density of the pumped fluid is an order-of-magnitude greater than for vapor phase alone. In this case a foamy mixture or a liquid saturated with gas is recirculated. 

Dr. Boyce has authored more than 100 technical papers and reports on Gas Turbines, Compressors Pumps, Fluid Mechanics, and TurboMachinery. He is a Fellow of the ASME, and the Institute of Diesel and Gas Turbine Engineers, U.K., and member of SAE, NSPE and several other professional and honorary societies. He is also a registered professional engineer in Texas. 

Figure 11-13. Reactors stirred by pumped fluid ID, Injector nozzle SK, float G, gas F, liquid. (Source Schuger [11].)...

Foreign matter in pumped fluid chewed up seal... 

Reflux overhead vapor recompression, staged crude pre-heat, mechanical vacuum pumps Fluid coking to gasification, turbine power recovery train at the FCC, hydraulic turbine power recovery, membrane hydrogen purification, unit to hydrocracker recycle loop Improved catalysts (reforming), and hydraulic turbine power recovery Process management and integration... 

In the Sundyne Canned Motor design, the entire outside of the motor is enclosed in a secondary leakage containment shell or can. Primary leakage protection is provided by corrosion resistant liners which are seal welded and 100% leak checked to assure that pumped fluid does not contact the stator windings or rotor core. There is no shaft protrusion to seal and thus no seals to leak. 

Motors are suitabie for use in generai purpose areas and in Class I, Division 2, Group C and D areas for a wide range of pump fluid temperatures. For Class I, Division 1 Group C and D U.L. iisted, expiosion proof motors are avaiiable. 

There are several similar relationships for centrifugal pumps that can be used if the effects of viscosity of the pumped fluid can be neglected. These relate the operating performance of any centrifugal pump for one set of operating conditions to those of another set of operating conditions, say conditions, and conditions 2. 

Start the mud pump, running as slowly as possible, to pump fluid at a rate of 1.5 to 2.0 bbl/min. This reduces fluid friction resistance pressures to a minimum and pumps at minimum standpipe pressure for circulation. The standpipe pressure (for 1.5 to 2.0 bbl/min) can be found from standard fluid hydraulic calculations. 

Having discussed how a simple mechanical seal is assembled in the stuffing box, we must now consider how the pumped fluid is stopped from leaking out to the atmosphere. 

As in the compressed packing gland, lubrication also must be provided in mechanical seals. The sealing area surfaces should be lubricated and cooled with pumped fluid (if it is clean enough) or an outside source of clean fluid. However, much less lubrication is required with this type of seal because the frictional surface area is smaller... 

Motor windings and Insulation systems are specially designed, developed and applied as an Integral part of the pump so that design life is at least as great as for conventional air cooled motors. Winding temperature is primarily influenced by pumped fluid temperature and secondarily by use of cooling jacket. Fluid temperature is considered In pump... 

A flow system has been designed to pump fluid through the flow cell. A piston-cylinder arrangement is used as a pump-like" device by... 

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