Direct drive pumps

Pump, direct-drive (vacuum technology) A mechanical pump, the moving parts of which... 

Centrifugal pumps Direct drive Ring- criled bearings With water cooling Ihrbine 250 350 120 155 47 minimum. .. 140 160... 

An alternative type of downhole mud motor is the mud turbine, (multistage axial flow turbine) which directly drives the bit. The tool consists of an upper section containing the turbine blades and lower section with bearings. As mud is pumped through the upper section the blades are turned. Turbines are designed to rotate at higher speed than the displacement motor. The higher rotation speed requires diamond or composite bits. 

Both reciprocating engines and turbines are used as prime movers in production facilities to directly drive pumps, compressors, generators, cranes, etc. Reciprocating engines for oil field applications range in horsepower from 100 to 3,500, while gas turbines range from 1,500 to in excess of 75,000. 

In positive lubrication systems, a gear-type pump is normally used to provide positive circulation of clean oil within the compressor. In some cases, the main compressor shaft directly drives this pump. In others, a separate motor-driven pump is used. 

The direction of motor rotation shall be checked with the intake and outlet ports open prior to installing the pump. The drive shaft, seen from the motor end, must rotate counter-clockwise. Note the arrow on the motor indicating the direction of rotation If the roots pump runs in the vwong direction, then it is reversed by interchanging two of the phases at the motor connection cord. 

The Croy E series direct-drive dual extraction pump can be adjusted to pump from 5 to 60 gal/min during fluid transfer, and 500 actual cubic feet per minute during ground water/vapor extraction. The unit can be purchased for 20,000 and rents for 2000 per month. All units can be trailer mounted for mobility. Trailer costs are dependent on system size, number of axles required for transport, and other factors (D17804V, p. 17). 

Power generation vs. direct drive. Power generation, a primary utility, was discussed in Part 1 in regard to type of configuration to save space once a power load is determined. To determine the peak power loads, decisions must be made early on prime movers for the main users of energy crude-shipping pumps, gas compression, and water-injection pumps. 

For many years the connection between the pump and motor was made with a V-belt, but direct-drive pumps are becoming common. The latter are more compact, smoother running, and perhaps a bit quieter and more reliable. On the other hand, the semiflexible coupler between the motor and pump shaft can... 

Pumps can also be divided into direct-drive or belt-driven models. Direct-drive models run faster and quieter, and they are smaller and lighter for the same level of performance. For many years they were not considered able to withstand the workloads of belt-driven pumps because they tended to wear out prematurely. Fortunately, direct-drive pumps have improved considerably over the years. 

In their early design, direct-drive pumps simply had the shaft of the motor extended, and a pump was placed on this shaft. Unfortunately, any minor variation in alignment caused excessive wear and tear on the pump bearings and vanes. Inexpensive direct-drive pumps that are in production today still have this inferior design. 

Currently, the motor section of the direct-drive pump is connected to the pump section by a coupling. This coupling allows acceptable variations in alignment between the motor and pump, but each component independently maintains their own tight tolerances. 

For table-top demonstrations and/or small experiments, a direct-drive pump is excellent. Its portability, low vibration, and generally quiet operation is important. 

For general experimentation, large manifold systems, and industrial operations, direct-drive pumps are also strongly recommended. If, however, you are pumping a dirty environment, belt-driven mechanical pumps should be considered because their greater oil chambers can better tolerate contamination (see Sec. 7.3.7). They can easily be placed in pans (to catch any accidental oil leaks) on the floor, and they can be left on for days and/or weeks of continuous operation. 

In addition, mechanical pump oils can be specialized for use in specific environments such as those with high-oxygen contents. Some are blended for use in specific types of pumps such as direct-drive pumps, belt-driven pumps, and rotary-piston pumps. As with most things, no single product fits the bill for all circumstances. Thus, there are many varieties, grades, and types of mechanical pump oils. 

Hydrocarbons (too many to list) These pump fluids are the cheapest and provide good, all-round protection for the pump. They can be specialized for specific pumps (such as direct-drive, belt-driven, piston, or vane), as well as for specific uses. Should not be used in systems that will be pumping pure oxygen. In harsh environments, should be changed very often. 

Direct-drive pumps, with an ultimate vacuum that is typically 5 mTorr, are increasingly becoming the dominant design since they are more compact and quieter. However, they are somewhat less durable, since the rotor operates at significantly higher speed than that of a belt-driven pump. A wide variety of pumps with different capabilities are available from Hyvac, Welch, Balzers, Kurt Lesker, Edwards, and Kinney. 

The vacuum pumps initially used in freeze-dryers were of the belt-drive type and, as such, extremely bulky and noisy by current standards. At present, most research-scale freeze-dryers use direct-drive pumps, which are much quieter than the previous models and also, frequently, very small. Because they are constructed from corrosion-proof materials, they are highly flexible in operation. 

One important aspect which should he pointed out is that there is a basic incompatibihty between GC and MSD, the mass spectrometer operate at pressures of 10- torr or less, whereas the gas chromatograph effluent operates at about 760 torr. An interface device is necessary to handle the pressure differences. The simplest and most efficient interface in GC/MSD is a direct capillary column interface. The low flow rate of the narrow bore column and the high pumping rate of an oil diffusion pump backed by a suitable direct drive mechanical pump assure pressures less than lO " torr and allow for the direct insertion of the colmnn end into the mass spectrometer. Interfacing megabore... 

The system uses a simple rotary pump and no diffusion pump is required. Any dual stage pump with a free air displacement of 20 liters per minute or more should be satisfactory, although larger free air displacements are advantageous in terms of routine working speed. We have found Leybold Heraeus model D2A direct drive pumps with free air displacements of 62.5 liters per minute to be particularly satisfactory, and very quiet in routine operations. 

IMM with an oil hydrauUc system provides the power to turn the screw to plasticate the plastic, inject the melt into the mold cavity, close the mold clamp, hold clamp tonnage, release the clamp, and eject the molded part. A number of hydraulic components are required to provide this power, including motors, pumps, directional valves, fittings, tubings, and oil reservoirs/tanks. See drive-system control hydraulic fluid influenced by heat, injection molding machine hydromechanical clamp See clamping, hydromechanical. 

In order to conduct microdialysis experiments, several other components are required. Syringe pumps are often used to control the perfusate flow rate. The pump has to be able to deliver flow rates precisely in the microliter per minute range. Tubing is needed to connect between the probe and the pump which drives the perfusion flow and, in some cases, between the probe and a sample collector as well. The total dead volume of tubing should also be maintained as small as possible to have better time resolution. The perfusion fluid is a medium resembling the composition of extracellular fluid with minimal or zero concentration of the molecules of interest. Dial-ysate exiting from the outlet of the microdialysis probe is usually collected in a vial for later analysis. It is also possible to coimect the outlet directly to an analysis instrument without using a collector, which is usually preferred, if possible, for its convenience and usually faster analysis results. 

Abrasion is usually a major consideration in pump selection. Except for the mild chemical-type duties already referred to, slurry pumps are of special construction, essentially to resist abrasion to the pump and its shaft seals but often also to permit fast maintenance and liner or component replacement for very abrasive duties. Generally either replaceable rubber lining or specially hard abrasion-resistant alloys are used shaft seals are of special design, and are usually continually flushed with clean water. Impeller tip velocities are kept within proven limits for the application. Power transmission is often through V-belts rather than direct-drive couplings, to permit exactly the required speed to be obtained (rather than synchronous speeds) and to permit speed optimization in service (varying the impeller diameter is not so convenient). 

---