Specific horsepower

Each compressor unit and condition has its own specific horsepower point or requirement for operation. However, the general characteristic shape will he about the same, and for a reasonable range of conditions, the general shape and effect of varying a particular condition can be relatively established even for gases of other k values. Of course, the curves can be recalculated and drawn for the particular gas under consideration. The peaks will be in about the same ratio. Note that Figures 12-26 and 12-27 were established using a bhp/MMCFD correction factor at a mean pressure of 200 psia for the lower compression ratios where this correction is required. ... 

Brake-Specific Horsepower (BSHP) This is a measure of the power output at the end of the crankshaft available for doing work. 1.36 bhp = 1.00 kW. 

NEMA also rates motors by level of performance, specifically horsepower, speed, torque, and locked-rotor current for each category of motor type and size. Tables specifying acceptable limits for each are too detailed to include here, but may be found in NEMA standard MGl-1993. 

Motor-driven, multistage reciprocating compressors have reportedly been the most popular choice for aeroderivatives. Motor-driven, oil-fiooded screw compressors are also used in some cases. High horsepower, multistage centrifugal compressors, similar to those used at many pipeline compressor stations, may be required for the newer heavy-duty units if the distribution pipeline pressure is insufficient (see Pipelines). Gas turbines have more stringent fuel-gas specifications in terms of cleanliness than do gas-fired boilers. Thus oil- and water-knockout systems, coalescing filters, and fine-mesh filters are used. 

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. 

Internal-combustion engines range in size from small portable gasoline engines to over 14,914 kW (20,000 hp) diesels for ship propulsion. They are usuaUy designed for particular industrial applications and to meet specific objectives as to weight per horsepower, reliabihty, and operating conditions. 

Development The following discussion relates specifically to the use of what could be called radial-inflow, centrifugal-pump power-recovery turbines. It does not apply to the type of unit nurtured by the hydroelecti ic industry for the 1 ge-horsepower, large-flow, low- to medium-pressure differential area of hydraulic water turbines of the Felton or Francis runner type. There seems to have been little direct transfer of design concepts between these two fields the major manufacturers in the hydroelectric field have thus far made no effort to sell to the process industries, and the physical arrangement of their units, developed from the requirements of the hydroelectric field, is not suitable to most process-plant applications. 

If the specific gravity at pumping temperature were not equal to 1.0, then the water horsepower would be adjusted by the spceifie gravity. 

In reality, the performance curve is easy to understand. It isn t rocket. science. The performance curve indicates that the pump will discharge a certain volume or flow (gpm) of a liquid, at a certain pressure or head (H), at an indicated velocity or speed, while consuming a specific quantity of horsepower (BHP). The performance curve is actually four curves relating with each other on a common graph. These four curves are ... 

Next, let s eonsider the eiierg) eurve, the brake horsepower (BHp), ree]uired by the pump. This curve is probably the easiest to interpret because it is practically a straight line. Con.sider the following the pump consumes a certain e]uantity of energy just to maintain shut-off head. Then, as flow begins and increases, the horsepower consumption normally increases. (On certain specific duty pumps, the BHp may remain mostly flat or even fall with an increa.se in flow.) The BHp eurve is normally seen this way (Figure 7-5). 

For the calculated shaft horsepower. Figure 2-13 presents the speed trend of present advanced bearing technology. Any speed below the limiting line can be used for calculating the specific speed. With N... 

To assist the engineer in making estimates, the curve in Figure 3-6 gives values of efficiency plotted against pressure ratios. The values on the curve include a 95% mechanical efficiency and a valve velocity of 3,000 feet per minute. Table 3-1 and Table 3-2 are included to permit a correction to be made to the compressor horsepower for specific gravity and low inlet pressure. They are included to help illustrate the influence of these factors to the power required. The application of these factors to... 

Today, almost all large motors are designed specifically for a particular application and for a specific driven machine. In sizing the motor for the load, the horsepower is usually selected so that additional overload capacity is not required. Therefore, customers should not be required to pay for capability they do not require. With the elimination of the service factor, standard motor base prices have been reduced 4—5% to reflect the savings. Users should specify standard horsepower ratings, without service factor for these reasons ... 

A solid-bowl centrifuge has the following dimensions Rj = 0.30 m, Rj = 0.32 m, = 0.30 m. It is designd to operate at 5,000 rpm, separating particles from a suspension where the particle specific gravity is 7.8. Determine the required horsepower needed to set the centrifuge into operation. 

Nutz-losigkeit,/. uselessness, -niessung,/. usufruct, use. -pferdestarke, /. effective horsepower. -pflanze,/. useful plant, specif, food plant or fodder plant. -Strom, m. (Elec.) useful current, -tier, n. useful animal. 

With use of electric and diesel-electric locomotives also came the ability to control power and tractive effort, not just for the unit in which a crew rides, but for multiple units (MU) coupled together in a locomotive consist—and this without need of additional crews in the following units. (A consist is the make-up of the train, in this case the full set of locomotives used.) With MU operation, locomotive managers had flexibility to size horsepower of the consist to operating requirements of a particular train and its territory or specific assignment. 

ATr = temperature rise, °F/min Pso brake horsepower at shutoff or no flow Wi = weight of liquid in pump, Ib.s Cp = specific heat of liquid in pump... 

In the example the manufacturer has been specified from available performance curves, and the details of construction must be obtained. The pump is selected to operate at 22 GPM and 196 to 200 feet head of fluid, and must also perform at good efficiency at 18 GPM and a head which has not been calculated, but w hich will be close to 196 to 200 feet, say about 185 feet. Ordinarily the pump is rated as shown on the specification sheet. This insures adequate capacity and head at conditions somewhat in excess of normal. In this case the design GPM w as determined by adding 10 percent to the capacity and allowing for operation at 90 percent of the rated efficiency. Often this latter condition is not considered, although factors of safety of 20 percent are not unusual. However, the efficiency must be noted and the increase in horsepower recognized as factors w hich are mounted onto normal operating conditions. 

For final design horsepower and equipment selection, the usual practice is to submit the refrigeration load and utility conditions/requirements to a reputable refrigerant system designer/manufacturer and obtain a warranted system with equipment and instrumentation design and specifications including the important materials of construction. Always request detailed operating instructions/controls and utility quantity requirements. 

In establishing specifications, the first important items to identify from the plant process material balance are normal, maximum, and minimum intake or suction flow rates together with corresponding conditions of temperature and pressure. The required discharge pressure must be established. If it is necessary or important to be able to operate at reduced or over-normal flow rates, these should be identified for the manufacturer, together with the length of time of such expected condition e.g., full time at one-half rate, 20 minutes out of every hour at 10% over normal, etc. These operating requirements may separate the types of equipment. Because it is uneconomical to purchase horsepower that cannot be used by the fluid system, ask that the manufacturer state the maximum load and/or conditions that will fully load the available horsepower of the compressor-driver unit. 

Impeller mach number at eye and at periphery. Maximum possible speed of compressor, also of driver. Maximum horsepower possible for driver to develop, with any changes necessary to bring up to this maximum (such as changing nozzles, nozzle ring of steam turbine, changing blades or buckets). Paint specifications for exterior of unit. 

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