Pumps, positive-displacement power pumps

The piston plunger pump is the simplest form of a positive displacement pump. These pumps can be powered by a variety of prime movers, internal combustion engines, and electric motors (and in some cases, powered by a gas turbine motor). In such applications, the separate pump unit is connected to the prime mover by a power transmission. 

POSITIVE DISPLACEMENT PUMP A pump that will continue to build pressure until the power source is stalled if the pump outlet is blocked. 

Whereas the total dynamic head developed by a centrifugal, mixed-flow, or axial-flow pump is uniquely determined for any given flow by the speed at whicdi it rotates, positive-displacement pumps and those which approach positive displacement will ideally produce whatever head is impressed upon them by the system restrictions to flow. Actually with slippage neglecTed, the maximum head attainable is determined by the power available in the drive and the strength of the pump parts. An automatic relief valve set to open at a safe pressure... 

This is the energy source for hydraulic systems. It converts electrical energy into dynamic, hydraulic pressure. In almost all cases, hydraulic systems utilize positive displacement pumps as their primary power source. These are broken down into two primary sub-classifications constant-volume or variable-volume. In the former, the pumps are designed to deliver a fixed output (i.e. both volume and pressure) of hydraulic fluid. In the later, the pump delivers only the volume or pressure required for specific functions of the system or its components. 

All positive-displacement pumps have one or more rotating shafts that provide power transmission from the primary driver. Narrowband windows should be established to monitor the actual shaft speeds, which are in most cases essentially constant. Upper and lower limits set at 10 per cent of the actual shaft speed is usually sufficient. 

Fig. 3 shows the experimental apparatus. The feed tank had a 50 gallon capacity and was equipped with a variable speed mixer. The feed pump was a flexible impeller, positive-displacement pump to minimize shearing of the feed emulsion. The pumping rate was regulated by a Graham Variable Speed Transmission. Each flotation tank was 11.5 in. ID with 6.5 in. liquid depth maintained by a CE IN-VAL-CO conductometric level controller with a pneumatically actuated control valve in the effluent line. The fourth cell was not equipped with an air inducer. The outer diameter of the air downcomers was 1.5 in. The rotor in each air inducer was a turbine taken from a 2 in. turbine flow meter. Each rotor was belt driven by a 10,000 rpm, 1/30 hp motor and all three motors were governed by the same variable transformer. Another pulley on each rotor shaft was attached to a non-powered belt connecting all three shafts to ensure that each rotor turned at the same speed. 

Centrifugal pumps require appropriately large circumferential speed of the impellers and a number of serially arranged stages, in order to obtain the high-pressure differences. For efficient and economic operation the specific speed, nq, of the individual pump stages (n<, = n V0,5 / H0 75 V m3/s H, m n, min 1) should stay above 10 to 20. Too small a capacity or hydraulic power transmission will not provide favourable operating conditions and it is then recommended to focus on positive-displacement pumps alternatively. 

A useful feature of the PD pump is that for a given power input Eqs. (159)—(161) allow the designer considerable flexibility in adjusting discharge pressure, cylinder capacity, and overall capacity. Positive displacement pumps are favorites on large-scale, high-pressure systems. Details of each of the various types of PD pump are best obtained from individual vendors. 

Type of power supply. Rotary positive-displacement pumps and centrifugal pumps are readily adaptable for use with electric-motor or intemal-combus-tion-engine drives reciprocating pumps can be used with steam or gas drives. 

You have a positive-displacement pump with a piston area of 1 m. The piston moves 4.63 m/hr to pump 4.63 m /hr of fluid. The required force will be 3450 kN. What is the power needed in kW ... 

Robotized dispensing of a high-quality bead of two-component structural adhesives (epoxy, polyurethane, acrylic) is possible with servo-powered equipment. Positive displacement pumps control the mix ratio and flow of low to high viscosity adhesives and sealants. 

Huid power is the product of flow rate by head. In an ideal positive displacement pump, flow rate is independent of head. Therefore, the maximum fluid power is approximately P = p Q = p ct V/3T. One actuator closes at each step, and two actuators must be held closed at each step. If energy act is required to close an actuator, and power / act is required to hold it closed, we see that each cycle requires total energy 3 act + PactT (we assume no energy is required to open an actuator). The total power consumed per cycle is (fiact/7) + 2/ aot> and the maximum efficiency is r] = pact W(3 act + 6PactT). 

Cracks in suction or discharge lines (10 cm) of a charging positive displacement pump in the Diablo Canyon 1 power station (1990), due either to excessive acceleration of the suction and to defective operation of the pressure peak damping chambers or bellows in the discharge side. 

Equations (3.3-1) through (3.3-5) hold for calculation of the power of positive displacement pumps. At a constant speed, the flow capacity will remain constant with... 

Power consmnption the operating point of centrifugal pump should be chosen at the highest efficiency possible. Generally, the vendors/manufacturers offer a range of models, which cover the requirements of capacity, head, etc. However, the final selection should be done while keeping in mind the most likely (normal) condition in which the pump will be ran. In case of positive displacement pumps the performance curves should be studied to select proper speed for the capacity and required head... 

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