Positive-displacement pumps piston

Unloader valves work like a spring-loaded bypass valve when the sprayer is operating. However, when the nozzles are shut down, they reduce strain on the pump by moving the overflow back into the tank at low pressure. These valves should be used on larger positive-displacement pumps (piston and diaphragm) to avoid damage to the pump or other system components when the nozzles are cut off. 

For small feed rates, it may be considerably cheaper to use a positive-displacement pump (piston type). Control may be by stroke adjustment on a constant-speed pump as shown by Figure 5.2A or by adjustment of a variable-speed drive of a pump with a fixed stroke as shown by Figure 5.2B. If the minimum stroke rate is at least three times the reciprocal of the feed-tray holdup time, no pulsation damper is required. 

There are four (4) major types of pumps (I) positive displacement, (2) dynamic (kinetic), (3) lift, and (4) electromagnetic. Piston pumps are positive displacement pumps. The most common centrifugal pumps are of dynamic type ancient bucket-type pumps are lift pumps and electromagnetic pumps use electromagnetic force and are common in modern reactors. Canned pumps are also becoming popular in the petrochemical industiy because of the drive to minimize fugitive emissions. Figure 10-24 shows pump classification ... 

Piston, or positive displacement pumps, are well known and much used. Centrifugal pumps are not as well understood. Consequently, piston pump performance is sometimes expected from centrifugal blowers. The main difference is that positive displacement or piston pumps generate flow, whereas centrifugal pumps produce pressure. With a piston pump, the pressure will increase to the level needed to maintain the flow set by the piston volume and stroking speed. In contrast, centrifugal pumps produce pressure the flow will increase until the pressure drop, produced by the flow, matches the pressure produced by the pump. 

This system is backed-up by a Standby Liquid Control System (SLCS) that injects sodium pentaborate into the moderator using a positive displacement pump (shown as a piston pump). Steam that originates in the core of a BWR, unlike the primary coolant in a PWR, exits the containment. The closing of the MSIVs isolates the radioactivity from the environment but when this is done, normal heat removal is not possible. The Residual Heat Removal (RHR) system... 

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. 

With the exception of piston-type pumps, most of the common positive-displacement pumps utilize rotating elements to provide a constant-volume, constant-pressure output. As a result, these pumps can be monitored with the following parameters hydraulic instability, passing frequencies, and running speed. 

With the exception of piston-type pumps, all positive-displacement pumps have one or more passing frequencies generated by the gears, lobes, vanes, or wobble-plates... 

Positive-displacement pumps can be divided into two major types rotary and reciprocating. All rotary pumps use some form of rotating element, such as gears, vanes, or lobes to increase the discharge pressure. Reciprocating pumps use pistons or wobble plates to increase the pressure. 

There are four (4) major types of pumps (1) positive displacement, (2) dynamic (kinetic), (3) lift, and (4) electromagnetic. Piston pumps are positive displacement pumps. The most common centrifugal... 

Positive-displacement pumps and those that approach positive displacement will ideally produce whatever head is impressed upon them by the system restrictions to flow. The maximum head attainable is determined by the power available in the drive (slippage neglected) and the strength of the pump parts. A pressure relief valve on the discharge side should be set to open at a safe pressure for the casing and the internal components of the pump such as piston rods, cylinders, crankshafts, and other components which would be pressurized. In the case of a rotary pump, the total dynamic head developed is uniquely determined for any given flow by the speed at which it rotates. 

Reciprocating or positive-displacement pumps with valve action piston pumps, diaphragm pumps, plunger pumps... 

Positive-displacement pump—A pump that conveys fluid by directly moving it using a suitable mechanism such as a piston, plunger, or screw. 

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 ... 

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