Positive Displacement Pump Types

The purpose of a pump is to move fluids. The two types of pumps are dynamic pumps, which use velocity to move fluid, and positive displacement pumps, which move fluid by trapping a fixed amount of fluid and then forcing (displacing) that trapped volume into the discharge pipe.
According to Rensselaer Polytechnic Institute, the three main positive displacement pump types are reciprocating, metering and rotary pumps.
Reciprocating Pumps
Reciprocating pumps use a piston and cylinder with suction and discharge valves built into the pump. The pump draws a volume of liquid into the cylinder through the suction valve on the intake stroke and discharges the liquid under positive pressure through the outlet valves on the discharge stroke.
Classifications of reciprocating pumps include direct acting or indirect acting, single or double acting, high pressure or low pressure, and vertical or horizontal.
One type of reciprocating pump is the direct-acting steam pump, which has a steam cylinder end that is in line with a liquid cylinder end, with a straight rod connection between the steam piston and the pump piston or plunger.
The diaphragm pump, which uses use a flexible diaphragm to move liquid, is a direct-acting reciprocating pump, commonly used to pump water from a ditch or sump.Another type is the power pump, which converts rotary motion to low-speed reciprocating motion using a speed-reducing gear. Power pumps are generally very efficient and can develop high pressures but do tend to be expensive.
Metering Pumps
Metering pump provides precision control that delivers a specific amount fluid into a system. Metering pumps are available that are compatible with a variety of flows, pressures and fluids. According to Engineer's Edge, metering pumps are used to control contamination or leakage between fluid systems, provide specific control flow relative to discharge pressure, maintain an accurate fluid output capacity or isolate a fluids system.
Rotary Pumps
Rotary pumps use a rotating vane, screw or gear to progressively create one or more chambers with each revolution of the drive shaft. Clearances between rotating parts, and between rotating and stationary parts, are kept to a minimum to reduce slippage (leakage of fluid from the pump's discharge back to its suction). According to Engineer's Edge, the close clearances in rotary pumps makes it necessary to operate them at relatively low speed for reliable operation and to maintain pump capacity.
The many types of positive displacement rotary pumps generally fall into three categories: gear pumps, screw pumps and moving vane pumps.

Definition of a Metering Pump

Metering pump has a variety of uses. Mainly seen in the chemical industry, they are made to accurately pump liquids at adjustable levels. There is more than one type of pump considered a metering pump.
Types
Perhaps the most popular metering pumps are piston and diaphragm types. Positive displacement pump operate with reciprocating pistons that move in and out of a comparably sized cylindrical chamber. Diaphragm pumps have reciprocating diaphragms that compress and decompress to move liquid. plunger pump is used in cases where the liquid being pumped is too toxic to risk leakage, because their design makes them less susceptible to leaks.
Function
With both mechanical piston and diaphragm pumps, the flow rate can be adjusted by changing the stroke length.
Price
Metering pump prices vary greatly. Diaphragm pumps are more expensive than piston-type pumps. The determining factor of price is horsepower. Large flow and head requirements require a larger-horsepower pump and therefore increase the pump cost greatly. As an example of price, in 2010 a 1-horsepower, 125-gallon-per-hour diaphragm cost about $5,000.

How to Clean a Concrete Pump

With a concrete pump parts you can pour more concrete faster, and with less work than you would be able to pour it by hand. A pump also allows you to pour in places that a mixing truck can't reach, like the second, third or fourth story of a building. However, they only work if they're properly maintained and kept clean. A dirty pump can be disastrous. Any concrete left to harden in the pump or pipes can cause a clog while pumping, damaging the pump and endangering those around it.
Instructions
1.Pump out all remaining concrete. After you finished with your pour, point your pump in a safe direction and let the remaining concrete run out. Be patient and keep the pump running until all rattling inside has ceased.
2.Rinse out and scrub the hopper---the basin where the concrete enters the pump---with a brush. Scrub thoroughly to make sure no setting concrete sticks to the sides of the hopper.
3.Run water through the metering pump. Using the water tanks on a mixing truck, a local source or the pumps reserve, run water through the pump to flush it out. Don't stop until the water is running clear.
4.Clean the joints. Remove the clamps holding the pipes together and clean the individual joints with the scrub brush.
5.Rinse the entire unit. A concrete pump can splatter concrete quite a distance from where it's pumping. Rinse the entire unit before leaving the job site, even the truck parts not used in the pumping.

How Does a Triplex Pump Work

The function of a plunger pump is to move different types of fluids from one place to another using mechanical action. These substances include liquids but also slurries and gases. They operate using one of three mechanisms: gravity, displacement and direct lift. Displacement pumps operate by holding a specific amount of a substance and then moving it out of the holding chamber. Triplex pumps are a type of displacement pump that uses cylinders to hold and then move the substances.
How Displacement Works
Displacement pumps operate with a system of cavities through which the fluids move. The pump opens, sucking fluid in and then sending it over to the discharge compartment, at which point the concrete pump parts closes, forcing the fluids out. Every time this happens, the volume of fluid moved is the same.
The Meaning of "Triplex"
One type of displacement pump uses a series of cylinders to move the fluid through the system. Ranging from the "simplex" (one cylinder) through the "quadriplex" (four cylinders), these pumps increase in volume capacity as you add cylinder. The "triplex" pump has a system of three cylinders bringing in fluids and sending them through the pump to the discharge pipe.
Components of a Triplex Pump
In a triplex pump, each cylinder has a plunger inside it, as well as valves for discharge and suction. When the pump opens to bring in fluid, the plunger goes in, opening the suction valve. As it closes, the plunger forces the fluid out into the next cylinder. A "triplex" system can move fluid more efficiently than a "simplex" one because, as the different cylinders operate in different phases, fluid moves more quickly than it would with three "simplex" pumps.

The Typical Installation of a Dosing Pump

Dosing pumps or metering pumps are pumps that pump liquids at a predetermined rate over a set period of time. There is no such specific pump design that can be called a dosing/metering pump, since the term refers more to how a pump is used than how it is specifically designed. That being the case, there are preferred pump designs which make for better dosing or metering than others, depending upon the dosing or metering need. Most of these pumps are made up of an electric motor that drives a pump head, and installing them is a fairly straightforward process.
Select the mounting location and position. Depending upon your dosing metering pump application, location and position are relatively flexible. If you do choose to mount it vertically, make sure the motor is positioned above the seals. Doing so prevents seal leakage into the motor. Seal leakage will damage the motor and/or potentially render it inoperable.
Dosing pumps play a key role in many industrial applications.
Add the fluid, per your application, to be pumped into the vacuum/suction and exit/discharge ports. This is called pre-wetting, and it "wets" the pump elements and mechanical seal. Pre-wet the pump before connecting it.
Install pump piping by following the drawings and hookup requirements that came with your particular positive displacement pump. Be careful to match the pipe size to the suction and discharge port diameters. Make sure the pipe is stiff and/or self-supporting so as to limit direct, excessive strain in any direction on the pump housings. Use Teflon tape or pipe lubricant/dope to assure a good seal and help make removing the lines easier, should the need arise.
Correct pump voltage is critical for proper pump function.
Refer to the wiring diagram in the terminal box or on the motor's nameplate to wire the pump in correctly. Be sure to observe all local and additional codes when doing so. Keep all voltage variances within 10 percent of the stated voltage on the nameplate. Verify that all power connections have the correct voltage within the stated range. Keep in mind that these pumps are equipped with overload protection.
Double-check the suction lines to be sure they are air tight on all self-priming pumps. When they are packed or pre-wetted, these pumps are capable of anywhere from 15 to 25 feet of suction lift. The two main variables being the thickness of the fluid pumped and that the suction lines are air tight.
Line capacity dictates pump lubrication potential.
Keep the sustained flow rate at no lower than 10 to 15 percent of full line capacity when these pumps are running, since they rely on the fluid they pump to keep them lubricated. Operate these pumps only within the temperature range for which they are suited. Thoroughly drain these pumps when they are not going to be used for extended periods.