Duplex pump

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A duplex pump is a double-acting piston pump that works without rotating parts. It is used to convey or increase the pressure of liquid media (water, oil, ...) and is driven by gaseous media ( steam , compressed air ). The American Samuel Worthington is considered to be the inventor.

Duplex pump of the Woltman steam tug , right the steam side, left the pump side
Two duplex pumps (above is the driving steam side). One pump is the operating pump, the other is the standby pump (redundancy)

construction

The housing of the pump cylinder on the opposite side is mounted on a cast iron frame with the housing of the horizontal and parallel working cylinders on one side. One working cylinder and one pump cylinder each lie exactly in line with one another. One piston rod each conducts the force from the working piston to the pump piston. In the middle of the piston rods there are drivers which operate the control slide (usually flat slide) of the other working cylinder via levers and slide rods. There are simple flap or seat valves in the pump housing that are opened and closed by the suction and pressure of the pumped medium.

function

When the pump is started up, the working medium in the valve body flows through the channel opened by the valve into the working cylinder and presses on the working piston. If the pressure is high enough, it starts moving and pushes or pulls on the piston rod and through it on the pump piston. This increases the space in the pump cylinder on one side of the pump piston (suction side) and decreases on the other (pressure side). Due to the negative pressure on the suction side, the suction valve opens and the pumped medium flows in. By reducing the space on the pressure side and the resulting increase in pressure, the outlet valve opens and the pumped medium flows into the pressure line. Shortly before reaching the piston end position ( dead center ), the driver attached to the piston rod causes the channel of the other working cylinder to open for the opposite direction. When the end position is reached, the other piston rod starts moving in the opposite direction. This enables a uniform, relatively pulsation-free delivery. The design makes them self-priming.

use

Duplex pumps were very common in the "steam engine era". They were used on land and on ships as boiler feed pumps, as universal pumps for cleaning, extinguishing fires, for draining pits and pumping ships, and for supplying water to small communities and industrial plants. With the disappearance of the steam engines and the introduction of powerful, simply constructed electric radial pumps and axial pumps , the number and importance of duplex pumps also decreased. Due to the system-related explosion protection and the enormous robustness and temperature resistance (media and ambient temperature up to 200 degrees Celsius), however, some of them are still in use today in refineries and - powered by compressed air - in mining .

Manufacturer

The best known and largest manufacturer was the inventor's company, Worthington. However, the pumps were manufactured under license all over the world, including in Germany by Schaefer & Urbach , which still manufactures and repairs duplex pumps today.

power

The performance spectrum of the duplex pumps is broad. The maximum delivery pressure ranges up to around 30 bar, the delivery volume up to around 60,000 l / h. The delivery pressure and volume can be varied structurally through the diameter ratio of the working piston / pump piston: If the ratio of the piston areas is 1, the theoretically achievable delivery pressure is just as high as the pressure of the working medium. In order to feed a pressurized steam boiler , the delivery pressure must be higher than the boiler pressure. Pump pistons with a smaller diameter are used here than those of the working pistons, thereby achieving a delivery pressure that is higher than that of the working pressure by the ratio of the piston areas. During operation, the delivery pressure can be regulated by adjusting the working pressure; the delivery volume can be adjusted over a wide range by throttling the working medium, which regulates the number of strokes.

See also

further reading

Web links