Duplex pumps

A two piston double-action pump is called a duplex pump. 

Mud pumps consume more than 60% of all the horsepower used in rotary drilling. Mud pumps are used to circulate drilling fluid through the mud circulation system while drilling. A pump with two fluid cylinders, as shown in Figure 4-99, is called a duplex pump. A three-fluid-cylinder pump, as shown in Figure 4-100, is called a triplex pump. Duplex pumps are usually double action, and triplex pumps are usually single action. 

The charts showing the p>erformance of duplex pumps are shown in Table 4-38 [17]. The charts showing the performance of triplex pumps are shown in Table 4-39 [17]. A chart listing the pump output required for a given annular velocity is shown in Table 4-40 [18]. A chart listing the power input horsepower required for a given pump working pressure is shown in Table 4-41 [19]. 

Theoretical output Q, (gal/min) for a double action duplex pump is... 

The volumetric efficiency Ti for duplex pumps or triplex pumps is... 

Figure 8.2. Delivery from (a) simples and (b) duplex pumps...

The rate of fluid discharge from the cylinder is zero at the beginning of a piston stroke and increases to a maximum value when the piston reaches full speed. If only one discharge cylinder is used, the flow rate will pulsate. These pulsations can be reduced by placing an air chamber on the discharge line or by using a number of delivery cylinders compounded. Simplex pumps have only one delivery cylinder, duplex pumps have two cylinders, and triplex pumps have three cylinders. 

Simple cylinder direct-acting duplex pumps are widely used for all purposes. Figure 2 shows a standard design. It consists of two steam cylinders and two water ends, arranged side by side. Each steam piston is directly connected to its... 

Fig. 2.—Simple cylinder direct-acting duplex pump.

Duplex pumps give an almost uniform flow of water and require only small air chambers. The speed is limited and those given in Table I should not be exceeded. The economy is low, because no cut-off is possible so that the steam is exhausted at full pressure and its expansive energy is not utilized. 

Single pumps are also tandem-compounded, but either the ratio of cylinders is less than for a duplex pump, due to the lack of the cross exhaust or a large receiver is inserted which serves a similar purpose as the cross exhaust. 

Duplex pumps are available (triplex pumps for ORLITA HS4). In these instances, the maximal flow-rate must be multiplied by 2 or 3, respectively. 

A simplex pump, sometimes referred to as a single pump, is a pump having a single liquid (pump) cylinder. A duplex pump is the equivalent of two simplex pumps placed side by side on the same foundation. 

The driving of the pistons of a duplex pump is arranged in such a manner that when one piston is on its upstroke, the other piston is on its downstroke and vice versa. This arrangement doubles the capacity of the duplex pump compared to a simplex pump of comparable design. 

In a duplex pump, the flow splits into two cylinders inside the pump, whereas in a triplex it splits into three cylinders. Table 9-2 compares both designs. 

For proper balancing, the pistons of duplex pumps are 180° out of phase (Figure 9-3), but for triplex pumps they are 120° out of phase with each other (Figure 9-4). 

Duplex and triplex slurry pumps are manufactured to a power frame of approximately 1500 kW (2000 bhp). The Black Mesa Pipeline featured 13 duplex pumps, each with a driving power of 1250 kW (1675 bhp) to transport 4.8 million tons of coal over a distance of 440 km (275 miles) (Wallrafen, 1983). Some of these pumps were manufactured by Wilson-Snyder in the United States. 

Piston slurry pumps are used extensively as mud transfer pumps. Gardner-Denver in the United States offers a range of duplex pumps in the power range of 12-76 kW 06-102 hp). 

FIGURE 9-6 Pulsation diagram for duplex pump. (Courtesy of Wirth Pumps.)... 

It applies to regular duplex or power duplex pumps, operating on 125-lb saturated steam on common refinery liquids. If greater accuracy is justified, the following multipliers can be applied ... 

---