CHAPTER 6
VELOCIS SOLUTIONS @2018
19
Reciprocating pump utilized systems have main concern related to velocity variation. To solve this
problem more than one pumping element in parallel are used. A simplex pump has one plunger or
piston, duplex has two and so on. Table 7.2 indicates velocity variation for different type of
reciprocating pump.
Number
Pump type
Velocity variation [%]
2
Duplex
160
3
Triplex
25
5
Quintuplex
7
6
Septuplex
4
Table 7.2 Velocity variation for different type of reciprocating pump
In glycol dehydration system single-acting triplex pump is mostly employed because of effective
compromise between pump complexity and surge control. The overall efficiency for powered
pump is the range of 85-92%. However, depending on speed direct-acting pump has lower
efficiency.
Figure 7.17: Correct hook-up for reciprocating pump
By-pass is supplied for start-up and capacity control.
Head of positive displacement pump is almost independent of flow rate of pump. Figure 7.18
compares performance curve of positive displacement pump to curve of centrifugal pump.
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