Quality
Waterjet Newsletter – 9/27/2005
A Hybrid Pump of Direct
Drive and Intensifier – An 22-year Old Idea From time to time, it is
interesting and necessary to look back to the history. WJTA has offered us
the convenience of reading the earlier literature by putting the proceedings
of the first four WJTA conferences online (www.wjta.org).
This article will review a paper by Nakaya et al.*,
presented on the 2nd WJTA conference. These two types of high-pressure
pumps are the most popular in the current waterjet industry: intensifier and
direct drive. Intensifier pumps have the advantage of easy adjustment of
operating pressure, while the direct drive pumps are superior in efficiency.
This paper described a hybrid pump of direct drive and intensifier. In this hybrid pump, as
illustrated in the following diagram, a hydraulic cushion cylinder was added
between the crankshaft and the plunger, compared to a typical direct drive
pump. The hydraulic pressure in the cushion cylinder P1 and the output water
pressure at the plunger side P2 follows the same principle as that of an
intensifier pump: P1×A1 = P2×A2. Therefore, the output pressure
P2 can be easily adjusted by changing P2 with a relief valve in the hydraulic
circuit.
Compared to an intensifier pump,
this hybrid pump has slightly higher efficiency (86% vs
77%). Its pressure pulsation is also less. The size of accumulator is only
70% of that in an intensifier pump. Compared to a direct drive pump, it gains
the advantage of easy pressure adjustment that is typically found on an
intensifier pump. Everyone can have his/her opinion
about this idea. Nevertheless, this paper is a great source of information if
you want to know how direct drive and intensifier pumps work. *Nakaya, M., Nishida, N., and
Kitagawa, T., “ Development of variable delivery triple reciprocating plunger
pump for water jet cutting,” Proceedings of the 2nd More For Less: Spare
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