While the first cost of the two systems are usually considered about equal, the gas- and mechanical-pumping systems have advantages and disadvantages.
Advantages of the gas-pumping system
• lower repair costs
• lesser potential for refrigerant leak
• no rigid requirements for NPSH
Advantages of the mechanical pump system
• usually lower pumping energy requirements
• no parasitic losses due to leaking three-way and check valves
• greater flexibility in changing pressures and flow rates of liquid delivered
• less space requirements
Even though logical points can be cited as advantages of one system over the other, the personal preference of the designer or owner continues to be an important factor in the choice. This reason may appear trivial, but when a designer or operator has the experience to operate one or the other system successfully, there is a persuasive reason for choosing that system on the next project.