The SMA 63/64 automatic minimum flow system is a protective pump fitting. It automatically protects centrifugal pumps against damage that may occur as a result of the partial evaporation of the pump content when the pumps are operated under low load. As soon as the main pump flow falls below a predetermined value, the valve opens the bypass and safely drains the minimum volume, even if the pumping volume in the main flow direction drops to zero.
The bypass is always completely opened or closed through its pilot-controlled valve piston (15/for illustration, see page 3 of SMA 63). This "ON/OFF" control makes it possible to increase the previous load limit of the valves from 200 bar to 400 bar (pumping pressure). The preferred utilization range is thus between PN 250 and PN 400 or ANSI CLASS 2500. The bypass amount may be up to 35% of the main pumping volume. The valve functions without an additional source of energy.
The properties of the SMA automatic minimum flow system make it the ideal fitting for the protection of pumps in the following fields of application: