17
Figure 4
(3) (4)
3.6 Limitations of the Pump
VERDER is strongly committed to the belief that the customer must always be given as much
information as possible in order to make the best possible pump selection. For this reason the
list below contains details of the few VERDERFLEX limitations:
• Hoses are available in Natural Rubber; Nitrile Buna rubber; EPDM rubber & CSM (Hypalon
Ò). This selection is suitable for the majority of applications, but there remain some products,
which are not compatible with the hose material;
• Hose pumps often appear bulky and large in size when compared to other positive
displacement pumps with moderate flow rates;
• When compressing the hose, the overall volume of the sliding shoe causes the volume of the
suction line to be transferred to the discharge line, temporarily stopping the flow in both the
suction and discharge lines;
• Pulsation dampeners are needed occasionally as an accessory if:
o the lines are hammering;
o lines are smaller than size of pump
o the process is hammering;
o lines are long
o severe pulsation is noticed;
o product as a high SG
• The capacity of the pump may drop below nominal due to high impulse losses on the suction
or discharge side:
o The maximum impulse loss possible on the suction side is 40 kPa/6 PSI;
o The maximum impulse loss possible on the discharge side is 750 - 1200 kPa/105 -
170 PSI, dependent on the pump type
