70
Equipment
‘
,
‘
maintain, and the larger models supply considerable amounts of air
and are quite adequate for multiple installations or for driving air—
powered cleaning tools (Figure 21). The most frequently encountered problem with this type
is noise and vibration, generated by the
diaphragm moving quite powerfully, usually at fifty impulses per
second, in sympathy with the frequency of the mains supply. Recent
models have been improved by positioning the diaphragm—actuating
lever so that it is not in contact with the coil (in older models the
.
coil was also the mounting for the lever), but though'noise problems
have thereby been minimised they have not been eliminated. Since
however, there is no other Comparable alternative to this type of
pump, the aquarist is recommended to try to understand the problems and then to eliminate their effects, which in all but the worst
cases can easilybe achieved.
Fig. 21. An air—operated water strainer and sediment
a useful cleaning
,
,
,
'
tool. (Coûrtesy North West Plastics)
‘
-
'
_