Alternating Pumps

Critical systems should always be equipped with more than one pump. Choosing between the installation of one or more backup pumps depends on the costs of the installation and

• how critical the operation of the system is - a water supply system for a hospital is more critical than a chilled water cooling systems for a home
• the delivery and installation time of a new pump

If two or more pumps are used, the operation between the pump should be systematically alternated to achieve equal wear.

Alternatives for Alternating Pumps

Pumps can be systematically alternated by

• manual alternation - where the operator selects the lead pump and the sequence of the lag pumps
• duty alternation - where the lead pump change every time the pump or system is stopped
• timed alternation - where the lead pump is switched by a timer or clock
• equal run time - where the lead pump is switched to achieve the same operating time for each pump

Note! Running an automatic system for equalizing the wear of the pumps

• has the advantage of extending the time before repair and reinvestments
• has the disadvantage that all pumps may wear out on at the same time - reducing the operation safety for the whole system

Temperature ^oC
K
^oF

Length m
km
in
ft
yards
miles
naut miles

Area m²
km²
in²
ft²
miles²
acres

Volume m³
liters
in³
ft³
us gal

Weight kg_f
N
lbf

Velocity m/s
km/h
ft/min
ft/s
mph
knots

Pressure Pa
bar
mm H₂O
kg/cm²
psi
inches H₂O

Flow m³/s
m³/h
US gpm
cfm