Pump cyclic applications
Pump cyclic applications
(OP)
Hi All,
I would like to know the impacts to life time of a centrifugal horizontal pump and motor with flow 80 m3/h, Head 100 meter, fluid water, motor 75 kW , insulation F, duty type S1 with cyclic operation around 24 cycles per day, each cycle is 6 minutes.
is the S1 motor duty and pump are suitable for cyclic operation?
thanks
I would like to know the impacts to life time of a centrifugal horizontal pump and motor with flow 80 m3/h, Head 100 meter, fluid water, motor 75 kW , insulation F, duty type S1 with cyclic operation around 24 cycles per day, each cycle is 6 minutes.
is the S1 motor duty and pump are suitable for cyclic operation?
thanks





RE: Pump cyclic applications
Want to expand your question?
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Pump cyclic applications
I see examples in industries that service water from service water tank that supply to service water pump and directed to the hydrostatic tank (with compressed air to maintain pressure) for consumers that consume water intermitently. When the selection of hydrostatic tank becomes beneficial than just to have pump that will operate cyclic ?
RE: Pump cyclic applications
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Pump cyclic applications
See http://www.engineeringtoolbox.com/iec-duty-cucles-... for a description of motor types.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Pump cyclic applications
The heat energy into the rotor is governed principally by the acceleration time, so starting a centrifugal pump will put far less energy into the rotor than starting a laden conveyor. You may well find that the motor is OK with this duty cycle unless it is operating at the standard 40°C ambient, is loaded to 100% of capability, starts against an open valve, and everything else goes against you.
RE: Pump cyclic applications
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Pump cyclic applications
That's unless of course we only have half a story which is not unusual.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Pump cyclic applications
RE: Pump cyclic applications
A cause of overheating is the number of start-stop cycles per hour. While starting, a typical motor draws five to six times the rated running current. This starting current accelerates heating dramatically. Most continuous-duty motor designs are intended to do just that, operate continuously. Though various provisions are made relative to loading and off-time, NEMA essentially limits a three phase continuous-duty motor to two starts in succession before allowing sufficient time for motor to stablize to its maximum continuous operating temperature. This is highly application-dependent, so its best to check with your motor manufacturer if you face a high cycle application. A custom design may be required.
Here is how NEMA addresses starting duty for standard motors. That will exclude motors which are required to drive more than the standard inertia.
NEMA MG 10-2001 Table 7 gives parameters labeled "A", "B", "C", as follows:
A - Max # of starts per hour, regardless of inertia WK^2
B - Max Product of [starts-per-hour] times [inertia=WK^2 in lb-ft^2].
C - Minimum time between starts (in seconds) to allow motor to cool sufficiently to allow another safe start.
Items A and B are used to attempt to limit long-term degradation due to cumulative damage from repeated starts with adequate cooling between starts, and item C ensures the motor is cooled sufficiently for another start (prevent short-term abuse which will cause immediate damage)
http://www.conae.gob.mx/woruk/sites/CONAE/resource...
For a 75 kw motor, NEMA is showing that the motor can be started 5.2 times per hour without effecting the service life of the motor.
RE: Pump cyclic applications
Also a smaller motor will be more efficient and likely will have a higher power factor which is important these days for keeping your entire facility's energy costs down.
Keith Cress
kcress - http://www.flaminsystems.com