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gcbhhb (Civil/Environmental)
1 Apr 11 9:41
I need to continuously pump water from a large ditch.  I will have water from the ditch flowing by gravity about 10-15cfs into a wet well which the pump will be placed in.  I will then need to pump the water out of the wet well at between 10-15 cfs.  This pump will run 24 hours a day for about 280 days out of the year.  Is there a pump/ pump manufacturer that can do this?  thanks
jonr12 (Mechanical)
1 Apr 11 10:00
Most water pumps are made to run that way.  Just make sure it says for "continuous duty".
gcbhhb (Civil/Environmental)
1 Apr 11 10:03
thanks.  One distributor I am dealing with says that all the pumps and manufacturer's he deals with are cycled.  One pump can not run continuously.  I would need to run 2 pumps that alternate cycles.
SteveWag (Civil/Environmental)
1 Apr 11 11:53
Your salesman is wrong. Most of the time, two pumps are installed so one acts as a back-up. Most of the time, the water falls in the sump and the running pump is shutoff. It makes sense to alternate the pumps on rising fluid so that a failure is both noted and maybe prevented. Only very cheap pumps are made for less than continuous duty. But, how will you control the pump? All pumps fail, even the very best. Can you stand to be down for a couple of days?
Steve
 
gcbhhb (Civil/Environmental)
1 Apr 11 12:13
water will continuously be dumped into the sump.  So there will always be a need for the pump to be running.  Haven't really got that far in regards to failing.  I think there would probably be a warning lite to go off or something along that line.
bimr (Civil/Environmental)
1 Apr 11 14:59
Any quality pump should be able to run continuously for 280 days. However, you may experience some type of power failure in that time.
ch81pc (Civil/Environmental)
2 Apr 11 16:16
What happens the other 85 days of the year? Always worth having a back up pump or facility to connect temporary pumps quickly.
micalbrch (Mechanical)
3 Apr 11 5:16
Pump availability of > 95 % isn't a big challenge for a pump manufacturer. And the availability you require is much less. I agree with SteveWag and bimr: There should not be any problem for a quality pump manufacturer to fullfil your requirements. The pump must not be sized borderlined - that might be the problem for some salesmen as oversizing makes the pump more expensive.  
BigInch (Petroleum)
3 Apr 11 17:18
Continuous and standby duty suitability will much more affect which motor you want to order than the pump.  Motor power output ratings are given for continuous and intermitent duty.  The same motor will have a lower rated output for continuous duty than it would have for intermitent duty periods and motors are selected accordingly.  

Let your acquaintances be many, but your advisors one in a thousand'  ...  Book of Ecclesiasticus

bimr (Civil/Environmental)
3 Apr 11 22:18
In practice, intermittent duty service is harder on an electric motor than continuous duty service. The reason is that more heat is generated during motor startup. The heat dissipates as a motor continues to run.

The standard pump motor is a NEMA B with 1.15 service factor. For a continuous duty service, you do not have to specify anything special.

http://www.electricmotors.com/right-size-motor.html

Heat is the main cause of reduced motor life. A continuous-duty electric motor is designed to produce its rated horsepower output without overheating and damaging the insulation on the motor coil windings. Expected motor life under proper operating conditions is S to 10 years of continuous operation.

http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/16125/ExtendingElectricMotorLife.pdf?sequence=1
BigInch (Petroleum)
4 Apr 11 11:56
While nobody argues that starting is hard on motors and machinery, its due to the accelerations, not the heat generated in the 1/2 second that the inrush current is high.  Starting is not the criteria that essentially governs duty period, as is better explained in your first reference.  Its the heat generated by the typically higher load rating that is given for short operating periods where the excess heat can be dissipated over the following shutoff time.  Since shutoff time is not relevant for continuous duty, load must be limited to lower levels for continuous duty motors, because there is never any cool off time available and the heat generated must be dissipated while operating continouosly.  

Let your acquaintances be many, but your advisors one in a thousand'  ...  Book of Ecclesiasticus

Artisi (Mechanical)
10 Apr 11 4:04
For a correctly selected and sized industrial pump  / coupling / motor combination -  24 x 7 x 365 is easily achievable. However, I would back it with a standby unit "just in case". Further you might consider alternating operation between the 2 units for duty sharing, this in effect doubles the time between a major overhaul.

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.)  

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