Queries of Dec 07 and Jan 08

Query From: K. Raman ram_ki17@yahoo.com ram_ki17@yahoo.co.in

Sent: Wednesday, November 14, 2007 

Query : Please suggest me a good book on centrifugal pump for reference.   

Reply Date: Wed, 14 Nov 2007 07

Better than books, a whole lot of information is available on internet,

along with good illustrations and animated diagrams. Websites such as 

www.lightmypump.com www.mcnallyinstitute.com make good browsing.

Query From: Arun Mehta <govind_ip1@sancharnet.in>

To: pumpsind@sancharnet.in 

Sent: Sunday, November 25, 2007 3:00 PM

Query Pump Selection 

We are Contractor for operation & Maintenance of large water supply

Scheme at Jaipur. 

We need  Pump Selection & sizing Guide lines. 

Could you please send us the same  & oblige. 

Reply Date: Sun, 25 Nov 2007

Indian Standards IS:6596 and IS:10596 are codes of practices for

Selection, Installation, Operation and Maintenance of Pumps for

agricultural and industrial purposes respectively.

Hpwever, for a given application and duty (primarily flow-rate and

head) there would be different options to be explored in the process of

selection and choosing the option with least Life Cycle Cost. To know

more about Life Cycle Cost, browsing at www.pumps.org would be useful.

Query From: dakshayani dachi_piduri@yahoo.com 

Designation : M.sc  Department :  electronics  

Address :  3-13-94/8/1, ramanthapur Hyderabad  Pin Code : 500013  

State : Andhra Pradesh  

Wednesday, November 21, 2007

Query : how the small water pump works. how we can get the water output. can we do the same from dc motors.   

Reply Date: Wed, 21 Nov 2007

Small water pump has an impeller inside, which sucks water from the source and throws it up and out by virtue of centrifugal force. 

It would work even with a DC motor, as long as the motor will deliver

required power at appropriate rpm.

Query From: rpatil_123@rediffmail.com

To: pumpsind@sancharnet.in

Sent: Saturday, December 15, 2007 11:01 AM

Name : ravindar m patil Designation : service enginner Department : pump Company : sahyadri Address : silvassa City : silvassa Pin Code : 396230

Query : why multistage centrifugal pump takes more power when flow is reduced?(i.e.near shuttoff head)?

Date: Sun, 16 Dec 2007

To: "Pumps India" , rpatil_123@rediffmail.com

Power characteristics of different pumps are different, depending upon type of impeller design.

Regenerative turbine type centrifugal pumps (IS-8472) have a power characteristics with maximum power at shut-off. Axial flow or propeller type centrifugal pumps also have similar characteristics.

Your reference to multistage centrifugal pumps seems to be to regenerative type centrifugal pumps. Multistage centrifugal pumps with radial flow impellers will have usual power characteristics with minimum power at shut-off.

Query From: mahaprasad.rai@rediffmail.com

To: pumpsind@sancharnet.in

Sent: Wednesday, January 16, 2008 8:48 PM

Name : MAHA PRASAD RAI Designation : DY. MANAGER Department : COGENERATION Company : HINDALCO Address : Cogeneration, Hindalco, Renukoot City : Sonbhadra Pin Code : 231217 State : Uttar Pradesh

My Query : How to proceed for efficiency calculation of Boiler Feed pump.Normaly these pumps are provided with standby pumps which are required to be kept available all the time and it is very much difficult to alter the flow of the running pump.what Data should one collect for the purpose. What remedial action one can take to improve the efficiency of the pump. Kindly suggest.

Reply Date: Mon, 21 Jan 2008 19:09:03 -0800 (PST)

Efficiency of a pump is (rho*Q*H / constant / Power Input / Efficiency of Motor).,

Where,
rho = density of liquid at pumping temperature. Since Boiler Feed water may be at higher temperature density at that temperature should be taken into account.

Q = Ultrasonic flow-meters would give fairly accurate flow-measurement. This is a good non-intrusive method, fairly independent of the pipe-size. But one has to know the flow cross-section inside the pipe.

H = Head, which can be calculated from the difference between the suction and discharge pressure gauges.

constant = when Q is in litres per second and H in mWC, constant for output power in kW is 102. If flow is measured in m3/h the constant will be 367.2

Input power is easily measured in kW

Efficiency of the motor would be related to the percentage loading. Usually load-efficiency data are available for motors. But this data relates to output of the motor versus efficiency. The graph needs to be reworked to get Input versus efficiency characteristics.

Otherwise (rho*Q*H / constant / Power Input) would give Overall Efficiency of the pump, without segregation of Pump and More efficiencies.