Baby BFP
Baby BFP
(OP)
Hi
I am not a pump engineer but basically an electrical engineer.I had come across a pump vendor who insists for a baby boiler feed water pump with a speed of 3350 RPM.It is used to maintain the water level in the boiler, during power failure when main BFPs could not be run due to DG capacity limitation.The higher RPM is required, which is more than the synchronous RPM of. 50HZ motor,to achieve higher efficiency,it is claimed.
My question is,for this kind of application,do we need to go for a VFD driven motor set up,necessarily, to achieve this higher speed?Is there any other options available?
I am not a pump engineer but basically an electrical engineer.I had come across a pump vendor who insists for a baby boiler feed water pump with a speed of 3350 RPM.It is used to maintain the water level in the boiler, during power failure when main BFPs could not be run due to DG capacity limitation.The higher RPM is required, which is more than the synchronous RPM of. 50HZ motor,to achieve higher efficiency,it is claimed.
My question is,for this kind of application,do we need to go for a VFD driven motor set up,necessarily, to achieve this higher speed?Is there any other options available?





RE: Baby BFP
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: Baby BFP
Pump has not yet been installed.It is a proposal for the project coming up.Will share more details shortly.
RE: Baby BFP
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: Baby BFP
If you try to speed up a pump then you have to also raise the voltage which starts to get complicated quickly.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Baby BFP
For a fixed duty point you should be able to find a pump to meet your duty at a fixed standard frequency.
If you can post the pump curve we might be able to see what he means but I think someone has an existing pump and needs to make it run faster for your duty. Plenty of pump vendors out there...
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Baby BFP
I used to deal with a mill where they had both 50Hz and 60Hz units in operation, due to legacy installations. It was something I learned to ask about first before going any further.
RE: Baby BFP
Without more background, a pump to introduce feedwater during a power outage seems like a terrible idea to me.
RE: Baby BFP
Kindly excuse me for the delay in responding to the various comments,since I could not get the details readily.
First and foremost,this small Boiler Feed Water pump will run not only during the power outage but during normal operation of the boilers along with Main feed water pumps of higher capacity.All the BFPs are connected to common suction & discharge headers.
There is a combination of Waste Heat Recovery Boilers (WHRB)and Circulating Fluidised Bed Boiler connected to a common steam header.A steam turbine generator catering to the captive power consumption of steel plant.
The starting of the plant will be with WHRB & as soon as the turbine starts CFBC will be started
Depending upon the steel plant operation scenarios,the power demand will vary.
In order to have flexibility in boiler operation, in line with plant power demand,a combination of BFPs of higher & smaller capacities will be running.
One of the scenario is power failure(turbine trip & grid not available).During that period the the smaller BFP will be run with an emergency DG,ensuring safety of WHRB.The baby BFP motor is LV and the rating is relatively less compared to Main BFP motor which is 11kV.
The rated flow of baby pump and main pump is 50 cu.m and 90 cu.m;rated speed 3350RPM and 2980RPM respectively.All other parameters like head,design &operating temp.NPSHa are identical.
Now,if you go to my question in OP, you may wish to throw some light with respect to the speed of Baby BFP.
RE: Baby BFP
Basically I can't see why this pump needs to run at any other speed than 2980.
The only reason I can think is that your pump vendor doesn't have a pump that matches your precise duty conditions ( 50 cu m/ hr?) @ xx mhead at 2980 and therefore is using the best pump he has available but that pump needs an increase in speed.
If design head is the same as the bigger pump, there isn't that much difference in power ( 5/9). I thought you were talking one was 10% of the big one, but in terms of your OP all this is irrelevant.
Makes no sense from what you've told us.
Can you post the pump curve?
Or ask another vendor. There are lots of options.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Baby BFP
Probably you maybe right.Instead of going for a customised design,to meet this particular duty, the pump vendor was offering his standard pump which calls for an increased speed.
Thanks.
RE: Baby BFP
There is no such thing as a "standard pump" for pumps of this sort of size - each pump model has a range of min to max impellor sizes which are machined to suit. Normally most pump vendors have overlapping sets of pump curves so a model 10 would go up to say 150m head and a model 20 starts at 130m and goes to say 250m.
This almost looks like he has a spare pump already machined and wants to get rid of it - but that's pure guesswork.
bottom line though - Do you need a VFD for this duty - In my opinion, no.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Baby BFP
Simply reply to the vendor, and say, 'we need a pump selected for 50hz speeds'. Should take about 90 seconds to resolve.