pump speck for nigative to positive pressure

[upm]

Gents,
i am trying to select a pump which can operate from nigative suction pressure to positive suction pressure. I know the range is wide but it is our process requirnments? a part from self priming pump, is ther any alternativs?
upm

 

[quark]

That is a better option. One thing you have to keep in mind is that, if your discharge pressure is constant and you are selecting a pump for negative suction, during positive suction the motor may overload. Better is to select the pump for negative suction and the motor for positive suction (i.e check the flow rate and power corresponding to the dP at positive suction). But this may operate your pump away from the BEP.

Other options

1. Use two pumps
2. Use positive displacement pumps

Regards,

 

[25362]

Can use external inductors or priming tanks. There are several approaches depending on the system and pumps used. Can you detail yours ?

 

[upm]

gents,
thanks alot for the hints,the process folks have specified the parameters as:
flow (t/h) : 3 to 17
suction pressure: vacuum(-0.3barg) to positive (0.5 barg)
LP steam condensate (dinsity is about 1000 kg/m3)
discharge press. 3.5 to 4.5 barg
i know the range is too wide nut i need to select the optimum. Currently we are dumping the water and i have installed a temporary single stage air operated diaphragm pump and it works fine. however, the diaphragms are getting raptured every often once pumpming vacuum
upm

 

[quark]

Why can't you use Pumping Traps/ Pressure Powered Pumps

http://www.armstrong-intl.com/products/condpumps/cp.php3

http://www.spiraxsarco.com/assets/uploads/PDFs/sb/P136_01.PDF

Why is it that suction pressure (or is it condensate pressure) is varying from -0.3 bar g to 0.5 bar g? Am I missing something?

Regards,

 

[TD2K]

I don't see the range of suction pressures as being a major problem since in any case, the condensate will be a bubble point lqiuid but the range of flowrates (3 to 17 t/hr) is going to require some sort of recirculation system back to the condensate receiver and pump suction.

If your flow and pressures can all vary independently, then you'll need to design the pump to handle from -0.3 barg suction to 4.5 barg discharge at 17 t/hr flow (plus any design allowances you might need). The control system and recirculation system would have to then be designed for the other possible high suction pressure, low discharge pressure, low flow operating conditions.

As Quark suggested, you might also want to look at a self powered condensate pump. I've put one of these in and it worked just as it was supposed to. It's bound to be a lot cheaper than a pump system, especially for these flows. You need to have a source of pressure to push the condensate out during the discharge cycle higher than the 4.5 barg condensate pressure.

Is the range of suction pressures due to the load or cleaniness of an upstream heat exchanger?

 

[upm]

TDk2,
you are exactly correct,h/e is upstream the new pump and based on the load the suction pressure varies.
what type pf pumps dod you install? brand name and address
upm

 

[TD2K]

Man, that was a LONG time ago, close to 20 years. I 'think' it was a Spirac Sarco, their website is

http://www.spiraxsarco-usa.com

to get the name of the representative in your area.

Someone else here is bound to have a more up to date recommendation. Several manufacturers make these, I'd talk to them, get some references and talk to the users about their experience in services similar to yours.

Armstrong also makes self powered pumping traps. There are bound to be lots more companies.

 

[upm]

thanks TD2K for the fast respons, what do think of disaphragm pumps with oil mist in the N2 line a(driving force)?
upm

 

[TD2K]

Sorry, no experience with diaphram pumps.

 

[jay165]

A Wilden pump would work, although I think it would use more energy than the pressured powered pump.

One of the things I love about this site is the users' expert command of spelling and English - eg, "nigative" pressure and diaphrams that are "raptured".

Smile of the day