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singlaatul
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Suction Nozzle Sizes

08/05/2009 11:47 AM

What is the reason behind keeping the size of suction nozzle of pump one size lesser than suction line size???

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devitg
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#1

Re: Size of the suction nozzle

08/05/2009 1:11 PM

suction line size , shall be sized , as to allow no more than 1,5 to 2 meter/second .

No matther what suction nozzle of pump is .

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singlaatul
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#2
In reply to #1

Re: Size of the suction nozzle

08/05/2009 2:11 PM

Please elaborate

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devitg
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#3
In reply to #2

Re: Size of the suction nozzle

08/05/2009 2:55 PM

Please read the books.

They don't bite

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PennPiper
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#4

Re: Suction Nozzle Sizes

08/05/2009 4:53 PM

Singlaatul,

You have it backwards. It is not that the pump is kept smaller than the suction line size, but it is the suction line size must be made larger than the pump nozzle size.

You see the Process Engineer provides to the Pump Engineer the preliminary data for the pump service. The commodity, the operating pressure, the operating temperature, the NPSHa (Net Positive Suction Head available) and the downstream head.

The Pump Engineer works with a pump vendor to select (or design) a pump to meet the needs. They try to select the most cost effective pump that meets the needs. This means the suction nozzle size, the impeller size, the volute size, the case size, the discharge nozzle size, the driver (motor) size, etc.

The suction line must be sized to provide a flooded suction to the pump at an acceptably low flow rate that reduces the potential for cavation erossion. Thus the suction will almost always be one or more sizes larger than the pump suction nozzle size.

I hope this helps.

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lyn
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#5
In reply to #4

Re: Suction Nozzle Sizes

08/06/2009 12:03 AM

Nicely done!
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singlaatul
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#6
In reply to #4

Re: Suction Nozzle Sizes

08/06/2009 1:07 AM

oh thanks.. i was looking for this kind of explaination...

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singlaatul
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#7
In reply to #4

Re: Suction Nozzle Sizes

08/06/2009 10:47 AM

Can u put some light for the similar situations on discharge side???

There also we r going for reducer or expander in most of the cases.

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PennPiper
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#8
In reply to #7

Re: Suction Nozzle Sizes

08/06/2009 11:53 AM

The answer to this question also has to do with "acceptably low flow rate" or velocity in the line. The velocity of the fluid in the discharge nozzle is very high but for only a short distance. The velocity in the remainder of the line should not be as high, therefore the line is larger than the pump nozzle.

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singlaatul
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#9
In reply to #8

Re: Suction Nozzle Sizes

08/06/2009 1:14 PM

So it is all about maintaining the flow velocity in the suction as well as discharge line (in the range of 1.5 - 2 m/sec), so this is the main reason of difference in sizes of nozzles and lines.

is the maximum desired velocity is 2m/sec or it may vary for some different fluid services?? And what impact will it make if it crosses the limit???

Difference in line sizes for suction as well as discharge lines is for the same reason or there is some different story???

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PennPiper
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#10
In reply to #9

Re: Suction Nozzle Sizes

08/06/2009 4:16 PM

You are getting into some very specific questions.

If you are working on a specific project I strongly recommend that you take the general information I have given you seek out the Process Engineer for the specific service and ask him (or her) for the answers you want. Also make sure you study the P&ID for the service you are asking about.

Please let us know what the process engineer says.

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lyn
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#11

Re: Suction Nozzle Sizes

08/06/2009 7:11 PM

I think it's time you sought professional help, or at least researched some texts on the subject. Something credible, that you can use in your defense when you are sued.

Maybe talk to the pump supplier?

You need help, and not from strangers, intelligent as they are on this forum.

Do as PennPiper suggested.
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devitg (2); lyn (2); PennPiper (3); singlaatul (4)

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