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maraamaram
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Join Date: Nov 2009
Location: Sharjah, UAE
Posts: 22

Pumps and Motor Size Calculations

12/07/2009 5:20 AM

Dear Friends,

I need approximate size of few pumps as follows: Liquid sp. gravity: 1. Liquid=LPG.

1. Liquid Flow Rate: 180 m3/hr & Diff. Head : 3.45 barg & Power 30KW.

2. Liquid Flow Rate: 45 m3/hr & Diff. Head : 20.7 barg, Power 45KW.

3. Liquid Flow Rate: 75 m3/hr & Diff. Head : 20.7 barg, Power 72KW.

4. Liquid Flow Rate: 15 m3/hr & Diff. Head : 20.7 barg, Power 15KW.

Fire Fighting System:

Main pump: Liquid Flow Rate: 750 m3/hr

Diesel pump: Liquid Flow Rate: 750 m3/hr

Jockey pump: Liquid Flow Rate: 20 m3/hr

For one working & one standby, Is there any minimum distance to be maintained bet. these two pumps.

Friends pls reply & need thumb rule to calculate.

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b v rao
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Join Date: Feb 2009
Location: India
Posts: 155
#1

Re: Pumps and Motor Size Calculations

12/07/2009 11:20 PM

Get the data from pump vendor of your city
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sabriahmad
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Join Date: Nov 2009
Posts: 78
Good Answers: 9
#2

Re: Pumps and Motor Size Calculations

12/08/2009 12:06 AM

Dear Maraamaram

The equation for pump hydraulic power is given by

P = QΔP/36

Where P is pump power in kW, Q flowrate in m3/h, ΔP pump differential head in bar

To obtain the motor power, divide hydraulic power by the overall efficiency (motor + shaft).

A word of caution is that you need to specify the right liquid S.G since I noticed that the S.G that you specified is 1 whereas the liquid is LPG (SG = 0.560). If you size the pump based on S.G = 1, the pump will be undersized for running LPG. This means that you will not get the pressure differential that you want.

For example, for 3.45 bar differential pressure and based on SG=1, then if you are running LPG then the differential pressure will be 1.9 bar.
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maraamaram
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Join Date: Nov 2009
Location: Sharjah, UAE
Posts: 22
#5
In reply to #2

Re: Pumps and Motor Size Calculations

12/09/2009 12:39 AM

Thanks a lot for your Good Answer.

I have to select the type of pump. This is the first time Iam handling the LPG pumps.

Can you pls guide me to select the type of the pump?

Best Regards,

Raghu

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sabriahmad
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Posts: 78
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#8
In reply to #5

Re: Pumps and Motor Size Calculations

12/09/2009 3:07 AM

Dear Maraamaram

The first choice is always a centrifugal pump because in general it has lower LCC (life cycle cost).

The easiest way is to supply enough information to vendor or supplier of pump and let them make the recommendation. (Use pump datasheet available in API 610 to supply the process data)

However, specify that the pump must meet the API STD 610 – Centrifugal Pump for Petroleum, Heavy Duty Chemical and Gas Industry Services.

For installation of LPG Pump follow API STD 2510 – Design and Construction of LPG Installation.

For safety reason, consider ESV (remote) for quick isolation in case of LPG leaks and specify the MAWP based on maximum possible pressure at the suction for determining the right design pressure of the pump casing. Do not forget to install minimum flow line. Normally pump vendor will provide the minimum flow requirement for the pump that they recommended.

Last but not least, witness the shop test before delivery and insist the vendor to supply the performance curve (result of the shop test).
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maraamaram
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Location: Sharjah, UAE
Posts: 22
#9
In reply to #8

Re: Pumps and Motor Size Calculations

12/09/2009 5:14 AM

Thanks a lot Mr. Sabriahmed,

You have given good guidance to me.

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chaitanya1986
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Join Date: Nov 2009
Posts: 7
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#10
In reply to #8

Re: Pumps and Motor Size Calculations

12/09/2009 5:37 AM

yes And while before testing please check the performance curve supplied by vendor with offer, is the pump really efficient to sustain at 150% of duty point flow with not less than 65% of rated head. And also the shut off head shoul not exceed more than 120% of rated (Duty Point Head).
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chaitanya1986
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Posts: 7
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#3

Re: Pumps and Motor Size Calculations

12/08/2009 2:18 AM

Ya i Agree with the equation thing mention by one of our friend but be careful while selecting the motor for fire fighting pump. One shoul always compare the power req at 150% flow and at rated* 1.2 which ever is higher you can select.

Regards,

CP
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maraamaram
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Location: Sharjah, UAE
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#6
In reply to #3

Re: Pumps and Motor Size Calculations

12/09/2009 1:31 AM

Thanks a lot Mr.Chaitanya

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sv13
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Location: Between India & Australia
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#4

Re: Pumps and Motor Size Calculations

12/08/2009 3:14 AM

Between the fire pumps, yes you should leave some space; not only for maintenance and access but also between diesel pump and electric pump from fire protection considerations. Actually, these should be in two separate compartments separated by a fire wall or space them adequately so the fire wall is not required.

To get an idea of the size of the pump, go to any pump vendor home page (Goulds etc.), select the pump model and then typical GA drawing. leave space for maintenance access atleast 150% of the pump slab width.

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maraamaram
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Location: Sharjah, UAE
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#7
In reply to #4

Re: Pumps and Motor Size Calculations

12/09/2009 1:56 AM

Thanks a lot Sir.

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b v rao (1); chaitanya1986 (2); maraamaram (4); sabriahmad (2); sv13 (1)

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