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How to Calculate NSPH of Pump with Examples and Illustrations

NPSH of pump (net positive suction head) should be calculated/predicted in the beginning of pump sizing. The purpose is to check if the pump will work appropriately. Liquid pressure will lower right in inlet of pump impeller. If pressure reduction is lower than vapor pressure, liquid phase will change to vapor phase. The impeller rapidly collapses vapor bubbles which cause cavitation and damage.

In this post I will share you how to calculate NPSH available, which is net positive suction head calculated based on system arrangement. The value of NPSH available (NPSHA) shall be greater than NPSH required (NPSHR), which is a function of pump and to be specified by pump manufacturer.

NSPH of pump is calculated as follow:

NPSH available (ft, m) = absolute pressure (ft, m)vapor pressure (ft, m) –  line loss (ft, m) ± elevation difference (ft, m) Read More

Centrifugal Pump Sizing Spreadsheet

Since past two days, people still celebrate new year, so office activity has not started yet. That means I actually still in holiday too. But I want to update this blog while enjoying my holiday. I cannot (or in a mood) to create full article. So, instead sharing full article, in this post, I want to share you centrifugal pump sizing spreadsheet.

I created pump sizing spreadsheet for my first LNG project. The inspiration came from Pump Sizing Calculation from CheCalc. But I made it better.

I think you should download this spreadsheet because it offers better features that online calculation fro CheCalc. 

  • The spreadsheet is simple. You just input the data in dark yellow highlight
  • Pump sizing is calculated based on rated flow rate. If you want to size based on normal flow rate, input 0 in percentage of rated flow rate
  • Pressure drop components is comprehensive, including pipe loss, fitting loss, and equipment loss
  • Pump data results is comprehensive, including:
    • Suction pressure
    • Discharge pressure
    • Differential pressure
    • Differential head
    • Hydraulic power
    • Pump BHP
    • Rated power (calculated)
    • Rated power (selected) : based on commercial output motor power
    • NPSHA
    • NPSHR
    • Shut in pressure

Stop reading! Start downloading! Hope you find this useful!

[button style=”btn-default btn-sm” icon=”glyphicon glyphicon-save” align=”left” iconcolor=”#4285bf” type=”link” target=”false” title=”Download Pump Sizing” link=”https://missrifka.com/?attachment_id=1791″]

illustration-for-pressure-loss-calculation

How to Properly Size Discharge Pressure of Pump

When sizing discharge pressure of pump, we need to consider at least two things: target pressure at destination point and pressure loss from source point to destination point. How if we have two different destination points? How do we properly size pump discharge pressure?

In this post I want to share you simple method to size discharge pressure of pump when you have more than one destination point. Read More

Understanding Pumps Terminology

As a process engineer, I sometimes dealing with pumps. I usually feel confuse when I read pump specification or graphs offered by vendors. Here in this post, I want to share you some knowledge about pumps terminology that you may hear before what don’t really understand the meaning.

I create mind map for several most-often-used pump terminology that come to my mind. I’m sorry if the arrangement is a bit messy :D.

pump-terminology Read More

Reciprocating Pump P&ID Configuration

Reciprocating pump is a class of positive displacement pump which includes piston pump, plunger pump, and diaphragm pump. It is often used where a relatively small quantity of liquid to be handled and where delivery pressure is quite large. Priming is not required because it is positive displacement pump. Reciprocating pumps have lower efficiency compared to centrifugal pump.

API 674 – Positive Displacement Pump – Reciprocating covers minimum requirements for reciprocating positive displacement pumps for refinery application. The standard also covers piping and instrumentation required for the pump. Read More

Hydraulic Pump Calculation

Yesterday I just finished doing hydraulic pump calculation for one of a project in my company. The purpose of the calculation was to determine suction pressure, discharge pressure, and pump differential head.

Pump calculation procedure is very simple.

First, you need to define pump operation condition. It includes fluid temperature, fluid specific gravity, fluid viscosity, pump normal capacity and design capacity.

Second, check your Piping and Instrumentation Diagram (P&ID) carefully. In this step you need to calculate pressure drop due to pipe line and fittings in the suction and discharge of pump. You need to list fittings and calculate pressure loss due to the fittings.

Total suction head = line loss + loss due to accessories + suction head

Do the same thing as for discharge head.

Differential head is calculated by this formula

Differential head = total discharge head – total suction head. 

 

Pump Inspection and Factory Acceptance Test

The opportunity to witness Factory Acceptance Test (FAT) of pumps came to me. About a week ago I visited our vendor’s factory at Industrial zone in Pulogadung, Indonesia. Our plan was to witness the performance of three different pumps.

www.torishimaguna.com

Our pumps were not API pumps therefore the performance test procedure was quite simple and quick. The performance test of one pump took less than 30 minutes. However, the preparation, such as mobilization of pump, installation, make sure there’s no leak in the pipe, took longer time than the test itself.

There are several parameters to be checked during test, suction head, discharge head, rpm, power, voltage, bearing temperature, vibration level, and noise level. The pumps were operated under different flow rate, such as 0%, 25%, 50%, 100%, and 120% capacity, and at minimum flow. Those parameters were checked at different flow condition.

After we got the actual parameters, we plotted on the graphs. Then we compare the actual performance with design performance. The deviation shall not more than 6%.