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DROPPING THE MIC ON DYNAMIC CENTRIFUGAL PUMPS

The Process Technology and Operator Academy Posted on by

 

I ain't gonna work on Maggie's farm no more
No, I ain't gonna work on Maggie's farm no more
Well, I try my best
To be just like I am
But everybody wants you
To be just like them

("Maggie's Farm," by Bob Dylan, 1965)

 

UPDATING THE DYNAMIC PUMP FAMLY TREE

Brilliant PTOA Readers and Students who are reading the PTOA Segments in the intended, sequential order learned in PTOA Segment #204 that there are only two classifications of pumps, Positive Displacement Pumps and Dynamic Pumps.

This Pump Classification Family Tree graphic is made up of Blue Blocks. The Dynamic Pump Family is on the Right Side. The two subsets of Dynamic Pumps are Centrifugal and Axial.

And brilliant PTOA Readers and Students also learned that there are two subsets of Dynamic Pumps  … Centrifugal Pumps and Axial Pumps …  as is shown on the right side of the nearby Pump Classification Family Tree diagram composed of "blue blocks."

No one would blame a PTOA Reader or Student for being confused when s/he or they run across a different version of the Pump Classification Family Tree like the one shown below:

This Classification of Pumps Family Tree with Examples shows the Positive Displacement Family Tree on the Right Side and the Dynamic Pump Family Tree in the Middle.

This "Classification of Pumps ... With Examples" diagram is nifty because there is a visual example of what each type of pump in each lineage line and subset looks like!

Okay, okay. The graphic is admittedly a little hard to read so Your Mentor will describe it in detail.

Note that both of the Pump Family Trees agree that there are only two main types of pumps … PD and Dynamic Pumps.

The "Classification of Pumps … With Examples" shows the Positive Displacement Pump lineage line on the right side of the graphic. Upcoming PTOA Segments will focus on PD Pumps so do not stress about the right side of the graphic at this moment!

Right now the focus is on the Dynamic Pump Lineage Line shown in the middle of the diagram.

Note that this  graphic splits the Dynamic Pump Family Line into two subsets: "(Dynamic) Centrifugal Pumps" and "(Dynamic) Special Pumps."

There are a couple concepts to unpack while gazing at "The Classification of Pumps … With Examples" diagram:

The Axial Flow Pump on the Left and very familiar Radial Flow Pump on the Right are both members of the same Centrifugal Pump Family because they both swap Fluid Velocity for PV Pressure.

First, the (Dynamic) Centrifugal Pump lineage line includes the very familiar Radial (Flow)  Pumps,vertically long Mixed Flow Pumps, and Axial Flow Pumps.

Second … this diagram infers that Axial Flow Pumps are a subset of Centrifugal Pumps and not their own family line!

Fred is confused! This new way to illustrate the Pump Family Tree differs from the more traditional "blue block Pump Family Tree diagram" above!

The "blue block Pump Family Tree diagram" declares the two Dynamic Pump subsets to be "Centrifugal Pumps" and "Axial Pumps." And there is no "Special Pump" lineage line in the "blue block Pump Family Tree" diagram.

Well, Fred … families grow and change!

Your Mentor writing the PTOA Segments.

This PTOA Segment #206 explores the nuances between Centrifugal Pump Family members in the Dynamic Pump classification.

The less popular members of the Dynamic Pump Family … the "Special (Dynamic) Pumps" lineage line … will be featured in the upcoming PTOA Segment #207.

And guess what?

The following paragraphs are THE LAST WORDs of PTOA content dedicated to describing the form and function of Centrifugal Pumps!

Hallelujah!

 

THE CENTRIFUGAL PUMP FAMILY MEMBERS

Radial (Flow) (Centrifugal) Pumps compared to Axial Flow (Centrifugal) Pumps

Your Mentor agrees with the nearby "Classification of  Pumps … With Examples" graphic! Axial Flow Pumps are a subset of Centrifugal Pumps and not a separate Dynamic Pump lineage line. Since the operational theory of both of these pumps is the PV Pressure ↔ Velocity Swap, both of these types of pumps should righteously be classified under the category of "(Dynamic) Centrifugal Pumps."

The visual examples of Radial (Flow) (Centrifugal) Pumps shown in the graphic are exactly the same Centrifugal Pumps that PTOA Readers and Students learned about while reading PTOA Segments #163 through #176.  The descriptor "Radial" just means this style of pump flings the pumped-up liquid radially outward from the eye of the Impeller into the Volute.

The Discharge PV Pressure from a Radial (Flow) (Centrifugal) Pump is moderately high.

However, the Radial (Flow) (Centrifugal) Pump cannot accommodate a high volume of flow … aka Capacity..

 

As PTOA Readers and Students learned in PTOA Segment #204,  the propeller-type Impeller of an Axial Flow (Centrifugal) Pump causes the liquid that is being pumped to flow parallel down the horizontal axis of the Shaft.

Compared to the Radial (Flow) (Centrifugal) Pump …

The propeller-type Impeller of the Axial Flow (Centrifugal) Pump cannot add much PV Pressure to the flowing liquid.

However the Axial Flow (Centrifugal) Pump can accommodate a much greater volume of flow … aka Capacity.

 

What is a Mixed Flow (Centrifugal) Pump?

Axial Flow = Pumped liquid flows parallel to Shaft (Low Discharge Pressure, High Volume Capacity). Radial Flow = Pumped liquid is flung outward from Impeller Eye to Volute (Much Higher Discharge Pressure, Much Lower Volume Capacity). Mixed Flow Pump yields lower Discharge Pressure than Radial Flow Pump but high Volume Capacity like the Axial Flow Pump.

Who amongst the brilliant PTOA Readers and Students would be surprised to learn that the Mixed Flow (Centrifugal) Pump is designed to include some flow characteristics of the Radial (Flow) (Centrifugal) Pump and some characteristics of the Axial Flow (Centrifugal) Pump?

Lo and Behold ...

The Mixed Flow (Centrifugal) Pump will have a discharge PV Pressure between the significantly higher PV Discharge Pressure of the Radial (Flow) (Centrifugal) Pump and the significantly lower PV Discharge Pressure of the Axial Flow (Centrifugal) Pump.

The Mixed Flow (Centrifugal) Pump can accommodate significantly greater flowrates compared to the  Radial (Flow) (Centrifugal) Pump.

 

A Mixed Flow Pump that excels at Flood Control.

Where would Mixed Flow Pumps and Axial Flow Pumps be used? Wherever a large volume of liquid needs to be moved fast, but a large Discharge Pressure is not needed. For example Axial Flow Pump capacities range from 2,000 gpm to 700,000 gpm with Discharge PV Pressures of 60 ft of head per Impeller stage. These pumps are well suited for flood control, irrigation and drainage projects, large scale primary water supplies, power plant condensing and other industrial process circulating systems.

Hey, Thanks to Mr. Shady from #shady_BHazy_Learn Engineering for making a nifty You Tube that illustrates the differences between Radial Flow, Axial Flow, and Mixed Flow Centrifugal Pumps!

Be certain to give Mr. Shady a Thumb's Up for taking the time to create a You Tube which explains "What is the difference between Radial , Axial & Mixed Flow Pumps?"

 

The Very, Very Last Words about Radial (Flow) (Centrifugal) Pumps

Before Your Mentor crosses the finish line on Radial (Flow) (Centrifugal) Pumps, "You Tube and Chill"  with a quick video review courtesy of Machine Tech Video Blog entitled "Centrifugal Pump Types." Be sure to give Machine Tech a Thumb's Up!

Your Mentor chose this You Tube because of the perspective from the Mechanic Tech's point of view. The video also features pumps operating in an industrial setting. Note that since the equipment is in operation, the Mechanic Tech should be wearing a hard hat.

PTOA Readers and Students are now proficient in understanding the form and function of Radial (Flow) (Centrifugal) Pumps.

Thus, no PTOA Reader or Student will have any problem understanding the jargon and concepts used in the video to describe:

 

 

Go ahead …

Drop that mic on (Dynamic) Centrifugal Pumps!

 

 

 

 

 

 

 

TAKE HOME MESSAGES: Pump technology evolves and so does the Pump Family Tree.

All Pump Family Trees to-date agree that there are only two kinds of Pumps … Dynamic Pumps and Positive Displacement Pumps.

More modern Pump Family Trees differ from the traditional Pump Family Trees by:

  • Classifying the Centrifugal Pump Family members according to how the liquid being pumped flows through the pump (e.g. radial flow, axial flow, or mixed flow).
  • Classifying Axial Flow Pumps within the Centrifugal Pump lineage line … which makes sense since the operational theory of both is the PV Pressure ↔ Velocity Swap.
  • Adding a "Special Dynamic Pump" category of Pumps which will be featured in the next PTOA Segment.

 

The following observations/conclusions can be made by comparing the three members of the Dynamic Centrifugal Pump Family:

The Radial Flow (Dynamic) (Centrifugal) Pump adds more PV Pressure into the liquid that is being pumped up, but cannot accommodate high flowrates (aka Capacity).

The Axial Flow (Dynamic) (Centrifugal) Pump can accommodate a high flowrate (aka Capacity) but cannot add much PV Pressure into the liquid that is being pumped up.

The Mixed Flow (Dynamic) (Centrifugal) Pump adds less PV Pressure to the pumped-up liquid than the Radial Flow (Dynamic) (Centrifugal) Pump can add ...  however this hybrid flow pump can add significantly more PV Pressure to the pumped-up liquid than the Axial Flow (Dynamic) (Centrifugal) Pump can. Mixed Flow (Dynamic) (Centrifugal) Pumps can also accommodate high liquid flowrates (aka Capacity).

PTOA Readers and Students have completed learning the Process Technology college class requirements for (Dynamic) Centrifugal Pumps ... the most popular industrial pump.

Well done!

©2020 PTOA Segment 0206
PTOA PV PRESSURE FOCUS STUDY AREA
PTOA ROTATING EQUIPMENT AREA - DYNAMIC AND POSITIVE DISPLACEMENT PUMPS

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