Quick Tips for Saving in Pumps

If you want to get some quick energy saving tips follow these guidelines to identfiy opportunities in CW pumping, Or may be in all pumps with slight care.

This is the method which also guarantee you minimum energy saving achievable in pumps. The actual savings will be higher always depending on various other factors. I used this method recently & saved ~15% power consumption in CW pumps i.e. ~600 kW out of 4000 kW load resulting in huge savings with a payback of merely 4 months.

Guidelines

• First of all make a list of all pumps with design flow & head in two different columns in an Excel sheet. Say column A with flow & Column B with head


• Now measure the power consumption in the field & put it in Column C.


• Now in Column D put calculated power consumption with efficiency available for new pump & high efficiency motors.


• New pump efficiency for CW flow of more than 300 M3/hr at 40 m head can be considered ~80% which can go as high as 85% for bigger size pumps beyond 1000 M3/hr.


• High efficiency motor can have efficiency in the range of 94%+for motors of >100 kW, which can be 96%+ for bigger motors >300 kW


• After getting the final figure of power consumption for a new pump, you can put the saving potential in the next column E.


• Put the investment required for motor & pump in next column F judiciously (you can ask me for indian cost roughly) Or get it from some vendor


• Put payback or ROI in the next column G

You are through now. Suggest the replacement to your management in a nice presentable format for approval. Mind it that this method gives you minimum guaranteed savings from these pumps because,

• This method is not considering any flow & head measurement therefore, you get minimum savings in case your pump is not delivering the design or considered flow. Anyway it can not deliver more than design without compromising on head.


• The chances of errors are very less as you are measuring only power which is measured reliably & more accurately.


• You do not have to deal with plant people convincing them about the accuracy of flow measurement. Because flow is the most troublesome area where mostly people do not believe (Or they dont want to) about large drops.


• This gives you option of selecting the latest & most efficient equipment in the market.

Don't you believe on this?

I Said......I have already saved 15% power i.e. ~600 kW.

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Equal Percentage Valves - Opening Vs Flow

In case of equal percentage valves, the flow varies according to the following definition.

'Any % change in the opening from its current existing value changes the flow by same percentage of its current value at current opening.'

Means if current opening is say 10% & u change it to 15% than the change in opening from its current value (of 10%) is 50%, so the flow will also increase by 50% of its existing value at 10% opening. This means if flow was say 20% of the total range (Or capacity of the valve) at 10% opening it will become 30% (50% higher compared to 20%) of the total range.

So how to calculate it????

Now you know the definition so you can generate an equation which gives you all the values where 0% opening or lift is 0% flow while 100% lift is 100% flow.

So the curve for these valves look like this.




Long back I generated an equation from a general curve for an equal percentage valve. Its fixed for all kinds of valves from any manufacturer generally. There may be minor variations in case of specially designed valves otherwise it is same.

The equation is.

% Flow is = .06 + 0.49 * X -.019 * X^2 +.0005 * X^3 - 0.0000502 * X^4 + 0.0000000242 * X^5

Where X is % Lift or opening , X = 60 for 60% opening & not 0.6

Hope it is useful for all.

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Pinch Technology: Some Basics

Most Industrial processes involve heat transfer from one process stream to another process stream (interchanging) or from a utility stream to a process stream. In the present energy crisis scenario, target in any industrial process is MER – Maximum Energy Recovery or Minimum Energy Requirements.



In the early days of pinch technology, the main emphasis was on heat exchanger network (HEN) design. Today pinch technology stretches far wider in the fields of overall process improvement and utility system design

Pinch Technology analyses process utilities (particularly energy and water) to find optimum way to use them, resulting in financial savings. It does this by making an inventory of all producers and consumers of these utilities and then systematically designing an optimal scheme of utility exchange between them. Energy and water re-use are at the heart of pinch technology.

With the application of pinch technology, both capital investment and operating cost can be reduced. Emissions can be minimized and throughput maximized.

What is Pinch Technology?
The term “Pinch Technology” was introduced by Linhoff and Vredeveld to represent a new set of thermodynamically based methods that guarantee minimum energy levels in design of heat exchanger networks. It also ensures minimizing the capital costs and fewer emissions.

Basis of Pinch Analysis

Pinch Technology represents a simple methodology for systematically analyzing chemical processes and the surrounding utility systems with the help of the First and the Second Law of Thermodynamics.

1st Law of Thermodynamics: Provides the energy equation for calculating the enthalpy changes (ΔH) in the streams passing through a heat exchanger.

2nd Law of Thermodynamics: Determines the direction of heat flow. That is, the heat energy may only flow in the direction of hot to cold. This prohibits ‘temperature crossovers’ of the hot and cold stream profiles through the exchanger unit.

In practice the hot stream can only be cooled to a temperature defined by the ‘temperature approach’ of the heat exchanger. The temperature approach is the minimum allowable temperature difference (ΔTmin) in the stream temperature profiles, for the heat exchanger unit. The temperature level at which ΔTmin is observed in the process is referred to as the “pinch point” or “pinch condition”. The pinch defines the minimum driving force allowed in the exchanger unit. Thus, the prime objective of pinch analysis is to achieve financial savings by better process heat integration (maximizing process-to-process heat recovery and reducing the external utility loads).



Pinch principle

The point where ΔTmin occurs is known as the “Pinch”. Once the pinch has been identified, it is possible to consider the process as two separate systems: one above and one below the pinch as shown in the figure.
The system above the pinch requires a heat input and is therefore a net heat sink. Below the pinch, the system rejects heat and so is a net heat source



To summarize, the understanding of the pinch gives three rules that must be obeyed in order to achieve the minimum energy targets for a process:

• Heat must not be transferred across the pinch, i.e., no temperature crossovers.
• There must be no external cooling above the pinch.
• There must be no external heating below the pinch.

JUST FOR FUN & General Knowledge
After so much of pinch technology I would like to mention a few more pinches here :)
Ever heard about Network Pinch, Hydrogen Pinch, Water Pinch or Z Pinch?

NETWORK PINCH:When optimizing energy consumption in an existing industrial process, a number of practical constraints must be recognized. Traditional Pinch Technology focuses on new network designs. Network Pinch addresses the additional constraints in problems associated with existing facilities.

HYDROGEN PINCH:The Pinch Technology approach applied to Hydrogen management is called Hydrogen Pinch. Hydrogen pinch enables a designer to set target for the minimum hydrogen plant production and/or imports without the need for any process design.

WATER PINCH:This is a systematic technique for analyzing water networks and reducing water costs for processes. It uses advanced algorithms to identify and optimize the best water reuse, regeneration, and effluent treatment opportunities. It has also helped to reduce losses of both feedstock and valuable products in effluent streams.

Z PINCH:In fusion power research, the Z-pinch, or zeta pinch is a type of plasma confinement system that uses an electric current in the plasma to generate a magnetic field that compresses it (Pinch). The name refers to the direction of the earliest experimental devices in England, where the current flowed down a vertical quartz tube, the Z-axis on a normal mathematical diagram.

By Associate Writer - Nidhi Garg

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Find out Pump Head without curve

You are handling lot many centrifugal pumps & is always struggling for design data which may or may not be available specially in case of vintage units its very difficult to recollect them.

Even in newer plants if you do not have all procedures in place for documents handling you might face the same problem. What to do in such a case? Boss is not ready to listen any excuse.....You know that there is something wrong which can be improved and therefore you get a good recognition.......But

Here is the answer....

Few rules are there based on data analysed by experts in this field which are generally true for conventional systems. Such rules can be utilized when you do not have any other source to know them...at least an initial guess is must.

Rule-1
Shut-off head can be calculated by obtaining the square of impeller dia in inches. This gives you shut off head in feet. That means if your dia is 15" then 15 x 15 = 225 feet will be the shut off head for water.

There are other conditions also in this rule.
1. This rule is applicable at 1800 RPM.
2. This rule is applicable for water so apply density correction for other fluids.
3. Its generally accurate by ~95%.
4. Its a guide line only.
5. Its applicable to 85% population with 15% being exceptions in design.
6. The rule do not apply to PD pumps.

What is the shutoff head? The shutoff head is the beginning of the pump curve. It represents maximum elevation (in feet or meters) at zero flow. The performance curve proceeds to and ends at a point called maximum flow at zero elevation.

Now how can you use this information. Say you measure the performance of a pump you have collected all the data but you dont have pump curve. But you know from maintenance person that impeller dia is 15". So you know that this can develop 225 feet of water head.

Let us say fluid is also different say alcohol where SG = 0.8
So you know that 225 feet is = 225 * .3048 meters of water = 68.6 meter
Now fluid is alcohol so new head shall be = 68.6 * 0.8 = 54.9 meter

So the differential pressure must be 5.49 Kg/cm2.

No....No....No you are ......wrong....This is shut off differential head i.e. zero flow. So as a thumb rule it must be ~85% of shut off head i.e. 5.49 * 0.85 = 4.66 Kg/cm2. So if your actual differential is significantly lower than you can say that the pump is having something wrong with it.

What is that something......Well you yourself have to identify it.????

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