by

ELGI EQ UIPMENTS LTD

New Trends in Design and Application Aspects of Compressors

Contents

Ø ELGI – capability & reach

Ø Need for Energy efficiency

Ø Energy efficiency in design

§ Efficiency relat ed terms

§ Sizing & Staging

§ Component selection

§ Manufacturing process

Ø Energy efficiency in application

§ Selecting the type of compressor

§ Maintenance & application engineering

Elgi completed its 50th year on 14th March 2010

Sales Turnover-5810 Million

Employees- More than1200

Global presence in over 60 countries

• One of the few companies in the world to design and manufacture rotors and airends

• State-of-the-art Horizontal, Vertical and CNC Machining Centers

Capability

In ChinaWholly-owned subsidiary with assembly plant

In Middle EastWholly-owned subsidiary with warehouse facility

In BrazilWholly-owned subsidiary with warehouse facility

In EuropeAcquired BELAIR of France, a company engaged in assembly, sales and serviceof industrial compressors and accessories.

Global footprint

ELGI factor y in Chi na

• Exports contribute to 20% of overall sales

• Expanding footprint in 63 countries with wide product range and deep reach

• Larger distribution network

• Well trained sales and service engineers

• Footprint in 63 countries

Reach

Contents

Energy efficiency in compressed air systems:

• 10 to 20% of power consumed is for production of compressed air

• It’s the most expensive energy available to us (8 times more expensive than electricity)

Energy efficiency in compressed air systems: Statistics indicate that

Ø The typical compressed air system uses only 50% of its air supply for production, the

rest is wasted or lost to air leaks

Energy efficiency in compressed air systems:

Ø In the cost of compressed air, approximately 76% is constituted by electricity /fuel cost

Assumptions in this example include a 75 HP compressor operated 2 shift a day 5 days a week at an aggregate electric rate of Rs. 4.5 / kWh over 10 year of equipment life

Typical Lifetime Compressed Air Costs in perspective –Costs Over 10 years

Energy efficiency in compressed air systems:

Contents

Energy efficiency in Design

Efficiency related terms

• Free Air Delivery: Actual Volume of the air delivered by the compressor within a unit

time calculated at inlet conditions. Units: m3/hr, m3/min, cfm

• Shaft Power: Actual power consumed by the compressor to compress a given volume of

air from inlet pressure to out let pressure. This includes the volumetric and mechanical

losses inside the airend. Units: kW, hp

• Volumetric efficiency: Ratio of Actual capacity (FAD) of the compressor to swept

volume •vol = (Swept volume – Leakage) / Swept Volume

• Adiabatic efficiency: Ratio of the actual power to the adiabatic power

•adiabatic = Adiabatic power / Actual power

• Specific Power consumption : Shaft power consumed for an unit volume of flow

delivered, Unit:kW/m3/minContents

Energy efficiency in Sizing :

Leakages : Air flowing back through the clearance volumes. Potential & Inherent source of ineffi ciency

• The clearance volumes are inevitable

• For a given size they need to be optimized

• By optimal sizing the leakages can be reduced

A screw compressor example….

Energy efficiency in Sizing :

A screw compressor

Optimizing Clearances that Affect Performance

• Discharge end clearance (60%) : The clearance between the end face of the rotor and the

Bearing housing

• Inter lobe Clearance (30%) : The clearance between the lobes of the male and female

rotor

• Rotor Tip Clearance (10%) : The clearance between the rotor housing and the male or

female rotor tip

Energy efficiency in Design

In design the focus is to get maximum flow at a given power

• Sizing / Staging

1. Size of the compressor

2. Speed of the compressor

3. Number of stages

Variation of Volumetric Efficiency and Isentropic Efficiency with RPM

0.75

0.8

0.85

0.9

0 1000 2000 3000 4000 5000 6000 7000

Male Rotor Speed (RPM)

Effic

ienc

y, %

Volumetric EfficiencyIsentropic Efficiency

• Recommended tip speed range 10 – 40 m/sec• Minimum & Maximum flow to be positioned in that range• Design point at the optimum value of both volumetric efficiency and isentropic

efficiency• Size of the compressor to match the above guide lines

Energy efficiency in Sizing

Variation of Specific Power for different sizes of compressors

6.000

6.200

6.400

6.600

6.800

7.000

7.200

7.400

7.600

7.800

8.000

5 10 15 20 25 30 35 40TIP SPEED (m/s)

SPEC

IFIC

PO

WER

(kW

/m3/

min

)

5373102

Energy efficiency in Sizing

Thus for the same flow selecting a higher size within the guidelines of tip speed will have a higher energy

efficiency. Volumetric efficiency increases linearly with increase in size, as the displacement linearly

increases with size, but the clearances do not

Single Stage and Two Stage Compressors

• In single stage compressor, the discharge pressure required is achieved in one stage,

where as in two stage compressors, it is achieved in two stages.

• Two stage compressors are preferred over single stage due to Energy benefit or for

high pressure applications

Two stage Compressors for Energy benefit

• Inter Cooling.

• Divided Pressure Ratio

Energy efficiency in Staging

Two stage Compressors for Energy benefit

• abcd single stage

• abefgd two-stage with inter cooling

•• Area under PV diagram is work

Energy efficiency in Staging

Contents

Energy Efficiency in system component selection

Sources of energy loss in a system:• Electrical equipment• Pressure drop across the system• Friction

Electrical equipment• Main motor - Super efficiency motors, permanent magnet motors, Eff1 replacing Eff2 motors• Fan motor - Eff1 instead of Eff2 & efficient solutions like use of plastic fan, fan controlled by a

thermal switch

Pressure drop across the system

• Suction pressure drop - Whatever lost in the suction is lost forever. Components like air filter and suction valve should be appropriately sized

• Discharge pressure drop - Pressure drop in down stream components results in higher shaft power consumption

It is a good practice to have indicators across the above components in the system to indicate the pressure drop

• For example the recommended accessories for various sizes of compressors is shown in table 1

MODEL 53 73 102 159 159 S 225 284

Power4 & 5.5

kW5.5 – 11

kW11 – 22

kW30 – 37

kW45 – 55

kW55 – 75

kW55 – 75

kW90 –

160 kW160 kW

Intake Valve Size 1.5” 1.75” 2.5” 3” 4” 4” 6” 6”

Oil Injection Orifice** 6 mm 4 mm 12 mm 10 mm 10 mm 15 mm 22 mm

Discharge Pipe Size (mm) 16 NB 32 NB 40 NB 65 NB 80 NB 80 NB 80 NB

Equivalent Discharge Pipe Size as per ASTM A

106 in inches- 1.25” 1.5” 2.5” 3” 3” 3”

Return Line Orifice 0.5 mm 0.8 mm 0.8 mm 1.5 mm1.57 mm

1.57 mm1.57 mm

Air Filter Capacity 40 cfm 75 cfm 171 cfm 275 cfm 430 cfm 565 cfm 565 cfm1200 cfm

1200 cfm

Air Filter Micron rating 1-3• 10• 8• 8• 8• 8• 8• 10• 10•

Separator Capacity 71 cfm 71 cfm 212 cfm 317 cfm 400 cfm 582 cfm 582 cfm1215 cfm

1215 cfm

Oil Filter Flow Rating 40 lpm 40 lpm 35 lpm 150 lpm 170 lpm 170 lpm 360 lpm 360 lpm

Oil Filter Micron Rating 10• 10• 10• 10• 10• 10• 10• 10•

Table 1 : Recommended accessories for various sizes of compressors

Energy Efficiency in system component selection

Friction

- Profile with rolling contact in a screw compressor

- Use of high energy efficient bearings to bring down the power loss in bearings

- To use high transmission effi ciency gears

- To use a belt transmission system with the least slip

- To optimize the oil flow to reduce the frictional loss due to viscous drag

Energy Efficiency in system component selection

Contents

Energy Efficiency in manufacturing

• Leakages through clearances can be reduced by using improved process eg: grinding

process instead of milling in manufacture of rotors enabling a minimum 3 %

improvement in flow for the same shaft power, for a given size

• Using high precision components facilitating a precise clearance setting, which ensures

the specified flow for a longer service life – no deterioration in specific power

• Use of high precision processes on critical parameters in components eg: like profile

milling of discharge port made in machining instead of castings etc.

Contents

Energy efficiency in application• Guideline for selecting the type of compressor

Contents

• Appropriate pressure & flow for the requirement - Sizing the accessories for the

compressor flow or matching the compressor flow for the accessory requirement in the application side

• Decentralization of the compressor – reducing pressure drop eliminating bends &

reducing length and leakages

• Ensure air intake to compressor is not warm and humid by locating compressors in

well-ventilated area or by drawing cold air from outside.

• Clean the system components regularly and ensure systematic maintenance

• Conduct periodic air audits and monitor the system efficiency & take corrective actions as

per recommendation

Energy efficiency in application

Best Practices in Application & Maintenance • Provide extra air receivers at points of high cyclic-air demand which permits operation

without extra compressor capacity

• Compressed air piping layout should be made preferably to ensure minimal pressure drop

• Provide ball valves at the user points to avoid wastage

Energy efficiency in application

Energy efficiency in application

We at ELGI

• Are committed to make energy efficient

products

• Support and educate the customer on

energy efficient practices

• Promote the culture of energy efficiency

in the society through our products and

services

THANK YOU