Module: IV Mine Fan - General

Dr. Nuhindro Priagung Widodo

Teknik Pertambangan

FakultasTeknik Pertambangan dan Perminyakan, Institut Teknologi Bandung

2009

NPW1

Mine Ventilation

Isi

NPW

1. Pengertian dan istilah

2. Klasifikasi dan cara kerja alat ventilasi mekanis

- Fan sentrifugal

- Fan axial

- Mixed-flow fan

3. Kurva karakteristik fan

4. Hukum-hukum fan

Klasifikasi alat ventilasi mekanis

untuk Tambang

NPW

Fans Centrifugal Radial tip

Forward curved

Backward curved

Axial Flow Tube-axial

Vane-axial

Compressors Centrifugal

Axial Flow

Positive displacement Rotary

Axial Flow

Injectors Cylindrical

Conical

Venturi

Fan

NPW Axial fan Centrifugal fan

Tube-fan

NPW

Mixed-flow fan

NPW

NPW

NPW

Axial fan

Centrifugal fan

Variable/adjustable Pitch Fan

NPW

Compressed-air injectors

NPW

NPW

NPW

NPW

ASSESSMENT OF FANS AND BLOWERS

NPW

What is fan efficiency / performance?

Fan efficiency is the ratio between the power transferred to the air stream and the power delivered by the motor to the fan. The power of the airflow is the product of the pressure and the flow, corrected for unit consistency.

Another term for efficiency that is often used with fans is static efficiency, which uses static pressure instead of total pressure in estimating the efficiency. When evaluating fan performance, it is important to know which efficiency term is being used.

The fan efficiency depends on the type of fan and impeller. As the flow rate increases, the efficiency increases to certain height (“peak efficiency”) and then decreases with further increasing flow rate. The peak efficiency ranges for different types of centrifugal and axial fans.

NPW

Penempatan Fan

NPW

2. Forcing system

3. Exhausting system

Fan

Outlet unit

Outlet unit

Fan

1. Fan with inlet-outlet duct

Fan sentrifugal

NPW

Backward bladed-Centrifugal Impeller

Velocity and Total Pressure

of Centrifugal Fan

NPW

a. Radial tip b. Forward-curved c. Backward-curved

Va =Vt + Vr cot q (m/s)

Pt = r Vt(Vt + Vr cot q)

Vt tangential velocity of blade

Va tangential velocity of air

U velocity of air relative to the blade

V absolute velocity of the air

qblade angle in degrees

n fan speed in rpm

D diameter impeller plus blade

Q quantity of air

Pt total pressure (Pa)

Pt = r Vt(Vt - Vr cot q)Pt = r VtVa

Pt = r Vt2

Vt = pDn/60 (m/s)

Vr = Q/A (m/s)

Theoretical Centrifugal Fan

Characteristic Curves

NPW

Actual Centrifugal Fan Characteristic

Curves

NPW

Axial Fan

NPW

NPW

Pt = r Vt(V1 – V2)

Typical Axial Fan Characteristic Curves

Vt tangential velocity of blade

(V1 – V2) change in the rotational component

of the absolute velocity.

(V1 – V2) is varies along radius.

Fan Laws

NPW

NPW

Perubahan blade angle terhadap kurva

karakteristik fan dan total efisiensi

NPW

Perubahan blade

angle terhadap kurva

karakteristik fan dan

Fan Power

NPW

Contoh fan

technical

specification

NPW

Contra-rotating axial fan

NPW

A modification of the axial-flow fan. It consists of two impellers with aerofoil shaped blades that

rotate in opposite directions. The drive is by means of a single motor through differential gears,

or two separate motors, one for each impeller. They are placed in the airstream and act as

streamlined hubs. These fans are available for auxiliary ventilation in mines.

Single vs. Contra-rotating axial fan

NPW

NPW

NPW

NPW

NPW

NPW

NPW

NPW

Fan kombinasi: Series

NPW

NPW

Fan kombinasi: Paralel

Typical pressure gradient

NPW

Fan Evases

and Diffusers

NPW

Re (m) Ae (m2) Teta Conv. Eff. Q v

Desain L (m) L/Rf Rf (m) Af (m2) Ae/Af (deg) m3/s m/s Hv (Pa) Hr (Pa) Pr (kW)

A 6.72 6 2 12.57 3.19 7.46 0.6 70 5.57 18.62 102.42 7.17

1.12 3.94 70 17.76 189.31

B 3.36 3 1.3 5.31 1.35 3.07 0.87 70 13.18 104.30 73.96 5.18

1.12 3.94 70 17.76 189.31

(Pa)

(Pa)

NPW

Air Demand for Stoping and

Development

42

Stoping Development

No. Description

Unit Q Q Q total

kW (m3

/min) (m3

/s) (m3

/s)

1 Mining equipment

1.1 Toro 6 loader 136 489.6 8.2

1.2 Truck; EJC 417 156 561.6 9.4

1.2 Jumbo (electric) 0 0 0.0

17.5

2 Underground Miners

2.1 Operator 3 18 0.3

2.2 Non operator 4 24 0.4

0.7

Air Requirement 18.2

Drilling and Mucking at Stope No. Description

Unit Q Q Q total

kW (m3

/min) (m3

/s) (m3

/s)

1 Mining equipment

1.3 Dozer 50 180 3.0

1.4 Elphinstone;1300 136 489.6 8.2

1.5 Shotcreting; 136 489.6 8.2

1.6 Agitator; mariner 55 114 410.4 6.8

26.2

2 Underground Miners

2.1 Operator 4 24 0.4

2.2 Non operator 8 48 0.8

1.2

Air Requirement 27.4

Development

Total Air Demand

43

Air requirement per unit diesel equipment 0.06 m

3/s/kW

human 0.1 m3/s/man

room 0.25 m3/s/m

2 area

No. Description

Unit Q Q Q total Unit Q Q Q total

kW (m3

/min) (m3

/s) (m3

/s) kW (m3

/min) (m3

/s) (m3

/s)

1 Mining equipment

1.1 Toro 6 loader 136 489.6 8.2 136 489.6 8.2

1.2 Truck; EJC 417 156 561.6 9.4 156 561.6 9.4

1.3 Dozer (?) 50 180 3.0 50 180 3.0

1.4 Elphinstone;1300 136 489.6 8.2 136 489.6 8.2

1.5 Shotcreting; 1 & 2 (?) 136 489.6 8.2 136 489.6 8.2

1.6 Agitator; mariner 55 114 410.4 6.8 114 410.4 6.8

43.7 43.7

2 Underground Miners

2.1 Operator 7 42 0.7 7 42 0.7

2.2 Non operator 12 72 1.2 12 72 1.2

1.9 1.9

3 Compressor 0.0 0.0

4 Workshop 0.0 0.0

Air Requirement 45.6 45.6

54.70 losses 20% 54.70

Cikoneng Cibitung

Fan curves

44

Cikoneng

Cibitung

Difficulties in assessing the

performance of fans and blowers

NPW

In practice certain difficulties have to be faced when assessing the fan and blower performance,

some of which are explained below:

Non-availability of fan specification data: Fan specification data (see Worksheet 1) are

essential to assess the fan performance. Most of the industries do not keep these data

systematically or have none of these data available at all. In these cases, the percentage of fan

loading with respect to flow or pressure can not be estimated satisfactorily. Fan specification

data should be collected from the original equipment manufacturer (OEM) and kept on

record.

Difficulty in velocity measurement: Actual velocity measurement becomes a difficult task in

fan performance assessment. In most cases the location of duct makes it difficult to take

measurements and in other cases it becomes impossible to traverse the duct in both directions.

If this is the case, then the velocity pressure can be measured in thecenter of the duct and

corrected by multiplying it with a factor 0.9.

NPW

Improper calibration of the pitot tube, manometer,

anemometer & measuring instruments: All instruments and

other power measuring instruments should be calibrated correctly

to avoid an incorrect assessment of fans and blowers.

Assessments should not be carried out by applying correction

factors to compensate for this.

Variation of process parameters during tests: If there is a

large variation of process parameters measured during test

periods, then the performance assessment becomes

unreliable.

Choose the right fan

NPW

Important considerations when selecting a fan are (US DOE, 1989):

• Noise

• Rotational speed

• Air stream characteristics

• Temperature range

• Variations in operating conditions

• Space constraints and system layout

• Purchase costs, operating costs (determined by efficiency and maintenance), and operating life

Maintain fans regularly

NPW

Regular maintenance of fans is important to maintain their

performance levels. Maintenance activities include (US DOE,

1989):

• Periodic inspection of all system components

• Bearing lubrication and replacement

• Belt tightening and replacement

• Motor repair or replacement

• Fan cleaning

NPW

NPW

NPW

NPW