06 mine fan general

Mine Fan - General

Nuhindro Priagung Widodo

Teknik PertambanganFakultas Teknik Pertambangan dan Perminyakan

Institut Teknologi Bandung 2014

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Isi

1. Pengertian dan istilah2. Klasifikasi dan cara kerja alat ventilasi mekanis

- Fan sentrifugal- Fan axial- Mixed-flow fan

3. Kurva karakteristik fan4. Hukum-hukum fan

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Klasifikasi alat ventilasi mekanis untuk Tambang

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Fans Centrifugal Radial tipForward curvedBackward curved

Axial Flow Tube-axialVane-axial

Compressors Centrifugal

Axial Flow

Positive displacement

RotaryAxial Flow

Injectors Cylindrical

Conical

Venturi

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Fan

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Tube-fan

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Mixed-flow fan

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Axial fan

Centrifugal fan

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Variable/adjustable Pitch Fan

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Compressed-air injectors

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ASSESSMENT OF FANS AND BLOWERSWhat 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.

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Fan Efficiency

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Penempatan Fan

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2. Forcing system

3. Exhausting system

Fan

Outlet unit

Outlet unit Fan

1. Fan with inlet-outlet duct

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Fan sentrifugal

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Backward bladed-Centrifugal Impeller

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Velocity and Total Pressure of Centrifugal Fan

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

Va =Vt + Vr cot (m/s)

Pt = Vt(Vt + Vr cot )

Vt tangential velocity of bladeVa tangential velocity of airU velocity of air relative to the bladeV absolute velocity of the airblade angle in degreesn fan speed in rpmD diameter impeller plus bladeQ quantity of air Pt total pressure (Pa)

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

Pt = Vt2

Vt = Dn/60 (m/s)Vr = Q/A (m/s)

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Theoretical Centrifugal Fan Characteristic Curves

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Actual Centrifugal Fan Characteristic Curves

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Axial Fan

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Pt = 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.

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Fan Laws

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Fan Laws

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Perubahan blade angle terhadap kurva karakteristik fan dan total efisiensi

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Perubahan blade angle terhadap kurva karakteristik fan dan

Fan Power

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Contoh fan technical

specification

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Contra-rotating axial fan

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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.

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Single vs. Contra-rotating axial fan

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Pengaturan Fan

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Pengaturan Fan

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Kondisi Stall

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Main Fan

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Auxiliary Fan

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Masalah dalam Instalasi Fan

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Pemeliharaan Fan

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Fan kombinasi: Series

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Fan kombinasi: Paralel

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Typical pressure gradient

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Fan Evasees and Diffusers

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

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Fan curves

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Cikoneng

Cibitung

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Difficulties in assessing the performance of fans and blowers

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.

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Difficulties in assessing the performance of fans and blowers

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.

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Choose the right fan

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

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Maintain fans regularly

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

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Power consumption among flow control options

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Perbandingan kelebihan dan kekurangan terhadap metode-metode pengaturan fan

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