Bucket Elevator Calculation

QUANG TRACH 1 THERMAL POWER PLANT - 2x600MW

BUCKET ELEVATOR CALCULATION Just downloaded this text from Scribd. For DL purposes only.

CONTENTS 1 PURPOSE..............................................................................................................2 2 TARGET OF DESIGN...........................................................................................2 3 STANDARDS AND CODES.................................................................................2 4 UNIT OF MEASUREMENT.................................................................................2 5 DESIGN PARAMETERS......................................................................................2 5.1. Input data.......................................................................................................2 5.2. Output data....................................................................................................2 6 BASIS OF CALCULATION..................................................................................3 6.1. Capacity.........................................................................................................3 6.2. Bucket types..................................................................................................3 6.3. Pulley revolution............................................................................................4 6.4. Peripheral force..............................................................................................4 6.5. Power............................................................................................................. 5 6.6. Determination of belt type.............................................................................5 7 CALCULATION RESULTS..................................................................................6 8 APPENDIXES........................................................................................................6

QT1-PVE-00HTK-M-M5A-0004

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BUCKET ELEVATOR CALCULATION

1

PURPOSE With bucket elevators, different bulk loads can be conveyed either vertically or sloping upwards. Belts with buckets attached are used as the carrying medium. They run with low noise levels and low vibrations at a relatively high speed. They require only a small ground area and are preferred in buildings, silos and warehouses. The bucket elevator selection through volumetric capacity, lift, lump size, material characteristics and operating conditions will determine necessary demand properly.

2

TARGET OF DESIGN Design is to provide the optimal engineering solution meet to safety, reliable & stable operating conditions for system.

3

STANDARDS AND CODES -

4

DIN 15234 – Bucket for Elevator.

UNIT OF MEASUREMENT The unit of measurement in the design shall be SI unit (International System of Units).

5

DESIGN PARAMETERS

5.1.

Input data

5.2.

-

Density of bulk material.

-

Lump size.

-

Working time.

-

Height of elevation.

-

Designed capacity.

Output data -

Bucket type.

-

Pulley revolution.

-

Peripheral force.

-

Power required.

-

Determination of belt type.


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6

BASIS OF CALCULATION

6.1.

Capacity

6.1.1. Volume capacity QV = 3.6 × v × ϕ ×

vB a

Where: QV

: Volume capacity (m3/h)

v : Speed (m/s) ϕ : Degree of filling, the measure of the effective utilization of the bucket capacity. vB a

: Nominal capacity of one bucket (litres) : Bucket pitch (m)

vB is determined from the geometric dimensions and a horizontal surface filling level (water filling). 6.1.2. Mass capacity Qm = QV × ρ Where:

6.2.

Qm

: Mass capacity (t/h)

ρ

: Bulk density of load (t/m3)

Bucket types The type of bucket is determined in the main by the material and the method of discharge either by continuous or centrifugal emptying. -

DIN 15231: Flat bucket for light loads such as flour, semolina, grain.

-

DIN 15232: Flat rounded bucket for light granulated loads such as grain.

-

DIN 15233: Medium deep bucket for sticky loads such as cane sugar.

-

DIN 15234: Deep buckets with a flat back wall for heavy pulverized loads or coarse ground loads such as sand, cement, coal.

-

DIN 15235: Deep buckets with curved back wall for light flowing or rolling loads such as fly ash and potatoes.


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6.3.

Pulley revolution n=

v × 60 π ×D

Where:

6.4.

n

: Pulley revolution (rpm)

D

: Pulley diameter (m)

Peripheral force The peripheral force FU is determined from the sum of resistances to motion: FU = FH + FB + FN Where: FU

: Peripheral force (N)

FH

: Main resistance (N)

FB

: Loading resistance (N)

FN

: Secondary resistance (N)

6.4.1. Main resistance The main resistance is derived from the capacity and the height: FH =

Qm × g × H 3.6 × v

Where: g

: Acceleration due to gravity (m/s2)

H

: Height of elevation (m)

6.4.2. Loading resistance The method of bucket loading and the force required to accelerate the load to conveying speed determines the loading resistance. FB is dependent upon the speed. The loading resistance can be accounted for with sufficient accuracy using an additional height factor: FB =

Qm × g × H 0 3.6 × v

Where: H0

: Additional height (m)

H0 = 4 × v + 4 QT1-PVE-00HTK-M-M5A-0004

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6.4.3. Secondary resistance The secondary resistance FN takes into account the frictional forces, flex resistances of the belt, pulley bearing resistance and acceleration to the circumferential speed of the drive pulley. FN is very small by comparison to the other resistances and is adequately covered by the factor cN as part of the total resistances. FN = ( cN − 1) × ( FH + FB ) Where: cN 6.5.

: ≈ 1.1

Power

6.5.1. Drive power at pulley PT =

FU × v 1000

Where: PT

: Drive power at pulley (kW)

6.5.2. Motor power PM =

PT η

Where:

6.6.

PM

: Motor power (kW)

η

: Degree of efficiency (in general 0.5 – 0.95)

Determination of belt type From the preceding calculations, the bucket capacity, the bucket width and thus the belt width can be determined. For further calculations especially that for belt safety factor, the belt type has to be assessed as well as the weight of the take-up (tension) pulley.

6.6.1. Nominal belt strength kN =

T1 × S B

Where: kN

: Nominal belt strength (N/mm)


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T1

: Belt tension (N)

S

: Safety factor

B

: Belt width (mm)

6.6.2. Belt type assessment For the assessment of a belt type, initially the belt stress T1 can be approximately estimated. T1 = FU + FSt + TV + TT FSt = H × 9.81 × ( m 'B + m 'G ) TV = c2 × k A × FU − FSt − TT TT = GT × 9.81/ 2 Where: FSt

: Slope resistance (N)

TV

: Pre-Tension (N)

TT

: Weight of take-up pulley (N)

m 'B : Weight of bucket and fastenings (kg/m) m 'G : Belt weight estimated depending on bulk density (kg/m), m 'G =11.5 × B PN PM

kA

: Start-up factor, k A = k ×

PN

: Installed power (kW)

k

: = 1.2 ÷1.6 depending on coupling

c2

: Drive factor

GT

: Weight of take-up pulley

If TV ≤ 0 then an additional pretension is not necessary. 7

CALCULATION RESULTS See attached documents.

8

APPENDIXES


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Table 8 – 1. Values for fill factor, bulk density and conveying speed

Table 8 – 2. Bucket according to DIN


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Table 8 – 2. Bucket according to DIN (cont.)


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Bucket Elevator Calculation

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