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Hardened &
Ground Gear Boxes
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Salient Features
The 'Nu-Ratio' gear reducers are designed as per DIN
Std. A starting torque equal to two times running torque
is considered while designing 'Nu-Ratio' gear reducers.
Gear Cases
The gear cases are manufactured in two pieces form graded
C. I. castings with rugged design, free from any blow
holes. They are corrosion resistant and can absorb shock
and vibration. The housing can also be manufactured
from M S. fabricated plates, and Stress relieved. Inspection
covers are provided for viewing gear contacts. Oil level,
dispstick and drain plug are fitted at proper places.
Gearing
The helical/spiral gears are manufactured from high
quality alloy steel, hobbed with protuberance type cutter.
The gears are case carburised, hardened and tempered
and precisely ground to give high efficiency and quiet
running.
Shafts and Bearings
Shafts are from alloy steel forgings or bars heat treated
to suitable BHN value. The bearings are antifriction;
Taper roller or / and spherical roller type fitted on
the ground journal. Low speed shaft can be solid or
hollow. The bearing life is 15000 working hours (min).
Sealing
Suitable spring loaded single lip type seals are used
to prevent the leakage of oil and entry of atmospheric
dust.
Cooling
Where the natural cooling from the exposed surface of
the gear box is not sufficient, the gear units are provided
with on/two cooling fans mounted on high speed shaft.
The gear units are also supplied with external forced
feed lubrication system where fan cooling is also not
sufficient to keep the temperature of the gear units
upto optimum.
Others
The gear units can also be provided with Backstop, baseplate
& preheating arrangement.
The tolerance on the nominal transmission ratio is 3%.
Following information is to be specified for selection
of gear units-
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1. |
Prime-mover |
7. |
Application |
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2. |
Prime
mover's power KW/HP |
8. |
Duty
Hours per day |
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3. |
Brake horse power |
9. |
Ambient temperature |
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4. |
Input speed, N1 |
10. |
Whether Backstop is
required? |
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5. |
Output Speed, N2 |
11. |
Hand of assembly
as described in the catalogue. |
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6. |
Required ratio |
12. |
Any other information |
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Example
Selection of 'Nu-Ratio' gear Reducers
Data Given:
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Prime mover
Motor Power
Input Speed
Output Speed
Frequency of starts/hr
Brake horse power
Parallel Shaft horizontal offset application
Duty
Ambient temperature |
-
-
-
-
-
-
-
-
- |
Electric Motor
305 KW (P1)
1500 RPM (n1)
115 RPM (n2)
1
305 KW (P2)
Plunger pump
24 hrs / Day
40° C |
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Select the suitable service factors from the tables
for the prime mover as electric motor and driving equipment
and plunger pump f1 = 1, f2 = 2 & f3 = 1
Calculate the nominal gear unit rating "PN"
PN=P1xf1xf2xf3 = 305x1x2x1=610 KW
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Refer the catalogue of two stage gearbox NHB and find
that the rating of the gearbox NHB - 360 is suitable
for the application at the nearest ratio 12.5:1
Thermal capacity of NHB - 360 is 285 KW without any
cooling i.e. Pth = 285 KW
Select the temperature factor at 40° C ambient temp.
as 0.82 100% duty cycle.
The actual thermal capacity of the gearbox at 40°
C=f4xPth = 0.82 KW = 233.7P1 <305 KW.
Therefore additional cooling is required with single
fan.
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Table 3 Factor
for Frequency of starts f3
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| Starts
per Hour |
Factor for processing
machine f2
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>1.0 |
>1.2 |
>1.4 |
>1.6 |
>1.8 |
>2.0 |
| 1-5 |
1.0 |
1.0 |
1.00 |
1.00 |
1.00 |
1.00 |
| 6-20 |
1.2 |
1.1 |
1.08 |
1.07 |
1.07 |
1.06 |
| 21-40 |
1.3 |
1.2 |
1.17 |
1.16 |
1.15 |
1.08 |
| 41-80 |
1.5 |
1.4 |
1.25 |
1.23 |
1.18 |
1.10 |
| 81-160 |
1.6 |
1.5 |
1.35 |
1.30 |
1.20 |
1.10 |
| Above 160 |
2.0 |
1.8 |
1.70 |
1.60 |
1.30 |
1.10 |
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Table 4 Factor
for Thermal Capacities f4
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| Ambient Temperature |
Duty Cycle
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| 100% |
80% |
60% |
40% |
20% |
| 20°C |
1.0 |
1.04 |
1.09 |
1.16 |
1.27 |
| 30°C |
0.9 |
0.95 |
1.0 |
1.07 |
1.18 |
| 40°C |
0.82 |
0.86 |
0.9 |
0.98 |
1.09 |
| 50°C |
0.73 |
0.77 |
0.82 |
0.89 |
1.0 |
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Table 1 Factor
for Propulsion Machines f1 |
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| Electric Motors Tubines |
Piston Engines 4-6 Cylinders Cycle
Variation 1:100 upto 1:200 |
Piston engines 1-3 Cylinders Cyclic
variation upto 1:100 |
| 1.0 |
1.25 |
1.5 |
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Table 2 Factor
for Propulsion Machines f2 |
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| Processing
Machines |
Daily
Service in Hours
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upto
3
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3-10
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10-24
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Blowers,
Fans
Axial blowers, Cooling Towers, Fans,
Induced draught blowers, Radial blowers
Rotary |
1.0
|
1.25
|
1.5
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| Turbo
blowers, mixers |
1.0
|
1.0
|
1.25
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| Chemical
Industry |
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| Agiatot
(Semi-liquid material) |
1.0
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1.0
|
1.25
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| Centrifigures |
1.0
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1.0
|
1.25
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| Rotary
Drying Kilns |
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1.5
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Condesors
Compressors, Rotary Piston Compressors
(UI: 100-200)
Rotary Piston Compressors (U<100)
Turbo Compressors |
1.5
|
1.75
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2.0
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| Conveyors |
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| Apron
Conveyors |
1.0
|
1.75
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1.5
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Ballast/Bucket
Elevators Belt Conveyors
(bulk material) |
1.0
1.0
|
1.25
1.0
|
1.5
1.25
|
Belt
Conveyors
(piece goods) |
1.0
|
1.25
|
1.5
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| Bucket
Conveyors |
1.5
|
1.5
|
1.5
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| Chain
Elevators |
1.25
|
1.5
|
1.75
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Circular
Conveyors
Drag Chain Conveyors
Gravel Conveyors |
1.0
|
1.25
|
1.5
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| Haulage
Winches |
1.25
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1.5
|
1.75
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| Hoists |
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2.0
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| Conveyors
/ lifts |
1.0
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1.25
|
1.75
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| Powder
elevator |
1.0
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1.0
|
1.25
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| Screw
Conveyors |
1.0
|
1.25
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1.5
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| Sinking
Machines |
1.5
|
1.75
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2.0
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| Drag
haulers |
1.0
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1.75
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1.5
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| Steel
Belt Conveyors |
1.0
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1.25
|
1.5
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| Crane |
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| Derricking
job gears |
1.0
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1.25
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1.5
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| Hoisting
gears / luffing gears |
1.0
|
1.0
|
1.25
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| Landing
gears |
1.5
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1.75
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2.0
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| Traversing
gears |
1.0
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1.25
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1.5
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| Winches |
1.0
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1.25
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1.5
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| Excavators
and Stackers |
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| Bucket
Conveyor excavation (k.loose) |
1.5
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1.75
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1.75
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| Bucket
Conveyor (K.tight) |
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2.0
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| Bucket
Wheels (Overburden / Limestone / Coal)
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1.5
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1.75
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2.0
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| Bucket
wheels for waste heap |
1.4
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1.5
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1.6
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| Cutter
heads |
1.5
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1.75
|
2.0
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Landing
gears (Caterpillar)
Landing gears (Rails) |
1.5
|
1.75
|
2.0
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Maneuvering
winches
Traversing gear / winche |
1.0
|
1.25
|
1.5
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| Suction
Pumps |
1.0
|
1.75
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1.5
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| Food
Industry Machinery |
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| Cane
Crushers |
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2.0
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| Cane
Knives |
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1.5 |
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| Processing
Machines |
Daily
Service in Hours |
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upto
3
|
3-10
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10-24
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| Filling
Machines |
1.0
|
1.0
|
1.25
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| Kneeding
Machines |
1.0
|
1.25
|
1.5
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| Mash
Tubs, Crystallizers |
1.5
|
1.75
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2.0
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| Packaging
Machines |
1.0
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1.0
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1.25
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| Sugar
beat Cutters |
1.0
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1.25
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1.5
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| Sugar
Cane Cutters |
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1.5
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| Generators
& Transformers |
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| Frequency
Transformers / welding generators |
1.5
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1.75
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2.0
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| Generators |
1.0
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1.0
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1.25
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| Water
Turbines |
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1.5
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| Iron
& Steel Industry |
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| Blast
urnace Blowers |
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1.5
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| Inclined
elevators or blast furnace |
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2.0
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| Laundry
Machines Rotary Drives / Washing Machines |
1.0
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1.25
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1.5
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| Metal
Working Machines |
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| Bending
Machines |
1.0
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1.25
|
1.5
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| Counter
Shafts / Line Shafts |
1.0
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1.0
|
1.25
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| Forging
Presses |
1.5
|
1.75
|
2.0
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| Hammers |
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2.0
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| Machine
tools, Auxiliary Drives |
1.25
|
1.5
|
1.75
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| Machine
tools, Main drives |
1.5
|
1.75
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2.0
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| Planning
Machines / |
1.5
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1.75
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2.0
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| Presses
/ Punching Presses / Straightening Machines
/ shearing Machines |
1.0
|
1.25
|
2.0
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| Mining
Stone & Soil working Machins |
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| Chain
Conveyors |
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1.5
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| Cone
crushers / Crushers, Gyrator, brakers
/ Hammer Mills / Impact Pulverizers
/ Jaw Crushers, Jaw Brakers |
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2.0
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| Mine
Blowers |
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1.5
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| Ram
Moulding Machines |
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1.75
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| Rod
Mills |
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2.0
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| Roll
Crushers |
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1.75
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| Rolling
Mills |
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2.5
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| Rotating
Cylindrical Kilns |
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2.0
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| Sharp
Point Brakers / Tube Mills |
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2.0
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| Wagon
Pushers |
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1.5
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| Oil
Industry |
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| Filter
Presses / Hydraulic Pumps |
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1.75
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| Pipeline
Pumps |
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1.5
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| Rotary
Drilling Equipments |
1.5
|
1.75
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2.0
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| Presses |
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| Bending
Presses / Brick Presses / Briquelting
Presses / Eccentric Presses / Forging
Process |
1.5
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1.75
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2.0
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| Processing
Machines |
Daily
Service in Hours |
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upto3
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3-10
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10-24
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Pumps
(Light Liquids) Centrifugal Pumps (Semi
Liquids) |
1.0
1.0
|
1.0
1.25
|
1.25
1.5
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Compression
Pumps
Piston Pumps
Piston Pumps (UI : 100-200)
Piston Pumps
(U < 100) |
1.5
|
1.75
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2.0
2.0
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| Rolling
Mills |
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| Billet
Shears |
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2.0
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| Capstan
Handles / Chain Transfers / Coiling
Machines |
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1.5
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| Cold
Rolling Mills |
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2.0
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| Continous
Casting Equip. |
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|
1.25
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| Cooling
Beds / Cropping Shears Cross Transfers |
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1.5
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| Descaling
Machines |
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2.0
|
| Draw
Benches for wire Drawing |
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|
1.5
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| Fast
Rollers |
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|
2.0
|
| Fix
Transportation (Rope) |
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|
1.5
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| Ingot
& Blooming Mills / Ingot Handling
Machinery / Ingot Pushers |
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2.0
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| Lift
Conveyors |
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|
1.75
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| Live
Roller Type Feeding Tables Manipulators
/ Revolving Turrets (Continous Casting) |
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1.5
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| Plate
Milts |
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2.0
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| Rolls
Straighteners |
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1.5
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| Roller
Adjustment Devices |
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2.0
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| Roller
Tables |
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2.0
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| Roller
Tables (Light) |
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1.5
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Roller
Tables (Heavy)
Roller Transporters / Sheet Rolling
Mills |
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|
2.0
|
| Shunting
Installation / Slow Rollers |
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|
1.5
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| Tape
Spools |
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|
1.75
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| Trimming
Shears |
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|
1.5
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Tube
Welding Machines
Winding Machines (Strip & Wire) |
1.5
|
1.75
|
2.0
|
| Wire
Drawing Machines / Wire Wheels / Wire
Rope Winches |
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|
1.5
|
| Rubber
& Plastic Machinery |
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| Calenders |
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|
2.0
|
| Crushing
Machines |
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|
1.5
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| Extruders |
1.5
|
1.75
|
2.0
|
| Mixers |
|
|
1.75
|
| Pug
Mills / Rolling Mills |
|
|
2.0
|
| Textile
Machinery |
|
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| Batchers
/ Calenders Looms Printing & Drawing
Machines |
1.0
|
1.25
|
1.5
|
| Water
Treatment |
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| Aerators |
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|
2.0
|
| Screw
Pumps |
1.25
|
1.5
|
1.75
|
| Wood
Working Machine |
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| Barkers
/ Saw Mills |
1.5
|
1.75
|
2.0
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| Planing
Machines |
1.0
|
1.25
|
1.5
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| Wood
Working Machines |
1.0
|
1.0
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1.25
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Since
Research & Development is an on-going activity,specifications
are subject to change without notice. |
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NHA
- Foot mounted units |
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