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On New Applications:
1. Calculate
the required torque
2. Select
the ETP Connection with the proper torque rating
3. Check
suitability of shaft and hub
4. Check
operating temperature
On Existing
Applications:
1. Select
the ETP Connection for the required shaft size
2. Check
the required torque
3. Check
operating temperature
4. Check
existing shaft and hub for a keyway
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Torque Calculations:
Given the horsepower
rating of the prime mover and the shaft rpm, the torque transmitted
is:
Calculating
the Required "Tr"
The required
torque transmission rating "Tr" is equal to the calculated
torque multiplied by service factor "a" which will account
for high starting torques, transient overloads, shock loads, pulsating
loads and alternating loads.
Certain types
of electric motors have starting torques as high as 2 to 2.5 times
rated torque which must be taken into consideration when selecting
the ETP. Recommended service factors for various types of applications
are shown in the following table:
| Service
Factors |
|
Driver
|
Electric
Motor
|
Internal
Combustion Eng.
|
| Type
Load |
Constant |
Pulsating |
Alternating |
Constant |
Pulsating |
Alternating |
| Fans |
1.0 |
- |
- |
1.5 |
- |
- |
| Rotary
Pumps |
1.0 |
1.5 |
- |
1.5 |
2.5 |
- |
| Generators |
1.0 |
1.5 |
- |
1.5 |
2.5 |
- |
| Centrifuges |
- |
1.5 |
- |
- |
2.5 |
- |
| Chain
Drives |
- |
1.5 |
- |
- |
2.5 |
- |
| Reciprocating
Compressors |
- |
- |
2.0 |
- |
- |
3.0 |
| Piston
Pumps |
- |
- |
2.0 |
- |
- |
3.0 |
| Conveyors
(belt) |
- |
- |
2.0 |
- |
- |
3.0 |
| Crushers |
- |
- |
2.0 |
- |
- |
3.0 |
| Rollings
Mills |
- |
- |
2.0 |
- |
- |
3.0 |
Example:
A piston
engine powered compressor (a = 3) with torque of 100 lb. ft. will
require an ETP with a torque rating of 300 lb. ft.
The formula
is: Required Tr = Tc x a
- Where: Tr
= torque rating of ETP
- Tc = calculating
torque
- a = service
factor
Shaft and
Hub Tolerances
ETP Connections
(inch series) are designed for the following tolerances:
| Tolerances: |
| ETP
SIZES |
SHAFT |
BORE |
| 3/4" |
+.000
-.0015 |
+.0010
-.000 |
| 7/8"-1
1/2" |
+.000
-.0020 |
+.0010
-.000 |
| 1
5/8"-1 15/16" |
+.000
-.003 |
+.0010
-.000 |
| 2"-4" |
+.000
-.0030 |
+.0014
-.000 |
Metric tolerance
shaft h8 to k6 (ETP-15 only h7) Hub H7.
Note: If the
ETP Connection is used in an application where tolerances lie outside
the recommended range, torque transmission (Tr) will be reduced.
The torque values in the tables of sizes are based on these tolerances.
If the shaft
and hub dimensions and tolerances are correct, there will be a clearance
between the clamping ring and flange (T).
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Stress in
Hub and Shaft
The stress is
a function of surface pressure and material thickness. At constant
surface pressure, increases with diminishing material thickness.
This applies both to hubs and hollow shafts. The table below shows
recommended OD/ID ratios for hubs made of different materials.
| Material |
OD/ID |
Steel
(high grade)
Steel (normal grade)
Cast Iron
Aluminum |
1.4
1.5
2.0
2.5 |
OD
= outside diameter of hub
ID = inside diameter of hub |
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Caution:
ETP Connections are designed for use in temperatures ranging from
-22°F to a maximum of +180°F.
When mounting
the ETP Connections over an existing keyway, the keyway must be
filled in.
Call factory
with any questions you may have.
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