|
Since
the belt itself is one of the most costly components of a typical
conveyor system, it is obviously important to select the right GRT
belt for the job. When recommending a belt, whether on a new system
or as a replacement on an existing system, an objective study of
the system and all the relevant operating conditions is of utmost
importance. Belt selection must take into account six key criteria:
system tension, load support, troughability, impact rating, pulley
diameters, and covers (compound and thickness).
Tension
The
tension members in a belt carcass provide the longitudinal strength
to move the load and also withstand torque from the system start
up. Belt tension is normally defined as required PIW (pounds per
inch of width) and can be calculated using the following quick method:
PIW = HP (1 + K) 33,000
S
x W |
|
PIW
|
.....Unit
Tension |
|
HP
|
.....System
Motor Horsepower |
|
K
|
.....Drive
Factor |
|
S
|
.....Belt
Speed (Foot Per Minute) |
|
W
|
.....Width
of Belt |
|
33,000
|
.....Constant |
| |
|
|
Drive
Pulley
Degree of
Wrap
|
Screw
Take-Up
|
Counterweight
Take-Up
|
|
Bare
Pulley
f=0.22
|
Lagged
Pulley
f=0.25
|
Bare
Pulley
f=0.30
|
Lagged
Pulley
f=0.35
|
|
180°
(a)
|
1.00
|
.84
|
.64
|
.50
|
|
200°
|
.86
|
.72
|
.54
|
.42
|
|
210°
(b)
|
.80
|
.67
|
.50
|
.38
|
|
220°
|
.74
|
.64
|
.46
|
.35
|
|
240°
|
.66
|
.54
|
.40
|
.30
|
|
300°
|
.46
|
.37
|
.26
|
.19
|
|
360°
|
.33
|
.26
|
.18
|
.13
|
|
420°
(c)
|
.25
|
.19
|
.12
|
.08
|
|
480°
|
.19
|
.14
|
.09
|
.06
|
While
this method is quick, it does not represent the most accurate method
for belt tension selection. A more precise and exact calculation
can be made by using the Conveyor
Belt Data Form supplied on this site (click here).
Completely fill in the form and send to the factory for review and
recommendation of a proper GRT belt for your use.
|
|
Load
Support
Proper
carcass traverse rigidity must be maintained throughout the belt
life to support the load capacity of the belt and bridge the idler
junction gaps. Load support values for GRT belts, based on the number
of plies and the type of belt, are provided in the proceeding pages
and stated as a maximum width in inches.
Troughability
In
addition to having adequate load support, the belt must still be
flexible enough to make proper contact with all three troughing
idler rolls when the belt is empty. If not, proper belt training
cannot be accomplished. Troughabiilty values for GRT belts are provided
in the preceeding pages and stated as a minimum width in inches.
Impact
Rating
The
type of fiber, or tension member, weave design, and number of plies
determines the impact rating of a belt, and its ability to absorb
impact energy. This information in addition to knowledge of the
size and type material to be conveyed, how the material is to be
loaded, and the conveyor system’s impact arrangement, allows
us to choose the proper GRT belt. Impact rating of a belt carcass,
as stated in drop to belt in inches, must not be exceeded.
Pulley
Diameters
Proper
sized pulleys allow the belt to operate at its full tension rating
without additional stress and compression on the inner plies. Minimum
pulley diameters for conveyor systems are stated in inches for various
belt carcasses and differing tension ratings.
Covers
Covers
are compounded for a wide variety of applications and are selected
to be compatible with the actual materials that are to be conveyed.
GRT offers a full line of cover compounds, as explained in the previous
pages that will handle almost any conveying applications. Cover
thickness for a specified compound is also a function of the application,
the type material to be conveyed, and frequency of the loading cycle.
A chart has been provide on page 10 for recommended thickness of
a GRT belt cover.
|
