design
Rope tension
Maximum rope tension (T) = H/COS (β1) where
β1 is the angle of inclination of rope at upper
saddle.
The rope tension should be calculated for both
dead load and full load condition. As stated above,
the maximum sag corresponding to the full load
is calculated either from iterative process or SAP
analysis.
3.1.6 Factor of safety adopted
At maximum load during the service, the ratio
of minimum breaking load of the rope and the
maximum rope tension in service, that is the factor
of safety shall not be less than the following:
Track rope 3.0
Haulage rope 3.5
The factor of safety should be checked for the
following load combinations:
IS 6594-1977 : Technical supply
conditions for wire ropes
and strands (first
revision)
IS 9282-1979 : Specification for wire
ropes and strands
IS 9182/II-1979 : Specification for
lubrications for wire
strands and ropes
2361:1984
: Bulldog grips –
specification
2315: 1978
: Thimbles for wire ropes
3.1.8 Working life of rope
The working life of the rope refers to the time
till number of broken wires remains acceptable
and distribution of those breakages in the rope is
lesser. The number and severity of bends mainly
influence the life span of the rope as given in the
relation below.
N=I .Td.h.nr
Track rope
i) Dead load + full wind load
ii) Full load + 1/3rd of wind load + 10 per
cent of impact load
Haulage rope
i) Dead load + full wind load
ii) Dead load + 1/3rd of wind load + 50 per
cent of impact load
3.1.7 Specifications
The rope material, its configuration and other
ropeway parts should comply with the following
IS code:
IS10887:2001
: Steel wire ropes for
winches and ropeways used in forestry and
agriculture (1st revision)
or,
IS 10891 (Part 1):1984 : Haulage rope
IS 10891(Part 2):1986 : Track rope
IS 1804:1992/1996 : Fibre core for steel
wire ropes (second
revision)
Where,
N = number of bends per year
I = number of carriage travelling per hour
h = number of working hours per day
nr = number of carriage pulleys
Td = number of working days per year
In practice, the carrying ropes of goods ropeway
can bear approximately 4,000,000 bends. So,
the working life of the ropes can be calculated by
dividing this value with calculated N.
3.1.9 Tests on wires and ropes
Ropes and wires are subjected to various tests
before putting them into operation to avoid
undesirable incidents. Regulations call first tests
on the wires and then on the ropes.
A) Tests on wire
The unstranded wires are subjected to tensile,
reverse bend, torsion and fatigue tests.
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