(a)
Factors of Safety for Wire Ropes.
(1) The
factor of safety for wire ropes shall be calculated by the following formula:
f = (S X N)/W
Where:
S = Manufacturer's rated breaking strength of one
rope.
N = Number of runs of rope under load (See
Note).
W = Maximum static load imposed on all car ropes with
the car and its rated load at any position in the hoistway.
NOTE: In the case of multiple roping, the number of
runs of rope (N) under load will be: For 2:1 roping, twice the number of ropes
use; for 3:1 roping, three times the number of ropes used;
etc.
(2) The factor of
safety for wire suspension ropes shall be not less than that determined by
Figure 3107 A2 for the various rope speeds.
Click
here to view image
Factors of Safety of Suspension Wire Ropes of
Power Passenger and Freight Elevators
FIGURE 3107 A2
(b) Design of Wire Rope Fastenings.
(1) Tapered babbitted-type rope sockets shall
be of a design shown in Figure 3107 B1 as follows:
(A) The axial length (L) of the tapered
portion of the socket shall be not less than 4 ¾ times the diameter of
the rope used.
Tapered Babbitted Rope Sockets
FIGURE 3107 B1
Click
here to view image
NOTE: Rope socket and shackle rod may be in one piece,
as shown
(B) The axial
length (L') of the open portion of the rope socket shall be not less than 4
times the diameter of the rope used.
(C) The length of the straight bore (L") at
the small end of the socket shall be not more than ½ in. (12.7 mm) nor
less than 1/8in. (3.2 mm) and its outer edge shall be rounded and free from
cutting edges.
(D) The diameter (d)
of the hole at the large end of the tapered portion of the socket shall be not
less than 2 ¼ times nor more than 3 times the diameter of the wire rope
used.
(E) The diameter (d') of the
hole at the small end of the tapered portion of the socket shall be not more
than shown in Table No. 3107 B1E.
TABLE NO. 3107 B1E
Relation of Rope Diameter to Small Diameter of
Socket
Nominal Rope Diameter
in. |
|
|
Maximum Diameter of Hole d',
in. |
3/8 to
7/16
inclusive.......................... |
..........................
3/22" |
|
larger than Nominal Rope Diameter |
½ to ¾
inclusive.......................... |
..........................
1/8" |
|
larger than Nominal Rope Diameter |
7/8 to 1 1/8
inclusive.......................... |
..........................
5/32" |
|
larger than Nominal Rope Diameter |
1 ¼ to 1 ½
inclusive.......................... |
..........................
3/16" |
|
larger than Nominal Rope Diameter |
GENERAL NOTE
1 in. = 25.4 mm
Title 24, Part 7, Section
7-3107.
(2) Types of rope fastenings other than
individual tapered babbitted rope sockets may be accepted by the division
subject to the following:
(A) Data is
submitted showing the results of adequate tensile and fatigue tests made by a
qualified testing laboratory.
(B)
The fastenings shall conform to the requirements of Section
3042(j).
(C) The rope socketing shall be such as to
develop at least 80 percent of the ultimate breaking strength of the strongest
rope to be used in such fastenings.
(D) U-bolt type rope clips (clamps) shall not
be used for such fastenings.
(3) Cast or forged steel rope sockets,
shackle rods and their connections shall be made of unwelded steel, having an
elongation of not less than 20 percent in a length of 2 inches, conforming to
ASTM A235 for forged steel, and to USAS G50.1 (ASTM A27) for cast steel, and
shall be stress relieved.
(4) The
shackle rod, eye bolt, or other means used to connect the rope socket to the
car or counterweight, shall have a strength at least equal to the rope
manufacturer's rated breaking strength of the rope.
(5) Eye bolts used as connections with
clevis-type sockets shall be of forged steel conforming to ASTM A235 without
welds.
(6) Rope sockets shall be of
such strength that the rope will break before the socket is perceptibly
deformed.
(c) Method of
Babbitting Wire Ropes in Tapered Sockets. Where the tapered babbitted type
socket is used, the method and procedure to be followed in making up the
fastening shall conform to the following:
(1)
Handling: The rope to be socketed shall be carefully handled to prevent
twisting, untwisting, or kinking.
(2) Seizing of Rope Ends: The rope ends to be
socketed shall be served before cutting with seizings in accordance with the
following:
(A) The seizing shall be done with
annealed iron wire, provided that other methods of seizing may be used which
give the same protection from loss of rope lay.
Where iron wire is used for seizing, the length of each
seizing shall be not less than the diameter of the rope.
(B) For nonpreformed rope, three seizings
shall be made at each side of the cut in the rope.
(C) For preformed rope, one seizing shall be
made at each side of the cut in the rope.
(D) For nonpreformed rope, the first seizing
shall be close to the cut end of the rope and the second seizing shall be
spaced back from the first the length of the end of the rope to be turned in.
The third seizing shall be at a distance from the second equal to the length of
the tapered portion of the socket.
For preformed rope, the seizing shall be at a distance
from the end of the rope equal to the length of the tapered portion of the
socket plus the length of the portion of the rope to be turned
in.
(3) Spreading
of Rope Strands: After the rope has been seized, it shall be inserted into the
socket through the hole in the small end a sufficient distance for
manipulation; and where nonpreformed rope is used, the first two seizings shall
be removed. The rope strands shall then be spread apart and where rope with
fiber core is used, the fiber core shall be cut away as close as possible to
the remaining seizing.
(4) Removal
of Grease or Oil: Grease and oil shall be removed by cleaning the outer surface
of the exposed rope strands with a nonflammable low-toxic solvent.
(5) Turning in of Rope Strands: The exposed
rope strands shall then be bent, turned in, and bunched closely together, each
strand being turned back the same distance. The portion turned in shall have a
length of not less than 2 ½ times the diameter of the rope and such
that, when the rope is pulled as far as possible into socket, the bend of the
turned-in strands shall be slightly overflush with the mouth of the tapered
socket (large end) and will be visible when the socket has been babbitted.
Where rope with steel core is used, the steel core shall be cut off even with
tops of the looped strands.
(6)
Insertion of Bent-In Rope Strands in Socket: The rope end shall be pulled as
far as possible into the socket so that the remaining seizing projects outside
the hole at the small end of the socket.
(7) Position of Socket Preparatory to Pouring
Babbitt: The socket shall be held in a vertical position with the large end up,
and the rope held in a position truly axial with the socket. Tape or waste may
be wound around the rope at the small end of the socket to prevent the babbitt
from seeping through, but shall be removed after the metal has
cooled.
(8) Heating of Babbitt: The
babbitt shall be heated to a fluidity just sufficient to char a piece of soft
wood such as white pine without igniting it. Care shall be taken not to
overheat the babbitt sufficiently to damage the rope.
(9) Heating of Socket-Basket and Pouring of
Babbitt: The rope socket-basket shall be heated by a blowtorch flame
sufficiently to prevent chilling of the babbitt and to insure that the babbitt
when poured will completely fill the basket, including all the spaces between
the rope strands. Following this the molten babbitt shall be poured slowly and
evenly into the basket until it is filled to a point level with the top of the
opening in the large end.
(10)
Babbitt metal shall contain at least 9 percent antimony and shall be clean and
free from dross.
(d)
Design of Suspension Rope Equalizers. Cable equalizers and their fastenings may
be of types other than individual compression spring type provided:
(1) Data is submitted to the division showing
that adequate tensile and fatigue tests have been made by a qualified testing
laboratory.
(2) The tests show the
ultimate strength of the equalizer and its fastenings in its several parts and
assembly, which shall be not less than 10 percent in excess of the required
strength of the suspension ropes.
(3) Equalizers of the single-bar type or
springs in tension shall not be used.