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(a) Where Safeties are Required.
The car of every personnel hoist shall be provided with one or more car safety devices of one of the types identified under Section 1604.19(d). The safeties shall be attached to the car frame or supporting structure.
All car safeties shall be mounted on a single car frame and shall operate either on one pair of guide members, on tension members conforming to Section 1604.19(p), or on one vertical rack.
(b) Function and Stopping Distance.
The safety device, or the combined safety devices, where furnished, shall be capable of stopping and sustaining the entire car with its rated load from governor-tripping speed.
Type B safeties shall stop the car with its rated load from governor-tripping speed within the range of the maximum and minimum stopping distances as determined in the following formulas:
(V)2 S = ------- + 0.84 81.144 (V)2 and S' = --------- 231,840
S = maximum stopping distance, in feet
S' = minimum stopping distance, in feet
V = governor-tripping speed, in feet per minute
Table 2 shows the maximum and minimum stopping distances for various governor-tripping speeds.
(c) Counterweight Safeties.
Counterweight safeties, where furnished shall conform to the requirements for car safeties.
1. Where otherwise specified in Section 1604.19.
2. For rated speeds of not over 150 feet per minute, counterweight safeties may be operated as a result of the breaking or slackening of the hoisting ropes and may be of the inertia or other approved type without governors.
(d) Types of Safeties.
Car safety devices (safeties) are identified and classified on the basis of performance characteristics. In general, there are three types of safeties that operate to apply pressure on the guide rails or tension members and one type that uses a separately mounted rack and accompanying pinion gear. The former are classified A, B, and C based upon how the safety begins to apply pressure.
(1) Type A Safeties.
These are safeties which develop a rapidly increasing pressure on the guide members during the stopping interval, the stopping distance being very short due to the inherent design of the safety. The operating force is derived entirely from the mass and the motion of the car or the counterweight being stopped. These safeties apply pressure on the guide or tension members through eccentrics, rollers, or similar devices without any flexible medium purposely introduced to limit the retarding force and increase the stopping distance.
(2) Type B Safeties.
These are safeties which apply limited pressure on the guide or tension members during the stopping interval and which provide stopping distances that are related to the mass being stopped and the speed at which application of the safety is initiated. Retarding forces are reasonably uniform after the safety is fully applied. Continuous tension in the governor rope may or may not be required to operate the safety during the entire stopping interval. Minimum and maximum distances are specified on the basis of governor-tripping speed.
(3) Type C Safeties (Type A With Oil Buffers).
These are safeties which develop retarding forces during the compression stroke of one or more oil buffers interposed between the lower members of the car frame and a governor operated Type A auxiliary safety plank applied on the guide or tension members. The stopping distance is equal to the effective stroke of the buffers.
(4) Rack and Pinion Safeties.
These are safeties in which a freely rotating safety pinion, a governor, and a safety device may form an integral unit mounted on the car. The freely rotating pinion travels on a stationary rack mounted vertically on the hoist structure. The rotating pinion drives the governor. When the downward speed of the car reaches the tripping value, the rotating governor actuates the safety device, which, in turn, brings the car to a gradual stop.
Table 2 Maximum and Minimum Stopping Distances For Other Than Instantaneous ------------------------------------------------------------------ Maximum Stopping Distances Governor-Trip (feet-inches) Rated Speed Speed (feet per minute) (feet per minute) Minimum Maximum ------------------------------------------------------------------ 0 to 125 175 0-1 1-3 150 210 0-2 1-4 175 250 0-3 1-7 200 280 0-4 1-10 225 308 0-5 2-0 250 337 0-6 2-3 300 395 0-8 2-9 350 452 0-1 03-4 400 510 1-1 4-10 450 568 1-5 4-10 500 625 1-8 5-8 600 740 2-4 7-7
(e) Safeties to Stop Ascending Cars or Counterweights.
Safeties shall not stop ascending car or counterweight.
EXCEPTION: Safeties of the rack and pinion type.
(f) Governor Actuated Safeties and Safety Switches.
(1) Car safeties and counterweight safeties, where provided, shall be actuated by separate speed governors.
EXCEPTION: Speed governors are not required for the operation of counterweight safeties of hoists having a rated speed of not more than 150 feet per minute.
(2) Every car safety shall be provided with a switch operated by the car safety mechanism. This switch shall conform to the requirements given under Section 1604.20(d).
(g) Limits of Use of Various Types of Safeties.
(1) Type A (Instantaneous) Safeties.
Type A safeties may be used on hoists having a rated speed of not more than 200 feet per minute.
(2) Type C Safeties.
Spring buffers may be substituted for oil buffers on Type C car safeties for rated speeds up to and including 300 feet per minute provided that the springs do not fully compress during the operation of the car safety with rated load in the car, and the rate of retardation conforms to the requirements of Section 1604.14(c)(1).
(h) Application and Release of Safeties.
(1) Means of Application.
Safeties shall be applied mechanically. Electric, hydraulic, or pneumatic devices shall not be used to apply the safeties required by Section 1604.19 nor to hold such safeties in the retracted position.
(2) Level of Car on Safety Application.
The application of the safety to stop the car, with one-fourth of its rated load distributed on each quarter of the platform symmetrically with relation to the center lines of the platform, shall not cause the platform to be out of level more than 3/8-inch per foot in any direction.
When car safeties are applied, no decrease in tension in the governor rope or motion of the car in the down direction shall release the safeties, but such safeties may be released by the motion of the car in the up direction.
(4) Force Providing Stopping Action.
Safeties shall be so designed that on their application the forces which provide the stopping action shall be compressive forces on either side of the guide or tension member section.
EXCEPTION: For rack and pinion safeties, the stopping action may be obtained by the engagement of the teeth of the safety pinion on the car and the stationary vertical rack.
(i) Minimum Clearance on Guide Members.
In the normally retracted position of the safety, the distance between the member gripping faces of the safety parts shall not be less than the thickness of the guide member plus 0.14 (9/64) inch, and the clearance on any side between the gripping face and the guide member shall be not less than 0.0625 (1/16) inch as measured on the side of the rail toward which the car frame is pressed with sufficient force to take up all clearances in the guide shoe assembly. Safety jaws, which in the retracted position, shall be so restrained as to prevent a reduction of this minimum clearance.
(j) Maximum Permissible Movement of Governor Rope or Car.
(1) Type B and C Safeties.
For all Type B and C safeties, the movement of the governor rope relative to the car or the counterweights, respectively, required to operate the safety mechanism from its fully retracted position to a position where the safety jaws begin to exert pressure against the guide members shall not exceed the following values based on rated speed:
(A) For car safeties: 200 feet per minute or less, 42 inches; 201 to 375 feet per minute, 36 inches; over 375 feet per minute, 30 inches.
(B) For counterweight safeties: all speeds, 42 inches.
Drum operated car and counterweight safeties, requiring continual unwinding of the safety drum rope to fully apply the safety, shall be so designed that not less than three turns of the safety rope will remain on the drum after the overspeed test of the safety has been made with rated load in the car.
(2) Rack and Pinion Safeties.
For rack and pinion safeties, the travel of the car measured from the governor-tripping time to the full-stop time shall not exceed the following values based on rated speed:
(A) For car safeties: 200 feet per minute or less, 64 inches; 201 to 375 feet per minute, 76 inches; over 375 feet per minute, 78 inches.
(B) For counterweight safeties: all speeds, 78 inches.
(k) Factors of Safety of Safety Parts.
Parts of safeties, except springs, shall have a factor of safety of not less than 3.5, and the materials used shall have an elongation of not less than 15% in a length of 2 inches. Forged, cast, or welded parts shall be stress relieved.
EXCEPTION: Safety rope drums, leading sheaves, and their supporting brackets and safety jaw gibs shall be made of metal and shall have a factor of safety of not less than ten.
Rope used as a connection from the safety to the governor rope, including rope wound on the safety rope drum, shall be not less than 3/8-inch in diameter and shall be made of a corrosion resistant metal. Tiller rope construction shall not be used. The factor of safety of the rope shall be not less than five.
All gears shall meet the following standards of the American Gear Manufacturers Association: AGMA 210.02, AGMA 220.02 and AGMA 240.01.
The factors of safety shall be based upon the maximum stresses developed in the parts during the operation of the safety when stopping rated load from governor-tripping speed.
Springs may be used in the operation of car or counterweight safeties. Where used, and where partially loaded prior to safety operation, the loading on the spring shall not produce a fiber stress exceeding one-half the elastic limit of the material. During operation of the safety, the fiber stress shall not exceed 85% of the elastic limit of the material. Helical springs, where used, shall be in compression.
Safety rope loading sheave brackets and other safety operating parts shall not be attached to, or supported by, wood platform members.
(l) Corrosion Resistant Bearings.
Bearings in safeties and of the safety operating mechanism shall be of corrosion resistant construction with one or both members of a bearing made of, or electroplated with, a corrosion resistant material.
(m) Marking Plates.
A metal plate shall be securely attached to each safety so as to be readily visible and shall be marked in a legible and permanent manner with letters and figures not less than 1/4-inch in height, indicating the following:
(1) The maximum tripping speed, in feet per minute, for which the safety may be used.
(2) The maximum weight, in pounds, which the safety as installed is designed to stop and sustain.
(n) Releasing Carriers.
The governor rope releasing carrier on the car or on the counterweight shall be set to require a tension in the governor rope, to pull the rope from the carrier, of not more than 60% of the pull through tension developed by the governor, and the carrier shall be designed so that the pullout tension cannot be adjusted in a normal manner to exceed the amount specified.
(o) Rail Lubricants.
Rail lubricants or coatings which will reduce the holding power of the safety or prevent its functioning as required in 1604.19(b) shall not be used. The use of graphite for lubricants shall be prohibited.
(p) Application of Safeties Upon Suspended Tension Members.
Safeties that apply on tension members suspended from the top of the hoistway and anchored in the pit in lieu of guide members shall be in conformity with the following requirements.
(1) The tension members shall have a minimum factor of safety of ten when the car and its rated load is stopped, with an average retardation of 32 feet per second per second.
(2) Steel wire rope tension members shall be inspected by the procedure set forth under Sections 1604.25(j) and 1604.25(k).
Table 3 Maximum Speeds, in Feet Per Minute, at Which Speed Governor Trips and Governor Overspeed Switch Operates ------------------------------------------------------------- Maximum Maximum Speed at Which Governor-Trip Governor Overspeed Rated Speed Speed Switch Operates, Down ------------------------------------------------------------- 0-125 175 175* 150 210 210* 175 250 225 200 280 252 225 308 277 250 337 303 300 395 355 350 452 407 400 510 459 450 568 512 500 625 563 600 740 703
* Governor overspeed switch not required on car speed governors.
Figure 3 - Maximum Governor-Tripping Speeds