| Return to index
(a) Stroke of Oil Buffers.
(1) The stroke shall be such that the car or the counterweight on striking the buffer at 115 percent of rated speed shall be brought to rest with an average retardation of not more than 32.2 feet per second per second, or
(2) Where an emergency terminal stopping device is installed which conforms to the requirements of Section 3039(c), and which will limit the speed at which the car or counterweight can strike its buffer, the buffer stroke shall be based on at least 115 percent of the reduced striking speed and on an average retardation not exceeding 32.2 feet per second per second.
(3) The following formula gives the value of the stopping distance based on gravity retardation from any initial velocity:
(V)2 S= ---------- 19,320
Where: V = Initial velocity in feet per minute
S = Free fall in inches (gravity stopping distance)
(4) Figure 3108 shows the gravity stopping distances based on the formula of Section 3108(a)(3).
(b) Retardation by Oil Buffers. Oil buffers shall develop an average retardation not in excess of 32.2 feet per second per second, and shall develop no peak retardation greater than 80.5 feet per second per second having a duration exceeding 1/25of a second with any load in the car from rated load to a minimum load of 150 pounds when the buffers are struck with an initial speed of not more than:
(1) One hundred fifteen percent of rated speed for buffers conforming with Section 3031(f), and
(2) One hundred fifteen percent of the predetermined reduced speed for buffers conforming with the exception to Section 3031(f).
(c) Factor of Safety for Oil Buffer Parts. The factor of safety of parts of oil buffers, based on the yield point for compression members and on the ultimate strength and elongation for other parts, at gravity retardation with the maximum load for which the buffer is designed, shall be not less than the following:
(1) Three for materials having an elongation of 20 percent or more in a length of 2 inches.
(3) Four for materials having an elongation of from 10 to 15 percent in a length of 2 inches.
(4) Five for materials having an elongation of less than 10 percent in a length of 2 inches, except that cast iron shall have a factor of safety of 10.
(d) L/R for Members Under Compression as Columns. The L/R ratio of members of oil buffers under compression as columns shall be not more than 80.
The L/R ratio specified applies only to those main buffer members which are subject to the impact of the fully loaded car when striking the buffer.
(e) Buffer Oil Requirements. Oils used in oil buffers shall have a pour point of zero degrees F. or lower as defined in ANSI Z11.5 (ASTM D97) and a viscosity index of 75 or higher as defined in ANSI Z11.211 (ASTM D2270).
(f) Approval of Oil Buffers.
(1) The buffer shall be approved on the basis of the engineering tests specified in ANSI A17.1, made by an approved testing laboratory or by the manufacturer and witnessed by a representative of such an approved testing laboratory or by a representative of the Divsion of Industrial Safety. Tests shall be made on a buffer of each type or design to be approved and having the following oil portings:
(A) The porting having the range of the maximum loads for which the buffer is designed.
(B) The porting having the range of the minimum loads for which the buffer is designed.
(2) The approval shall include buffers of the same type or design having a greater or shorter stroke, up to a maximum of 7 feet, and having oil portings for any load range within the maximum and minimum loads for which the buffer has been tested, provided that the buffer will conform to the requirements of Section 3031(f).
(3) Certification. When the buffer has been subjected to all of the specified tests and all test records and data indicate that it conforms to the requirements of Sections 3031 and 3108, the laboratory shall issue to the manufacturer a test report and a certificate stating that the buffer of the particular stroke, and having the portings tested, has met the requirements for the maximum and minimum loads as stated in the certificate.
A copy of the test reports, together with drawings and descriptions of the buffer to allow field identification, shall be submitted to the division with the request for approval.
(g) Impact on Buffer Supports. The following formulas give the buffer reaction and the impact on the car and counterweight oil buffer supports resulting from buffer engagement:
R = W (1 + [v2/2gS])
P = 2R
The following formulas give the buffer reaction and the impact on the supports of car and counterweight spring buffers which do not fully compress under the conditions outlined in Section 3019.
R = 2W (1 + [v2/2gS])
P = R
R = Buffer reaction in pounds.
P = Impact in pounds.
W = Weight in car plus rated load in pounds.
v = Speed in feet per second at impact.
S = Buffer stroke in feet.
g = 32.2 feet per second per second.
1. Amendment of subsections (e) and (f)(1) filed 6-23-77;effective thirtieth day thereafter (Register 77, No. 26).
2. Editorial correction of subsection (g) formulas (Register 95, No. 34).
Go Back to Article 18 Table of Contents