California Code of Regulations
Title 8 - Industrial Relations
Division 1 - Department of Industrial Relations
Chapter 4 - Division of Industrial Safety
Subchapter 6 - Elevator Safety Orders
Group II - Elevator Installations for Which the Installation Contract Was Signed Before October 25, 1998
Article 12.6 - Screw Type Elevators
Section 3088 - Screw Type Elevators

(A) Hoist motors, rotors, brakes and reduction gears may be located on the car top or in the pit provided.

(B) Screw fastenings, car lowering mechanisms and car overspeed governors may be housed in a removable enclosure secured against unauthorized access.

(C) Where the drive unit of a screw type elevator is located in the elevator pit, a permanent means shall be provided in the pit to support the car and platform during repairs or adjustments of the unit. Clear headroom under the platform shall be not less than 7'0" when the elevator is landed on the supports.

(A) Elevator top and bottom clearances and runbys shall comply with Section 3017 for elevators with electric drive motors and Section 3054 for elevators with hydraulic drive motors.

(B) The bottom runby required by Section 3088(a)(3) may be eliminated where spring buffers complying with Section 3088(b)(1)(C) are provided and the speed of the elevator as it approaches the landing is not more than 10 feet per minute and the spring buffers are not compressed under normal operating conditions.

(A) Spring buffers used on elevators with screw type drive machines shall be so designed and installed that they will not be fully compressed when struck by the car with its rated load at governor tripping speed.

(B) Buffer design shall consider the energy of the rotating machinery and shall provide an average deceleration of not more than 1.0g for oil buffers and a maximum deceleration of 2.0g for spring buffers.

(C) Where recoil of the car upon impact with the spring buffers is detrimental to the screw, dampening shall be provided by means of a hydraulic or pneumatic device to eliminate any recoil.

(D) Calculations satisfactory to the Division shall be provided for each spring buffer design and rating.

(A) In the design of screw machines, the load to be used in computing factors of safety shall be the maximum load imposed when lifting 125% of the rated load.

(B) For design purposes, screw machines shall include hoist and pump motors, gear boxes, sprockets, brakes, brake drums or discs, screws, screw supports and fastenings, rotors, lowering mechanisms, pumps, hoses, and other equipment necessary to raise and lower the elevator.

(C) The hoisting screws of screw machines shall have a factor of safety of not less than 15 based on combined tension and torsion stresses when lifting 125% of rated load and combined compression and torsion stresses when the screw is supporting 125% of rated load when used as a column.

(D) Where the rotor or nut travels with the elevator, the machine except for the screw, shall be inaccessible from the elevator car top and from outside the hoistway. Provisions shall be incorporated in the design of such a system for manually lowering the elevator, from the bottom machine room, to gain access to the machine. This manual control shall be failsafe and have a dead-man control. The lowering means shall be adjustable so the lowering speed is less than one-half rated speed with rated load on the car and shall stop and hold a load of 125% of rated load. This adjustment shall be set and sealed at the time of the initial inspection and at periods not exceeding 5 years.

(E) Machines in which the screw is stationary shall have the screw restrained at both the top and bottom ends to prevent the screw from rotating except when the car is being lowered as required by Section 3088(b)(3)(D).

(F) The screw shall be supported vertically and horizontally in such a way as to eliminate those forces or torques not taken into consideration in the design. Factors of safety required by Section 3104 shall be based on loads when lifting 125% of rated load.

(G) Drawings showing details of the entire screw machine and appropriate calculations by a California Registered Engineer shall be provided before the first machine of a kind and rating is installed and when requested by the Division. The calculations shall show the stress in all critical support members and major components of the machine. Where screws are spliced, the details of the splice shall be acceptable to the Division.

(H) The hoist machine brake shall be located so there is no coupling between the brake and screw or rotor.

(I) Belts and chains shall not be used except where multiple-link silent chain is enclosed in a transmission housing. When multiple-link silent chain is used, its wear shall be monitored with a chain switch to remove power from the drive machine motor and brake when chain wear or stretch becomes excessive.

(J) Hoist machine brakes shall be released electrically or hydraulically and applied by springs.

(K) A flexible hose supplying high pressure fluid to the hoisting rotor motor shall comply with requirements of Section 3068(a)(3)(B) except that where the failure of a hose will not result in lowering the car the hose shall have a bursting strength sufficient to withstand only 4 times the working pressure and shall be tested in the factory or in the field prior to installation of a pressure of at least 2 times the working pressure. Flexible hoses shall in addition to other criteria be designed to withstand the flexing to which they are subjected.