Submittals

Manufacturer's drawings shall be submitted for approval in at least two copies. Drawings shall include the following information:

1. Outline and clearance dimensions
2. Crane data
3. Unit weight and shipping weight

At time of shipment, 2 sets of operation instructions, maintenance manuals and spare parts information shall be furnished.

General

Manufacturer shall provide evidence of Product Liability insurance coverage of a minimum of $1,000,000 per occurrence.

Manufacturer shall provide evidence of General Liability insurance coverage of a minimum of $1,000,000 per occurrence.

Manufacturer shall demonstrate a financial net worth at least 10 times the value of the equipment to be provided under this specification.

Each individual overhead crane covered by this specification shall be considered an "end product" and as such shall be in compliance with the Buy American Act (41 U.S.C. 10).

General

Bridge cranes shall be of the top running types traveling on ASCE standard runway rails.

Girders

Crane girders for double girder cranes shall be box sections fabricated from plate, using ASTM A-36 material for the webs, top plate and bottom plate, so as to provide for maximum strength at minimum dead weight. Maximum allowable vertical girder deflection shall be 1/888 of span.

Crane girders for single girder cranes shall be box sections fabricated from plate, using ASTM A-36 material for the webs and top flange, and ASTM A-572 material for the bottom flange, so as to provide for maximum strength at minimum dead weight. Maximum allowable vertical girder deflection shall be 1/600 of span.

End Trucks

End trucks shall be of box section type having double flanged wheels supported on rotating axles. The axles shall be supported by dual anti-friction bearings having a minimum B-10 life in accordance with CMAA specifications. Wheels shall be cast and machined from spheroidal graphite/nodular iron material. Wheels shall be designed to carry the rated load without undue wear to themselves or the crane runways rails. Wheels shall have a wear characteristic equal to steel wheels with a tread hardness of 320 Brinnell. End trucks shall be fitted with bumpers capable of decelerating and stopping the crane within the limits stated by OSHA and CMAA.

Girder To End Truck Connection

End trucks shall be bolted to girder ends to form a rigid friction connection. Connection bolts shall have a minimum yield of 150,000 PSI. Bolts in shear or welded connections shall not be used.

Crane Drives

Horizontal bridge drives shall be of the CMAA type A-4 type. Motors shall be totally enclosed, fan cooled type and drive fully enclosed gearing. All gear reduction stages shall be oil bath lubricated. Open, grease lubricated gearing is not acceptable. The gear reducers shall directly drive the wheel axles through splined shafts.

To minimize load swing, acceleration and deceleration rates shall be less than 1.0 ft/sec/sec and shall not be noticeably affected by variation of live load or by location of live load on bridge span. Manufacturer shall present drives calculations confirming compliance with these acceleration and deceleration rates during the submittal process.

Motors have Class "F" insulation and shall be thermally protected by heat sensors imbedded in the windings. Bridge drives shall have a minimum ratio of high speed to low speed of 4:1. This shall be accomplished by one of the following methods:

Provide two-speed, two winding motors of 2 pole/8 pole or 2 pole/12 pole design.

or

Provide variable speed, AC frequency inverter drives with single speed squirrel cage motors. The motors shall be designed for inverter operation.

The drive shall be capable of providing spotting accuracy of at least 1/8 ".

Hoist Specification

Motor

Hoist motors shall develop sufficient power to lift the rated load at the specified speed. Motor windings shall have Class F insulation. Motors shall be rated for the number of starts per hour expected in the application and for duty cycle (on-time vs. off-time). Ratings such as "30 minute" or "60 minute" shall not be accepted as they do not represent testing criteria which simulate hoisting service.

Motors shall not be mounted inside the hoist drum due to insufficient heat dissipation and difficulty of maintenance.

The hoist shall be capable of providing speeds over at least a 10:1 range. This may be accoplished by one of the following methods:

or

A mechanical creep speed drive consisting of a single or two speed main motor and a creep motor with intermediate gear reducer.

or

Thyristor controlled DC drives with closed loop feedback.

or

AC frequency inverter drives with closed loop feedback sensing motor speed and direction. Open loop frequency inverters will not be accepted for hoisting.

All motors shall be protected from overheating by thermal protectors imbedded in the windings.

Hoist Brake

The hoist holding brake shall be an electrically opened, mechanically closed unit. It shall be a conical or shoe type having a minimum torque rating of 150% of motor full load torque. Control braking means shall be electrical and shall be capable of maintaining controlled lowering speed within 120% of rated lifting speed. Brake material shall not contain asbestos. Hoist shall have an emergency device acting directly on the rope drum to stop and hold the load in the event of an overspeed condition in the lowering direction, or in the event of slippage in the primary braking system when at rest. This device shall meet NASA flight hardware requirements for redundant braking.

Weston type mechanical load brakes located in the hoist gear case shall not be acceptable for this purpose due to excessive heating and possible loss of load control in the event of gear or shaft failure.

Hoist Gearing

Motor torque shall be transmitted to the reduction gear through a flexible coupling to dampen load peaks. All gears shall be ground, hardened and operate in an oil bath. Gear reducers shall be of the planetary type for balanced load distribution, with helical first stages. Gear lubricant shall be synthetic and should not require replacement for the normal life of the hoist.

Rope Drum

Rope drum shall be of welded construction, machine grooved to a minimum depth of 0.375 times the rope diameter. Drum shall be supported at each end by sealed antifriction bearings. Drum shall be driven by a central, splined shaft.

Rope

The hoisting rope shall be of proper design and construction for hoist service. The rated capacity load divided by the number of parts of rope shall not exceed 20% of the breaking strength of the rope.

Rope Guide

To assure positive winding of rope on the drum and to prevent rope overlapping and potentially dangerous groove peak contact, a hoisting rope guide shall be employed. Double wrapping of rope shall not be permitted.

Bottom Block

Bottom block shall have a totally enclosed housing fabricated of steel. The rope sheaves shall be supported on anti-friction bearings and the hook shall be forged of steel and supported on an anti-friction thrust bearing. Hook shall be equipped with a heavy spring safety latch.

Trolley Wheels

Trolley wheels shall be cast and machined from spheroidal graphite nodular material for best wear characteristics. They shall be double flanged and shaped to match the running surface.

Trolley Drives

Horizontal bridge drives shall be of the CMAA type A-4 type. Motors shall be totally enclosed, fan cooled type and drive fully enclosed gearing. All gear reduction stages shall be oil bath lubricated. Open, grease lubricated gearing is not acceptable. The gear reducers directly drive the wheel axles through splined shafts. To minimize load swing, acceleration and deceleration rates shall be less than 1.0 ft/sec/sec and shall not be measurably affected by variation of live load. Manufacturer shall present drives calculations confirming compliance with these acceleration and deceleration rates during the submittal process.

Motors have Class "F" insulation and shall be thermally protected by heat sensors imbedded in the windings.

Trolley drives shall have a minimum ratio of high speed to low speed of 4:1. This shall be accomplished by one of the following methods:

Provide two-speed, two winding motors of 2 pole/8 pole or 2 pole/12 pole design.

or

Provide variable speed, AC frequency inverter drives with single speed squirrel cage motors. The motors shall be designed for inverter operation.

The drive shall be capable of providing spotting accuracy of at least 1/8 ".

Motors have Class F winding insulation and shall be totally enclosed. Motors shall be protected from overheating by thermal protectors imbedded in the windings.

Electrification

Electrification across bridge for power and control circuits shall consist of an enclosed steel track and trolleys carrying flat cable designed specifically for crane service.

Overload Protection

Hoist shall be equipped with a geared upper and lower limit switch. This switch shall be adjustable to set the extreme upper and lower limits of hook travel.

Painting