Terminology Associated with Gantry Cranes

Terminology Associated with Gantry Cranes

• Span (A) : The span is the overall length of main beam.
• Height Under the Beam (B) : The H.U.B is the measurement from the floor to the underside of the main beam.
• Overall Height (C) : The overall height is the measurement from the floor to the top of the gantry hangers on the main beam.
• Clear Span (D) : The clear span is the unobstructed work area between the braces.
• Brace Length (E) : Attached midway down each leg bolted to the hangers.
• Beam Flange Width (W) : The width measurement of the beam flange
• A Frame Width (F) : The "A" frame width is the overall measurement of the "A" frame at the base.
• Hangers : Four (4) individual pieces welded to the top of the beam to which the legs and braces are bolted.
• Clear Lift : The maximum vertical travel a load can be lifted. A number of factors determine the range of vertical travel. The headroom of the hoist/trolley, depth of lifting beam or special rigging. The overall height of these products must be deducted from the available height under the beam, the net difference is the clear lift available.
• Full Beam Trolley Travel : By extending the hangers of the gantry to fit the width of the hoist/trolley, the legs and braces of the gantry arc now positioned far enough away from the main beam to allow the hoist/trolley to travel under them. Now the hoist/trolley are not limited by the clear span and run the full length of the beam.
• Directional Locks : 4-position locks (4PL) allow the user to lock the direction of the wheel in a north, south, easy or west position. For power driven units, only 2 (4PL) or I set, would be required if necessary.
• Port-A-Cart System : With minor changes, Motivation Industrial Equipment can take the spreaders and a caster of our gantry crane and transforms them into a transport cart.
• Jack Kit : Used on adjustable height gantries only, 2 are requited for most gantry and 4 (I for each leg) are required for high capacity gantries. A screw jack allows height adjustment without the use of an overhead device or forklift.

Gantry Construction

Pre casting the box girder segments speeds up the construction of the bridge structure in two ways:

1. It permits to be fabricated elsewhere (precast) while the substructure (i.a, piles, footings, pier column and pier segments) is being built.

2. It allows rapid assembly of the segments when building the cantilevers since the delays in waiting for newly cast concrete to harden arc eliminated.

The decision to precast obviously requires a method for transporting the segments in place to assemble them on the structure. Often times, when bridges are constructed over water, the segments can be shipped to the site on barges and lifted into place by equipment positioned at the end of the cantilevers. Most of the river is not deep enough to readily permit barging without "dredging" of lowering a portion of the river bed.

The massive size and length of the gantry is not so much for lifting the segments but to allow it to move from pier to pier as it completed one section of the bridge and moves on to the next. It normally sits on supports near the center and the rear of the gantry while lifting segments so build a cantilever. With the aid of temporary props, the gantry can be raised so the supports can be moved to the next pier. The gantry then follows by sliding along the top of the supports.

Advantages of Gantry Cranes are:

• Can be used where overhead runways arc not practical.
• A much greater bridge weight than an equivalent overhead crane.

Because of these design limitations, Gantry Cranes are generally used for moving heavy loads, often outdoors.

Gantry Cranes - Uses in Various Plants-Power Plant, Steel Plant, Air Craft Manufacturing Plant.

ISO STANDARDS OF GANTRY CRANES

ISO TR 16890:2004

Collects the design and manufacturing requirements and recommendations for bndge and gantry cranes in ISO and IEC International Standards.

ISO 4301-5:1991

Cranes - Classification - Gantry cranes and Overhead traveling cranes. Establishes the cranes based on the number of operating cycles to be carried out during the expected life of the appliance and its mechanisms, and a load spectrum factor, which represents the nominal state of loading.