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Bridge Crane Description:

A bridge crane runs on an elevated runway system along the length of a factory and provides three axis of hook motion (X, Y, and Z). The hoist moves the load up and down, the trolley moves the load right and left, and the bridge of the crane moves the load forward and backward. Both single and double girder overhead traveling bridge crane designs allow very precise hook positioning and gentle load placement. Double girder cranes typically provide better hook height, but single girder cranes offer other advantages depending on your application. Visit the double girder vs. single girder cranes page for more information comparing these types of cranes (such as height, cost, and spans). To save North American Industries contact information to discuss questions or specifications, download our vCard.

Advantages of a bridge crane:

• greatest flexibility for hook coverage and control over the load
• fewest number of physical obstructions on your factory floor
  

Types of Bridge Cranes

Top Running Bridge Crane:

An ASCE rail or 2" by 2" square bar is installed on top of the runway beams. The wheels ride on the rail rather than directly on the runway beam.

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Top Runner Bridge Crane:

By incorporating a pair of single flange wheels, the bridge crane can ride directly on top of our runway beam, without using a costly crane rail. A top runner, as opposed to a top running bridge crane can provide substantial savings in eliminating the need for both purchase and installation of the crane rail. Top runner cranes are just as durable and long lasting; they are built to the same CMAA Class D heavy duty standards for decades of use.

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Underhung Bridge Crane:

The end trucks of the underhead bridge crane ride on the bottom flange of the runway beam. Typically, an underhung runway is suspended from the roof of the building and is available only on lighter capacities, usually 10 tons or less. Visit the underhung crane page for more details.

Class D

North American Industries produces Class "D" heavy duty bridge cranes rather than Class "C" moderate duty cranes. Class D cranes are more efficient and require less maintenance. They are designed to make twice as many lifts in an hour and lift the full rated load 30% more often than a moderate duty Class "C" crane.

Hoists supplied on our cranes are rated by HMI (Hoist Manufacturers Institute) as H-4 for heavy-duty use. Many competitors supply H-3 average duty hoists, or H-2 infrequent use hoists. See our parts department for further information on hoists.

Motors on the bridge and the trolley are 60-minute motors. A Class "C" crane uses 30 minute motors. All motors have Class "F" insulation, which allows the motor to run hot and still work well. Competitors’ cranes often have Class "B" insulation, which would cause the motor to burn out at temperatures that our Class “F” motors can withstand easily.

NAI Cranes solve the problems you may have encountered with previous cranes:

Crane Travels Too Far Before Stopping?
If your crane coasts more than a few feet, then it is likely that it uses electric motor brakes and that, like most cranes, the brake pads haven't been replaced (they require replacing or adjusting every 3 months).

We use a mechanical braking system that never needs adjusting or replacing. This provides a gentle, consistent coasting stop that does not vary over time. For cranes that travel over 100 FPM or require quick stopping, we suggest considering the soft-stop feature of a variable speed inverter.

Bearings wearing out too soon?
We use a minimum of 2 bearings per wheel. All of our bearings are Class "D" which means they are designed with a minimum life expectancy of 10,000 hours of actual motor on-time. This is double the Class "C" rating - bearings for Class “C” cranes have a minimum life expectancy of 5,000 hours. Our Class "D" bearings are also sealed-for-life and never need lubricating.

Contactor problems?
Our contactors, rated for 20,000,000 stop / start cycles if used in conjunction with inverters or electronic soft start features, should never need replacing under normal operating conditions. See our Technical Report entitled "Electrical Contactors: How Long Should They Last?"

Broken Push Button Pendant or Cable?
NAI pendants are ergonomically designed to be easily held in one hand, and are constructed of a durable thermoplastic material. The pendant cable has 2 steel wires built into the cable jacket for permanent strain relief.

Parts Availability Problems?
Our components--bearings, contactors, gearboxes, motors and electrical systems--are designed to industry standards, and most are readily available throughout the U.S. All motor name plates and gearbox name plates are clearly labeled with the original manufacturing information. And virtually every spare part for the crane (excluding the hoist) is in stock here at North American and can be shipped immediately.

Brakes wearing out or not working properly?
Our mechanical braking system on the trolley and bridge eliminates the need to adjust brakes on a regular basis (typically every 3 months). There are no brake pads to change or adjust with our mechanical brakes. This will reduce overall maintenance and extend the life of the wheel gears and pinions.

Most North American Industries’ cranes also have:

• Sealed ball bearings, which never need lubricating and keep out dirt and grit – a major cause of bearing failures in cranes.
• Gearboxes with high-grade synthetic oil that never needs changing.
• Automatically resetting thermal overloads, instead of fuses, which must be replaced. These overloads are placed inside all 3 motor windings to assure the most accurate measurements.
• A cable for the push button with 2 steel cords built into the jacket. The cable holding the push button is usually abused, scraped and used as a ladder. Ours are able to handle the strain. The wires in the cable all lay straight, and are never spiral wrapped.
• No electric brakes on the bridge and trolley. Electric brakes have brake pads that must be continually adjusted and changed every 1–2 years. If they are not changed, the crane rolls 10 to 20 feet before stopping. The operator, in turn, learns to reverse the crane to stop it. This "Reverse Plug" will damage the gearbox. A North American crane uses a mechanical brake (high ratio worm gear reducer) which stops the crane gently. This device has no brake pads to change and lasts 20 years.
• Approximately 10–20% spare conductors for our bridge electrification cable and our pendant cable. If a wire breaks, you don't have to replace the cable, just connect the spare conductor.
• Engineered features for easy maintenance. When maintenance is needed, our cranes are designed to allow quick repairs. Our wheels can be removed from above. You do not have to lift the crane off the runway rails. Our electrical panels are not crowded, and the wiring diagram is mounted inside the panel.

See our Technical Reports:

• Class C vs. Class D cranes
• D+ upgrades
• Single Girder vs. Double Girder cranes
• Heavy Duty Top Runner Cranes