Dearborn Mid-West Company

Overhead Monorail Systems


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An Overhead Monorail Conveyor (OHM) consists of a system of trolleys that hang from a structural "I" track supported by overhead steel structures. The trolleys are linked together and driven by a drop forged X-458 or X-678 chain. Loads are suspended from attachments that are bolted directly to the trolley brackets. Different carrier, hook, and tray arrangements are specifically designed and fabricated to suit the parts being transported.

6” OHM – Frame Delivery Conveyor

OHM Selection

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OHM conveyors are commonly used as production conveyors within a manufacturing process or as delivery conveyors that travel from one production zone to another. They are well suited for transporting loads through hazardous environments such as paint shops, plating operations, or foundries.

Loads on an OHM are suspended on fixed centers that vary based on the part configuration and production rate. An OHM conveyor should not be selected if the application requires accumulation or buffer zones. However, OHM conveyors can serve a buffering function when they are used as a separate handling system, and not tied into operations such as production.

The most productive use of OHMs is for applications where tasks are performed while the loads are in transit. The loading / unloading of parts on an OHM is usually performed manually while the conveyor is moving. Stopping the conveyor to load / unload will affect production since it stops the entire conveyor.

4” OHM – Fascia Delivery Conveyor

Manufacturing and Production Flexibility

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OHMs are used to carry almost any type of load through a series of manufacturing operations. Conveyor paths can be designed for a high degree of production flexibility. Loads carried travel in a closed loop at predetermined elevations. Use of horizontal turns and vertical curves enables the OHM to be flexible enough to avoid interfering with adjacent processes.

Reliability and Maintainability

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OHM conveyors are maintenance friendly and have earned a reputation for being extremely reliable and durable. In an industrial application, it is not unusual for an OHM conveyor to log up times and availability percentages in excess of 99% while being operated on a multi-shift basis.

Lubrication is key when maintaining OHM systems. Conveyor chain and trolleys, roller turn rollers, and traction wheel bearings, all require regular lubrication, either manually or through automatic lubricators. Drip pans are commonly added to prevent lubricants, dirt and dust from spilling onto products. Conveyor drives and take-up units are commonly installed at higher points of elevation and may require ladders and/or platforms for maintenance access.

4” OHM – Door Delivery System

Protecting Product Quality

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A wide variety of load-supporting devices such as hooks, baskets, trays, fixtures, etc., can be custom-designed and positioned to carry products in such a way as to promote safe travel and the highest level of efficiency.

Operator Safety Issues

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OHM systems are designed for a safe interface between the worker and the product. In production areas, the conveyors move at fairly slow speeds. Typical safety features on these systems include wire mesh guarding in elevated areas, anti-runaway devices to prevent a runaway load due to chain breakage, light screens, safety mats, and accessible emergency stops.

4” OHM – Instrument Panel Build / Delivery System

Equipment Cost Considerations

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The simplicity and rugged character of OHM systems also makes them low cost solutions to many handling scenarios. Maintenance and training costs are also low, due to the overall simplicity of the system, and the use of standardized components. OHM conveyors cost more than other non-accumulation trolley conveyors such as cable conveyors, but the advantages of increased load capacity, speed, durability, and longer conveyor lengths must be factored into the cost-justification equation.

Types of OHM

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DMW offers OHM conveyors in standard 4"(101.6 mm) and 6"(152.4 mm) track sizes which are integrated with a standard chain X-458 and X-678 drop forged chain with trolleys. Loads of up to 5,000 lbs.(2268 kg.) can be carried (using tandem trolley carriers where necessary). Common applications of OHM conveyors include conveying engines, chassis, fascia, and instrument panels.