If you walk through almost any type of plant, transport equipment is moving through the manufacturing process. Adjustable speed are used to control the operation of many of the conveyors used in a wide variety of industries. This article describes the function of speed in transport applications and presents the factors that must be considered in the selection and implementation of the adjustable speed.

Carriers can be used to move bulk material, either as coal or unit elements as the bodies of cars. Management unit of the types of conveyors, roller conveyors include, conveyor belts and chains with hooks or carriers. Any of the conveyor belts feeding or screws can be used to move material in bulk. Although truckers can have many configurations mechanics, his unit requirements are generally similar.
Requirements of the unit

Carriers are inherently constant torque machines. This means a constant level of torque required to drive the conveyor, regardless of the operating speed. Figure 1 is a typical graph of load torque versus speed conveyor belt. Note that the curve is essentially a horizontal line, indicating that the load torque remains relatively constant over the range of operating speeds possible.

In most cases, all of the power required for a transport unit is used to overcome the friction of various mechanical elements of the load. In vertical or inclined conveyors, some of the driving energy is used to lift a mass at a higher altitude. Sometimes, the units are obliged to provide material braking as he moves from a higher elevation to a lower altitude. In most applications of transport, only a very small percentage of the torque supplied by the unit is used to accelerate the inertia. Most carriers have a relatively high burden of friction compared with the inertia that reflects the shaft of the motor. The unit can be subjected to shock loading when a mass that is moving relatively slowly is transferred or loaded onto a conveyor belt that moves into a higher gear.

Sometimes transport units should provide a high torque to overcome the friction of the belt and mechanical drive components. In Figure 1, the torque requirement is almost like a segment of the vertical speed torque curve compared to the rate at zero. In some applications, high torque may be necessary because the ice or solidified bulk material must be broken as the conveyor starts to move.

Carriers often operate through a relatively narrow range of speeds near the maximum speed, but long periods of low speed operation may be necessary to accommodate create needs. You may also need to operate at low speed, while making adjustments to the cleaning process or equipment.
Performance requirements and control strategies

drivesConveyors transportation systems have a wide range of static and dynamic performance requirements. In most applications, a speed of the unit is used because the ability to adjust the speed of operation provides a means to control the process. Understanding the relationship between speed and the process is the key to defining the performance requirements of the unit.

Consider filling a bottle of application in which a packaging line is used by more than one size of the bottle. Suppose the bottle fillers can fill bottles at a rate of 120 gallons per minute, regardless of the size of the bottle. When the line is set up to a-gallon bottles, the conveyor speed must be adjusted to move the bottles through the filler to 120 bottles per minute. If the line created to fill half gallon bottles, the carrier must move the bottles to 240 bottles per minute.

Since each revolution of the screw meters out a fixed amount of material, speed control power screw conveyors can be used to regulate the flow of bulk materials. For example, a screw conveyor can be used to control the speed at which coal is fed into a furnace. The feed rate could be changed to regulate the heat or to maintain a steady rate of combustion with variable fuel quality.

Most types of adjustable rate that regulate the speed so that the operating speed drops no more than 5% of the maximum speed when the load does not increase the load to full load. Many units offer 3% or even regulation of 0.5% as a standard of regulation and options for 0.5% to 0.01% regulation. Very precise speed regulation is essential in some applications for transportation, 5%, but the regulation is perfectly adequate for many applications. Note that the load presented to the unit by a conveyor belt does not vary almost as much as the no-load to full load variation corresponding to the maximum speed of change. It is also important to remember that the regulation is usually expressed as a percentage of maximum speed. If the unit is operating at half the speed limit, 5% of the maximum speed represents 10% of the set speed.

To determine the speed with accuracy how it should be regulated, it is necessary to determine how it affects the variation in speed of the process. In some applications, a result of variations in speed only the variations in the amount of product produced per hour. A 5 or 10% change per hour can be completely insignificant in comparison with other factors that affect the daily production. The quality of the product depends on the frequency precise speed regulation. For example, if a unit of a food ingredient to a process of speed changes during the course of one day, there will be a variation in the percentage content of that ingredient in the final product. For example, if small changes in the content of pigment result in detectable changes in color, very precise speed regulation may be needed for units that feed on paint pigments in a manufacturing process.

Most applications of transport involves a basic strategy for controlling the speed at which the unit simply regulates the speed of operation at a point that can be adjusted from time to time. The speed setpoint can be set manually by an operator or automatically by computer control or monitoring. When a speed of the unit is used with a conveyor belt to regulate a process variable, the indirect control is often used instead of direct control. Conveyor speed control is often used to control processes such as cooking, drying or curing of any material or product. Using indirect control, the carrier is simply operating in the optimum speed that has previously been given to a particular process recipe.

Many applications require a degree of control of the system to provide the coordination between the unit and the process. Many units have built-in standard features or optional features that enable the demands of the unit to provide a basic level of system control. Control of external devices such as small PLC and the specialized control modules can also be used to provide control functions of the system of stand-alone units. A teacher outside of the control system is generally used in applications with complex process control requirements or coordinated control of multiple stand-alone units.

In some applications, the speeds of several conveyors correspond so that they act as if it were a conveyor belt continues. The speeds of May adjacent carriers must correspond very closely to prevent damage to the goods that are transferred between the carriers. Adjacent conveyors are sometimes operates a difference between the speeds of their control. Unlike speed can be used to change the spacing between the points where the transfer of a conveyor to another. If truckers are used to transport a sheet of material such as paper or fabric, the application is classified as a web. Process of Web applications are beyond the scope of this article.

Position synchronization or relative position of control is used to maintain a relative position relationship between two points in the carriers that operate at the same speed. When two carriers bringing in buckets or slots, the objects can be transferred smoothly from one conveyor belt to the other if the cubes maintain their relative positions, as they move opposite each other at the transfer point.

Gentle acceleration and deceleration control is an important element of many transport applications. Linear acceleration and deceleration control limits of the forces that are applied to accelerate or decelerate the load. Although the limits of linear acceleration that the level of force applied to the load, the full acceleration of force is still applied all at once. This sudden application of force can apply a mechanical shock or jerk of the load. With S-curve acceleration and deceleration control, acceleration or deceleration of force is gradually increased to full strength. The application of force gradually, the limits on the provision of mechanical shock soft starts and stops.

A conveyor is a mechanical system that often extends over a considerable distance. The power used for a transport unit is used to overcome the friction of that burden is distributed over the entire length of the belt. If one engine is used to drive the transporter, the power applied in a place that must be moved mechanically along the conveyor. This means that all the mechanical parts must withstand the stress involved in the transfer of power from one place to all parts of the belt. If several motors are located at several locations along the conveyor belt, power is transmitted electrically to places closer to the point of use. There are several methods for the design of an engine manifold system conveyor so that the burden is shared equally among the engines. Exchange systems burden will be a future article.

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How to design transport systems to protect your employees and your business
Visible signs, like this
of Emedco are an excellent idea of security
Emergency stop and other safety designs cost more, but make your people and your business safe.
Transport to be accessible to the operators must be equipped with emergency stops. (Note that our design systems with these precautions – the carriers do not fall within the scope of this article).
Guarded by location
The only carriers that do not require them are systems that are mounted more than eight feet above the work surface, as they are held by his elevation called “guarded by location.”
When any transportation system is not accessible to operators, is guarded by location. The carrier is not accessible to workers from storage, and can only be accessed by maintenance personnel that can block or label of the belt before servicing.
All the circuits of emergency stop should not in the case of a power loss to the emergency stop circuit.
In the event of an emergency stop is activated, the transport system must be inspected for unsafe conditions or box jam by operators. Once it is verified that the condition has been resolved the system can be restarted.
Security by design
Cisco-Eagle designs of our control systems so that, in order to restart the system, two things must happen. First, the emergency stop button or pull the cord on the conveyor belt is restored, and then the start button on the panel is activated.
Once the system is rebooted the horn warning system must sound before departing again conveyors. All Cisco-Eagle of transport systems will be equipped with an audible warning horn.
In order to provide a safe working environment for our customers and employees of any power of the machine, Cisco-Eagle adheres to these minimum safety requirements and operations stops.
Safety Standards
The following are excerpts from the policies of Occupations Safety and Health Administration, the American Society of Mechanical Engineers and the National Fire Protection Association in relation to the transmission of energy and transport.
OSHA 1926,555 (a)
(1) Means to stop the engine or the engine will notify the station operator. Transport will be equipped with an audible alarm that sounded just before the start of the belt.
(2) If the operator of the station is in a remote location, similar provisions to stop the engine or the engine must be always on the engine or motor location.
(3) emergency stop switches are arranged so that the carrier can not start again until the drive lights has been implemented or “on” position.
ASME B20.1-2003 Section 5.11.2
(a) Monitoring stations should be arranged in such a way and found that the operation of the equipment is visible from them, and must be clearly marked or labeled to indicate the function controlled.
(b) a conveyor belt that would cause injury when it starts did not begin until personnel in the area were alerted by a signal or by a designated person that the carrier is about to begin.
(1) When a carrier that would cause injury when it starts as an automatic or controlled to be monitored from a remote location, an audible device shall be provided that can be heard clearly at all points along the conveyor belt, where staff can be present. The device must be powered by the device driver start of the belt and continue for a period of time before the conveyor starts. A flashing light or similar visual warning can be used in conjunction with or instead of the acoustic device more effective if under certain circumstances.
(c) and automatic remote-controlled carrier, and operates stations that are not manned or are beyond voice and visual contact of the unit areas, areas of cargo transfer points, and other potentially dangerous places on the conveyor unguarded path to the location, position, or guards shall be provided with emergency stop buttons, pull wires, limit switches, similar devices or emergency stop.
(1) All emergency stop devices shall be readily identifiable in the vicinity of the places least policed by the location, position, or guards. Where the design, function and operation of this type of transport clearly is not dangerous for staff, an emergency stop device is not necessary.
(2) The emergency stop device must act directly on the control of the carrier in question and do not depend on the halting of any other team. The Emergency stop devices will be installed so that it can not be annulled elsewhere.
(d) idle and unused actuators, controllers, and wiring should be removed from the monitoring stations and panel boards, along with outdated patterns, indicators, control of labels and other materials that can serve to confuse the operator.
ASME B20.1-2003
Security arrangements Section 5.11.3
All security arrangements, including the electrical wiring of safety devices, be willing to operate in such a way that a power failure or failure of the device itself does not lead to a dangerous condition.
ASME B20.1-2003
Section 5.11.4
Conveyor controls will be ready so that in case of emergency stop, reset manually or from the place where the emergency stop was initiated will be necessary for the carriers and associated equipment to resume operation.
Before restarting a conveyor that has been stopped because of an emergency, an inspection of the belt will be done and the cause of the stay determined. The device should be blocked or tagged before any attempt is made to eliminate the cause of the suspension, unless the operation is necessary to determine the cause or safe to eliminate unemployment. Refer to ANSI Z244.1-1982 American National Standard for protection of personnel – Lockout / Tagout of energy sources – minimum safety requirements.
ASME B20.1-2003 Section 5.12
(b) In the event that security depends on stopping devices or the beginning of devices or both, must be kept free of obstructions that could endanger the staff.
NFPA 79 Section 9.2.5.4.1.1
In addition to the requirements to stop, the top emergency shall have the following requirements:

(1) override all other functions and activities in all modes.
(2) power to the machine drive, leading to situations of danger (s), shall be removed as quickly as possible without creating other risks (for example, the provision of mechanical means of detention that do not require external power, by reverse current braking for a Category 1 stop).
(3) Restoring an emergency stop circuit does not initiate a restart.

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