Keeping Conveyor Operators Safe with Emergency Stops
How we design conveyor systems to protect your employees and your business
Visible
signs, such as this one
from
Emedco are an excellent safety idea
Emergency stops and other safety designs cost more, but they make your people and your business safer.
Conveyor systems that are accessible to operators must be equipped with emergency stops. (please note that we design our systems with these precautions - individual conveyors do not fall under the scope of this article).
Guarded by location
The only conveyors that don’t require them are systems that are mounted more than eight feet above the working surface, since those are guarded by their elevation—called “guarded by location.”
When any conveyor system isn't accessible to operators, it is guarded by location. The conveyor isn’t accessible to warehouse workers, and can only be accessed by maintenance personnel who can lock out or tag out the conveyor before performing maintenance.
All Emergency Stop circuits should fail in the event of a power loss to the Emergency Stop Circuit.
In the event that an Emergency Stop is activated, the conveyor system must be inspected for unsafe or box jam conditions by the operators. Once it is verified that the condition has been resolved the system may be restarted.
Safety by design
Cisco-Eagle designs our controls systems so that in order to restart the system, two things have to happen. First, the emergency stop pull cord or push button at the conveyor is reset, and then the start button at the panel is activated.
Once the system is restarted the warning horn on the system must be sounded prior to conveyors starting again. All of Cisco-Eagle’s conveyor systems will be equipped with an audible warning horn.
In order to provide a safe work environment for our customers and their employees any powered machinery provided by Cisco-Eagle adheres to these minimum requirements for safety stops and operations.
Safety Standards
The following are excerpts of Policies by Occupations Safety and Health Administration, American Society of Mechanical Engineers and the National Fire Protection Association regarding powered transmission and conveyor.
OSHA 1926.555 (a)
(1) Means for stopping the motor or engine shall be provided at the operator’s station. Conveyor systems shall be equipped with an audible warning signal to be sounded immediately before starting up the conveyor.
(2) If the operator’s station is at a remote point, similar provisions for stopping the motor or engine shall be provided at the motor or engine location.
(3) Emergency stop switches shall be arranged so that the conveyor cannot be started again until the actuating stop switch has been reset to running or “on” position.
ASME B20.1-2003 Section 5.11.2
(a) Control stations should be so arranged and located that the operation of the equipment is visible from them, and shall be clearly marked or labeled to indicate the function controlled.
(b) A conveyor that would cause injury when started shall not be started until personnel in the area are alerted by a signal or by a designated person that the conveyor is about to start.
(1) When a conveyor that would cause injury when started is automatically controlled or must be controlled from a remote location, an audible device shall be provided that can be clearly heard at all points along the conveyor where personnel may be present. The warning device shall be actuated by the controller device starting the conveyor and shall continue for a required period of time before the conveyor starts. A flashing light or similar visual warning may be used in conjunction with or in place of the audible device if more effective in particular circumstances.
(c) Remotely and automatically controlled conveyors, and conveyors where operator stations are not manned or are beyond voice and visual contact from drive areas, loading areas, transfer points, and other potentially hazardous locations on the conveyor path not guarded by location, position, or guards shall be furnished with emergency stop buttons, pull cords, limit switches, or similar emergency stop devices.
(1) All such emergency stop devices shall be easily identifiable in the immediate vicinity of such locations unless guarded by location, position, or guards. Where the design, function, and operation of such conveyor clearly is not hazardous to personnel, an emergency stop device is not required.
(2) The emergency stop device shall act directly on the control of the conveyor concerned and shall not depend on the stopping of any other equipment. The emergency stop devices shall be installed so that they cannot be overridden from other locations.
(d) Inactive and unused actuators, controllers, and wiring should be removed from control stations and panel boards, together with obsolete diagrams, indicators, control labels, and other material that might serve to confuse the operator.
ASME B20.1-2003
Section 5.11.3 Safety Devices
All safety devices, including wiring of electrical safety devices, shall be arranged to operate such that a power failure or failure of the device itself will no result in a hazardous condition.
ASME B20.1-2003
Section 5.11.4
Conveyor controls shall be so arranged that, in case of emergency stop, manual reset or start at the location where the emergency stop was initiated shall be required for the conveyors and associated equipment to resume operation.
Before restarting a conveyor that has been stopped because of an emergency, an inspection of the conveyor shall be made and the cause of the stoppage determined. The starting device shall be locked or tagged out before any attempt is made to remove the cause of the stoppage, unless operation is necessary to determine the cause or to safely remove the stoppage. Refer to ANSI Z244.1-1982, American National Standard for Personnel Protection – Lockout/Tagout of energy Sources – Minimum Safety Requirements.
ASME B20.1-2003 Section 5.12
(b) Where safety is dependent upon stopping devices or starting devices or both, they shall be kept free of obstructions that could endanger personnel.
NFPA 79 Section 9.2.5.4.1.1
In addition to the requirements for stop, the emergency top shall have the following requirements:
(1) It shall override all other functions and operations in all modes.
(2) Power to the machine actuators, which causes a hazardous condition(s), shall be removed as quickly as possible without creating other hazards (e.g. by the provision of mechanical means of stopping requiring no external power, by reverse current braking for a Category 1 stop).
(3) Reset of an emergency stop circuit shall not initiate a restart.
