Access Areas and Controls
This section addresses access to electrical and mechanical hazards.
7.1 Operator Access Areas
7.1.1 Definition. Any area:
1. That can be accessed without the use of a tool.
2. That is defined by the manufacturer as an operator service area.
3. Where the means of access is deliberately provided to the operator.
7.1.2 Operator Exposure. Operators shall not be exposed to:
1. Energy levels of 240 VA or more.
2. Stored energy levels of 20 J or more.
3. Potentials in excess of 42.4 V peak (30 VRMS) or 60 VDC in dry areas.
4. Potentials in excess of 10 VAC or DC in wet areas.
7.1.3 Operator Protection. The operator(s) shall be protected from electrical and mechanical hazards by one or more of the following:
1. Enclosures, shields, and covers that require a tool to open.
2. Interlock switches on doors, shields, and ovens.
3. Grounded or insulated handles, levers, knobs, shields and covers that are touched held or actuated in normal use.
7.2 Service Access Areas
7.2.1 Definition. All areas not defined as operator access areas that skilled service personnel must gain access to service or maintain the equipment
7.2.2 Service Personnel Exposure. Service personnel shall not be exposed to inadvertent contact with hazardous potentials or energy levels.
7.2.3 Service Personnel Protection. Service personnel protection requirements are:
1. Protection shall be provided:
a. Where service is required with power on and inadvertent contact is likely.
b. Where it is necessary to reach over, under, around, or in close proximity to hazards.
c. Where dropped tools could cause shorts and arcing.
2. Protection shall be provided by one or more of the following:
- Remote or external test points.
- Insulated potentiometer extensions.
- Access holes.
-Separation of low voltage and line voltage terminal blocks and relays.
3. Equipment requiring manual adjustments shall be so designed that adjustment does not expose personnel to electrical or mechanical hazards.
4. Shafts of operating knobs, handles, etc., shall not be in contact with hazardous live parts. Handles, levers, and knobs which are held or actuated in normal use shall be grounded, of insulating material, or adequately covered by insulating material if parts are likely to become energized.
7.2.4 Maintenance Access. Maintenance access shall be provided for servicing equipment.
1. Machines that require service and have access covers shall have a minimum of 28 in. clear space. This does not apply to movable units.
Note: Clear space is measured from any protrusions, auxiliary units, etc., not from the main frame to the wall or any other obstructions.
2. Large equipment shall be equipped with maintenance cat walks, access ladders, crossovers, etc., to facilitate safe access to valves, motors, dampers, pumps, motor drives, and other components.
7.2.5 Working Space. Sufficient working space shall be provided for servicing electrical equipment having energized hazardous potentials or energy levels.
1. Depth- Working space shall be at least 36 in. When voltages exceed 150 V to ground, the depth may have to be increased.
2. Width- working space shall be 30 in. in front of the exposed voltage.
3. Access- There shall be at least 28 in. of clear access to the working space.
4. Clear Space- Working space shall remain clear and shall not be used for equipment of storage.
7.3 Safety Interlocks
7.3.1 Requirements. Hardware based interlocks are required whenever access can be gained, without the use of a tool, to an area which would allow the inadvertent contact with electrical or mechanical hazards, such as:
- Remote or programmed machine starts.
- Moving mechanical parts.
- Hazardous potentials.
- Hazardous energy levels.
- Hazardous gas flow.
- RF energy.
- Laser beams.
- Capacitor discharge.
7.3.2 Interlock Location. Safety interlocks shall be hardwired between the logic output (switching) device and a fail-safe magnetic device that controls the hazardous energy.
7.3.3 Interlock Bypass. Safety interlocks shall require an intentional operation to bypass and shall comply with the following:
1. Removing or opening interlock covers shall remove associated hazards.
2. To restart equipment for service, interlocks must be bypassed and then start circuits manually reactivated.
3. Equipment shall not be operable unless covers are reinstalled (closed) and interlock function restored.
7.3.4 Programmed Machine Controls. Equipment with programmed machine controls (software based logic circuits) shall comply with the following:
1. Programmed machine controls shall not be used as safety interlocks.
2. Safety interlocks shall remove hazard independently of programmed machine controls.
3. Hardwired safety interlocks shall override associated machine controls. See 7.5.2.
7.4 Hand Controls
7.4.1 General Requirements. Equipment must have adequate operator controls.
1. The quantity and type of controls are dictated by equipment size and complexity.
2. "Power On" conditions and equipment operation status must be visually and reliably indicated.
3. Indicating lights and lighted switches shall comply with 3.4.
4. Circuit breakers or circuit protectors shall not be used as operator controls for on / off or start / stop functions.
5. Control switches shall comply with 3.3.
Note: Equipment that functions independently of operator interaction or exposure does not require operator controls. See 8.1.5.
7.4.2 Start (ON) Switch. Start switches shall comply with the following:
1. Should be momentary contact push button with recessed or flush type head.
2. Other types are allowed.
See Sec. 6.3 and 10.6.
3. Shall be located or designed to prevent accidental operation.
7.4.3 Stop (OFF) Switch. Stop switches shall comply with the following:
1. Shall be momentary contact push button with extended type head.
2. Other types are allowed. See Sec. 3.3 and 7.6.
3. Shall be located or designed to prevent accidental operation.
4. Mushroom head switches shall not be used.
5. Shall take precedence over the associated start / on switch. See TEST under 7.6.
7.4.4 Emergency Off (EMO) Switch. EMO switches shall comply with the following:
1. Shall be labeled "EMERGENCY OFF."
2. Shall be pushbutton with red mushroom type head.
3. The mushroom head shall be a minimum of 1.25 in. in diameter.
4. Resetting switches shall not restart the equipment.
5. Shall be located to prevent accidental operation:
- Shall not be recessed.
- Should not be guarded.
6. Shall not be used in place of normal stop / power off switch.
7. Shall take precedence over all other controls. See TEST under 7.6.
7.4.5 Service Safety Switch. Service safety switches shall comply with the following:
1. Shall clearly indicate ON / OFF status.
2. Shall be lockable in the open position.
3. Shall be within sight from the equipment or component to be serviced.
4. Shall remove power from the equipment or component to be serviced.
Note: The supply disconnect switch may serve as the service safety switch.
7.4.6 Two Hand Cycle Start Controls. When dual, series connected hand controls are required to isolate the operator from the hazards, the hand controls and / or control circuit shall comply with the following:
1. The hand controls shall be momentary contact pushbutton switches with black or green mushroom type heads.
2. Each hand control shall be protected against unintended operation.
3. Each hand control shall by design, construction and / or separation so that the use of both hands is required to start the machine cycle. Typically, they should be mounted at least 24 in. apart in the same vertical or horizontal plane.
4. Both hand controls shall be depressed within one second of each other in order for the machine to cycle.
5. Both hand controls must be depressed until the hazard no longer exists.
6. The control system shall incorporate an anti-repeat feature that limits the machine to one cycle for each depression of the hand controls.
7. The control system requires an anti-tie-down feature that requires the release of both hand controls between cycles.
8. For a typical circuit see Figure 16.
Note: Timer 1TR shall be: one second, fixed, time delay on release.
Figure 16. Typical Two Hand Cycle Start Circuit
7.5 Machine Controls
7.5.1 Undervoltage Protection. Undervoltage protection shall be provided for all equipment which may initiate a hazardous motion upon the return of power after an undervoltage condition.
7.5.2 Solid State and Programmed Controls. Solid state and programmed controls shall not be relied upon for personnel or equipment safety because they are not fail-safe. Electromechanical devices shall be used.
7.5.3 Safety Controls
1. Appropriate safety controls shall be installed, such as:
- Over temperature controls.
- Under temperature controls.
- High level controls.
- Low level controls.
- High and low pressure controls.
- Pressure relief controls.
- Over limit controls.
- Ground Fault Circuit Interruptors.
2. Safety controls and switching devices shall override associated solid state or programmed machine controls and final control elements.
See 3.9 and 8.1.4.
7.6 Fail-Safe Controls and Switching Devices--All controls and switching devices shall be applied in a fail safe design that complies with the following:
1. Shall start through energization.
2. Shall stop through de-energization, i.e., shunt trip units are not allowed.
3. Stop switches shall take precedence over associated start switches.
a. Hold stop / start switch open.
b. Close start / on switch.
c. Equipment shall not start, power up turn on or cycle.
7.7 Control Location
7.7.1 Operator Controls. Operator controls:
1. Shall be within easy reach by operator in normal operating position.
2. Shall not require the operator to reach past spindles or other moving parts.
7.7.2 Nonoperator Controls. Nonoperator controls shall be located such that accidental or unauthorized operator adjustment or operation is unlikely and will not create a hazard.
7.7.3 Control Enclosures. Control enclosures shall be designed to prevent accidental operation of controls by the equipment or the operator. They:
1. Shall be securely mounted in a clean and dry location.
2. Shall be mounted not more than 6.5 ft. or less than 12 in. above the operating floor line.
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