There are ways that companies and industry standards give specific requirements, but this is to capture the ideas and objectives to reduce risk of injury, specifically musculoskeletal disorders, and to minimize process upsets caused by human error about equipment layout, stairs and ladders, clearance, etc.
Equipment Layout of the facility / unit.
Layout of machinery and heat exchangers should allow sufficient clearance and access to enable removal with mobile hoisting equipment for maintenance and quick turnaround. Alternatively, fixed overhead lifting facilities should be provided as well for lifting heavy item such as motor and transformer.
Self Contained Breathing Apparatus and firefighting equipment should be determined by personnel usage of such equipment during emergency response (i.e., the emergency response task analysis).
The layout of auxiliary equipment, valves, controls, and displays for parallel units (e.g., spared pumps) should be identical in relation to the equipment controlled.
Valve stations with similar purposes should have similar arrangement and appearance.
Platforms, stairs and ladders consideration
Platforms should be provided for the equipment involved unless the equipment or facilities are accessible from grade or from other permanent platforms. Access to these platforms should be by permanently installed stairs or ladders.
Stairs, not ladders, should be provided where:
- Personnel are required to carry large tools or pieces of equipment up or down the structure.
- Equipment must be accessed or personnel evacuated during emergencies (e.g., battery limit valves, manual sampling of dangerous materials).
- Equipment is frequently accessed (at least once per shift on average).
- Stairs and ladders to a platform should not terminate in front of a manway.
Indoor and outdoor stairs, ladders and platforms that could become slippery due to environmental or production conditions should be slip resistant.
The maximum horizontal reach from a platform or ladder should not exceed 20 inch. The maximum overhead grip reach from grade or a platform should not exceed 6 ft.
Access from a ladder onto the platform should be through a self-closing safety gate.
The minimum vertical clearance under burners of fired heaters, measured to the lowest point of overhead structural framing (including fireproofing), piping (including insulation), conduits, or equivalent, should be 6 ft 6 in.
Accessibility to valves is the most common operation for plant folks. Valve handwheels/handles should be readily accessible and positioned to be within normal reach for operation. Access should be from permanent ladder, rolling stairs, platform, grade, or other means as required for operations, maintenance, inspection and emission monitoring.
In order to avoid knuckle injuries, minimum clearance should be 3 inch between adjacent valve handwheels, equipment and structures; and 2 inch between the back of the handwheel and insulation on the line. Additional clearance should be provided for wrench-assisted operation of valve handwheels and handles of ball-and-plug type valves.
Valve handles should be oriented such that they do not turn to restrict the access or walk-through pathway in front of the valve.
Manual operation of valve handwheels, manual gear operators, levers, or chain operators should not require application of force exceeding 80 lb. Operating valves that require a greater force to turn, or that require more than 40 turns from open or close position, should be motor-operated to reduce the likelihood of musculoskeletal and repetitive motion injuries.
Valves should be selected and installed to ensure the consistent operating stereotype of increasing flow when the actuator is turned counter-clockwise, moved from left to right, front to back or upwards.
The below figure illustrates the location of Valve Handwheels that one should consider.
Means of Egress
- Egress into walkways or platforms from doors that swing outward should include the swing radius of the door plus the width of the walkway in the area of the door.
- Maximum difference in elevation at the threshold of doors that swing outward into walkways or platforms should be no more than 1 inch.
- Panic and fire exit hardware (e.g., horizontal bar for opening door) should be installed on doors intended for use as exterior doors for emergency egress (e.g., for motor control centers [MCCs], switchgear, battery rooms, laboratories).
- Stairway landings at outwardly swinging doors should have a minimum 30 × 30-inch landing area that is clear of the swing of the door.
- A secondary means of egress (ladder or second stairway), should be required in either of the following locations:
- Elevated work locations 10 feet or more above grade or floor that have 200 square feet or greater total platform area.
- Elevated locations in which a potential hazard or injurious chemical exposure may block access to an exit.
- A secondary means of egress should also be required from rooms that contain equipment in excess of 480 V (MCCs and switchgear buildings only), or where a potential hazard or injurious chemical exposure may block access to an exit (this may be a door).
- The location of the secondary means of egress should provide an alternate means of escape to a place of safety.
- Multiple exits for an area should be located as far from each other as possible, but not more than 75 feet from any point where employees may be present unless automatic sprinkler protection is provided.