Platforms, Ladders, Stairs, and Handrails Design Requirements in Plants

 

1. What is Purpose of this article?  This article describes the minimum design requirements to ensure safe access to structures and plant items.

2. SCOPE

This standard applies to platforms, fixed ladders, stairs, inclined passageways, handrails, and toe-boards designed by Company.

RELATED DOCUMENTS

3.1     Engineering Documents

Supply and Fabrication of Structural Steelwork

STANDARD CIVST 0050        Ladders and safety gate

STANDARD CIVST 0051        Access ladder guards

STANDARD CIVST 0052        Stairs and handrails

STANDARD CIVST 0053        Ladders and safety gate – DIN standard

STANDARD CIVST 0054        Ladders and safety gate – Italian standard

3.2      British Standards Institute (BSI)

BS 4211   Specification for permanently fixed ladders

BS 4592   Industrial type flooring, walkways and stair treads

4. PLATFORMS

1. Platforms shall be provided to give access to all appliances above grade level that require regular access for operation and maintenance. They shall allow a minimum unobstructed access space of 500 mm and a minimum unobstructed headroom of 2.2 m.
2. The flooring of platforms shall consist of panels of open-grid type flooring, banded on all sides (including cut-outs). The platforms/flooring shall be capable of sustaining a uniformly distributed live load equivalent to 5 kN per square metre, or alternatively, a single point- load of 5 kN at mid-span, whichever produces the greater stress.
3. When platforms are made from plate to match existing works, they shall be of a raised pattern, self-draining type.
4. The top flanges of the members supporting the flooring shall be tied at intervals sufficiently close to prevent them from buckling. The horizontal loads on handrails (see paragraph 8.2) shall be taken into consideration in the design of intermediate floor ties.

3. LADDERS

1. Ladders shall be vertical or inclined at a minimum angle of 70 degrees to the horizontal. They shall be designed according to the standard drawings listed in paragraph 3.1.
2. Ladders shall be designed to carry a suspended load of 2 kN when inclined at 70 degrees to the horizontal. There shall be a minimum clearance of 230 mm between the centreline of the rungs and the nearest structure.
3. Stringers, rungs, and safety hoops are clearly defined and illustrated on STANDARD CIVST 0050 (or STANDARD CIVST 0053 or STANDARD CIVST 0054). Additional straps shall be fitted between the lowest hoop of a ladder cage and the top handrail of a platform whenever the handrail is less than 1.3 m from the centreline of the ladder. Details of the additional straps are shown on STANDARD CIVST 0051.
4. If the vertical distance travelled exceeds 9 m, intermediate rest platforms shall be provided. They shall be at least 1 m square.
5. Consecutive lengths of ladder shall be offset laterally from each other. Ladders rising 2.5 m or more from the ground, and all other ladders in elevated positions, shall be provided with the self-closing safety gate shown on STANDARD CIVST 0050 (or STANDARD CIVST 0053 or STANDARD CIVST 0054).
6. Ladders shall be of the “side-step” type in which access to or from a landing or platform is made by stepping sideways off the top of the ladder. Two-way access ladders are not permitted.
7. Any bolts used to secure safety hoops or straps shall be either cup-headed or countersunk to leave a flush inner face.

6. STAIRWAYS

1. Stairways shall be provided when frequent access to elevated structures is required. This requirement shall be assessed by the lead piping designer. They shall be designed according to STANDARD CIVST 0052.
2. Stairways shall be between 610 mm and 750 mm wide between stringers, and handrails shall be provided on both sides.
3. The maximum permitted vertical rise of any stairway is 3.3 m. Intermediate landings shall be provided for greater heights; they shall have a minimum length of 1.0 m.
4. Treads and risers shall be uniform. No tread shall be narrower than 230 mm including the overlap, and the back edge of each tread shall not be forward of the nose of the tread above.
5. The preferred inclination of the stairway is 42 degrees to the horizontal. The inclination shall not exceed 45 degrees.
6. The headroom between the outer edge of any stair tread and the underside of the steelwork of the landing above shall be at least 2.2 m.

7. INCLINED PASSAGEWAYS

The inclination of passageways shall not exceed 20 degrees to the horizontal. Handrails shall be provided in all cases. The framework shall be designed to safely carry a uniformly distributed load of 5 kN per square metre.

8. HANDRAILS AND TOE-BOARDS

1. Handrails and toe-boards, according to STANDARD CIVST 0050 (or STANDARD CIVST 0053 or STANDARD CIVST 0054), shall be provided around the outer edges of all elevated access areas and platforms. Toe-boards shall also be provided around penetrations through platforms when more than one pipe occupies a single penetration.
2. Handrails shall be capable of resisting a uniformly distributed horizontal load of 750 N per metre run applied at the top of the handrail. The maximum spacing of handrail standards shall be 2.0 m on platforms and 1.5 m on stairways (measured on plan).