GB/T 31255-2014Safety of machinery—Safety specification for the design of industrial type stairs, working platforms and walkways (English PDF)

6.6 Tolerance

The consistency of the step spacing h and the tread distance g is the most important for the safety of the user. The tolerance of the step spacing h and the tread distance g shall be ± 5 mm within the same stair section of a stair.

6.7 Outdoor stairs

If the stairs are exposed to the outside AND are not only for access to the fixed facilities of the machinery, the rising height H shall not exceed 6 m. Otherwise, it shall be protected, such as enclosed with non-combustible materials (SEE 9.7).

6.8 Step

The step shall comply with the safety requirements as specified in Chapter 4 of GB 17888.3-2008; AND it shall take appropriate anti-slip measures OR at least have a non-slip leading edge with a width of not less than 25 mm.

For hollow step stairs, the overlapping part of the step shall not be less than 16 mm, AND the depth of the leading edge shall be between 25 mm ~ 50 mm, in order to improve visibility.

6.9 Stair beam

The stair beam shall have sufficient rigidity to minimize the lateral deflection;

AND the distance beyond the leading edge of the bottom step shall not exceed 50 mm (SEE Figure 1).

6.10 Stair platform

The stair platform shall be designed to comply with the requirements of Chapters 7 and 8.

The length of the stair platform l (SEE Figure 3) shall not be less than the stair net width or 850 mm, whichever is greater.

6.11 Handrails

Straight staircase, stair section platform and helical & spiral stairs shall have continuous handrails complying with the relevant requirements of Chapter 9.

7.3 Fixation

Working platforms and walkways shall not be fixed by their own weight.

When the fixation element which depends on tensile force only is used only, its working load factor shall be not less than 1.5.

The designer shall consider whether the corrosion or fatigue stresses will have a significant effect on the fixation of the working platform or walkway.

7.4 Handrails

All open sides of the working platform and walkway shall be fitted with handrails that comply with the relevant requirements of Chapter 9.

7.5 Skirting board

All open sides of the working platform and walkway as well as the downside of the first step of the open stair shall be installed with the skirting boards complying with the requirements of Chapter 8.

7.6 Walkway

The walkway shall generally be horizontal. However, if it is unavoidable to use inclined walkway, it shall pay special attention to ensure that personnel use the walkway can get enough friction. The slope of the walkway shall not exceed 10°.

7.7 Leading edge

If the walkway does not have anti-slip measures, the tops of all stairs and the positions accessing to the stairs shall have anti-slip leading edges, which shall match with the leading edge of the stair steps (SEE 6.7).

The joints of the continuous guardrail shall be located at the minimum stress point AND shall not exceed 150 mm to the center line of the post. The position of the joint shall not be located outside the end post OR between the two continuous posts at the corners. The joint shall be free from any sharp edges or burrs.

9.4 Post

The posts shall not be installed on the skirting board unless otherwise they can be used as the structural elements of skirting board.

9.5 Clearance

To ensure that the hand can firmly grasp the handrails, it shall provide more than 75 mm clearance below the handrail.

9.6 Self-closing door

At a potentially dangerous area, such as the gap at the stair top handrail, it shall be protected through using the self-closing door. […]