In underground pipeline maintenance operations, inspection chambers are the essential access points for personnel entry and exit. However, fall accidents caused by corroded and broken steps, loose anchoring, or slippery treads continue to occur in various locations. Behind these accidents, the same issue often emerges: the material, structure, and installation standards of the steps have not been strictly implemented. The ductile iron manhole steps produced by SOLID (Shanxi Solid Industrial Co., Ltd.) are manufactured with this safety imperative in mind.

1. Small Steps, Yet They Carry Human Life Safety

Manhole steps are foot supports installed on the inner walls of inspection chambers for workers to climb up and down, consisting of a tread surface and anchoring legs on both sides. They account for a small quantity and low unit cost within the entire pipeline network system, yet they directly affect the personal safety of every descent operation.

For this reason, countries have established clear mandatory safety indicators for manhole steps. Taking China's national standard drawing set 14S501-1 as an example, the bending resistance of steps must be greater than 5kN, and the pull-out resistance must be greater than 10kN—meaning a single step must withstand a bending load of approximately 500 kilograms or more without failure. The step spacing should be 360mm, the horizontal distance between the centers of two vertically adjacent steps is 300mm, and the radially exposed length of the step centerline is 100mm. These seemingly simple figures reflect careful consideration of human climbing mechanics and rescue convenience.

2. Material Determines Service Life: Why QT500-7

SOLID manhole steps are made from QT500-7 ductile iron, conforming to the GB/T 1348 standard. This material choice is not accidental:

The graphite in ductile iron is distributed in spherical form, effectively reducing stress concentration, giving it a tensile strength of > 500 MPa and an elongation of ≥7%, combining high strength with good toughness. Compared with ordinary gray cast iron, ductile iron is less prone to brittle fracture under impact loads; compared with cast steel, it offers better corrosion resistance, making it more suitable for long-term burial in the humid environment of concrete chamber walls.

For anti-corrosion treatment, SOLID steps were tested by immersion in a 1% HCl solution for 72 hours, with no significant corrosion observed on the outer coating. The ductile iron body also remains stable in the alkaline environment of concrete, resisting rust failure.

3. Anchoring Structure: The Key to Whether Steps Are “Secure”

The primary form of step failure is not tread fracture, but overall pull-out caused by loose anchoring. SOLID step legs feature wedge-shaped teeth or barb structures. After being embedded into the reserved holes in the chamber wall, the tooth profile forms a mechanical interlock within the concrete, creating reliable pull-out-resistant anchoring. Installation requires only inserting the legs into the reserved holes and hammering them into place, with no additional fasteners needed—convenient construction with reliable anchoring.

4. Standards and Specifications

SOLID ductile iron manhole steps are manufactured in strict accordance with the following standards:

· 14S501-1: Construction of ductile iron single-layer manhole covers and steps

· 15S501-3: Ductile iron composite resin manhole covers, water grates, and steps

· GB/T 1348: Ductile iron castings

· EN 13101: Safety requirements for steps in underground inspection chambers

Products are available in multiple specifications, with step leg configurations (curved hook inward/outward) selectable according to project requirements, and customized production based on customer drawings is supported.

5. Application Scenarios

Municipal Water Supply and Drainage Inspection Chambers. In water supply, stormwater, and sewage inspection chambers, steps withstand humidity and hydrogen sulfide gas corrosion, providing safe access for maintenance personnel.

Power and Communication Chambers. In cable trenches and communication manholes, anti-slip treads ensure a stable footing for maintenance personnel carrying tools.

Industrial Plant Maintenance Chambers. In valve chambers and maintenance chambers of chemical and metallurgical plants, the corrosion resistance and load-bearing capacity of ductile iron steps meet the demands of frequent operation.

Rail Transit and Utility Tunnels. As components of emergency maintenance access, they provide reliable climbing support for operations personnel.

About SOLID

Shanxi Solid Industrial Co., Ltd. is a professional enterprise specializing in the R&D, production, and sales of pipeline products, headquartered in Taiyuan, Shanxi. Its product range includes ductile iron pipes and fittings, carbon steel pipes and fittings, stainless steel fittings, valves, flanges, manhole covers and steps, and other series. Products are manufactured in strict compliance with international standards including ISO, EN, BS, DIN, ANSI, and AWWA, and have been exported to 109 countries and regions worldwide. The company is committed to providing high-quality pipeline connections and supporting solutions for global pipeline engineering projects.