Coating the inner wall of ductile iron pipes with cement mortar and conducting curing and hardening is a common process for achieving internal lining corrosion protection. The core function of this process is to isolate the water being transported from the pipe body, effectively protecting the direct contact of the pipe's iron layer with corrosive substances.

I. Material Requirements

01 Cement

The cement used for the inner lining of ductile iron pipes and pipe fittings should comply with the relevant provisions of GB/T 175 "General Portland Cement", GB/T 201 "Aluminate Cement" and GB/T 748 "Anti-Sulfate Portland Silicate Cement". To suit the fluid being transported, the type of cement to be used should be determined by the manufacturer, or it can be decided through negotiation between the supplier and the buyer.

02 Sand

The sand used should have a controlled particle size distribution ranging from fine to coarse. The particles should be clean, inert, hard, firm and stable. The particle size curve of the sand should meet the requirements of the coating method, inner lining thickness and surface condition specified in the standard.

03Configure water

The water used for preparing the mortar should be drinking water, and the water temperature should be controlled between 7℃ and 35℃.

II. Centrifugal Dewatering Process

The centrifugal force generated by the high-speed rotation of the equipment evenly disperses the cement mortar injected into the pipe onto the inner wall of the ductile iron pipe.

1. When the pipe rotates at the centrifugal station, it should avoid significant radial displacement and prevent the pipe from moving towards the socket.

2. After each pipe is filled with water, the mud and water stains inside the socket and the outer wall of the socket need to be cleaned to ensure both ends are clean.

Ⅲ. Steam Preservation Technology

After the cement mortar coating is applied to the ductile iron pipe, it needs to undergo steam curing to promote the solidification of the inner lining. The pipe is lifted and transported to the curing pool by an intelligent crane. It is then maintained in a high-temperature, high-pressure, and humid steam environment to accelerate the hardening of the cement and prevent cracking, thereby enhancing the strength of the inner lining. The steam curing time is approximately 8 hours.