In general, manholes are the way to access to pipeline. The access may needed because of one of following issues:
Dredge pipeline
Pipeline inspection
Pipeline repair
One other purpose of use of PE manholes is to integrate the pipelines. For this purpose of use, the output of the manholes could be same size of inlet diameters or bigger. In integration point there is a possibility that the pipeline is plugged. So, it’s recommended to use HDPE manholes instead of HDPE Tee or intersection connections. The steps are installed inside the manholes to make the access of human easier. The distance between steps is about 30cm – ۳۵cm. It’s recommended to make the design of pipeline so the inlets to the manholes connected at the bottom of the manhole. Otherwise, access will be difficult or impossible.
Manholes of Tosee Mehvar Sharayan Kav Co. is produced by the design of the customers after evaluation via design department of the company.
Manholes are divided to two parts of Tangent manholes and Straight manholes. Straight manholes contains one shaft which is bigger than the diameter of the inlet and outlet. Outlets and inlets inserting from different angles to this shaft and the bottom of this shaft is covered by PE sheet. This kind of manholes, mostly, used for the pipeline with maximum diameter of 1000mm. Minimum shaft is usually is 800mm. For better access conditions it’s recommended to design the shaft with diameter of minimum 1000mm.
Tangent manholes, also, consist of a shaft (normally with the diameter of 1000mm) which is connected from one side to the pipeline. There is a possibility to connect inlets from other side of pipeline. Some advantages of these manholes are: reducing the costs of manholes, increasing the speed of installation, decreasing the trench width in the location of manholes, straight flow of fluid, and increasing flow rate. For the pipe lines with the diameter of 1200mm or bigger it’s strongly recommended to use these kind of manholes for decreasing the costs and increasing the speed.
Generally, PE manholes decrease the costs and increase the speed. It has more longevity than other manholes. For the reason of low roughness coefficient and high flexibility against landslide and earthquake it can increase the quality of pipeline.