CPVC power pipe and cable protection construction scheme: high temperature environment and sealing treatment

CPVC power pipe is an important material for cable protection in high temperature environment, and its construction quality is directly related to the safe and stable operation of the power system. Combined with engineering practice, this paper expounds the key technologies of CPVC power pipe construction in high temperature environment from the three dimensions of material pretreatment, installation process and sealing protection.

1. Key points of construction technology in high temperature environment

1. Material pretreatment process

CPVC pipe needs to be tested for high temperature performance before entering the site to ensure that the vicat softening temperature is 93 ° C and the tensile strength is 60 MPa. During summer construction, the pipe should be stored in a cool and ventilated place to avoid direct sunlight causing the temperature of the pipe body to exceed 40 ° C. The cutting operation needs to be carried out when the ambient temperature is lower than 35 ° C. The incision is treated with a special chamfering device to ensure that the groove angle is 305 and the surface roughness is Ra6.3μm.

2. Groove excavation and base treatment

Under high temperature environment, the trench excavation should be constructed in sections, the length of each section should be controlled within 50 meters, and the slope support should be set when the excavation depth exceeds 2 meters. The base treatment is backfilled with graded sand and gravel, with a layered compaction degree of 93%, a 200mm thick medium coarse sand cushion is laid, and a flat vibrator is used to vibrate tightly. The surface flatness error is 5mm/2m.

3. Pipe laying process

Before laying, the pipe should be preheated to control the temperature of the pipe body at 25-30 ° C. When installing by mechanical traction method, the traction force should be 15kN, and the traction speed should be maintained at a constant speed of 0.8m/min. An elastic buffer layer is set at the pipeline interface, which is sealed with butyl rubber gasket. The interface gap is controlled at 1.5-2 mm, and the axis deviation is 10mm/10m.

Second, the sealing treatment special project plan

1. The socket interface sealing process

adopts "double sealing ring + elastic sealant" composite sealing structure: the first sealing ring is made of EPDM rubber, with a Shore hardness of 705HA, and the compression amount is controlled at 35% -40%; the second sealing ring is made of water-swollen rubber, with an expansion ratio of 300%. Apply high temperature resistant sealant evenly on the inside of the interface, and the thickness of the rubber layer is 1.2-1. 5mm, and the surface dry time is 30min.

2.

Flexible waterproof casing is set up at the connection between the cable working well and the pipeline. The gap between the casing and the pipe is filled with polyurethane foam, and the density is 60kg/m ³. The outside of the well wall is painted with a 2mm thick polyurea waterproof layer, with an elongation of 300% and an adhesion of 5MPa. The wellhead is sealed with a cast iron manhole cover and a built-in nitrile rubber water stop ring. The compression amount is controlled at 25% 3%.

3. Special part sealing measures

Adopt MPP reinforced protective pipe jacket to cross the road section. The casing and the CPVC pipe are filled with fireproof rock wool, with a density of 120kg/m ³. The two ends are sealed with fireproof sealing cement, and the expansion rate is 250%. A waterproof shoulder platform is set up in the high and low difference area. C25 concrete is poured. The slope is controlled at 5-8. The surface is painted with permeable crystalline waterproof paint. The dry film thickness is 1.0mm.

Third, quality control and safety measures

Quality control points should be set every 200 meters during the construction process. The testing items include: pipeline elevation deviation of 10mm, axis displacement of 30mm/100m, interface sealing test pressure of 0.6MPa, and pressure holding for 30min without pressure drop. During high temperature operation periods, 11:00-15:00 should be avoided. The construction site is equipped with forced ventilation equipment. Outdoor operation is stopped when the ambient temperature exceeds 38 ° C.

This scheme can effectively solve the construction problems of CPVC power pipes in high temperature environments through material scientific selection, refined construction technology and multiple sealing protection system. After engineering verification, the cable protection system constructed by this scheme can be guaranteed to be 50 years without leakage under 80 ℃ environment. The insulation resistance is 1000MΩ · km, which provides reliable guarantee for the safe operation of power engineering in extreme environments. The whole construction process should strictly implement the relevant standards of "Code for Design of Electric Power Engineering Cable Lines" GB50217 and "Technical Specifications for Buried Polyethylene Drainage Pipeline Engineering" CJJ143.