Precautions for JRPP Pipe Installation During Winter Construction

The core of winter construction for JRPP (reinforced polypropylene) pipes lies in avoiding low-temperature brittleness, ensuring fusion quality, and implementing effective anti-freezing and protective measures. Below are the key considerations by phase, balancing material properties and construction standards.

1. Pre-construction Preparation

Material Storage and Preprocessing

Pipes and fittings should be stored in warehouses or simple sheds, avoiding exposure to freezing temperatures and direct sunlight outdoors. The stacking height should be ≤1.5m to prevent deformation from heavy pressure. Do not throw, drop, roll, or drag during handling to avoid hidden damage.

If there is a significant temperature difference between the site and the storage location, place the pipes and fittings at the site for more than 24 hours before installation to allow their temperature to approach the construction environment, thereby reducing potential connection hazards caused by thermal expansion and contraction.

Before construction, inspect each pipe individually and remove those with stress-induced whitening, scratches, or internal wall damage to eliminate hidden defects.

Environmental and Personnel Control

When the ambient temperature falls below 5°C, warming and insulation measures (such as building insulated sheds or using air heaters) must be taken. Below 0°C, outdoor construction should be minimized, and operations must be suspended during rainy, snowy, or windy weather to prevent joint moisture or brittle cracking of pipes.

Construction personnel must undergo specialized training to become familiar with the adjustment of hot-melt/electric-melt parameters and emergency handling procedures at low temperatures.

Preparation of Tools and Auxiliary Materials

Inspect specialized tools such as hot melt/electric melt welders and cutting machines to ensure they are functioning properly. Prepare auxiliary materials including anhydrous ethanol, fine sandpaper, insulation materials, and sand.

Prepare windproof, rainproof, and thermal insulation facilities, such as thermal blankets and tarps, to avoid interference from environmental factors during the welding process.

II. Construction Process Control

(1) Cutting and Preprocessing

Use a dedicated pipe cutter (≤40mm) or a rotary cutting machine (>40mm) to make vertical, slow cuts. After achieving a smooth cut, remove burrs and rough edges with fine sandpaper. Avoid using hacksaws or gas cutting to prevent cracking or deformation of the cut.

If stress whitening is observed at the pipe end before cutting, discard it immediately. Before connecting, wipe the pipe and fitting connection surfaces with anhydrous ethanol to remove oil stains and dust. When performing electrofusion connection, scrape off the 0.1-0.2mm oxide layer on the pipe surface.

Mark the hot melt insertion depth to ensure proper connection.

(2) Fusion Welding Construction (Core Process)

Connection Method  Low-Temperature Adjustment Points  Operation Specifications

Hot melt connection  Temperature 260±10°C; heating time extended by 50% when ambient temperature <5°C  Insert the heating sleeve/header to the marked depth without rotation, then quickly straight-line对接 without rotation after heating. Cooling period (typically ≥30 seconds) prohibits movement, rotation, or pressure application

Electrofusion Connection  Adjust the heating time according to the manufacturer's parameters, and extend it appropriately at low temperatures.  Keep the fusion surfaces dry.  Straighten the coaxial alignment, connect the power supply for heating, and stop immediately when the signal eye shows molten material overflowing.  During the cooling period,严禁外力干扰 (strictly prohibit external interference)

(3) Installation and Fixation

Installed pipelines are strictly prohibited from being struck or subjected to heavy pressure. Insulating cotton or protective sleeves must be used to cover overhead or vulnerable sections prone to external forces.

For long-distance laying, thermal expansion allowances must be reserved by installing expansion joints or natural compensation sections (such as L-shaped bends) to mitigate low-temperature shrinkage stress.

The spacing of supports and hangers shall be set according to the specifications to prevent pipe sagging or vibration; metal sleeves shall be installed when crossing walls or foundations, with insulation material filled between the sleeves and pipes.

3. Pressure Testing and Backfilling / Protection

hydrostatic test

Pressure testing is required after installation, backfilling, or before concealed laying: The test pressure for cold water pipes shall be 1.5 times the working pressure and ≥0.9MPa, while for hot water pipes, it shall be 2 times the working pressure and ≥1.2MPa. Maintain the pressure for 30 minutes; the pressure drop must be ≤0.05MPa with no leakage to be considered qualified.

After pressure testing, immediately drain the accumulated water in the pipes to prevent freezing, expansion, and cracking. For pipelines that will be left unused for an extended period without reliable insulation, the remaining water must also be drained.

Backfilling and Frost Protection

When backfilling buried pipelines, first fill with sand or fine soil with particle size ≤12mm up to 0.3m above the pipe top, compact it, and then backfill with the original soil to avoid sharp or hard objects scratching the pipe wall.

Exterior exposed pipes must be wrapped with specialized insulation sleeves or thermal insulation cotton, with additional thickened protection for exposed joints. Buried pipelines must meet the design requirements for burial depth, ensuring sufficient backfill thickness to prevent freezing.

IV. Safety and Finished Product Protection

Open flames are strictly prohibited at the construction site. Do not use open flames to bake pipes and fittings to prevent material deterioration or safety hazards.

After concealed installation, mark the pipeline routes to avoid damage during secondary renovations; place warning signs on completed pipelines to prevent stepping on or collision.

Establish a construction ledger to record environmental temperature, welding parameters, pressure test results, and other data for easy traceability and inspection.

V. Emergency Handling

If leakage is found at the joint after fusion, the joint must be cut off and refused. Repairing at the original joint location is strictly prohibited.

In case of sudden temperature drop, immediately suspend construction, cover installed pipelines with insulation materials, drain accumulated water inside the pipes, and resume work only after temperatures rise and warming measures are implemented.