What are the main functions of Plastic Pipe Fitting?

1. Connecting and branching pipelines: Pipe fittings are key components for reliably connecting different pipe sections, allowing fluids or gases to flow smoothly within the system.

2. Ensuring sealing: Tight seals are achieved through heat fusion, threads, or clamps to prevent leaks, meeting the needs of various scenarios such as urban water supply, irrigation, and industrial transportation.

3. Reducing flow resistance and maintenance costs: PVC-U and other plastic pipe fittings have smooth walls, low flow resistance, and a long service life, significantly reducing operating energy consumption and subsequent maintenance costs.

What are the common maintenance methods for Plastic Pipe Fitting?

1. Regular cleaning: Use a dedicated high-pressure spray system to remove residues inside the fittings, preventing deposits from causing blockages or corrosion.

2. Inspecting seals: Visually inspect and replace threads, O-rings, gaskets, and other sealing components to prevent leaks due to aging.

3. Corrosion and UV Protection: In outdoor or chemical environments, regularly apply corrosion inhibitors or use UV-stable materials to extend service life.

4. Records and Traceability: Establish a maintenance log to record the time and part number of each inspection, cleaning, and replacement, facilitating subsequent quality traceability and preventative maintenance.

What are the differences in pressure and temperature resistance between different types of Plastic Pipe Fitting?

Differences in Pressure and Temperature Resistance between Different Types of Plastic Pipe Fitting

1. PVC-U (Unplasticized Polyvinyl Chloride)

Pressure Resistance: Operating pressure can reach PN10~PN16 (approximately 1.0~1.6MPa) at room temperature (20°C). During pressure testing, 1.5 times the design pressure is often used.

Temperature Resistance: The applicable temperature range is generally 0~60°C. Exceeding this range will cause the material to soften and its strength to decrease rapidly.

Applicable Scenarios: Water supply, drainage, and general industrial transportation, especially outstanding in systems with high corrosion resistance requirements but low temperatures.

2. HDPE (High-Density Polyethylene)

Pressure Resistance: For the same diameter, HDPE's working pressure is often higher than PVC-U, reaching PN10~PN20 (approximately 1.0~2.0 MPa), and in hydrostatic testing, a more stringent requirement of 1.7 times the design pressure is often used.

Temperature Resistance: Continuous operating temperature generally does not exceed 70°C, while instantaneous temperature can reach 90°C. Increased temperature will decrease strength, but good toughness is still maintained.

Applications: Chemical, water supply, gas, and other systems requiring high working pressure and relatively moderate temperatures.

3. PP (Polypropylene) and PP-R/PP-RT

Pressure Resistance: Working pressure is similar to HDPE, commonly PN10~PN12 (approximately 1.0~1.2 MPa), maintaining a certain strength even at high temperatures.

Temperature Resistance: Long-term operating temperature can reach 90°C, and instantaneous temperature can reach 95°C, suitable for hot water or hot media transportation.

Applications: Hot water, HVAC, and industrial pipelines requiring certain temperature resistance. 4. CPVC (Chlorinated Polyvinyl Chloride)

Pressure Resistance: Operating pressure at room temperature is comparable to PVC-U, but due to its higher rigidity, it can maintain the same pressure rating at higher temperatures.

Temperature Resistance: Can be used continuously within the range of 0~80°C (some high-end products can reach 100°C), with significantly better temperature resistance than PVC-U.

Suitable Applications: Hot water, steam, and chemical media requiring high-temperature resistance.

5. PVDF (Polyvinylidene Fluoride)

Pressure Resistance: Operating pressure is similar to PVC-U, approximately PN10 (1MPa), but due to its high rigidity, it maintains sealing performance at high temperatures.

Temperature Resistance: Widest applicable temperature range, -20~100°C, commonly used in highly corrosive environments and special conditions with large temperature fluctuations.

Suitable Applications: Seawater, acid and alkali media, and high-temperature chemical processes.

6. Metal-lined Plastic Pipe Fittings (e.g., stainless steel lined)

Pressure Resistance: Relying on the metal matrix, they can withstand pressures far exceeding those of ordinary plastic pipe fittings (up to tens of MPa).

Temperature Resistance: The metal lining can operate within a range of 273°C~816°C (316SS) or 454°C (304SS), far exceeding the temperature limit of the plastic body.

Applicable Scenarios: High-pressure steam, hot oil, and extreme high-temperature processes.

How to determine if Plastic Pipe Fitting is suitable for high-pressure systems?

Key Steps to Determine if Plastic Pipe Fitting is Suitable for High-Pressure Systems

1. Determine the System Design Pressure (MAWP)
First, determine the Maximum Allowable Working Pressure (MAWP) of the pipeline. This is the benchmark for all subsequent judgments.

The design pressure should be calculated based on process requirements, media characteristics, and temperature coefficients, with a safety factor (usually 1.5 to 2 times).

2. Verify the rated pressure rating of pipe fitting materials.
Material-pressure correspondence tables (PVC-U, PE, PP, CPVC, PVDF, metal lining, etc.) can be found in the relevant national or international standards.

For example, the PE-100-RC series can withstand a maximum working pressure of 25 bar (≈2.5 MPa) according to ISO 4427-5; PVC-U is commonly rated at PN10~PN16 (≈1.0~1.6 MPa).

3. Check temperature compatibility. High pressure is often accompanied by high temperature; it is essential to confirm that the material maintains its rated pressure at the operating temperature.

CPVC can operate continuously from 0 to 80°C, while PE-100-RC maintains its strength within the range of -20 to +70°C.

4. Confirm Compliance with Relevant Technical Standards or Certifications

Domestic: GB/T13663.5-2018 (Polyethylene Piping Systems for Water Supply - Part 5) specifies the testing requirements for internal pressure, external pressure, bending resistance, and tensile strength of pipe fittings. Only products that pass these tests can be used in high-pressure systems.

International: ISO17885-2021 provides unified regulations for the pressure resistance, leak tightness, and long-term water pressure strength of mechanical pipe fittings.

Certification: Certification systems such as DINCERTCO and EN12201-3 also provide a conformity mark of "Pressure Rating ≥ PN10".

5. Conduct On-site or Laboratory Water/Air Pressure Tests

Strength Test: The test pressure is usually 1.5 × MAWP, and many standards require it to be no less than 0.4 MPa (as shown in the *Construction Handbook*).

Leakage Test: Maintain the pressure under MAWP conditions for more than 1 hour and observe for any leakage.

Burst strength: Many standards require a burst strength ≥ 4 × MAWP (e.g., ABS rules).

6. Consider installation method and fit tolerances.
When using different connection methods such as heat fusion, clamps, or threads, it is necessary to check the tolerances of the mating surfaces, the smoothness of the sealing surfaces, and whether they meet the pull-out resistance requirements (to prevent the fittings from detaching under high pressure).

7. Refer to the supplier's technical documents and measured data.
The supplier should provide material certificates, pressure rating markings, and test reports. Compare these documents with the above standards, and only use the fittings after confirming that there are no discrepancies.

How to select the appropriate Plastic Pipe Fitting size and specifications?

1. Determine the nominal diameter of the pipe (DN / IPS / CTS).
Based on the pipe design flow rate: First, calculate the required pipe diameter based on the system's design flow rate and allowable pressure drop (common formula Q=A·v) to obtain a nominal diameter.

Use standard size series: The nominal diameter of plastic pipe fittings is typically in the IPS (Iron Pipe Size), IPS/CTS, or DN (Nominal Diameter) series. ISO 265-1 (PVC-U) clearly specifies the range of selectable nominal diameters: 40mm, 50mm, 63mm, 75mm, 90mm, 110mm, 125mm, 160mm, etc.

Refer to industry manuals: The Plastics Pipe Institute Handbook lists multiple size systems such as IPS, DIPS, CTS, and Metric to help confirm the correspondence between pipes and fittings.

2. Matching Wall Thickness (Schedule) and Material Grade: Wall thickness determines pressure resistance: For fittings of the same nominal diameter, the larger the wall thickness (Schedule), the higher the working pressure it can withstand. PVC-U, PE, PP, and other materials all have corresponding Schedule 40, 80, 120, etc. grades.

Select a rating appropriate for the system pressure: The *Ultimate Guide to PVC Pipe Fittings* states that "Schedule refers to pipe wall thickness; selecting the same Schedule as the pipe will yield optimal strength and durability."

Temperature's effect on wall thickness: High temperatures reduce the material's yield strength. When selecting a pipe, refer to a temperature-pressure cross-reference table (such as the *Essential Guide to Plastic Fittings*) to ensure that the design pressure is met even at the highest operating temperature.

3. Confirm connection method and fit tolerances

Connection methods: Common methods include butt fusion, electrofusion, threaded connections (NPT/BSPT), clamps/flanges, etc. Different methods have different requirements for pipe diameter tolerances. For example, JG Speedfit specifies that fitting dimensions must match the pipe within ±0.1mm.

Fit tolerances: ISO 265-1 provides unified specifications for key dimensions such as D, εmin, and z to ensure a tight fit between fittings and pipes and prevent leakage.

Special requirements: If the system requires a reduction, reducer, or flange, the corresponding dimension table should be consulted (such as the “Dimension-Flange-Nozzle” comparison table provided in the PSI Design Manual).