Polyethene Pipes for the Supply of Gaseous Fuels

IS 14885: Scope - Key Specifications & Tables

Scope Summary:
Covers dimensions, tolerances, performance, and sampling for polyethylene pipes.

1. Length of Pipe (Clause 6.4)

• Length of straight pipes/coils as agreed between manufacturer & purchaser.
• Ends: Cleanly cut, square to axis within tolerances (see Table 6).

2. Wall Thickness Tolerances (Table 5, Clause 6.2.1.1)

Tolerance increases with thickness; refer to full table for detailed values.

3. Out of Square Tolerance of Pipe Ends (Table 6, Clause 7)

4. Sampling for Visual & Dimensional Checks (Table 10, Clause 9.2.3.1)

5. Coil Dimensions (Table 13, Clause K-3.1)

| Nominal OD (mm) | Min Internal Coil Diameter (m) SDR 11 | Max External Coil Diameter (m) | Max Surface

IS 14885 Key References: Sampling, Testing & Dimensional Tolerances

1. Sampling for Visual & Dimensional Checks (Table 10)

• Sampling method: Select every r-th pipe, where r = floor(N/n).

2. Sampling for Hydraulic & Material Tests (Table 11)

3. Dimensional Tolerances (Table 5)

• Wall thickness tolerance varies with nominal thickness, e.g.:
  • 2.0 to 3.0 mm: +0.4 mm
  • 10.0 to 11.0 mm: +1.2 mm
  • 29.0 to 30.0 mm: +3.1 mm

4. Out of Square Tolerance (Table 6)

IS 14885: Key Definitions & Sampling Specifications

Sampling for Visual & Dimensional Requirements (Clause 9.2.3.1)

Sampling for Hydraulic Tests (Clause 9.2.2)

IS 14885: Designation of Pipes - Key Specifications & Tables

1. Pipe Designation (Clause 4.1)

Format:
Material Grade DN Nominal Diameter x Nominal Wall Thickness SDR GAS

• Example: PE-80 DN 200 x 11.4 SDR 17.6 GAS
  • PE-80 = Material grade
  • DN 200 = Nominal diameter 200 mm
  • 11.4 mm = Minimum wall thickness
  • SDR 17.6 = Standard Dimension Ratio
  • GAS = For gaseous fuel application

2. Material Grades & Strength (Clause 4.2.1, Table 1)

3. Nominal Diameters (Clause 4.3)

• Standard nominal diameters (DN):
  16, 20, 25, 32, 40, 50, 63, 75, 90, 110, 140, 160, 180, 200, 225, 250, 280, 315, 355, 400, 450, 500, 560, 630 mm

4. Wall Thickness Tolerances (Table 5, Clause 6.2.1.1)

Tolerance increases with thickness; refer to full table for specifics.

5. **Out of Square Tolerance of Pipe Ends (Table 6, Clause

IS 14885: Materials and Compound Quality Key Points

1. U.V. Stabilizer (Clause 5.3)

• Max 0.5% by mass of finished resin.
• Certificate from raw material supplier mandatory.

2. PE Compound Characteristics (Table 2, Clause 5.1)

3. PE Compound Quality Evaluation (Clause 5.6)

• Supplier must provide certified test results for:
  • PE compound classification (Table 1)
  • Characteristics (Table 2)
  • Tensile tests for each batch
• Additional type approval test:
  • Long-term hydrostatic strength @ 20°C for 10,000 hours (once)

Summary Diagram: Material Quality Flow

flowchart TD
    A[Raw Material Supplier] -->|Certificate + Test Results| B[Pipe Manufacturer]
    B -->|Batch-wise Testing| C[PE Compound Quality Evaluation]
    C -->|Long-term Hydrostatic Test| D[Type Approval]

Note: Ensure all tests comply with referenced IS methods for certification and quality control.

IS 14885: Key Specifications for Pipe Dimensions

1. Nominal Outside Diameter (Clause 6.1 & Table 3)

• Nominal diameters covered: 16 mm to 630 mm (Clause 4.3).
• Maximum ovality limits vary by pipe type and diameter:

2. Wall Thickness Tolerances (Table 5, Clause 6.2.1.1)

• Plus tolerance depends on nominal wall thickness (en):

(Refer to full Table 5 for detailed values)

3. Length and End Tolerances

• Length: As agreed between manufacturer and purchaser (Clause 6.4).
• Ends must be square within tolerance (Table 6):

Summary Diagram: Ovality vs Diameter for Straight Pipes

graph LR
A[Diameter ≤ 75 mm] -->|Ovality =

IS 14885: Pipe Ends and Length Tolerances Key Points

1. Length of Pipe (Clause 6.4)

• Length is as agreed between manufacturer and purchaser.
• Ends must be cleanly cut, square to the axis, with tolerances per Table 6.

2. Out of Square Tolerance of Pipe Ends (Table 6)

3. Wall Thickness Tolerances (Table 5)

• Plus tolerance varies with nominal wall thickness (en).
• Example: For 5.0–6.0 mm thickness, tolerance = +0.7 mm.

4. Ovality Limits (Clause 6.1, Table 3)

• Straight pipes ≤ 75 mm: Max ovality = 1 + 0.008 × d (d = outside diameter)
• Straight pipes > 75 to ≤ 250 mm: Max ovality = 0.02 × d
• Straight pipes > 250 mm: Max ovality = 0.035 × d
• Coiled pipes ≤ 180 mm:
  • SDR 11: 0.06 × d
  • SDR 17.6: 0.15 × d

Summary Diagram: Pipe End Tolerances

flowchart TD
    A[Pipe Ends] --> B[Cleanly Cut & Square]
    B --> C{Diameter Range}
    C -->|16 to <90 mm| D[Max Out of Square: 2 mm]
    C -->|≥90 to <140 mm| E[Max Out of Square: 3 mm]
    C -->|≥140 to <200 mm| F[Max Out of Square: 4 mm]
    C -->|≥200 to <315 mm| G[Max Out of Square: 5 mm]
    C -->|≥315 mm| H[Max Out of Square: 7 mm]

IS 14885: Performance Requirements Summary

1. Dimensional Tolerances

• Wall Thickness Tolerance (Table 5):
  Varies with nominal wall thickness (en). For example:

  Nominal Thickness (mm)	Plus Tolerance (mm)
  2.0 - 3.0	0.4
  10.0 - 11.0	1.2
  29.0 - 30.0	3.1

• Out of Square Ends Tolerance (Table 6):
  Depends on pipe outside diameter:

  Outside Diameter (mm)	Max Out of Square (mm)
  16 to < 90	2
  ≥ 90 to < 140	3
  ≥ 315	7

2. Surface & Length Requirements (Clause 6.4)

• Pipes must have smooth, clean internal surfaces free from defects affecting performance.
• Length of pipes/coils as per agreement.

3. Acceptance Tests (Table 9)

Key Formula for Hydrostatic Pressure Resistance:

[ \sigma = \frac{P \times d}{2 \times t} ]

• ( \sigma ) = hoop stress
• ( P ) = internal pressure
• ( d ) = pipe outside diameter
• ( t ) = wall

IS 14885: Acceptance Tests (Clause 9.2)

1. Types of Acceptance Tests (Table 9.2.1):

2. Acceptance Tests for Lot (Table 9):

3. Sampling Size for Visual & Dimensional Checks (Table 10):

IS 14885: Marking and Identification Key Points

• Marking Method (Clause 10.1 & 10.2):

  • Marking must be permanent, legible, and impressed ≤ 0.2 mm depth.
  • Should not cause cracks or failures.
  • Must remain legible through storage, weathering, processing, and installation.

• Marking Location (Clause 10.3):

  • Pipes ≤ 32 mm nominal size: single marking strip.
  • Pipes > 32 mm nominal size: two marking strips on opposite sides.

• Marking Content (Clause 6.2 references):

  • Visual appearance
  • Marking information (manufacturer, size, standard, etc.)
  • Hydrostatic pressure resistance at 80°C for 165 h (plain and notched pipes ≥ 63 mm)
  • Pigment dispersion
  • Thermal stability (Oxidative Induction Time, OIT)

Summary Table: Marking Requirements

Important Notes:

• Marking depth ≤ 0.2 mm prevents structural weakening.
• Hydrostatic resistance at 80°C for 165 h confirms pipe durability.
• Marking must withstand environmental and handling stresses.

flowchart LR
    A[Pipe Size ≤ 32 mm] --> B[Single Marking Strip]
    A2[Pipe Size > 32 mm] --> B2[Two Marking Strips (Opposite Sides)]
    B & B2 --> C[Marking Depth ≤ 0.2 mm]
    C --> D[Include Manufacturer, Size, Standard, Pressure Rating]
    D --> E[Marking Legibility Maintained During Life]

This ensures pipe traceability and quality throughout service life.

Hydrostatic Pressure Creep Rupture Test (IS 14885)

Key Specifications (from Table 7, Clause 8.1 & 9.1.2):

Test Method (Annex A):

• Pipes are subjected to internal pressure at specified temperature & duration.
• No localized swelling, leakage, weeping, or bursting allowed.
• Samples: 3 per test, same pressure class and size.

Induced Stress Calculation (General Formula):

[ \sigma = \frac{P \times d}{2t} ] Where:

• (\sigma) = Induced hoop stress (MPa)
• (P) = Internal test pressure (MPa)
• (d) = Outside diameter of pipe (mm)
• (t) = Wall thickness (mm)

Summary:

• Hydrostatic creep rupture test ensures long-term pressure resistance.
• Tests at 20℃ for ≥100h and 80℃ for 1000h are mandatory.
• Induced stresses differ for PE-80 and PE-100 materials.
• Testing frequency varies from 2 to 4 years depending on test conditions.

flowchart TD
    A[Select 3 Samples] --> B[Apply Internal Pressure]
    B --> C{Temperature}
    C -->|20℃| D[Maintain Pressure for ≥100h]
    C -->|80℃| E[

IS 14885: Preparation of Longitudinally Notched Test Pieces – Key Points

1. Measurement Instruments (Clause 3.2)

• Use a micrometer accurate to 0.01 mm for width and thickness measurements.

2. Test Piece Dimensions (Clause J-4 & Fig. 6)

• Test Piece Type 1/2 for smaller diameter pipes.
• Key dimensions:
  • H = 60 ± 5 mm (initial clamp distance)
  • Other dimensions per Fig. 6: A, B, C, D, E, G (refer IS 14885 Fig. 6 for details).

3. Notch Machining (Clause B-3.5)

• Three additional notches machined circumferentially aligned.
• Ligament thickness of all notches identical.

4. Notch Depth Calculation (Clause B-4)

[ N = 0.5 \times \left( d_m - \sqrt{d_m^2 - 12} \right) + 0.866 \times L ]

• (N) = notch depth (mm)
• (d_m) = mean outside pipe diameter (mm)
• (L) = width of machined notch surface (mm)

5. Ligament Thickness

• Ligament thickness = wall thickness - notch depth
• Acceptance: ligament thickness between 0.78 to 0.82 times minimum specified wall thickness.

6. Milling Cutter Specifications (Clause 12.5)

• Cutter: 60° included angle 'V' cutter, 12.5 mm wide
• Cutting rate: 0.010 ± 0.002 mm/rev/tooth
• Example: 20 teeth, 700 rpm, 150 mm/min feed → 0.011 mm/rev/tooth
• Replace cutter after 100 m of notching.

7. Test Piece Length

• Free length = 10 × outside diameter (min 250 mm, max 750 mm)

Summary Table for Notch Depth Calculation

IS 14885 - Determination of Oxidation Induction Time (OIT)

Key Specifications (Clause 8.5 & Annex D)

• Minimum OIT: ≥ 20 minutes at 200 ± 0.1°C.
• Sample: Core drill samples from pipe wall; test pieces ~15 ± 0.5 mg discs from inner, outer, and mid-wall.
• Pans: Open aluminium pans sized to hold test pieces.

Test Procedure Summary

1. Gas flow: Nitrogen at 50 ml/min ±10% initially.
2. Heating: Ramp at 20°C/min to 200°C ± 0.1°C; hold isothermally.
3. Switch gas: After 5 min nitrogen, switch to oxygen at 50 ml/min ±10%.
4. Record thermogram: Plot temperature differential vs. time.
5. OIT determination: Time from oxygen introduction to intersection of baseline and tangent at max exotherm slope.

Interpretation (D-4)

• OIT = time (min) from oxygen start to oxidation exotherm onset.
• Average at least 5 measurements for thermal stability.

Test Report Must Include (D-5)

• Test piece ID
• Reference to IS 14885 method
• Individual OIT results (min)
• Test date

Diagram: OIT Determination Thermogram Concept

graph LR
A[Nitrogen Flow] --> B[Heat to 200°C]
B --> C[Hold Isothermal]
C --> D[Switch to Oxygen]
D --> E[Oxidation Exotherm]
E --> F[Draw Tangent at Max Slope]
E --> G[Extend Baseline]
F & G --> H[OIT = Intersection Time]

Additional Notes

• Anti-oxidant content ≤ 0.3% by mass (IS 2530).
• Follow instrument manufacturer instructions except where IS 14885 specifies otherwise.

This method ensures reliable assessment of polymer thermal stability via OIT.

IS 14885: Squeeze-Off Test Method (Clause 8.9 & Annex G)

Key Specifications:

• Pipe Size: Up to 400 mm diameter.
• Conditioning: Pipe conditioned at 0°C (+0, -5°C) for minimum 10 hours.
• Squeeze-Off: Within 10 min after conditioning, the pipe center is squeezed-off to the smaller separation value specified by the manufacturer or code.
• Squeeze-Off Duration: Maintain squeeze-off for at least 60 minutes.
• Test Temperature: Specimen tested at 80°C.
• Stress Levels:
  • PE-80: 4.6 MPa
  • PE-100: 5.5 MPa
• Test Duration: Must withstand stress for minimum 165 hours.

Mandrel Size:

• As per ASTM F 1041-92 (mandrel size corresponds to pipe diameter and squeeze-off level).

Minimum Squeeze-Off:

• 30% minimum squeeze-off (i.e., pipe diameter reduced by at least 30%).

Post-Test Requirements (Clause 8.8):

• Hydrostatic strength at 80°C for 165 h.
• Minimum elongation at break: 350%.
• Oxidative Induction Time (OIT) after weathering at 200°C.

Summary Table:

Process Flow (Mermaid Diagram):

flowchart TD
    A[Condition pipe at 0°C for 10 h] --> B[Squeeze-off pipe center to ≤ specified separation]
    B --> C[Maintain squeeze-off for 60 min]
    C -->

IS 14885: Testing Machines & Test Pieces - Key Points

1. Measuring Instruments (Clause 3.2)

• Use a micrometer accurate to 0.01 mm for measuring width and thickness of test pieces.

2. Test Pieces (Clause J-4 & Fig. 6)

• Type 1/2 Test Piece: For tensile properties of smaller diameter pipes.
• Key dimensions:
  • H (initial clamp distance): 60 ± 5 mm
  • Reference lines: A (length), B (width ends), C (calibrated length), D (calibrated width), E (radius), G (distance between lines).

3. Selection of Test Pieces (Table 12, Clause 4.2.2)

• Machined pieces: Thickness reduced to 10 mm; inside surface machined for first series.

4. Tensile Test Conditions (Clause 8.7.1)

• Temperature: 23 ± 1°C
• Speed:
  • Thickness < 5 mm: 100 mm/min ± 10%
  • Thickness > 5 mm: 25 mm/min
• Minimum requirements:
  • Tensile Yield Strength: 15 MPa
  • Elongation at Break: 350%

5. Acceptance Tests (Table 9, Clause 9.2.4.1)

Includes:

• Dimensional checks
• Visual appearance
• Marking info
• Hydrostatic pressure resistance (80°C, 165 h)
• Reversion, Density, MFR, Pigment dispersion, Thermal stability (OIT)
• Tensile test

Summary Diagram: Test Piece Dimensions

graph LR
A[Minimum Total Length] --> C[