Polyethene Fittings for use with Polyethylene Pipes for the Supply of Gaseous Fuels, Part 3: Electro Fusion Fittings

Scope of IS 15927 Part 3: Polyethylene Electro Fusion Fittings

• Application: Buried polyethylene electro fusion fittings with integral heating elements.
• Compatible Pipes: Polyethylene pipes per IS 14885 and fittings per Part 2 of IS 15927.
• Pipe Sizes: Nominal outside diameters from 16 mm to 315 mm.
• SDR Ratings: SDR 11 and SDR 17.6.
• Material Grades: PE 80 and PE 100.
• Pressure Ratings: 5.5 bar and 7 bar.
• Operating Temperature: -5°C to 40°C.
• Gaseous Fuel Supply: Designed for gas distribution systems.

Key Specifications:

Related Standards Referenced:

• IS 14885: Polyethylene pipes for gaseous fuels.
• IS 15927 Part 1 & 2: Socket and spigot fittings.
• IS 2530, IS 7328, IS 15430: Material and testing methods.

Hydrostatic Pressure Test (Clause 10.7)

Sampling Plan for Visual & Dimensional Requirements (Table 10)

| Lot Size (No. of Fittings) | First Sample Size | Acceptance No. | Rejection No

Here are key formulas, tables, and specifications from IS 15927 Part 3 relevant to fittings and pipes:

1. Wall Thickness Relationship (Clause 9.1, Table 2)

• E = fitting wall thickness
• en = pipe wall thickness

2. Hydrostatic Strength at 80°C (Table 7)

3. Pressure Drop Through Electro Fusion Tapping Tees (Table 8)

4. Acceptance Tests & Sampling (Tables 9, 10, 11)

• Visual, dimensional, MFR, density, carbon black content, thermal stability, hydrostatic resistance, etc.
• Sample sizes vary

IS 15927 Part 3: Key Definitions, Formulas & Tables Summary

1. Definitions (Clause 5.5 & General)

• Applies to buried polyethylene electrofusion fittings with integral heating elements.
• Suitable for polyethylene pipes per IS 14885.
• Covers sizes 16 mm to 315 mm, SDR 11 & 17.6, materials PE 80 and PE 100.
• Operating pressures: 5.5 bar and 7 bar.
• Operating temperature range: -5°C to 40°C.

2. Wall Thickness Relationship (Clause 9.1 & Table 2)

• (E) = fitting wall thickness
• (e_n) = pipe minimum wall thickness
• For fittings beyond 2L/3 distance from entrance face, (E \geq e_{min}) if same MRS.

3. Lot Definition & Sampling (Clause 11.1 & Tables 10 & 11)

• Lot = production from machine start until shutdown, max 170 h or 10,000 components.
• Sampling for visual/dimensional checks (Table 10) and hydraulic/thermal tests (Table 11) based on lot size.
• Acceptance/Rejection criteria specified for defective fittings.

4. Hydraulic Pressure Test (Clause 10.7 & Table 6)

IS 15927 Part 3: Electro Fusion Fittings - Key Dimensions & Specifications

1. Electro Fusion Socket Fittings (Clause 4.1, Fig. 1A)

• Key Dimensions:
  • ( d_s ) = Mean inside diameter of socket fusion zone
  • ( L_1 ) = Penetration depth (socket insertion depth)
  • ( L_2 ) = Apparent fusion zone length

2. Electro Fusion Tapping Tees (Clause 4.2, Fig. 1B)

• Key Dimensions:
  • ( h ) = Height of service pipe (axis main pipe to axis service pipe)
  • ( L ) = Width of tapping tee (axis main pipe to spigot mouth plane)
  • ( H ) = Height of tapping tee (top of main pipe to top of tapping tee)

3. Material Specifications (Clause 6.1)

• Polyethylene compound must comply with IS 14885 Table 2.
• Additives must be uniformly dispersed and not impair fusion.
• No visible water content.

4. Reducer Lengths (Table 4, Clause 9.3)

5. Spigot Outlet Dimensions for Tapping Tees (Table 5, Clause 9.4.1)

| Outer Diameter (mm) | Min Spigot Length (mm) | Min Spigot Wall Thickness | |----------------

IS 15927 Part 3: Material Requirements Key Points

1. Grade of Material (Clause 5.2 & 5.2.3)

• Raw material supplier must provide material grading.
• Material grading ensures traceability and compliance with specified properties.

2. Minimum Required Strength (MRS) (Clause 3.14)

• MRS = Minimum long-term hydrostatic strength (LTHS) in MPa.
• Used for design and classification of pipes and fittings.

3. Wall Thickness Relationship (Clause 9.1 & Table 2)

• ( E ) = Wall thickness of fitting
• ( e_n ) = Minimum wall thickness of pipe

4. Additional Wall Thickness Clause (9.1a)

• For fittings and pipes of the same MRS, fitting thickness ( E ) must be ≥ pipe thickness ( e_{Min} ) beyond ( \frac{2L}{3} ) from the fitting entrance face.

Summary Formula:

[ E \geq \begin{cases} e_{Min}, & \text{if same MRS and beyond } \frac{2L}{3} \ 0.8 \times e_n, & \text{PE80 pipe, PE100 fitting} \ \frac{e_n}{0.8}, & \text{PE100 pipe, PE80 fitting} \end{cases} ]

This ensures mechanical compatibility and long-term durability of pipe-fittings assemblies.

IS 15927 Part 3 – Marking and Identification of PE Fittings

Key Specifications (Clause 13.2 & 13.3)

• Marking must be permanent, legible without magnification, and not cause cracks or failures.
• Marking should remain legible under normal handling, storage, and installation.
• Marking methods must not affect fitting performance.

Required Marking Information (Clause 13.2):

Practical Notes:

• Use indelible ink, embossing, or engraving that does not weaken the fitting.
• Marking location should be accessible and visible after installation.

flowchart LR
    A[Fitting] --> B[Marking]
    B --> C{Legible?}
    C -->|Yes| D[Permanent & Non-damaging]
    C -->|No| E[Re-mark or Reject]

This ensures traceability, quality control, and safe installation per IS 15927-3.

IS 15927 Part 3: Jointing Procedure & Fusion Parameters

1. Jointing Time (Clause 8.5)

• Jointing time = Fusion time + Cooling time.
• Cooling time for fittings is per Annex C (manufacturer's declared max cooling time applies).

2. Appearance of the Joint (Clause 7.4)

• No melt exudation outside or into the inner cold zone (except fusion indicators).
• No significant voids or pipe collapse at fusion interface.

3. Geometrical Characteristics (Clause 9)

• Nominal diameters: 16 to 315 mm.
• Measurements after 24 hours of manufacture.
• Ovality ≤ 0.015 × nominal diameter (d).
• Inner cold zone of sockets:
  • For d ≤ 125 mm: ≥ (0.1d + 5) mm
  • For d > 125 mm: ≥ 0.1d mm

4. Coupler Dimensions (Table 3 & Fig 1A)

5. Joint Reheating (Clause 7.5)

• Fittings for SDR 11 & SDR 17.6 pipes allow one reheating cycle.
• Cooling to 27 ± 2°C before reheating.
• No deterioration allowed after reheating.

Summary Diagram: Socket Fitting Dimensions

flowchart LR
    A[Socket Fitting] --> B[Lead-in for assembly]
    A --> C[Inner Cold Zone]
    C --> D{Size d}
    D -->|d ≤ 125 mm| E[≥ 0.1d + 5 mm]
    D -->|d > 125 mm| F[≥ 0.1d mm]
    A --> G[Ovality ≤ 0.015d]
    A --> H[Minimum fusion length per Table 3]

IS 15927 Part 3: Heating Element & Electrical Characteristics

Key Points from Clauses:

• Heating Element Resistance (Clause 8.2):

  • Manufacturer declares nominal resistance per size/type.
  • Resistance tolerance ≤ ±10%.
  • Must prove joint quality at resistance extremes (Annex B method).

• Heating Element Definition (Clause 3.28):

  • Resistance wire heating fitting/pipe surface for fusion.

• Short/Open Circuit (Clause 8.3):

  • Design prevents short circuits & local overheating.
  • Protective coatings must not harm joint quality.

Typical Specifications:

Electrical Characteristics Formula:

[ R = \rho \frac{L}{A} ]

• (R) = Resistance (Ω)
• (\rho) = Resistivity of wire material (Ω·m)
• (L) = Length of heating element (m)
• (A) = Cross-sectional area (m²)

Fusion Joint Heating:

• Uniform heat distribution is critical.
• Avoid local overheating to maintain joint integrity.

flowchart LR
    A[Heating Element] --> B[Resistance Wire]
    B --> C[Heat Generation]
    C --> D[Surface Heating of Pipe/Fitting]
    D --> E[Fusion Joint Formation]
    B --> F[Resistance Measurement & Tolerance ±10%]
    F --> G[Joint Quality Validation (Annex B)]

For detailed testing methods, refer to Annex B of IS 15927 Part 3.

IS 15927 Part 3: Geometrical Characteristics Key Points

1. Overall Dimensions (Clause 9.4.1 & 4.2)

• Dimensions to specify:
  • h (height of outlet)
  • L (length of branch)
  • H (overall height)
• Outlet types:
  • Spigot type (dimensions per Table 5)
  • Electro fusion type (dimensions per Fig. 1B)

2. Nominal Diameters Covered (Clause 9)

• Sizes: 16, 20, 25, 32, 40, 50, 63, 75, 90, 110, 125, 140, 160, 180, 200, 225, 250, 280, 315 mm

3. Wall Thickness Relationship (Clause 9.1 & Table 2)

• E = fitting wall thickness
• en = pipe wall thickness
• For fittings and pipes of same MRS, fitting thickness ≥ minimum pipe thickness beyond 2L/3 from entrance face.

4. Jointing Time (Clause 8.5)

• Jointing time = fusion time + cooling time
• Cooling time per Annex C; max cooling time declared by manufacturer

Summary Diagram: Dimension Parameters of Tapping Tee

graph TD
    A[Overall Tapping Tee] --> B[h (Outlet Height)]
    A --> C[L (Branch Length)]
    A --> D[H (Overall Height)]
    B --> E[Spigot or Electro Fusion]

Note: Always measure dimensions after 24 hours of manufacture for accuracy.

IS 15927 Part 3: Performance Requirements & Tests Summary

1. Lot Definition & Sampling (Clause 11.1)

• Lot size: Max 170 hours production or 10,000 components.
• Sampling: Visual/dimensional samples per Table 10; hydraulic and thermal tests per Table 11.
• Acceptance criteria: Defect limits per Table 10 columns 6 (acceptance) & 7 (rejection).

2. Hydrostatic Pressure Test (Table 6 & 7)

• Hydrostatic strength at 80°C: Use Table 7 for stress vs minimum failure time correlation.
• Test medium: Water-in-water.
• End caps orientation: Not applicable.

3. Sampling Plans

• Visual & Dimensional (Table 10): Sample sizes vary by lot size (e.g., 13 to 200 fittings).
• Hydraulic & Thermal Tests (Table 11): 3 to 7 samples depending on lot size.

4. Other Key Tests (Table 9)

• Visual appearance, dimensions, melt flow rate, density, carbon black content/dispersion, thermal stability, fusion indicator operation, heating element resistance, decohesion, hydrostatic resistance, end reversion.

5. Pressure Drop for Electro Fusion Tapping Tees (Table 8)

• Max pressure drop ranges from 0.10 to 0.90 mbar depending on fitting and pipe size.

Key Formula: Hoop Stress for Hydrostatic Test

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

• ( \sigma_h )

IS 15927 Part 3 — Acceptance Tests Summary

1. Hydrostatic Resistance Test Parameters (Clause 10.7, Table 6)

2. Hydrostatic Strength at 80°C (Stress vs Minimum Failure Time) — Table 7

3. Sampling Plans

• Visual & Dimensional (Table 10): Sample sizes and acceptance/rejection criteria vary by lot size (e.g., up to 150 fittings: 13 samples, acceptance 0, rejection 2).
• **Hydraulic & Thermal Tests (Table 11

IS 15927 (Part 3): Type Tests Summary

Purpose (Clause 12.1)

• Type tests validate new compositions, techniques, or fitting sizes.
• Required only for changes in manufacturing or new fitting sizes.

Sample Selection (Clause 12.2)

• Random samples of same pressure class and size.
• Prepared as per Table 12 and tested as per Table 13.

Key Test Parameters & Acceptance Criteria (Table 6 - Hydraulic Pressure Test)

• Test medium: Water-in-water.
• Conditioning: 1h at 20°C, 12h at 80°C.
• End caps orientation: Not applicable.

Hydrostatic Strength at 80°C (Table 7)

Acceptance Tests (Table 9)

• Visual appearance, dimensions, melt flow rate, density, carbon black content & dispersion, pigment

IS 15927 Part 3: Marking and Packaging of Fittings

Marking Requirements (Clause 13.2 & 13.3)

Each fitting must be clearly marked with:

• Manufacturer's identity
• Nominal diameter and SDR rating
• Date of manufacture or batch number
• Fusion time (seconds)
• Cooling time (minutes)
• Material type (e.g., PE + Designation)

Marking must remain legible during handling, storage, and installation.

Packaging Specifications (Clause 14.3)

• Fittings individually packed in transparent polyethylene bags (minimum 75 µ thickness) to prevent deterioration.
• Outer packaging (cardboard boxes/cartons) must be suitable for stacked storage.
• Outer pack marked with:
  • Manufacturer’s identity
  • Nominal diameter & SDR rating
  • Date/batch number
  • Fitting type and quantity

Type Tests Summary (Table 13)

flowchart TD
    A[Individual Fitting] --> B[Polyethylene Bag (≥75µ)]
    B --> C[Outer Carton/Box]
    C --> D[Stacked Storage]
    C -->

IS 15927 Part 3: Packaging of Fittings (Clause 14.3 & Table 14)

• Individual packing: Each fitting must be packed in transparent polyethylene (or equivalent) bags with a minimum thickness of 75 microns to prevent deterioration.
• Outer packing: Use cardboard boxes or cartons suitable for stacked storage.
• Marking on outer pack: Include information as per Clause 13.2 (a), (b), (c), plus:
  • Fitting type
  • Quantity in the pack

Summary Table for Packaging of Fittings

Additional Notes:

• Packaging ensures protection against moisture, dust, and mechanical damage.
• Proper marking aids in identification and inventory management.

flowchart TD
    A[Fitting] --> B[Polyethylene Bag (≥75μ)]
    B --> C[Cardboard Box/Carton]
    C --> D[Stacked Storage]
    C --> E[Marking: Manufacturer Info, Fitting Type, Quantity]

This ensures fittings maintain quality during storage and transport per IS 15927 Part 3.

IS 15927 Part 3: Test Methods & Additional Requirements Summary

1. Hydrostatic Strength Test (Clause 10.7 & Table 6,7)

• Note: For 80°C hydrostatic tests, only brittle failure counts; ductile failure requires stress adjustment per Table 7.

2. Hydrostatic Strength Correlation at 80°C (Table 7)

3. Sampling & Acceptance (Clause 11.1, Tables 9-11)

• Lot Size: Max 170 h or 10,000 fittings.
• Sampling for Visual/Dimensional Tests (Table 10):

| Lot Size | Sample Size (1st/2nd) | Acceptance No. | Rejection