Thermoplastics Pipes and Fittings - Methods of Test

Scope of IS 12235 Part 1-19 (Flattening Test)

• Purpose: Specifies the flattening test method to assess the ductility and quality of pipes.
• Test Principle: Pipes are flattened between plates until failure or a specified deformation.
• Evaluation: Based on the number of blows and failures from test specimens.

Key Formulas (Clause 6.5)

Boundaries for failure regions in the test are calculated by:

[ S_{A/B} = np - 0.55 - \mu \sqrt{np(1-p)} ]

[ S_{B/C} = np - 0.55 + \mu \sqrt{np(1-p)} ]

Where:

• Use Table 3 for final evaluation.
• If blows > 124, refer to the graph for result assessment.

Important Notes

• Results must be rounded as per IS 2:1960.
• Test specimens: Minimum 5 specimens per Clause 6.5.
• The flattening test is part of a broader suite of tests (Parts 1-19 cover various tests).

Summary Table of Parts (for context)

flowchart LR
    A[Prepare 5 Test Specimens] --> B[Conduct Flattening Test]
    B --> C[Record Number of Blows and Failures]
    C --> D[Calculate Boundaries using formulas]
    D --> E[Evaluate Results using Table 3]
    E --> F{Blows > 124?}
    F -- Yes --> G[Refer to Graph for Assessment]
    F -- No --> H[Use Table 3 for Final Decision]

This scope covers the flatten

IS 12235 Part 1-19: Normative References Summary

This part of IS 12235 references multiple related standards, each addressing specific test methods or properties of pipes and materials. These referenced parts are normative, meaning compliance with them is mandatory when applying IS 12235.

Key Points:

• Referenced Parts & Topics (selection):

  • Part 1: Measurement of dimensions
  • Part 2: Vicat softening temperature
  • Part 9: Impact resistance at 0°C
  • Part 13: Tensile strength and elongation
  • Part 18: Ring stiffness
  • Part 19: Flattening test

• Rounding Off: Use IS 2:1960 rules for rounding test results, maintaining the same significant figures as specified.

• Test Evaluation Formula (for boundaries in blow count tests):

  [ S_{A/B} = np - 0.55 - \mu \sqrt{np(1-p)} ] [ S_{B/C} = np - 0.55 + \mu \sqrt{np(1-p)} ]

  Where:

  • ( n ) = number of blows
  • ( p = 0.10 ) (10% one-sided TIR)
  • ( \mu = 1.282 ) (standard normal deviate for 10% one-sided)
  • ( np ) = expected failures

• Test Specimens Table: Refer Clause 6.5, Table 5 for specimen details.

Diagram: Normative Reference Structure

graph TD
    A[IS 12235 Standard] --> B[Part 1: Dimensions]
    A --> C[Part 2: Vicat Softening Temp.]
    A --> D[Part 9: Impact Resistance]
    A --> E[Part 13: Tensile Strength]
    A --> F[Part 18: Ring Stiffness]
    A --> G[Part 19: Flattening Test]

Note: Always verify the latest editions of referenced standards for compliance.

IS 12235 Part 1-19: Terms and Definitions - Key Points

• The standard emphasizes rounding off final values per IS 2:1960, maintaining the same significant figures as specified.
• Definitions relate to various test methods for thermoplastic pipes and fittings, including:
  • Measurement of dimensions
  • Vicat softening temperature
  • Opacity, water composition effects
  • Mechanical and chemical resistance tests
  • Density/relative density (specific gravity)
  • Tensile strength and elongation
  • Ring stiffness and flattening tests

Important Formulas and Tables

1. Standard Deviation Calculation (Clause 8.4):

[ s = \sqrt{\frac{\sum x^2 - n \bar{x}^2}{n-1}} ]

• ( s ) = estimated standard deviation
• ( x ) = individual observation
• ( n ) = number of observations
• ( \bar{x} ) = arithmetic mean

2. Deflection Speeds for Compression Testing Machine (Table 1, Clause 4.1):

3. Boundary Calculation for Number of Failures (Clause 6.5):

[ SA/B = np - 0.55 - z \sqrt{np(1-p)} ]

[ SB/C = np - 0.55 + z \sqrt{np(1-p)} ]

• ( \mu = 1.282 ) (for 10% one-sided)
• ( p = 0.10 ) (Total Indicated Rate, TIR)
• ( n ) = number of blows

IS 12235 Part 1-19: Apparatus and Equipment Key Points

1. Calibration Requirements

• Temperature, pressure, and time measurement equipment must be calibrated for accuracy compatible with their scales.
• Calibration frequency should match the conditions of use.
• Use of master gauges for calibration is recommended (Clause 2.4.2).

2. Testing Machine Specifications (Clause 4.1)

• Use a compression testing machine with:
  • Force-measuring accuracy within ±2%.
  • Constant-rate-of-crosshead-movement type.
  • Sufficient force and travel to achieve specified deflection.

3. Deflection Speed Table (Table 1)

Summary Diagram of Calibration & Testing Flow

flowchart TD
    A[Start: Prepare Apparatus] --> B[Calibrate Temp, Pressure, Time]
    B --> C{Use Master Gauges?}
    C -- Yes --> D[Calibrate with Master Gauges]
    C -- No --> E[Calibrate with Standard Procedures]
    D --> F[Set Testing Machine]
    E --> F
    F --> G[Select Deflection Speed (Table 1)]
    G --> H[Perform Compression Test]
    H --> I[Record Results]

This ensures reliable, repeatable testing in compliance with IS 12235 standards.

IS 12235 Part 1-19: Test Specimens Summary

1. Dimensions of Test Specimens (Clause 4.1)

• Specimens must follow dimensions as per Fig. 1 (standard shape and size).
• If standard specimens cannot be used, a proportional specimen with constant dimension ratios is allowed (Clause 4.1.2).
• Adjust grip separation rate to maintain the same strain rate on the specimen’s middle parallel part.

2. Measurement Accuracy (Clause 4.4)

• Length: ±1 mm
• Internal diameter: ±0.5%
• Change in inside diameter (loading direction): ±0.1 mm or 1% of deflection, whichever is greater.

3. Deflection Range

• Deflection across specimen diameter: 1% to 4%

4. Grip Distance (IS 12235 Part 13)

• Initial distance between grips: 115 ± 5 mm

5. Statistical Evaluation of Results (Clause 6.5)

• Number of blows (n), failures, and probability (p = 0.10) used to evaluate results.
• Boundaries between regions calculated by:

[ SA/B = np - 0.55 - z \sqrt{np(1-p)} ] [ SB/C = np - 0.55 + z \sqrt{np(1-p)} ]

Where:

• ( z = 1.282 ) (for 10% one-sided confidence)
• ( p = 0.10 ) (Total Indicated Rating, TIR)
• ( n = ) number of blows

Diagram: Specimen Dimensions & Measurement

graph LR
A[Grip 1] -- 115±5 mm --> B[Parallel Middle Part] -- 115±5 mm --> C[Grip 2]
B -- Internal Diameter --> D[Measured ±0.5%]
B -- Length --> E[Measured ±1 mm]
B -- Deflection --> F[Measured ±0.1 mm or 1%]

Use these guidelines to ensure test specimens conform to IS 12235 standards for reliable testing and evaluation.

IS 12235 Part 1-19: Conditioning of Specimens

Key Specifications (Clauses 7.1 & 7.4, Table 4)

• Conditioning Temperature: 0 ± 1ºC
• Conditioning Medium: Liquid bath or air
• Conditioning Period (Table 4):

• If the specimen exceeds the allowed interval before testing, re-condition for minimum 5 min (Clause 7.4).

Additional Conditioning Guidelines

• If no specific directive, condition specimens at 27 ± 2ºC and 65 ± 5% RH for 24 h (Clause 6).
• Pre-test conditioning: 5 min at ~50ºC below expected VST (Clause 4.2).

Summary Flowchart

flowchart TD
    A[Specimen Preparation] --> B{Conditioning Medium?}
    B -->|Liquid Bath| C[Condition at 0±1ºC]
    B -->|Air| C
    C --> D{Wall Thickness (e) mm}
    D -->|<8.6| E[15 min (Liquid) / 60 min (Air)]
    D -->|8.6-14.1| F[30 min (Liquid) / 120 min (Air)]
    D -->|>14.1| G[60 min (Liquid) / 240 min (Air)]
    E --> H[Test Specimen]
    F --> H
    G --> H
    H --> I{Interval exceeded before test?}
    I -->|Yes| J[Re-condition 5 min]
    I -->|No| K[Proceed to Test]

Use these conditioning times and temperatures strictly to ensure test validity and reproducibility.

IS 12235 Part 1-19: Test Methods - Key Formulas, Tables & Specs

1. Rounding Off (IS 2:1960)

• Final test values are rounded to the same significant figures as specified.

2. Test Specimens & Evaluation (Clause 6.5)

• Number of blows (n), failures, and boundaries between regions calculated by:

[ SA/B = np - 0.55 - z \sqrt{np(1-p)} ]

Where:

• ( p = 0.10 ) (10% one-sided TIR)
• ( z = 1.282 ) (standard normal deviate)
• ( n = ) number of blows

3. Standard Deviation Calculation (Clause 8.4)

[ s = \sqrt{\frac{\sum x^2 - n \bar{x}^2}{n-1}} ]

• ( s ) = standard deviation
• ( x ) = observation
• ( n ) = number of observations
• ( \bar{x} ) = mean

4. Tensile Test Reporting (Part 13)

• Include: material ID, conditioning, specimen prep, test speed, tensile stress at yield & break, elongation %, standard deviations, test date.

5. Deflection Speed for Compression Test (Clause 4.1, Table 1)

6. Density / Relative Density (Part 14)

• Determined by weighing specimen in air and water (displacement principle).

Determination of Ring Stiffness (IS 12235 Part 1-19)

Key Definition (Clause 3.6)

• Ring Stiffness, S = (\frac{\text{Force per unit length}}{\text{Deflection}}) × factor
• Units: kN/m²

Procedure Highlights

• Plot force vs. deflection curve (Clause 7.6 & Annex A).
• If zero point is uncertain, extrapolate initial linear portion to intersect horizontal axis as origin (Fig. 5).
• Calculate ring stiffness for three specimens: (S_a, S_b, S_c).

Formula (from ISO 9969:1994)

[ S = \frac{F}{\Delta D} \times k ]

Where:

• (F) = force per unit length (kN/m)
• (\Delta D) = deflection (m)
• (k) = correction factor (typically 1 for direct ratio)

Typical Calculation Steps:

1. Measure force (F) at prescribed deflection (\Delta D) (usually 5% of diameter).
2. Calculate (S) for each specimen.
3. Average (S_a, S_b, S_c) for final ring stiffness.

Summary Table

graph LR
A[Apply Load F per unit length] --> B[Measure Deflection ΔD]
B --> C[Plot Force vs Deflection Curve]
C --> D{Zero Point Accurate?}
D -- No --> E[Extrapolate Initial Linear Portion]
E --> F[Determine Origin (0,0)]
D -- Yes --> F
F --> G[Calculate Ring Stiffness S = F/ΔD × k]

For detailed procedure, refer to Annex A of IS 12235 and ISO 9969:1994 for

Hydrostatic Pressure Testing per IS 12235 Part 1-19

Key Formula for Test Pressure (Clause 5.2.2)

[ \boxed{ p = \frac{2 \sigma_{h} e_{min}}{d_{em} - e_{min}} } ]

• p = Test pressure (MPa)
• σₕ = Hoop stress to be induced (MPa)
• dₑₘ = Measured mean outside diameter (mm)
• eₘᵢₙ = Measured minimum wall thickness (mm)

Conditioning of Test Specimens (Clause 6 & Table 1)

• Specimens must be clean, dry, and filled with water (preheated ≤ 5℃ above test temp).
• Immerse specimens in water bath for the specified conditioning period.
• Testing should not occur within 24 hours of pipe production, except for manufacturing checks.

Pressurizing Equipment Requirements (Clause 3.4)

• Apply pressure gradually and smoothly.
• Maintain pressure constant within ±7% tolerance.
• Prefer individual specimen pressurization or use isolation valves to prevent failure interference.

flowchart LR
    A[Prepare Specimen] --> B[Clean & Dry]
    B --> C[Fill with Water (≤5℃ above test temp)]
    C --> D[Immerse in Water Bath]
    D --> E[Conditioning Period per Table 1]
    E --> F[Apply Hydrostatic Pressure Gradually]
    F --> G[Maintain Pressure ±7%]
    G --> H[Observe for Failure]

This ensures accurate and reliable hydrostatic testing as per IS 12235 standards.

Leak-tightness Testing of Elastomeric Sealing Ring Type Socket Joints
(IS 12235 Part 8/Sec 2: 2004 & related clauses)

Key Specifications:

• Test Specimen: PVC-U pipe mounted into PVC-U socket or ductile iron socket with elastomeric sealing ring.
• Test Conditions:
  • Positive internal pressure
  • Angular deflection applied to the pipe in the socket
  • Specified temperature range (per referenced standard)
• Test Duration: As per standard; equipment failure protocols in Clause 7.4 allow continuation under controlled conditions.

Assessment of Results (Clause 8):

• Failure Types:
  • Brittle failure: No visible plastic deformation in failure zone.
  • Ductile failure: Visible plastic deformation (bulging/stretching) without magnification.
• Failure Location: Breaks less than mean outside diameter (d_em) distance from end cap are ignored and test repeated.

Testing Notes:

• Pressure monitored for leakage during angular deflection.
• Test pressure and number of specimens as per referenced standards.

Typical Test Parameters (to be set by referencing standard):

Important Formula:

• Mean Outside Diameter (d_em):
  Used to evaluate failure location distance from end cap.

flowchart TD
    A[Test Specimen: Pipe + Socket] --> B[Apply Internal Pressure]
    B --> C[Apply Angular Deflection]
    C --> D[Monitor for Leakage]
    D --> E{Failure?}
    E -- No --> F[Pass]
    E -- Yes --> G[Check Failure Type & Location]
    G --> H{Distance from End Cap < d_em?}
    H -- Yes --> I[Ignore & Repeat Test]
    H -- No --> J[Record Failure Type: Brittle or Ductile]

**

Impact Resistance Testing (IS 12235 Part 1-19)

Test Setup:

• Striker mass and shape specified.
• Striker drops from adjustable height up to 2 m ± 10 mm above specimen.
• Specimens: length 200 ± 10 mm, ends square and undamaged.
• For pipe OD > 40 mm, multiple impact points along circumference; for ≤ 40 mm, only one blow per specimen.

Key Formulas for Statistical Evaluation (Clause 6.5)

• Number of blows: ( n )
• True Impact Rate (TIR): ( p = 0.10 ) (max acceptable failure rate)
• Standard normal deviate: ( \mu = 1.282 ) (for 10% one-sided confidence)

Boundaries for failures ( SA/B ) and ( SB/C ):

[ SA/B = np - 0.55 - \mu \sqrt{np(1-p)} ] [ SB/C = np - 0.55 + \mu \sqrt{np(1-p)} ]

Where:

• ( n ) = total blows,
• ( p ) = TIR (0.10),
• ( \mu ) = 1.282 (z-value for 90% confidence).

Failure Definition (Clause 2.2)

• Failure: Shattering, cracks, or splits visible to naked eye.
• Not failure: Indentation only.

Summary Table for Number of Blows (Clause 6)

Test Evaluation

• If failures exceed limits from formula, batch fails.
• If blows > 124, use graph (not provided here) for assessment.
• Max allowable TIR = 10%.

flowchart LR
    A[Select Specimen] --> B[Prepare Specimen (200±10 mm)]
    B --> C[Mark Impact Points (if OD > 40 mm)]
    C --> D[Set Striker Height (up to 2 m)]
    D --> E[Drop Striker & Count Blows]
    E --> F{Inspect for Failure

Opacity Measurement as per IS 12235 (Part 3): 2004

Key Formula (Clause 2.5)

[ \text{Percentage of Light} = \frac{D}{D_M} \times 100 ]

• D = Maximum deviation produced by the light flux passing through the test specimen
• D_M = Maximum deflection produced directly by the light from the source

Procedure:

• Take three measurements per test specimen.
• Calculate the mean of these three.
• Perform this for four test specimens.
• The highest mean value among the four is the opacity value.

Calibration (Clause 2.4.1.3)

• Use a standard gray glass filter with calibrated absorption ≈ 0.2%.
• Desired accuracy: ±0.02% in the 0 to 0.2% range.

Summary Table

flowchart LR
    A[Light Source] --> B[Test Specimen]
    B -->|Light deviation D| C[Detector]
    A -->|Max deflection D_M| C
    C --> D[Calculate % Light = (D/D_M)*100]
    D --> E[Repeat 3 times per specimen]
    E --> F[Mean per specimen]
    F --> G[Repeat for 4 specimens]
    G --> H[Select highest mean as opacity]

This method ensures consistent and precise opacity measurement of plastic pipes and fittings.

Determination of Ash Content as per IS 12235 (Part 1-19) and related clauses:

Key Specifications:

• Sample mass (mo): 2 g to 5 g (Clause 5.1.2)
• Calcination temperature: 850 ± 50°C (Clause 5.2.4)
• Residue: White ash after complete combustion
• Number of determinations: Minimum 2; results must agree within ±10% of mean (Clause 6)

Formula for Ash Content (% by mass):

[ \text{Ash Content} = \left(\frac{m_1}{m_0}\right) \times 100 ]

• (m_0) = mass of test portion (g)
• (m_1) = mass of ash obtained after calcination (g)

Procedure Summary:

1. Weigh sample (2-5 g) in a crucible.
2. Slowly heat to avoid ash loss; burn until no smoke evolves.
3. Place crucible in muffle furnace at 850 ± 50°C until constant mass.
4. Cool and weigh ash residue.
5. Repeat twice; calculate mean ash content.
6. Report all details including method (A: ash, B: sulphated ash), sample ID, individual and mean results.

Reporting Requirements:

• Reference to IS 12235 standard
• Sample details (type, code, trade name)
• Method used (ash or sulphated ash)
• Masses of test portions
• Individual and mean ash content
• Note if constant mass not reached after 3 hours

flowchart TD
    A[Weigh Sample (2-5g)] --> B[Slow Heating to Burn Sample]
    B --> C[Place in Muffle Furnace (850 ± 50°C)]
    C --> D[Calcine to Constant Mass]
    D --> E[Cool & Weigh Ash Residue]
    E --> F[Calculate Ash Content %]
    F --> G{Repeat 2 Times}
    G -->|Results within ±10%| H[Report Mean Ash Content]
    G -->|Not within ±10%| B

This method ensures precise ash content determination critical for material characterization and quality control.

Key Specifications & Formulas for Determination of Vinyl Chloride Monomer (VCM) Content (IS 12235 Part 15:2004)

1. Sample Preparation & Analysis

• Solvent: NN-dimethylacetamide (DMA)
• Equilibration Temperature: 45°C in sealed vial
• Analysis: Gas Chromatography (GC) of headspace vapor

2. Calibration & Standards

• Pure VCM (>99.5%) stored in 500 ml stainless steel cylinder.
• Calibration standards prepared with VCM in air or nitrogen (100 µl/l to 1000 µl/l).
• Identification confirmed by mass spectrometry.

3. Detection Limits & Accuracy

• Detection limit: ~0.3 mg/kg (pipe wall sections)
• Possible error:
  • ±25% for <0.05 mg/kg
  • ±6 to 10% for >0.05 mg/kg

4. Reporting

• VCM content to nearest 0.5 mg/kg
• Include pipe/fitting type, size, configuration

5. Gas Chromatographic Columns (Annex A)

IS 12235 Part 1-19: Test Reporting and Documentation - Key Points

1. Test Specimens & Evaluation (Clause 6.5)

• Number of specimens: 5 per test.
• Evaluation based on Table 3 (not provided here).
• For number of blows (n) > 124, use graph for result assessment.
• Boundary equations between regions:

[ S_{A/B} = np - 0.55 - \mu \sqrt{np(1-p)} ] [ S_{B/C} = np - 0.55 - p \sqrt{np(1-p)} ]

Where:

• ( \mu = 1.282 ) (10% one-sided confidence)
• ( p = 0.10 ) (Tolerance Interval Ratio, TIR)
• ( n = ) number of blows

2. Arithmetic Mean (Clause 8.3)

• Calculate mean of 5 specimens.
• Report to 3 significant figures (except elongation: 2 significant figures).

3. Standard Deviation (Clause 8.4)

[ s = \sqrt{\frac{\sum x^2 - n\bar{x}^2}{n-1}} ]

• ( s ) = estimated standard deviation
• ( x ) = single observation
• ( n ) = number of observations
• ( \bar{x} ) = arithmetic mean
• Report to 2 significant figures

4. Test Report Requirements (Clause 2.6 & IS 12235 Part 13)

Include:

• Material ID (type, source, manufacturer)
• Conditioning procedure
• Specimen preparation method
• Atmospheric conditions
• Number of specimens tested
• Testing speed
• Average tensile stress at yield & max load/break
• Average elongation at yield/break
• Standard deviations
• Date of test

5. Density Determination (IS 12235 Part 14)

• Use displacement method: weigh specimen in air & water.
• Follow IS 13360 (Part 3/ Sec 1) for atmospheric conditions.

flowchart LR
    A[Test Specimens (5)] --> B[Perform Tests]