Methods of sampling of steel for prestressed and reinforced concrete, Part 1: Prestressing steel

IS 10790 Part 1 - Scope Key Points

1. Scope Overview (Clause 2.0 & 3.1)

• Ensures conformity of materials to specifications via process inspection.
• Manufacturer performs regular tests during production for quality control.
• Purchaser inspects to verify specification compliance.

2. Process Inspection Levels (Table 1, Clause 3.1)

3. Sampling & Acceptance (Table 2, Clause 4.3.1.2)

Summary:

• Process control is critical at each manufacturing stage.
• Sampling size and acceptance numbers vary with lot size and inspection type.
• Visual and dimensional/weight inspections have separate acceptance criteria.

flowchart LR
    A[Raw Material Inspection

IS 10790 Part 1: Key Definitions, Sampling & Testing Specifications

Definitions (Clause 2.0 & 3.3)

• Lot: A batch of manufactured items considered for inspection.
• Test Certificate: Issued by manufacturer based on process inspection data confirming conformity.
• Statistical Data Presentation:
  • Part 1: Tabulation and summarization.
  • Part 2: Diagrammatic representation.
• Statistical Tests: t-test, Normal, F-test, Chi-square (χ²), regression, correlation, and ANOVA.

Sampling & Acceptance (Clause 4.3.1.2 - Table 2)

Tensile & Mechanical Testing (Clause 4.3.2.2)

• Number of specimens for tensile strength, proof stress, ductility, and elongation per Table 3 (not provided here).
• Specimens taken from items passing visual, dimensional, and weight tests.

Summary:

• Use Table 2 for sampling size and acceptance criteria.
• Statistical tests ensure lot conformity.
• Test certificates validate compliance.

flowchart TD
    A[Manufactured Lot] --> B[Visual, Dimensional & Weight Inspection]
    B -->|Pass| C[Prepare Test Specimens]
    C --> D[Tensile & Mechanical Tests]
    D --> E{Conformity?}
    E -->|Yes|

IS 10790 Part 1: Process Inspection Key Points

Objective

• Purchaser inspection: Ensure material conforms to specifications.
• Manufacturer inspection: Ensure conformity and maintain uniform quality during production.

Process Inspection Levels (Clause 3.1, Table 1)

Acceptable Quality Level (AQL) (Clause 2.11)

• Maximum % defective acceptable as process average during sampling inspection.

Statistical Quality Control (Clause 3.3)

• Manufacturer issues test certificates based on process inspection data.
• Use statistical methods (t-test, F-test, chi-square, regression, ANOVA) for data analysis and control.

flowchart TD
    A[Raw Material] -->|Test 1 coil/heat| B[After Patenting]
    B -->|Test 2 coils/batch| C[Before Final Pass]
    C -->|Dimensional check every 4 hrs| D[After Final Pass]
    D -->|Dimensional + UTS each coil| E[After Stress Relieving]
    E -->|Every 5th coil: mechanical tests| F[Monthly coil: relaxation & corrosion tests]

This ensures continuous quality monitoring and conformity to IS 10790 requirements.

IS 10790 Part 1 — Lot Inspection Key Points

Sampling & Acceptance Criteria (Clause 4.3.1.3 & Table 2)

Procedure:

• Step 1: Inspect random samples for visual defects per col 2 & 3.
• Step 2: If accepted, inspect for dimensional and weight requirements per col 4 & 5.
• Step 3: If defectives ≤ acceptance number, lot is accepted; else rejected.
• Defectives are counted per sample size, not the entire lot.

Additional Notes:

• Samples for dimensional/weight inspection are taken from visually accepted items.
• Manufacturer may issue test certificates based on process inspection data (Clause 3.3).
• If visual inspection fails, entire lot may be inspected and defectives removed by mutual agreement.

This method ensures statistical quality control and compliance with specifications.

IS 10790 Part 1: Sampling Scale & Criteria for Conformity

1. Sampling & Acceptance for Visual, Dimensional, and Weight Characteristics (Clause 4.3.1.2)

• Visual conformity checked first.
• Then dimensional & weight samples taken from visually conforming items.
• Lot accepted if defectives ≤ acceptance number.

2. Sampling for Physical and Chemical Tests (Clause 4.3.2.2)

Summary Flowchart

flowchart TD
    A[Start: Lot Received] --> B[Visual Inspection]
    B -->|Defectives ≤ Acceptance Number| C[Dimensional & Weight Sampling]
    B -->|Defectives > Acceptance Number| D[Lot Rejected]
    C -->|Defectives ≤ Acceptance Number| E[Lot Accepted]
    C -->|Defectives > Acceptance Number| D

Use these tables and criteria for sampling and acceptance decisions per IS 10790 Part 1 Clause 4.3.

Selection and Examination of Samples as per IS 10790 Part 1 (1984):

1. Sampling for Visual, Dimensional & Weight Characteristics (Clause 4.3.1.1 & 4.3.1.2)

• Samples must be randomly selected (refer IS:4905-1968 for random sampling methods).
• Associated AQL (Acceptable Quality Level) = 2.5% for larger lots.

2. Sampling for Physical and Chemical Tests (Clause 4.3.2.2)

Summary:

• Use Table 2 for visual, dimensional, and weight checks.
• Use Table 3 for physical and chemical testing.
• Ensure random selection to maintain statistical validity.
• Follow AQL 2.5% for acceptance criteria.

This systematic sampling ensures quality control and compliance with IS standards.

IS 10790 Part 1 — Visual, Dimensional & Weight Characteristics

Key Specifications (Clause 4.3.1)

• Inspection is done in two stages:
  1. Visual characteristics (freedom from defects)
  2. Dimensional & weight requirements (after passing visual inspection)

Sampling & Acceptance Criteria (Table 2)

Procedure Summary

• Select sample as per lot size (col 1 & 2).
• Inspect for visual defects; if defectives ≤ acceptance number (col 3), accept lot.
• From visually accepted items, select sample for dimensional & weight checks (col 4).
• If defectives ≤ acceptance number (col 5), lot conforms; else reject.
• If lot fails visual inspection, full lot may be inspected and defective items removed by mutual agreement.

Visual Flow Diagram

flowchart TD
    A[Select Sample for Visual Inspection] --> B{Defectives ≤ Acceptance Number?}
    B -- Yes --> C[Select Sample for Dimensional & Weight Inspection]
    B -- No --> D[Inspect Full Lot and Remove Defectives (if agreed)]
    C --> E{Defectives ≤ Acceptance Number?}
    E -- Yes --> F[Lot Accepted]
    E -- No --> G[Lot Rejected]

This ensures quality control by statistically verifying visual and

IS 10790 Part 1: Visual Characteristics Inspection

Key Points from Clause 4.3.1.2 and Table 2

• Inspection: Items selected per Table 2 (cols 1 & 2) must be visually inspected for defects.
• Acceptance: If defectives ≤ acceptance number (col 3), the lot passes.
• Reinspection: If failed, entire lot may be inspected and defectives removed by mutual agreement.

Sampling & Acceptance Criteria (Table 2 excerpt)

Procedure Summary

1. Select sample size for visual inspection based on lot size.
2. Count defectives; if ≤ acceptance number, lot passes visual inspection.
3. If passed, select sample for dimensional and weight inspection.
4. Apply acceptance criteria similarly for dimensional and weight defects.

flowchart TD
    A[Start: Lot Received] --> B{Select Sample Size<br>from Table 2}
    B --> C[Visual Inspection]
    C --> D{Defectives ≤ Acceptance Number?}
    D -- Yes --> E[Dimensional & Weight Inspection]
    D -- No --> F[Reject or 100% Inspection]
    E --> G{Defectives ≤ Acceptance Number?}
    G -- Yes --> H[Lot Accepted]
    G -- No --> F

This ensures quality

IS 10790 Part 1: Physical Characteristics Testing

Sampling Scale for Physical & Chemical Tests (Clause 4.3.2.2)

Sampling & Acceptance for Visual, Dimensional & Weight Characteristics (Clause 4.3.1.2)

Key Notes:

• Acceptance Number: Maximum allowable defective samples for acceptance.
• Sampling ensures representative testing for quality control.
• Use this scale for planning physical and chemical tests per lot size.

flowchart LR
    A[Lot Size] --> B{Select Number of Samples}
    B -->|Up to 50| C[2 Samples]
    B -->|51 to 150| D[3 Samples]
    B -->|151 to 500| E[5 Samples]
    B -->|501 and above| F[8 Samples]

    A --> G{Visual & Dimensional Tests}
    G --> H[Refer Table for Sample Size & Acceptance Number]

This concise guide ensures compliance with IS 10790 Part 1 for physical testing sampling.

IS 10790 Part 1: Statistical Evaluation & Record Keeping

Key Clauses & Specifications:

• Clause 3.2.2:

  • Inspection/testing results must be recorded and statistically evaluated.
  • Records should be preserved for 2 to 3 years for future reference.

• Clause 3.3:

  • Manufacturer may issue a test certificate based on process inspection data to confirm lot conformity.

• Clause 4.3.1.2 - Sampling & Acceptance (Table 2):

Statistical Tests Referenced:

• t-test, Normal test, F-test (Part 1)
• Chi-square (χ²) test (Part 2)
• Regression and correlation methods
• Analysis of variance (ANOVA)

Summary:

• Use sampling plans from Table 2 for visual and dimensional/weight inspections.
• Perform statistical evaluation of inspection data using standard tests.
• Maintain records for 2-3 years for traceability.
• Issue test certificates based on statistical conformity.

flowchart LR
  A[Inspection & Testing] --> B[Record Data]
  B --> C[Statistical Evaluation]
  C --> D{Conforms to Spec?}
  D -->|Yes| E[Issue Test Certificate]
  D -->|No| F[

Handling Non-Conforming Lots as per IS 10790 Part 1

Key Points from Clauses 4.3.1.3 & 4.3.1.2:

• Step 1: Inspect the lot visually.
• Step 2: If visually satisfactory, randomly sample for dimensional and weight checks.
• Sampling size and acceptance criteria depend on the lot size (see Table 2).
• If defectives ≤ acceptance number, lot is conforming; otherwise, non-conforming.

Table 2: Sampling and Acceptance Numbers

Summary of Procedure:

flowchart TD
    A[Start: Lot Inspection] --> B{Visual Inspection}
    B -- Pass --> C[Random Sampling for Dimensional & Weight]
    B -- Fail --> D[Lot Non-Conforming]
    C --> E{Number of Defectives ≤ Acceptance No.?}
    E -- Yes --> F[Lot Conforming]
    E -- No --> D

Note:

• Lot = material batch of same grade, size, and processing conditions (Clause 4.1).
• Sampling is random and from visually conforming items only.

This method ensures statistically controlled quality assurance during production.

IS 10790 Part 1: Reporting and Documentation Key Points

1. Test Certificate Issuance (Clause 3.3)

• Manufacturer issues test certificate based on process inspection data.
• Certificate confirms lot conformity to specification requirements.

2. Statistical Data Presentation

• Part 1: Tabulation and summarization of data.
• Part 2: Diagrammatic representation (control charts, histograms).
• Statistical tests include:
  • t-test, Normal test, F-test (Part 1)
  • Chi-square (χ²) test (Part 2)
  • Regression, correlation, and analysis of variance (ANOVA).

3. Sampling and Acceptance (Clause 4.3.1.2, Table 2)

4. Rounding Off Results

• Follow IS 2-1960 for rounding test or analysis results.

5. Control Charts

• Refer to Part 2 for control charts for attributes and defect counts.

flowchart TD
    A[Inspection Data] --> B[Test Certificate]
    B --> C[Reporting]
    C --> D[Tabulation & Summarization]
    C --> E[Diagrammatic Representation]
    D --> F[Statistical Tests: t, F, Normal]
    E --> G[Control Charts, χ² Test]
    F --> H[Regression & AN