General Requirements for Enamelled Cast Iron Sanitary Appliances
1973 Edition

IS 772 Scope - Essential Specifications and Tables

• Scope Description (Clause 2.0):
  Establishes terminology and rounding rules referencing IS:2-1960 for test outcomes.

• Dimensional Requirements and Tolerances (Clause 1.2):

  • Appliances must conform to designated dimensions with a tolerance of ±3%
  • Exceptions apply for dimensions marked as maximum, minimum, or approximate

• Sampling and Acceptance Protocols (Clause 6.2, Table 1):
  Defines sample sizes and allowable defect counts based on lot quantities:

• Rounding Procedures (Clause 0.3):
  Test results are rounded as per IS:2-1960, preserving the number of significant digits specified.

This section ensures consistency in dimensional accuracy and quality control.

IS 772 - Definitions and Rounding Rules

1. Terminology (Clause 2.0):

   • Sets forth definitions relevant to the standard's application.
   • Numerical values are rounded following IS:2-1960, maintaining precision.

2. Rounding Off (Clause 0.3):

   • Final analytical and test values are rounded consistent with IS:2-1960 standards.

3. Dimensional Tolerances (Clause 1.2):

   • Dimensions must stay within ±3% tolerance unless noted otherwise.

4. Sampling Table (Clause 6.2):

This table guides quality acceptance thresholds for lot sampling.

IS 772: Materials and Production Standards

1. Allowed Surface Defects in Enamelled Cast Iron (Clause 4.4.1)

2. Sampling and Acceptance (Clause 6.2, Table 1)

• Lot acceptance: A batch is accepted if the number of defectives does not exceed the limits for warpage and resistance tests.

3. Manufacturing Inspection

• Appliances are to be examined through an inspection window to assess surface quality.

IS 772: General Mandates, Formulas, and Test Specifications

1. Sampling and Acceptance Criteria (Clauses 6.2 & 6.7)

• Acceptance: The lot is approved if defectives are within allowed limits.

2. Rounding Rules (Clause 0.3)

• Test results are rounded as per the IS:2-1960 standard, retaining the original number of significant figures.

3. Testing Requirements (Clauses 6.1 & A-6.1)

• Test specimens must fulfill the criteria in Clause 5.3.
• Tests include warpage, acid and alkali resistance, and abrasion resistance.

Summary:

• Employ sample sizes and acceptance limits from Table 1.
• Reject lots exceeding permissible defect numbers.
• Apply IS rounding protocols for test data.
• Testing ensures compliance with quality standards.

IS 772: Specifications for Base Metal Thickness

• Minimum Thickness (Clause 4.1):
  The cast iron base must be no less than 6.5 mm thick.

• Material Quality (Clause 3.1):

  • Must be cast iron complying with Grade 15 as per IS:210-1970.
  • The base should be a single piece, structurally sound, correctly shaped, and free from porosity or flaws.

• Inspection Guidelines (Clause 6.4):
  Check for:

  • Base material compliance.
  • Visual surface defects.
  • Base metal thickness.
  • Dimensional accuracy.
  • Enamel coating thickness.

• Enamel Coating Thickness (Clause 4.5):
  Enamel applied on flat surfaces must have a minimum thickness of 0.5 mm, measured via electromagnetic methods.

Specification Summary:

This ensures mechanical strength and longevity.

IS 772: Warpage Control and Evaluation

Warpage Tolerances (Clause 4.3):

• For edges positioned against walls, floors, or roll rims: maximum warpage is 5.0 mm per metre.
• For all other edges: allowable warpage up to 7.5 mm per metre.

Testing Method (Clause 4.3.1):

• Place the appliance on a flat, level surface.
• Use a feeler gauge matching the allowed warpage thickness.
• If the gauge slides easily beneath the appliance, warpage exceeds the allowed limit.
• If the item rocks on two opposite corners:
  • Insert a feeler gauge beneath the lower corner and hold it firmly.
  • Check if a second gauge can be inserted elsewhere.
  • If not, warpage is acceptable.

Sampling and Acceptance (Clauses 6.6 & 6.7):

• Tests conducted on sub-samples as per Table 1.
• Lot acceptance depends on the number of defective units not exceeding specified limits.

Warpage Limits Table:

Ensures proper fit and function in installation.

IS 772: Surface Finish and Defect Standards for Enamelled Cast Iron

Defect Acceptance (Clause 4.4.1):

Abrasion Testing (Clause 5.1.1):

• Abrasive powder particle size between 212 and 250 microns.
• Powder spread over approx. 1.6 cm² enamel surface.
• Covered with chamois leather, weighted with 1 kg over the same area.
• Weight moved 10 to 12 times over a 13 mm distance.
• Surface examined under 8x magnification for scratches; none allowed.

Sampling and Acceptance (Clause 6.2, Table 1):

Ensures enamel durability and aesthetic quality.

IS 772: Permitted Surface Defects on Enamelled Cast Iron (Clause 4.4.1)

Sampling and Acceptance (Clause 6.2, Table 1):

This maintains surface quality and service life.

IS 772: Enamel Thickness Requirements and Abrasion Resistance Tests

Enamel Thickness (Clause 4.5):

• Minimum enamel thickness on flat surfaces must be at least 0.5 mm.
• Thickness is measured using an electromagnetic thickness gauge.

Abrasion Resistance Test (Clauses 5.1 & 5.1.1):

• Enamel must withstand abrasion by powder number 5 (apatite) on the Mohs scale.
• Particle size of powder: passes 250-micron sieve, retained on 212-micron sieve.
• Test procedure:
  • Sprinkle powder over approximately 1.6 cm² enamel surface.
  • Cover with chamois leather.
  • Apply a 1 kg weight (same base area).
  • Move the weight 10-12 times over 13 mm without extra pressure.
  • Examine surface under 8x magnification for any scratches.
• No visible scratches are permitted.

Acid and Alkali Resistance (Clause 4.6):

• Enamel must pass all acid and alkali resistance tests as outlined in Clause 5.

Ensures enamel durability against mechanical and chemical wear.

IS 772: Enamel Quality and Resistance Tests

Enamel Thickness (Clause 4.5):

• Minimum 0.5 mm thickness on flat surfaces, measured electromagnetically.

Acid and Alkali Resistance (Clause 4.6):

• Enamel must withstand acid and alkali exposure without degradation, passing all tests in Clause 5.

Abrasion Resistance (Clauses 5.1 & 5.1.1):

• Tests use powder number 5 (apatite) from the Mohs hardness scale.
• Powder particle size complies with IS 460-1962 standards (between 212 and 250 microns).
• Procedure includes applying powder on enamel, covering with chamois leather, applying weight, and moving it repeatedly.
• Surface is inspected with an 8x magnifier; no scratches allowed.

Mohs Scale for Abrasive Powders:

Ensures enamel meets required durability and resistance standards.

IS 772: Procedures for Testing Enamel Properties

1. Abrasion Resistance (Clauses 5.1 & 5.1.1):

• Objective: Verify enamel's resistance to scratching by abrasive powders, especially powder No. 5 (apatite).
• Abrasive powders correspond to Mohs hardness scale 1 to 10.

• Test steps:
  • Powder particle size between 212 and 250 microns.
  • Apply powder on 1.6 cm² enamel area.
  • Cover with chamois leather.
  • Place 1 kg weight on leather.
  • Move weight 10-12 times over 13 mm.
  • Inspect surface under 8x magnification.
  • No scratches allowed.

2. Acid Resistance Test (Clause 5.2):

• Enamel must endure citric acid exposure without damage.
• Confirms resistance to acid and alkali conditions.

Additional Notes:

• Use separate chamois leather pieces for different powders.
• Conduct tests on inconspicuous areas to prevent visual damage.

Ensures enamel quality and longevity.

IS 772: Abrasion Test Summary

Abrasion Test (Clauses 5.1 & 5.1.1):

• Purpose: Evaluate enamel's scratch resistance using powders on Mohs hardness scale.

• Procedure:

  • Powder particle size: pass 250 micron sieve, retain on 212 micron sieve.
  • Sprinkle powder (~1.6 cm²) on enamel surface.
  • Cover with chamois leather.
  • Apply 1 kg weight with 1.6 cm² base.
  • Move weight back and forth 10-12 times over 13 mm.
  • Examine under 8x magnification for scratches.
  • Test passes if no scratches are visible with powder No. 5.

• Important: Use separate chamois leather pieces for each powder to prevent contamination.

Test Setup Diagram:

graph LR
A[Enamel Surface] --> B[Apply Powder No. 5 (Apatite)]
B --> C[Cover with Chamois Leather]
C --> D[Place 1 kg Weight (1.6 cm²)]
D --> E[Move Weight 10-12 Times over 13 mm]
E --> F[Inspect at 8x Magnification]
F --> G{Scratches Present?}
G -- No --> H[Pass]
G -- Yes --> I[Fail]

Reference: IS 772 Clauses 5.1 and 5.1.1.

IS 772: Guidelines for Inspection and Sampling

Sampling Plan (Clause 6.2 & Table 1):

• Sample sizes depend on lot size.
• Permissible defect quantities define acceptance criteria for various parameters.

Inspection Details (Clause 6.4):

• Examine samples for:
  • Base material compliance.
  • Visual surface defects.
  • Base metal thickness.
  • Dimensional accuracy.
  • Enamel thickness.

Inspection Window (Clause 2.1):

• A 75 mm diameter flexible circle is used to detect surface imperfections by sliding over the appliance.

Acceptance Criteria (Clause 6.7):

• A lot passes warpage, acid/alkali, and abrasion testing if defectives are within permissible limits.

Summary:

• Use Table 1 for sampling and defect limits.
• Conduct thorough inspections per Clause 6.4.
• Employ inspection window for surface defect detection.
• Lot acceptance is based on compliance with defect limits.

IS 772: Inspection Procedures and Manufacturer Certification Requirements

Inspection (Clauses 6.2 & Table 1):

• Sampling sizes and permissible defect counts vary with lot size:

• Lot is accepted if defectives do not exceed allowed numbers for warpage and resistance tests.

Manufacturer's Certificate (Clause 7.3):

• If purchaser inspection is not conducted, the manufacturer must provide certification of full compliance with IS 772.

Inspection Window (Clause 2.1):

• A 75 mm diameter flexible inspection tool is used to check for enamel surface defects.

Summary:

• Follow Table 1 for sampling and defects.
• Certification ensures compliance if inspection is waived.
• Inspection window facilitates practical surface defect detection.

IS 772: Criteria for Acceptance and Rejection of Lots

Sampling and Acceptance (Clause 6.2, Table 1):

Defect Limits on Enamelled Cast Iron (Clause 4.4.1):

• Crazing: None allowed.
• Dimples, Rundown, Sagging: Allowed only if not clearly visible.
• Blisters: Maximum 2 on interior; must resist fingernail pressure.
• Pinholes: Max 2 for coloured, 4 for white; no clustering; no enamel penetration.
• Specks: Up to 5 under 1 mm; no grouping; <0.25 mm ignored unless causing discoloration.
• Flaws:

Lot Acceptance (Clauses 6.5 & 6.7):

• A lot passes if defective units in the sample are within limits for all tests.

Summary ensures strict quality control and consistent product standards.