plastic seats and covers for water closets, Part 2: Thermoplastic seats and covers

IS 2548 Part 2: Scope & Key Specifications Summary

This standard covers thermoplastic seats and covers for water-closets with key dimensional and material specifications.

Key Dimensions (Table 1, Clause 6.1)

Buffers (Clause 6.1)

• Rubber/plastic buffers: 25 mm × 40 mm × 10 mm minimum for closed front seats.
• Minimum 4 buffers for open front seats.
• Buffer projection: 10 mm clear from base.
• Larger buffers allowed if they do not protrude beyond the seat.

Material & Hinging Device (Clause 4.2)

• Hinging device materials:
  • Bronze/brass with nickel-chromium plating (IS 1068:1993)
  • Mild steel with nickel-chromium plating (IS 1068:1993)
  • Aluminium alloy with anodic coating (IS 1868:1982)

Rounding Off (General)

• Final test values rounded per IS 2:1960 rules.
• Retain significant figures as per specified values.

flowchart LR
    A[Thermoplastic Seat & Cover] --> B[Dimensions per Table 1]
    A --> C[Buffers: 25x40x10 mm]
    A --> D[Hinging Device: Bronze/Steel/Aluminium]
    B --> E[Min/Max values for A-G, thickness]
    C --> F[Minimum 4 buffers for open front]
    D --> G[Plating per IS 1068

IS 2548 Part 2 (1996) - Key Specifications & Tables for Thermoplastic Seats and Covers

1. Dimensions of Seats and Covers (Table 1, Clause 6.1)

All dimensions in mm:

2. Buffers (Clause 6.1)

• Rubber/plastic buffers: 25 mm × 40 mm × 10 mm (minimum size)
• Minimum 4 buffers for open front seats
• 10 mm = clear projection from base
• Larger buffers allowed if they don’t protrude beyond seat

3. Deflection Limits for Covers (Clause 9.4.2)

No fractures or edge push-through allowed after load removal.

4. Materials for Hinging Devices (Clause 4.2)

• Bronze/brass with Ni-Cr plating (IS 1068:1993)
• Mild steel with Ni-Cr plating (IS 1068:1993)
• Aluminium alloy with anodic coating (IS 1868:1982)

5. Testing & Rounding Off

• Follow IS 2:1960 for rounding test results to match specified significant digits.

flowchart TD
    A[Seat Dimensions] --> B{Key Dimensions}
    B -->|A| C[Distance hinge to front rim: 445-475 mm]
    B -->|

IS 2548 Part 2 — Key Definitions & Specifications

1. Deflection Limits for Covers (Clause 9.4.2)

• Tested per Annex G.
• Maximum deflection after loading:

• No fractures or edge push-through allowed after load removal.

2. Seat Dimensions (Clause 6.1)

• Seats must conform to dimensions in Table 1 and Fig. 1.
• For open front design, the seat plus reasonable outline extensions must meet Fig. 1 plan dimensions.

3. Sampling Plan for Quality Control (Clause 1.2, Table 2)

4. Rounding Off (General Clause)

• Use IS 2:1960 rules.
• Retain the same significant figures as the specified value.

flowchart LR
    A[Load Applied on Cover] --> B{Deflection ≤ Limit?}
    B -- Yes --> C[No Fracture or Edge Push-Through]
    B -- No --> D[Reject Cover]
    C --> E[Cover Accepted]

This summarizes key definitions and specifications for covers and seats per IS 2548 Part 2.

IS 2548 Part 2: Key Material Specifications for Hinging Devices and Thermoplastic Seats

Materials for Hinging Devices (Clause 4.2, Annex A):

• Bronze or brass with nickel-chromium plating (IS 1068:1993)
• Mild steel with nickel-chromium plating
• Aluminium alloy with anodic coating (IS 1868:1982)
• Reinforced suitable plastic meeting:
  • Water absorption ≤ 0.6% by mass (24 hrs immersion)
  • Elongation ≥ 15%
  • Thermal stability up to 55°C without deformation

Mechanical Properties (Clause 31.5):

• Tensile Strength: ≥ 31.5 MPa (IS 13360 Part 5/Sec 1, 2)
• Impact Strength: > 0.3 MPa (notched specimen, IS 13360 Part 5/Sec 4)
• Water Absorption: ≤ 0.04% by mass (IS 867:1963)
• Deflection Temperature Under Load: ≥ 54°C (IS 867:1963)
• Surface Hardness: Rockwell Hardness Number (HR) ≥ L45 (Annex L)

Summary Table

IS 2548 Part 2: Design and Dimensions Key Points

1. Seat & Cover Dimensions (Clause 6.1, Table 1)

• Note: Open front seats must conform to these dimensions including reasonable outline extensions.
• Hinges may allow longitudinal adjustment.

2. Buffers (Clause 6.1)

• Rubber/plastic buffers: 25 × 40 × 10 mm (minimum size).
• Minimum 4 buffers for open front seats.
• Buffers must be securely fixed and not protrude beyond the seat.

3. Cover Deflection Limits (Clause 9.4.2, Annex G)

• No fracture or edge push-through after load removal.

flowchart LR
    A[Seat Dimensions] -->|Conform to| B[Table 1 & Fig. 1]
    B --> C[Buffers: 25x40x10 mm, min 4 (open front)]
    B --> D[Thickness ≥ 3 mm]
    A --> E[Hinging Device: Adjustable Longitudinally]
    F[Cover] -->|Deflection Limits| G[Grade 1: 25 mm, Grade 2: 40 mm]

Summary: Follow Table 1 for precise seat and cover dimensions, use specified buffer sizes, and ensure cover deflection limits per grade for safety

IS 2548 Part 2 (1996) — Buffers and Distance Pieces

Buffers (Clause 8.1.1 & Fig.1)

• Material: Rubber or plastic
• Size: Minimum 25 mm × 40 mm × 10 mm (length × width × clear projection)
• Quantity:
  • Closed front seats: at least 3 buffers
  • Open front seats: at least 4 buffers
• Position: Securely fixed to the underside of the seat without protruding beyond the seat edges.

Distance Pieces (Clause 8.2)

• Used if buffers are not provided
• Number: 4 radial ribs molded integrally with the seat
• Height: Raise seat by ≥ 3 mm above the rim surface
• Dimensions:
  • Radial length: ≥ 45 mm
  • Width on plan: ≥ 3 mm
• Spacing: Distance between adjacent ribs ≥ 100 mm

Key Dimensional Table (Clause 6.1, Table 1)

flowchart LR
    Seat -->|Buffers| Buffers[Rubber/Plastic Buffers]
    Seat -->|Distance Pieces| DistancePieces[4 Radial Ribs]
    Buffers -->|Size| Size25x40x10[25×40×10 mm]
    DistancePieces -->|Height| Height3mm[≥ 3 mm]
    DistancePieces -->|Length| Length45mm[≥ 45 mm]
    DistancePieces -->|Spacing|

IS 2548 Part 2: Hinging Devices - Key Specifications & Formulas

1. Dimensions (Clause 6.2)

• Cover dimensions must follow Table 1 and Fig. 1 (refer to IS 2548 Part 2 for exact values).

2. Hinging Pins (Clause 7.1.2)

• Minimum diameter of hinging pins: 5 mm

3. Alternative Hinging Devices (Clause 7.1.1)

• May use suitable designs agreed between manufacturer and purchaser.

4. Materials for Hinging Devices

• Bronze or brass with nickel-chromium plating (IS 1068:1993)
• Mild steel with nickel-chromium plating
• Aluminium alloy with anodic coating (IS 1868:1982)
• Reinforced plastics meeting:
  • Water absorption ≤ 0.6% by mass (24h immersion)
  • Minimum elongation: 15%
  • Temperature resistance: up to 55°C without deformation

5. Testing Standards

• Density & relative density: IS 13360 (Part 3/Sec 1):1995
• Tensile properties: IS 13360 (Part 5/Sec 1):1996

Summary Table: Materials & Requirements

flowchart LR
    A[Hinging Device] --> B[Material Selection]
    B --> B1[Bronze/Brass + Ni-Cr plating]
    B --> B2[Mild Steel + Ni-Cr plating]
    B --> B3[Aluminium Alloy + Anodic Coating]
    B --> B4[Reinforced Plastic]

IS 2548 Part 2: Construction and Surface Finish Key Points

1. Surface Hardness (Clause 9.7 & Annex L)

• Test: Rockwell Hardness (HR), tested per Annex L.
• Minimum Hardness: HR L45
• Purpose: Ensure seats and covers resist unacceptable indentation.

2. Deflection Limits for Thermoplastic Seats and Covers (Clause 9.4.2)

• After load removal:
  • No fractures
  • No edge pushed through seat opening

3. Material Grades (Clause 9.4.1)

• Grades: 1 and 2 based on deflection characteristics.
• Application: Helps select suitable thermoplastic seats/covers based on load and flexibility needs.

4. Surface Finish Testing (Clause 2.5)

• Test with various cleansers/polishes.
• Check for changes in color or surface characteristics at each treatment stage.

Summary Diagram: Surface Finish Requirements

flowchart TD
    A[Start: Seat & Cover] --> B[Surface Hardness Test (Annex L)]
    B -->|HR ≥ L45| C[Pass Hardness]
    B -->|HR < L45| D[Fail Hardness]
    C --> E[Deflection Test (Annex G)]
    E --> F{Grade?}
    F -->|Grade 1| G[Max Deflection ≤ 25mm]
    F -->|Grade 2| H[Max Deflection ≤ 40mm]
    G & H --> I[No fracture & no edge push-through]
    I --> J[Surface Finish Test (Clause 2.5)]
    J --> K[Check color/surface changes]

Use these criteria to ensure compliance with IS 2548 Part 2 for construction and surface finish of thermoplastic seats and covers.

IS 2548 Part 2: Test Requirements Summary

• Rounding Off (IS 2:1960)
  Final test values must be rounded to the same number of significant digits as specified in the standard.

• Endurance Test (Clause 9.8 & Annex M)

  • Applies to seats, covers, and buffers.
  • No damage or dislocation allowed after testing.
  • Type test frequency: Once every 6 months.

• Sampling for Tests (Clause 2.2 & Table 2)

  • Number of seats and covers to test per Table 2, column 4.
  • Samples selected from those chosen as per Clause N-1.2.

• Surface Hardness (Clause 9.7 & Annex L)

  • Minimum Rockwell Hardness Number (HR) = L45.

Key Table Extract (Sample Sizes from Table 2, IS 2548 Pt 2)

Endurance Test Concept (Mermaid.js)

flowchart TD
    A[Start Endurance Test] --> B{Seat, Cover, Buffer}
    B --> C[Test as per Annex M]
    C --> D{Damage or Dislocation?}
    D -- No --> E[Pass Test]
    D -- Yes --> F[Fail Test]

Note: Refer to Annex L and M for detailed test procedures and equipment specifications.

IS 2548 Part 2: Ordering and Inspection Key Points

Sample Size & Permissible Defectives (Table 2)

Sampling Procedure (Clause N-1.2.1)

• Calculate r = floor(N/n) (N = lot size, n = sample size).
• Starting from any seat, select every r-th seat until n samples are obtained.
• Ensures randomness and representativeness.

Ordering Requirements (Clause 10.1 & 10.2)

• Clearly specify:
  • Type of seats and covers (see 3.1).
  • Material of hinging device.
  • Required colour (Clause 5.3).
  • Preferred design for seats (Clause 5.1.1.1).
• Purchaser may inspect finished goods before delivery.
• Right to reject non-conforming articles.

Marking

• Each seat/cover must be indelibly marked on the underside with:
  • Manufacturer's name/ID.
  • Grade.
  • Material of hinging device (on label/packing slip).

flowchart TD
    A[Start: Lot Size N] --> B[Calculate Sample Size n from Table 2]
    B --> C[Calculate r = floor(N/n)]
    C --> D[Select every r-th seat randomly]
    D --> E[Inspect samples for defects]
    E --> F{Defectives ≤ Permissible?}
    F -->|Yes| G[Accept Lot]
    F -->|No| H[Reject Lot]

This ensures quality control through statistically valid sampling and clear ordering/inspection protocols.

IS 2548 Part 2: Marking and Labelling Key Points

• Clause 14.2 - Informative Labelling:

  • Informative labels may be provided on each seat and cover assembly.
  • These labels typically include manufacturer details, material specifications, and batch numbers.

• Clause 14.3 - BIS Certification Marking:

  • Each seat and cover may bear the BIS Standard Mark.
  • Use of the Standard Mark is regulated by the Bureau of Indian Standards Act, 1986.
  • Manufacturers must obtain a license from BIS to use this mark.

• Material Specification (Annex A):

  • For polypropylene seats and covers:
    • Density: 0.900 to 0.910 g/ml (IS 13360 Part 3/Sec 1:1995)
    • Refer to tensile strength requirements for quality control.

Summary Table for Labelling

Notes:

• Always ensure labelling complies with BIS licensing.
• Labelling aids traceability and quality assurance.

flowchart LR
    A[Seat & Cover Assembly] --> B[Informative Labelling]
    A --> C[BIS Standard Mark]
    C --> D[BIS License Required]
    B --> E[Manufacturer Info]
    B --> F[Material Specs]

IS 2548 Part 2: Sampling & Criteria for Conformity

1. Sampling Procedure (Clause N-1.2, N-1.2.1)

• Sample Size (n) depends on lot size (N) per Table 2.
• Select samples randomly using systematic counting:
  • Calculate ( r = \lfloor \frac{N}{n} \rfloor ).
  • Starting from any item, pick every ( r^{th} ) seat/cover until sample size is reached.

2. Sample Size & Permissible Defectives (Table 2)

3. Sub-sample Testing (Clause N-2.2)

• Number of seats/covers tested = Sub-sample size (col 4).
• Select from the already chosen sample.

4. Criteria for Conformity (Clause N-3)

• Lot conforms if:
  • Number of defectives ≤ permissible defectives.
  • All sub-sample tests meet specified requirements.

flowchart TD
    A[Lot Size N] --> B[Calculate Sample Size n (Table 2)]
    B --> C[Calculate r = floor(N/n)]
    C --> D[Select every rth item randomly]
    D --> E[Sample of size n]
    E --> F[Select sub-sample (col 4)]
    F --> G[Test sub-sample]
    G --> H{Defectives ≤ Permissible?}
    H -- Yes --> I[Lot Conforms]
    H -- No --> J[Lot Rejected]

Summary: Use Table 2 for

Water Absorption Test (IS 2548 Part 2)

Objective:
Ensure seat or cover durability and hygiene by limiting water absorption.

Test Procedure (Annex C, Clause 9.2 & 2.2)

1. Conditioning:

   • Keep samples at ambient temperature & humidity for ≥ 24 hours.

2. Initial Weighing:

   • Weigh the dry seat/cover → M1 (g) (nearest 0.1 g).

3. Immersion:

   • Submerge fully in water for 24 hours (use vessel as per Clause C-2.2).

4. Post-Immersion Weighing:

   • Remove, blot surface water, weigh → M2 (g).

5. Calculate % Increase in Mass:

[ \text{Water Absorption (%)} = \frac{M2 - M1}{M1} \times 100 ]

Acceptance Criteria (Clause 9.2)

• Maximum water absorption: 0.75% by mass.
• No visual impairment in surface characteristics after immersion.

Additional Notes

• Inspect for any surface changes post-immersion.
• Material water absorption per IS 867:1963 should be ≤ 0.04%.
• Tensile strength ≥ 31.5 MPa (IS 13360).
• Impact strength > 0.3 MPa (notch type test).

flowchart TD
    A[Condition sample 24 hrs] --> B[Weigh dry sample (M1)]
    B --> C[Immerse in water 24 hrs]
    C --> D[Remove & blot surface water]
    D --> E[Weigh wet sample (M2)]
    E --> F[Calculate % increase = ((M2-M1)/M1)*100]
    F --> G{Is % increase ≤ 0.75%?}
    G -- Yes --> H[Pass]
    G -- No --> I[Fail]

Summary: Water absorption test ensures seats/covers absorb ≤ 0.75% water by mass after 24-hour immersion, maintaining durability and hygiene as per IS 2548 Part 2.

IS 2548 Part 2: Impact Resistance Test for Seats — Key Points

1. Test Setup (Clause 9.3 & Fig. 3)

• Seat assembled on water-closet, placed in frame.
• Seat raised to vertical position, supported to freely fall after impact.
• Pendulum raised to horizontal position and released to strike seat centrally at the extreme point.
• Pendulum has a steel disc with rubber facing.

2. Test Procedure

• Pendulum swings down, impacts the raised seat.
• Seat, buffers, hinges inspected for damage.
• Ensures seat and hardware withstand impact loads typical in use.

3. Deflection Test for Rigidity (Clause 9.1 & Fig. 5)

• Seat placed on supports.
• Measure height X1 (base to seat underside).
• Load applied via loading bar.
• After 10 minutes, measure height X2.
• Deflection ( \delta = X_1 - X_2 ).
• Inspect for fractures.

4. Material Properties (Clause 31.5, A-3, A-4, A-5)

5. Summary Diagram: Impact Test Setup

flowchart LR
    A[Pendulum Raised Horizontally] --> B[Pendulum Released]
    B --> C[Pendulum Strikes Raised Seat]
    C --> D[Seat Free to Fall]
    D --> E[Inspect Seat, Buffers, Hinges for Damage]

Note: This test ensures durability against impact loads and verifies seat rigidity under load, critical for user safety and product longevity.

IS 2548 Part 2: Impact Resistance Test for Covers

Key Points from Clauses and Annexes

• Objective (Annex E, Clause 9.3.2):
  Ensure covers withstand impact loads both when raised and when striking the seat; hinges and buffers must also resist these impacts.

• Test Setup (Clause 2.4, Fig. 3):

  • Seat assembled to water-closet, raised vertically and supported to fall freely after impact.
  • Pendulum released from horizontal to strike seat centrally at the extreme point.

• Impact Test Procedure:

  • Strike cover at one point with indentor (Annex E).
  • Repeat at a different point (Clause 3.2).
  • Measure deflection:
    [ \text{Deflection} = X_2 - X_1 ] where (X_1) and (X_2) are initial and final measurements (Annex G).

• Acceptance Criteria (Clause 9.4.2, Table 9.4.2):

• Post-Test Inspection:
  Check for fractures, deformation, or any part of the cover edge pushed through the seat opening.

Summary Table

flowchart LR
    A[Assemble seat & cover] --> B[Raise cover vertically]
    B --> C[Release pendulum from horizontal]
    C --> D[Impact on cover]
    D --> E[Measure deflection (X2 - X1)]
    E --> F{Deflection ≤ Max allowable?}
    F -- Yes --> G[Inspect for fractures and edge intrusion]
    F -- No -->