Pillar Taps for Water Supply Purposes

IS 1795: Introduction and Revision History - Key Specifications & Tables

1. General Specification

• Pillar taps' inlet/outlet must have squared faces for pressure testing (Clause 6.8).
• Washers for cold water taps follow ISO metric screw threads standards (Parts I-VI).
• Pipe thread dimensions and tolerances are standardized (Parts I-III).

2. Key Tables for Dimensions

Table 4: Bonnet and Gland Dimensions (Clause 6.3.1)

Table 5: Capstan Heads, Spindles, and Washer Plates (Clauses 6.4.5 & 6.5.7)

IS 1795: Scope Key Specifications & Dimensions Summary

This code covers dimensions and specifications for valves including body, bonnet, gland, capstan head, spindle, and washer plates.

1. Body Dimensions (Table 2, Clause 6.2.8)

2. Bonnet and Gland Dimensions (Table 4, Clause 6.3.1)

IS 1795: Designation and Nominal Size Key Data

1. Designation and Nominal Size

• Nominal sizes: 15 mm and 20 mm (common pillar tap sizes).
• Designation includes nominal size and corresponding screw thread sizes for components.

2. Key Dimensions of Body (Table 2, Clause 6.2.8)

3. Back Nut Dimensions (Table 3, Clause 6.2.8)

IS 1795: General Requirements — Key Dimensions & Specifications

1. Dimensions of Body (Clause 6.2.8, Table 2)

*Note: D can be reduced by 0.5 mm for outlets only.

2. Dimensions of Back Nut (Clause 6.2.8, Table 3)

IS 1795: Construction Details - Key Dimensions & Specifications

1. Capstan Head and Spindle (Table 5)

2. Bonnet and Gland (Table 4)

3. Body Dimensions (Table 2)

IS 1795 - Key Specifications for Body and Outlet (Clause 6.2.8)

Table 2: Dimensions of Body (mm)

*Note: Minimum thickness D may be reduced by 0.5 mm for outlets.

Table 3: Dimensions of Back Nut (mm)

IS 1795: Bonnet and Gland Dimensions (Clause 6.3.1, Table 4)

Additional Notes:

• The spindle must project at least 0.7 mm beyond the bonnet face when fully open.
• A recess at the top of the internal thread equals the thread depth and max length D.

Summary Diagram (Mermaid.js)

graph LR
A[Bonnet Flange] -->|External Thread (A,B)| B[Spindle Internal Thread (C)]
B -->|Recess (D)| C[Spindle Projection ≥ 0.7 mm]
A -->|Stuffing Box Length (E)| D[Gland External Thread (F)]
D -->|Gland Flange Thickness (G)| E

IS 1795 - Capstan Head and Spindle Key Specifications (Clause 6.4.5, Table 5):

Additional bonnet and gland dimensions (Clause 6.3.1, Table 4):

• External thread size on bonnet flange: 15mm → M30×1, 20mm → M39×1.5

IS 1795 - Washer Plate and Washer Key Specifications

From Clause 6.5 & 6.5.7:

• Washer plate and washer dimensions must conform to Table 5 of IS 1795.
• The outside diameter (M) of a flat washer plate is specified in Table 5.
• The thickness of washer plate (R) is given in Clause 17.9 and Table 5.

Typical Dimensions (from Table 5):

Notes:

• Washer plates distribute load and prevent bolt head or nut from damaging the surface.
• Thickness (R) ensures adequate strength and stiffness.
• Always refer to IS 1795 Table 5 for exact values per bolt size.

flowchart LR
    A[Bolt] --> B[Washer]
    B --> C[Washer Plate]
    C --> D[Structural Member]
    style B fill:#f9f,stroke:#333,stroke-width:2px
    style C fill:#bbf,stroke:#333,stroke-width:2px

This diagram shows the load transfer path: Bolt → Washer → Washer Plate → Structural Member.

IS 1795 - Screw Threads (Clause 6.6 & 6.6.2)

Key Specifications:

• Screw threads for valve components follow ISO metric thread standards (IS:4218).
• Threads have tolerances:
  • m = Medium
  • f = Fine
  • c = Coarse
• External threads have bolt tolerances, internal threads have nut tolerances.

Table 6: Dimensions of Screw Threads for Pillar Tap Components

Notes:

• For detailed dimensions and tolerances, refer to IS 4218.
• All threads conform to ISO metric screw thread standards (Parts I to VI).

Summary:

• Use ISO metric threads with specified pitch and tolerance class.
• Match internal and external threads according to Table 6.
• Ensure bolt/nut tolerance compatibility for proper fit.

flowchart LR
    Body_Internal -->|Engages| Bonnet_External
    Bonnet_Internal -->|Engages| Spindle_External
    StuffingBox_Internal -->|Engages| Gland_External

This ensures correct mating of components in pillar taps per IS 1795.

IS 1795 - Mass Requirements & Key Dimensions Summary

1. Minimum Finished Mass (Clause 7.1)

• 15-mm size pillar taps: Minimum mass = 650 g
• 20-mm size pillar taps: Minimum mass = 1175 g

2. Thread Tolerances (Clause 1.5)

• Thread types:
  • m = Medium tolerance
  • f = Fine tolerance
  • c = Coarse tolerance
• Refer IS 4218 for detailed thread dimensions and tolerances.

3. Key Dimensions for Capstan Heads, Spindles & Washer Plates (Table 5, Clause 6.4.5)

IS 1795 - Sampling and Testing Procedures

Key Table: Sample Size & Acceptance Criteria (Table 7)

Sampling Procedure (Clause 2.1 & 9.1)

• Random sampling as per Table 7.
• All taps in the sample are examined for:
  • Material quality
  • Workmanship
  • Construction
  • Finish
  • Dimensions
  • Minimum finished mass

Criteria for Conformity

• Number of defective items in sample must be ≤ permissible defective number.
• Sub-sample size refers to the number of taps tested for specific properties like finish and mass.

This ensures statistically valid quality control for tap lots per IS 1795.

IS 1795: Marking and Certification Key Points

1. Marking (Clause 11.1.1)

• Pillar taps may be marked with the ISI Certification Mark.
• ISI Mark assures compliance with Indian Standards under strict inspection, testing, and quality control.
• Use of ISI Mark is governed by the Indian Standards Institution (Certification Marks) Act.

2. Rounding Off (Clause 0.3)

• Test results must be rounded off as per IS:2-1960.
• Retain the same number of significant digits as the specified standard value.

3. Sampling and Conformity (Clause 9.1, Appendix A, Table 7)

• These criteria define sample sizes and allowable defective units for lot acceptance.

Summary

• ISI Mark ensures quality and standard compliance.
• Sampling plans ensure product conformity.
• Test results must follow IS rounding rules.

flowchart TD
    A[Manufacture Product] --> B[Inspection & Testing]
    B --> C{Meets IS Standards?}
    C -- Yes --> D[Apply ISI Certification Mark]
    C -- No --> E[Reject or Rework]
    D --> F[Continuous ISI Surveillance]

IS 1795: Criteria for Conformity and Sampling

Key Specifications (Clause 2.1.1, Table 7)

Sampling Procedure (Clause 9.1, Appendix A)

• Sampling follows random selection from the lot.
• All taps in the sample are checked for:
  • Material quality
  • Workmanship
  • Construction
  • Finish
  • Dimensions
  • Minimum finished mass

Criteria for Conformity

• The number of defective items in the sample must not exceed the permissible number in column 3.
• Sub-samples are used for detailed testing of specific properties.

Summary Flow of Sampling & Conformity Check

flowchart TD
    A[Start: Lot Size Determination] --> B[Select Sample Size from Table 7]
    B --> C[Random Sampling of Taps]
    C --> D[Examine Material, Workmanship, Finish, Dimensions, Mass]
    D --> E{Defective Count ≤ Permissible?}
    E -- Yes --> F[Lot Accepted]
    E -- No --> G[Lot Rejected]

This ensures quality control per IS 1795, balancing inspection effort and reliability.