Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
ASME Z32.2.3-1949 — Graphical Symbols for Pipe Fittings, Valves, and Piping
🔧 ASME Z32.2.3-1949 (originally ASA Z32.2.3-1949, reaffirmed 1953) is the American standard defining graphical symbols for pipe fittings, valves, and piping used on engineering drawings. It was developed by the ASA Sectional Committee on Standardization of Graphical Symbols and Abbreviations for Use on Drawings (Z32), under the joint sponsorship of the American Institute of Electrical Engineers and The American Society of Mechanical Engineers. It is the second standard of the group that revises and expands the earlier Z32.2-1941 (the first being the Z32.2.1-1949 welding symbols). In preparing the symbol list, over one hundred companies and their representatives were consulted, and great care was exercised to avoid conflicts with symbols being assembled by committees in allied fields. The Standard provides 73 symbols as a minimum requirement for piping engineering drawings.
💡 The distinctive feature of this Standard is the systematic representation of connection types: the same piping element is drawn in five connection variants — flanged, screwed, bell & spigot, welded, and soldered — so a single drawing conveys the assembly requirements.
1. Overview and Scope 📌
The basic principles are the same as those of the companion Z32-series standards:
- Clarity and simplicity: symbols are kept simple, drafting is simplified first, and identification letters are used only where similar shapes could cause error;
- National consensus: only symbols with nationwide agreement are included; industry-specific symbols (for example, petroleum piping) are not covered.
The proposal was approved by the American Standards Association on April 8, 1949, and designated as Z32.2.3-1949. The symbol system is organized in three blocks: pipe fittings, valves, and piping annotations; every fitting and valve symbol is provided in five connection-type variants.
⚠️ The 73 symbols are a minimum requirement. Many specialized piping symbols (for example, in petroleum piping) are not included; project drawings should supplement them per industry codes and define the additions in the legend.
2. Pipe Fitting Symbol System 🔩
The fitting symbols (Nos. 1–14) cover:
| Category | Symbol Items | Notes |
|---|---|---|
| Joints and transitions | Bushing, cap, reducer (concentric/eccentric), sleeve, union | Distinguish by reduction direction and eccentricity |
| Tees and crosses | Cross (reducing/straight), tee (straight/outlet up/outlet down/double sweep/reducing/single sweep/side outlet) | Outlet direction and reduction shown by variants |
| Elbows | Elbow (90°/45°/turned down/turned up/base/double branch/long radius/reducing/side outlet/street elbow) | A dozen-plus variants by angle and form |
| Others | Crossover, lateral, orifice flange, reducing flange, plugs (bull plug/pipe plug), joints (connecting pipe/expansion) | Connection and metering items |
Each fitting carries five connection-type variants — flanged, screwed, bell & spigot, welded, and soldered — and the drafter selects the variant that matches the actual assembly method.
3. Valve Symbol System 🚰
The valve symbols (Nos. 15–27) cover the common control and safety valves:
- Basic valves: angle valve, check valve (angle/straight-way), gate valve (elevation/plan), globe valve (elevation/plan), hose angle valve;
- Automatic valves: automatic valve (by-pass/governor-operated/reducing), pressure-reducing valve;
- Special valves: cock, diaphragm valve, float valve, gate valve (with angle-gate and hose-gate), globe valve (with angle-globe and hose-globe), hose valve, lockshield valve, wick-opening valve, safety valve, stop valve.
The Standard notes that the general gate/globe symbols may also serve as the general stop-valve symbol when amplified by a specification, preserving flexibility in design expression.
💡 Gate valves are drawn in both elevation and plan; motor-operated valves add a drive mark to the base valve symbol. Decide the valve type and installation view first, then select the matching symbol.
4. Piping Annotation System 📏
The piping annotations (Nos. 28–73) use “abbreviation text + line” to denote each medium and are organized in three main groups:
| System | Typical Line Annotations |
|---|---|
| Air conditioning | Brine return/supply (BR), chilled/hot-water flow and return (CH, CHR), condenser-water supply/return, drain, humidification, make-up water, refrigerant discharge/liquid/suction |
| Heating | Air-relief line, boiler blow-off, compressed air, condensate or vacuum-pump discharge, feedwater-pump discharge, fuel-oil flow/return, fuel-oil tank vent, high-pressure return/steam, hot-water heating supply/return, low-pressure steam, medium-pressure return/steam |
| Plumbing | Acid waste, cold water, compressed air, drinking-water supply/return, fire line, gas, hot water, hot-water return, soil/waste/leader (above/below grade), vacuum cleaning, vent |
| Others | Pneumatic tubes, sprinklers (branch and head, drain, main supplies) |
🚨 Line annotations depend entirely on text abbreviations (e.g., HP Steam, CW, HWR). Abbreviations must be unique within a drawing set and the legend must be complete; otherwise systems such as high-pressure steam and hot-water return can be confused, causing construction errors.
5. Engineering Practice Essentials 🛠️
- 📋 Complete legends: list every connection-type symbol and line abbreviation in the drawing legend so drafting and construction interpret identically.
- ✏️ Match symbols to assembly: the choice of screwed/flanged/welded variants must match pipe material and pressure class — the symbol itself is the assembly requirement.
- 🔄 Cross-standard consistency: piping symbols are usually issued with Y32.4 (plumbing), Y32.2.4 (HVAC), and Y32.2.6 (heat-power) symbols; all share the same origin, so keep one unified legend.
- 📐 Complement the flow sheet: process flow diagrams (Y32.11) show overall equipment relationships, while these detailed symbols are used on construction and piping layout drawings.
6. Frequently Asked Questions ❓
❓ Q: What are the “five connection types”?
A: Flanged, screwed, bell & spigot, welded, and soldered. The same fitting is drawn with the variant matching the actual assembly process.
A: Flanged, screwed, bell & spigot, welded, and soldered. The same fitting is drawn with the variant matching the actual assembly process.
❓ Q: Why do gate and globe valves have both elevation and plan drawings?
A: The elevation shows the valve body projected on a vertical plane, while the plan shows it on the horizontal plane; together they express the spatial orientation of the valve. Pick the drawing per the installed orientation.
A: The elevation shows the valve body projected on a vertical plane, while the plan shows it on the horizontal plane; together they express the spatial orientation of the valve. Pick the drawing per the installed orientation.
❓ Q: Can the text abbreviations be omitted from line symbols?
A: No. Line symbols express the medium through “abbreviation text + line” (e.g., HP Steam for high-pressure steam, CW for cold water); omitting the abbreviation makes the systems indistinguishable.
A: No. Line symbols express the medium through “abbreviation text + line” (e.g., HP Steam for high-pressure steam, CW for cold water); omitting the abbreviation makes the systems indistinguishable.
🔍 Q: How does this relate to ASME Y32.2.3-1949 (1999)?
A: Z32.2.3-1949 is the original ASA designation; the series was later folded into the Y32 numbering system as Y32.2.3 and carried into the 1999 reaffirmed edition. The content is of the same lineage; cite the edition you rely on.
A: Z32.2.3-1949 is the original ASA designation; the series was later folded into the Y32 numbering system as Y32.2.3 and carried into the 1999 reaffirmed edition. The content is of the same lineage; cite the edition you rely on.
