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ANSI Z21.93-2017 (CSA 6.30-2017): Standard for Excess Flow Valves for Natural Gas and Propane
Technical, Performance, and Compliance Requirements for Automatic Gas Shutoff Devices in Distribution Systems
Scope and Purpose
ANSI Z21.93-2017 (CSA 6.30-2017) establishes uniform requirements for excess flow valves (EFVs) intended for use in natural gas and propane fuel gas piping systems. The standard applies to EFVs rated for pressures up to 125 psig (862 kPa) and designed to automatically close when the flow rate exceeds a predetermined threshold, thereby stopping the flow of gas in the event of a downstream line rupture or uncontrolled release.
The scope covers both new and replacement EFVs for residential, commercial, and industrial applications where the gas service line is connected to a distribution system. The standard is jointly adopted by the American National Standards Institute (ANSI) and the Canadian Standards Association (CSA), ensuring harmonized requirements across North America.
Tip: ANSI Z21.93-2017 is referenced in the National Fuel Gas Code (NFPA 54) and many local building codes. Verification of compliance is essential for any gas installation where line-break protection is required.
Technical Requirements
Design and Construction
EFVs covered by this standard must be constructed from materials compatible with natural gas and propane, including resistance to corrosion, temperature cycling, and vibration. Valves must be designed to provide a permanent identification of flow direction, rated pressure, and closure flow rate range. The valve must remain in the full open position under normal operating conditions and close automatically when the flow surpasses the specified threshold, without external energy.
Performance Criteria
The standard defines specific performance tests including:
- Activation flow test: The valve must close within 60 seconds when flow reaches the activation rate at 15 psig (103 kPa) inlet pressure.
- Residual flow test: After closure, the leakage rate must not exceed 0.5% of the activation flow for the standard size.
- Endurance test: The valve must withstand 10,000 cycles of full open to full close without failure.
- Hydrostatic strength: The valve body must withstand four times the rated pressure without rupture.
- Durability to debris: The valve must continue to operate properly after exposure to particulate contaminants typical of gas piping systems.
Performance Requirements Summary
| Parameter | Requirement | Test Condition |
|---|---|---|
| Activation Time | ≤ 60 seconds | At 15 psig, specified flow rate |
| Leakage After Closure | ≤ 0.5% of activation flow | At 15 psig, sealed downstream |
| Endurance Cycling | 10,000 cycles | Full open to full close |
| Hydrostatic Strength | 4× rated pressure | No rupture or permanent deformation |
| Operating Temperature Range | −40°F to 140°F (−40°C to 60°C) | Continuous exposure |
Implementation Highlights
Successful application of an EFV conforming to Z21.93-2017 requires careful consideration of system parameters. The valve must be sized so that its activation flow rate is between the normal maximum demand flow and the flow expected in a downstream rupture scenario. This ensures the valve does not nuisance trip during peak usage while still providing protection. The standard requires that the EFV be installed in the service line ahead of the meter, or immediately downstream of the meter if allowed by local code.
Warning: An EFV cannot protect against minor leaks that do not generate flow above its activation threshold. It is not a substitute for regular leak detection and emergency response procedures. Confirm sizing with the gas utility or an engineer before installation.
Marking requirements include the manufacturer’s name, model number, rated pressure, closure flow range, and the standard designation ANSI Z21.93-2017 / CSA 6.30-2017. The valve must be permanently labeled so it is visible after installation.
Compliance Notes
To claim compliance, the manufacturer must subject the EFV to type testing by a nationally recognized testing laboratory (such as CSA or UL) and maintain a quality assurance program in accordance with ISO 9001 or equivalent. The standard also includes provisions for field inspection—installers must verify that the valve is rated for the gas type (natural gas or propane) and that the activation flow range matches the system design. Certification marks from accredited bodies are mandatory for market access in jurisdictions that adopt Z21.93 as code.
Compliance Success: Many gas utilities now mandate EFVs on all new service lines. Selection of a Z21.93/CSA 6.30 certified device simplifies permitting and ensures alignment with the latest safety requirements for both natural gas and propane systems.
Important: There is a known compatibility limitation: EFVs certified under Z21.93-2017 are not required to operate correctly when downstream piping includes excess flow valves in series. Engineers must evaluate system design to avoid stacking of automatic shutoff devices.
FAQs
Q: What is an excess flow valve and how does it work?
A: An EFV is a mechanical device that continuously monitors the flow of gas through the pipe. When the flow rate exceeds a factory-set threshold—usually because of a line break—the valve closes automatically to stop the gas flow. It remains in the closed position until manually reset (or replaced). The exact activation flow is determined by the valve size and design, as specified in the standard.
A: An EFV is a mechanical device that continuously monitors the flow of gas through the pipe. When the flow rate exceeds a factory-set threshold—usually because of a line break—the valve closes automatically to stop the gas flow. It remains in the closed position until manually reset (or replaced). The exact activation flow is determined by the valve size and design, as specified in the standard.
Q: When will an EFV not activate?
A: An EFV will not activate for small leaks that produce a flow rate below its threshold, such as a pinhole in a pipe or a slowly leaking fitting. It also will not close if the damage occurs on the supply side of the EFV (upstream) or if the downstream valve is already closed (stagnant line conditions).
A: An EFV will not activate for small leaks that produce a flow rate below its threshold, such as a pinhole in a pipe or a slowly leaking fitting. It also will not close if the damage occurs on the supply side of the EFV (upstream) or if the downstream valve is already closed (stagnant line conditions).
Q: What are the limitations of an EFV per this standard?
A: The standard only covers valves for natural gas and propane. It does not cover EFVs for other gases, for use in corrosive atmospheres, or for systems with operating pressures exceeding 125 psig. Additionally, the standard does not require the valve to close for downstream shut‑in situations—only for flowing breaks.
A: The standard only covers valves for natural gas and propane. It does not cover EFVs for other gases, for use in corrosive atmospheres, or for systems with operating pressures exceeding 125 psig. Additionally, the standard does not require the valve to close for downstream shut‑in situations—only for flowing breaks.
Q: How is an EFV different from a gas service line valve (ANSI Z21.80)?
A: A Z21.80 line valve is a manually operated shut‑off device that isolates the service line; it does not automatically close. An EFV (Z21.93) provides automatic flow‑sensing shutoff. Both are typically installed together, with the EFV providing an extra layer of safety in the event of unintended line opening.
A: A Z21.80 line valve is a manually operated shut‑off device that isolates the service line; it does not automatically close. An EFV (Z21.93) provides automatic flow‑sensing shutoff. Both are typically installed together, with the EFV providing an extra layer of safety in the event of unintended line opening.