Overview - EN ISO 13758:1996/A1:2020 (Valve freeze method for propane dryness)
EN ISO 13758:1996/A1:2020 is a CEN-adopted amendment to ISO 13758:1996 that updates the standardized valve freeze method for assessing the dryness (water content risk) of propane in liquefied petroleum gases (LPG). The amendment adds a mandatory apparatus verification clause and a normative Annex A that defines a verification procedure to ensure correct flow through the test valve before carrying out the freeze test.
Key topics and technical requirements
- Purpose: Assessment of the dryness of propane using the valve freeze technique to detect moisture that could cause valve icing or downstream operational issues.
- New normative references:
- Replaces the previous citation of ISO 4257:1988 with ISO 4257 - Liquefied petroleum gases: Method of sampling.
- Apparatus verification (new Clause 7):
- Verify correct flow rate through the test valve per Annex A; valves failing verification or suspected defective must be reconditioned/recalibrated by the manufacturer.
- Annex A - Verification of correct flow rate (normative):
- Required equipment:
- Flow meter calibrated in ml/min, readable in the 500–900 ml/min range.
- Reference valve with a flow-rate calibration certificate.
- Adaptor and seal to connect valve vent hole to flow meter.
- Verification gas and conditions:
- Nitrogen at 275 kPa ± 5 kPa at 21 °C.
- Key procedural points:
- Measure flow via the valve side vent with valve in analysis mode.
- Do not use purge mode with the flow meter (purge ≈ 5 l/min may damage meter).
- Reference valve check: 700 ml/min ± 100 ml/min.
- Test valve acceptance: flow must be between 600 ml/min and 800 ml/min.
- If out of range, adjust per manufacturer’s instructions or return valve for recalibration.
Applications and who uses this standard
- Primary users:
- LPG producers, bottlers and distributors
- Quality control and testing laboratories
- Valve and cylinder manufacturers
- Inspection bodies, safety auditors, and regulatory agencies
- Practical uses:
- Pre-use verification of valve function before conducting the valve-freeze dryness test
- Routine QA to prevent valve icing, unsafe deliveries, equipment failure or customer complaints
- Supporting compliance with national/regional LPG safety and quality requirements
Related standards and context
- ISO 13758:1996 (original standard) - valve freeze method for propane dryness
- ISO 4257 - Liquefied petroleum gases - Method of sampling (now the normative sampling reference)
- Developed by ISO/TC 28 and adopted by CEN; applicable across CEN member countries
Keywords: EN ISO 13758, ISO 13758 amendment, propane dryness, valve freeze method, liquefied petroleum gases, flow rate verification, LPG testing, CEN standard.