ISO 4256:1996 PDF

Liquefied petroleum gases — Determination of gauge vapour pressure — LPG method

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Title (English):

ISO 4256:1996

Liquefied petroleum gases — Determination of gauge vapour pressure — LPG method

Document status:: Active
Format:: Electronic (PDF)
Number of pages:: 8
Publication date:: October 17, 1996
Edition:: ISO IS 4256 edition 2 version 1
ICS:: 75.160.30

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Description (English):

La présente Norme internationale prescrit une méthode pour la détermination des pressions de vapeurs relatives des gaz de pétrole liquéfiés (voir l'article 3) à des températures comprises entre 35 °C et 70 °C. NOTES 1 Les renseignements à propos de la pression de vapeur des gaz de pétrole liquéfiés sont nécessaires pour résoudre les problèmes de choix des capacités des récipients de stockage, de transport et des équipements dans lesquels les GPL sont utilisés, en vue d'assurer une manipulation sans danger de ces produits et pour assurer que les pressions maximales de service envisagées n'excèdent pas celles dans les conditions ambiantes de fonctionnement prévues. 2 La pression de vapeur des gaz de pétrole liquéfiés est une mesure indirecte de la température minimale de début de vaporisation. Elle peut aussi être considérée comme une indication sur le constituant le plus volatil présent dans le produit.

Technical details

Technical committee: ISO/TC 28 - Petroleum and related products, fuels and lubricants from natural or synthetic sources
SKU: ISO 4256:1996

Abstract

Overview

ISO 4256:1996 specifies a laboratory method - the LPG method - for determining the gauge vapour pressure of liquefied petroleum gases (LPG). Intended for temperatures approximately 35 °C to 70 °C, the standard describes the required test apparatus, sampling and handling, test procedure (purging, filling, equilibration), measurement corrections and reporting. It replaces the first edition (ISO 4256:1978) and includes normative annexes for equipment and safety.

Key topics and technical requirements

Scope: Measurement of LPG gauge vapour pressure (absolute vapour pressure minus atmospheric pressure) as an indicator of volatility and storage/handling requirements.
Test apparatus: Two-chamber assembly (upper and lower chambers) with specific dimensional and volumetric requirements. Upper chamber dimensions and two options for lower chamber volume (33 1/3% or 20% configurations) are specified to meet volumetric ratios required by the method.
Pressure measurement: Use a Bourdon-type gauge of appropriate range. Readings must be corrected for gauge error by calibration (dead-weight tester or certified secondary gauge).
Temperature control: Constant-temperature water bath capable of maintaining test temperature within ±0.1 °C for ≤50 °C tests and ±0.3 °C for >50 °C tests. Thermometer ranges and placement are specified.
Hydrostatic and leak tests: Assembled chambers must be certified to withstand high hydrostatic pressures (manufacturer certification ~7 000 kPa) and must pass a leak test at ~3 500 kPa in a water bath prior to use.
Procedure highlights: Purge apparatus, fill with sample, invert and shake, immerse in bath, perform timed agitations and readings until two consecutive readings differ by ≤5 kPa. Correct measured values for gauge error and ambient barometric pressure (converted to the standard 101.3 kPa).
Precision: Repeatability r = 12 kPa; reproducibility R = 19 kPa.
Safety: The standard includes warnings and an annex on safety precautions for handling flammable LPG.

Applications and users

Practical applications:
- Determining LPG volatility for design of storage vessels, cylinders and transport containers
- Verifying LPG specifications for safe handling and customer use
- Quality control in LPG production, distribution and import/export testing
Who uses it:
- Petroleum and LPG laboratories, testing houses and refineries
- Equipment designers and manufacturers (pressure vessels, regulators)
- Regulatory agencies and safety inspectors
- Shipping and storage operators requiring vapour-pressure data for safe operation

Related standards

ISO 3007:1986 - Petroleum products - Determination of vapour pressure (Reid method)
ISO 4257:1988 - Liquefied petroleum gases - Method of sampling
ISO 4256:1978 - First edition (superseded)

Keywords: ISO 4256:1996, LPG vapour pressure, liquefied petroleum gases, gauge vapour pressure, vapour pressure test, pressure gauge, hydrostatic test, LPG method.

Related standards

Standards mentioned in the description

Abstract

Overview

Key topics and technical requirements

Scope: Measurement of LPG gauge vapour pressure (absolute vapour pressure minus atmospheric pressure) as an indicator of volatility and storage/handling requirements.
Test apparatus: Two-chamber assembly (upper and lower chambers) with specific dimensional and volumetric requirements. Upper chamber dimensions and two options for lower chamber volume (33 1/3% or 20% configurations) are specified to meet volumetric ratios required by the method.
Pressure measurement: Use a Bourdon-type gauge of appropriate range. Readings must be corrected for gauge error by calibration (dead-weight tester or certified secondary gauge).
Temperature control: Constant-temperature water bath capable of maintaining test temperature within ±0.1 °C for ≤50 °C tests and ±0.3 °C for >50 °C tests. Thermometer ranges and placement are specified.
Hydrostatic and leak tests: Assembled chambers must be certified to withstand high hydrostatic pressures (manufacturer certification ~7 000 kPa) and must pass a leak test at ~3 500 kPa in a water bath prior to use.
Procedure highlights: Purge apparatus, fill with sample, invert and shake, immerse in bath, perform timed agitations and readings until two consecutive readings differ by ≤5 kPa. Correct measured values for gauge error and ambient barometric pressure (converted to the standard 101.3 kPa).
Precision: Repeatability r = 12 kPa; reproducibility R = 19 kPa.
Safety: The standard includes warnings and an annex on safety precautions for handling flammable LPG.

Applications and users

Practical applications:
- Determining LPG volatility for design of storage vessels, cylinders and transport containers
- Verifying LPG specifications for safe handling and customer use
- Quality control in LPG production, distribution and import/export testing
Who uses it:
- Petroleum and LPG laboratories, testing houses and refineries
- Equipment designers and manufacturers (pressure vessels, regulators)
- Regulatory agencies and safety inspectors
- Shipping and storage operators requiring vapour-pressure data for safe operation

Related standards

ISO 3007:1986 - Petroleum products - Determination of vapour pressure (Reid method)
ISO 4257:1988 - Liquefied petroleum gases - Method of sampling
ISO 4256:1978 - First edition (superseded)

Keywords: ISO 4256:1996, LPG vapour pressure, liquefied petroleum gases, gauge vapour pressure, vapour pressure test, pressure gauge, hydrostatic test, LPG method.

ISO 4256:1996 PDF

Technical details

Abstract

Overview

Key topics and technical requirements

Applications and users

Related standards

Related standards

Abstract

Overview

Key topics and technical requirements

Applications and users

Related standards

Related standards

Liquefied petroleum gases — Determination of vapour pressure — LPG method

Petroleum products — Determination of vapour pressure — Reid method

Liquefied petroleum gases — Method of sampling