ISO 4268:2000

Overview

ISO 4268:2000 - Petroleum and liquid petroleum products: Temperature measurements - Manual methods provides internationally agreed manual procedures, equipment guidance and safety precautions for measuring the temperature of bulk petroleum and petroleum products in storage tanks. The standard emphasizes accurate determination of mean tank temperature because temperature error is often the largest contributor to uncertainty in volume-at-standard-temperature and mass calculations. The preferred technique recommended is the use of portable electronic thermometers (PETs), with alternative methods described for liquid-in-glass thermometers, sampling thermometers and permanently installed spot devices.

Key topics and technical requirements

ISO 4268:2000 covers practical and technical points including:

• Scope and applicability for manual temperature measurement of bulk storage tanks, road/rail tankers, barges and ship cargo tanks.
• Safety and procedural precautions to protect personnel and ensure repeatable, reliable measurements.
• Equipment specifications and selection criteria:
  • Portable electronic thermometers (accuracy, sensing elements, electrical safety, operation)
  • Liquid-in-glass thermometers (accuracy, resolution, armoured cases, periodic checks)
  • Bimetal dial thermometers, angle-stem and tank-bottom thermometers
  • Vapour-lock samplers, cup-case and flushing-case thermometers, sampling-bottle methods
• Measurement procedures for different tank types and conditions:
  • Pressurized tanks, vapour-tight tanks
  • Non-pressurized tanks at/near ambient temperature, and at temperatures differing by >15 °C from ambient
  • Vertical, horizontal, floating-roof and inclined tanks, rail wagons, road vehicles, ships and barges
• Corrections and verification: emergent-stem correction, verification procedures for permanently installed thermometers, and verification of representivity for single-point spot measurements.
• Exclusion: automatic averaging thermometers used in automatic gauging systems (covered by ISO 4266).

Applications and users

ISO 4268 is intended for professionals involved in custody transfer, inventory control and tank management who require reliable temperature measurement for volume correction and mass determination:

• Terminal operators and tank farm personnel
• Petroleum gaugers and surveyors
• Ship and barge cargo inspectors
• Road and rail tanker operators
• Quality control laboratories and inspection bodies
• Regulatory and standards authorities

The standard is practical for on-site manual measurements, training gaugers and establishing workplace procedures to minimize measurement uncertainty.

Related standards

• ISO 4266 - Automatic methods for temperature and level measurement (averaging thermometers)
• ISO 3170 - Manual sampling of petroleum liquids
• ISO 386 - Liquid-in-glass laboratory thermometers - design and use

Note: National regulations may supersede parts of ISO 4268; where conflicts exist, mandatory laws prevail.