Leak Detection and Repair (LDAR) method constitutes a key element of strategies aimed at minimizing emissions of volatile organic compounds (VOCs) from industrial installations. Among potential emission sources, process valves play a particularly important role due to their large numbers, wide variety of designs, and placement within process lines, all of which result in a significant contribution to the overall emission balance. Leakages occurring in valves, flanged connections, and other valve components may lead to raw material losses as well as the release of hazardous substances into the atmosphere.

Mechanisms of leakage formation

The complex geometry of process valves, especially control and isolation valves, includes numerous elements susceptible to degradation, such as packing glands, flanged joints, valve bodies, and actuator systems. Potential leakage sources include, among others:
•    mechanical wear of sealing elements,
•    improper installation,
•    material aging,
•    corrosion,
•    gas permeation through construction materials.

Criteria for selecting LDAR methods

The selection of an appropriate LDAR method depends not only on valve design, but also on valve location, the type of medium being conveyed, and applicable emission standards.

Applied Leak Detection methods

Visual inspection – the simplest and least costly method, involving periodic inspection of valves to identify visible signs of leakage (liquid, condensate, corrosion). Effective mainly for detecting large leaks.

Portable detectors – enable emission detection using methods such as infrared (IR) spectroscopy or flame ionization detection (FID). They provide high sensitivity and allow identification of small leaks.

Continuous monitoring systems – advanced measurement systems enabling real-time monitoring of valve condition and automatic leak notification. They offer the highest effectiveness but also involve the highest capital investment costs.

Challenges in implementing LDAR programs

Effective implementation of an LDAR system requires:
•    qualified personnel,
•    access to valves located in hard-to-reach areas,
•    adaptation of measurement methods to the specific characteristics of different valve types.
Although initial implementation costs may be significant, LDAR programs lead in the long term to reductions in raw material losses and operating costs.

Planning and optimization of an LDAR program

The basis for effectiveness is the development of a detailed plan including:
•    identification of valve types,
•    determination of inspection frequency,
•    selection of detection methods,
•    repair procedures.
This process should make use of specialized software supporting LDAR data management and risk analysis. Such analysis requires the acquisition of fugitive emission data, which may originate from operational measurements or manufacturer documentation.

Tightness Standards and Regulations

Key standards include, among others:
•    API 624 – an American standard developed by the American Petroleum Institute, defining emission requirements for valves under extreme conditions (e.g. −29 °C).
•    API 625 – addresses leak assessment methods for valves and piping systems, focusing on VOCs emission reduction.
•    EN ISO 15848 – a European standard defining procedures for tightness testing and compliance with TA-Luft requirements.
•    EPA Method 21 – a method developed by the U.S. Environmental Protection Agency for detecting leaks in industrial installations, including valves.

Summary

The application of properly selected LDAR methods, combined with compliance with stringent tightness standards, enables significant reduction of VOCs emissions from industrial installations. Integration of inspection activities, precise measurements, and systematic maintenance improves operational efficiency while reducing negative environmental impact.

 
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Example procedure for valve monitoring within an LDAR program at a chemical installation

Objective: To minimize emissions of volatile organic compounds (VOCs) through regular monitoring and, where necessary, repair of valve leakages within the installation.
Scope: The procedure covers all valves within the installation that may potentially be sources of VOCs emissions. Particular focus is placed on valves operating under pressure and temperature and handling VOCs-containing media.
Monitoring Frequency:
•    High-risk valves: Monthly monitoring (valves located in areas with high VOCs concentrations).
•    Medium-risk valves: Quarterly monitoring (valves located in areas with moderate VOCs concentrations).
•    Low-risk valves: Semi-annual monitoring (valves located in areas with low VOCs concentrations).
Monitoring Methods:
•    Visual inspection: Checking for visible leaks (mist, liquid droplets).
•    VOCs detector measurements: Measurement of VOCs concentration near the valve using a portable detector, applying EPA Method 21 or an equivalent method.
•    Documentation: Recording monitoring results, including date, time, valve location, monitoring method, and measurement results.
Acceptance / rejection criteria:
•    Acceptance: No visible leaks and VOCs concentration below the regulatory threshold (most commonly 2.5% by volume of VOCs in air).
•    Rejection: Detection of visible leaks or VOCs concentration exceeding the threshold value.

Corrective Actions: If leakage is detected, corrective actions must be undertaken immediately. Repairs should be documented, including date, time, type of repair, and responsible personnel. Photographic documentation is recommended.

Personnel: Valve monitoring is performed by designated employees trained in appropriate monitoring and repair methods.

Equipment: Properly calibrated VOCs detectors and suitable valve repair tools must be used for monitoring activities.

Recording and reporting: All monitoring results and repairs must be recorded and reported in accordance with internal company procedures and applicable regulations.

Procedure review: The procedure should be regularly reviewed and updated based on operational experience and regulatory changes to ensure continued effectiveness and compliance.