According to the EN590 standard, the maximum acceptable amount of water in diesel fuel is 200 milligrams per kilogram (200 ppm). This is the precise limit set to ensure optimal performance and longevity of diesel engines and fuel systems.
Understanding Water Limits in Diesel Fuel
The presence of water in diesel fuel, even in small quantities, can lead to significant operational issues and damage to fuel systems. International standards like EN590 define the permissible water content to safeguard fuel quality.
What is EN590?
EN590 is the European standard that specifies the requirements for diesel fuel to be sold and used in the European Union and several other countries. It covers various properties of diesel fuel, including density, cetane number, sulfur content, and, crucially, water content. Adhering to this standard ensures that diesel fuel is suitable for modern diesel engines and helps prevent common fuel-related problems.
Why Water in Diesel is a Problem
Even if within the 200 ppm limit, understanding the implications of water in diesel is crucial for maintenance and performance. Water can cause:
- Corrosion: Water promotes rust and corrosion within fuel tanks, lines, and engine components, especially high-pressure common rail systems that are highly sensitive to contamination.
- Microbial Growth: Free water creates an ideal environment for bacteria, fungi, and yeasts to grow. These microbes form a sludge that clogs fuel filters, contaminates fuel, and can cause severe system damage.
- Reduced Lubricity: Water displaces diesel fuel, reducing its inherent lubricating properties, which can lead to increased wear on fuel pumps and injectors.
- Fuel System Damage: At high pressures and temperatures, water can cause cavitation damage to fuel injectors and pumps. In cold weather, it can freeze, forming ice crystals that block fuel lines and filters.
- Combustion Issues: Water does not burn, leading to incomplete combustion, reduced engine power, increased emissions, and potential engine stalling.
Acceptable Water Content Overview
| Standard / Measurement | Limit | Explanation |
|---|---|---|
| EN590 | 200 mg/kg | European standard for diesel fuel quality. This equates to 200 parts per million (PPM). |
| PPM (Parts Per Million) | 200 PPM | A common unit of measurement, indicating 200 parts of water for every million parts of fuel by mass. |
Sources of Water Contamination
Water can enter diesel fuel at various points:
- Condensation: The most common source. As temperatures fluctuate, moist air in fuel tanks condenses on tank walls, forming water droplets that fall into the fuel.
- Delivery: Contaminated fuel deliveries from suppliers.
- Storage: Poorly sealed tank caps or vents can allow rainwater or moisture-laden air to enter.
- Handling: Improper fuel transfer or storage practices.
Practical Insights & Solutions
While the EN590 standard sets the acceptable limit, proactive measures can significantly reduce water content and prevent issues:
- Regular Fuel Tank Draining: Periodically drain the lowest point of fuel tanks (sump) to remove accumulated water and sediment.
- Fuel Filtration: Utilize high-quality fuel filters with water separators designed to remove both particulate matter and free water. Modern fuel systems often incorporate multi-stage filtration.
- Tank Maintenance: Ensure fuel tank caps are properly sealed and vents are equipped with breathers to minimize moisture ingress.
- Fuel Additives: In some cases, specific fuel additives (demulsifiers or dispersants) can help separate water or keep it finely dispersed so it can be removed by filters. However, always consult engine manufacturer recommendations before using additives.
- Monitoring: Implement regular fuel quality checks, especially for bulk storage tanks, to detect water contamination early. Fuel testing kits can provide quick indications of water presence.
Maintaining diesel fuel quality, particularly concerning water content, is paramount for the efficient and reliable operation of diesel engines. Adhering to the EN590 standard's 200 ppm limit for water is a critical aspect of this.
