API Bottom Loading

Bottom Loading Overview

Bottom loading is a method of filling tank trucks by pumping petroleum products into cargo tanks through a system of valves and fittings mounted under a truck. Human safety, product contamination, environmental pollution, and economic benefits are the factors driving the adoption of bottom loading systems.

The traditional method of loading involves filling through the open manhole covers on the top of the tank truck. This top loading approach has several disadvantages:

• The operator works on top of a tank truck, often more than three meters above the pavement.
• Positioning the loading arm into the manhole while standing on top is cumbersome.
• Operators breathe in hazardous petroleum vapors during loading.
• Contamination of the medium is more likely with top loading (due to rain, dust, etc.).
• Splashing product can lead to significant static electricity build-up within the compartment.

Historical Context

Considering safety and contamination as prime factors, the development of early bottom loading systems by the aviation industry began in the early 1950s, particularly to address jet fuel contamination. Oil companies in the USA and Europe began experimenting with bottom loading for similar reasons. Two critical events facilitated the widespread adoption of bottom loading:

1. The American Petroleum Institute (API) recognized the value of the bottom loading concept and strongly encouraged its practice.
2. API understood the necessity of an industry standard before large-scale implementation, followed by the European CEN standard.

In 1967, the API published the first edition of API Recommended Practice 1004, which is regularly revised and has expanded to include vapor recovery and high-level sensing systems. It is now the standard for bottom loading in the USA, Europe, and many other parts of the world. The standardization of bottom loading equipment and processes has made its expansion possible.

API Recommendations and Regulations

The API makes recommendations regarding safety matters and equipment compatibility. The result is a uniformly acceptable safety standard that ensures a properly equipped truck can load safely at almost any terminal. Another major factor influencing the adoption of bottom loading was the implementation of anti-pollution laws, which mandated the capture of gasoline vapors rather than allowing them to escape into the atmosphere.

The final implementation of bottom loading in various countries depended on leading oil companies recognizing its advantages and local regulations enforced by governments to ensure safer loading practices.

Key Advantages of Bottom Loading

Apart from safety and environmental benefits, bottom loading offers several additional advantages:

• Fire Prevention: Top loading can lead to fluid splashing, increasing the risk of electrical charges and sparks. Bottom loading minimizes this risk.
• Spill Prevention: The dry disconnect features of API bottom loading standards significantly reduce the potential for spills at both loading terminals and service stations.
• Operator Safety: Bottom loading allows operators to remain safely on the ground during loading, enabling quick responses in emergencies.
• Vapor Recovery: Bottom loading facilitates efficient vapor recovery, achieving up to 99% recovery in a safe manner.
• Avoidance of Product Contamination: Unlike top loading, where manholes are exposed to contamination, bottom loading uses a closed system.
• Faster Truck Loading: Bottom loading is generally quicker due to easier maneuverability and the ability to fill multiple compartments simultaneously.
• Cost-Effectiveness: Bottom loading islands are less expensive to build and maintain compared to top loading islands.
• Enhanced Safety Features: Regulations ensure that all fuel tankers are equipped with electronic overfill prevention sensors, enhancing safety during loading.

Loading Arms and Equipment

Among the equipment specified in the API Recommended Practice 1004, loading arms are critical to the setup of a bottom loading island. The characteristics of bottom loading arms are similar to those of top loading arms, but they feature a dry disconnect coupler for safety.

The API coupler must meet specific size and design criteria to ensure compatibility across various tank trucks. The design allows for flexibility, including a "cross over" capability, enabling simultaneous loading of different petroleum products.

Testing and Compliance

Tankers should be tested to conform with ADR Appendix B.1a sections 5 marg 211 150 and 211 151. The manhole is equipped with a lockable PAF (Pressure Activated Fillcover) for added security.

The bottom valve (EN certified) installed at the bottom of the tank truck opens at 4-bar pressure. The VFC controls pneumatic bottom and vapor valves, ensuring safety with features like quick closure through a STOP button.

The key bottom loading and offloading valve, API RP-1 004, is designed to handle loading rates of 2,400 l/p.m. This valve conforms to API and EU (CEN) standards at a working pressure of 5 bars, and includes interlock valves, vapor line valves, and overfill prevention systems.