API Bottom Loading

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 pollutions and economic benefits are the factors driving the adoption of bottom loading systems.

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. The opposite is the traditional method of loading through the open manhole covers on the top of the tank truck. Top loading has several disadvantages, such as: the person operates on the top of a tank truck, which is often more than three (3) meters above the pavement. standing on top of the tank truck the operator needs to position the loading arm into the manhole. during loading the operator, who is often standing on top of the tank truck, breaths in petroleum vapours, which is hazardous to his health. contamination of the medium with top loading is more likely to occur (rain and dust). top loading means splashing of product in the tank compartment, which may cause a significant build-up of static electricity charges within the compartment itself. Considering safety and contamination as the prime factors, the development of the earliest bottom loading systems, used by the aviation industry, began in the early 1950s. Especially the contamination of jet fuel was an important safety issue. For the same reasons, oil companies in the USA and Europe began experimenting with bottom loading. In this development, two events were critical in the widespread adoption of bottom loading: Recognising the value of the bottom loading concept by the American Petroleum Institute (API). They felt that the advantages were significant enough to strongly encourage the practice. API realised that an industry standard was required before bottom loading could be implemented on a large scale followed by the European CEN standard. Accordingly, further studies were undertaken and in 1967 the API published the first edition of API Recommended Practice 1004. This standard is revised regularly and has been expanded to include vapour 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. In many respects, the standardisation of bottom loading equipment and processes made expansion of the practice possible. The API makes recommendations regarding safety matters and compatibility of equipment. The result of the API 1004 RP recommendations is a uniformly acceptable safety standard and assures that a properly equipped truck will be able to load safety at almost any terminal. Another major factor influencing the adoption of bottom loading was the implementation of anti pollution laws. These laws made it necessary to capture gasoline vapours as opposed to letting them escape into the atmosphere. Final implantation of bottom loading in different countries was a function of the leading oil companies, who saw the advantages of bottom loading as well as local regulations, which were enforced by governments to achieve a safer way of loading tank trucks. Apart from the advantages regarding safety and environmental issues, bottom loading also has a number of additional benefits. A review of the key advantages. Fire prevention: the process of top loading involves the splashing of fluids during loading. This causes a significant build-up of electrical charges within the compartment itself. Electrical discharges can occur for many reasons. The chances for generating a spark are increased by the presence of moving men and equipment on the top of the truck. Eliminating this reduces risk. Grounding systems associated with the overfill prevention system reduce the chances for sparks even further. Spill prevention: every petroleum product spill is potentially serious, taking fire hazards, safety, pollution control and loss of valuable products into consideration. The dry disconnect features associated with the API bottom loading standards almost eliminates the potential for product spills at both loading terminal and the service station. Also the overfill prevention system as specified by the API prevents the possibility of serious product spill at the terminal. Operator safety: loading a tank truck from the top requires that a person work on a narrow walkway on the top of the truck high above the pavement. The operator has to handle awkward equipment and takes different positions to perform his task. At the same time, the operator may be outside in poor weather conditions and he may well be breathing high levels of petroleum vapours, which could affect his health seriously. The same operator is responsible to react quickly in case of an emergency. On the contrary, loading a tank truck from the bottom, the operator is standing safely on the ground throughout the loading process. This ensures he can react quickly in case of an accident or emergency. Vapour recovery: the transfer and transportation of petroleum products contribute significantly to the levels of pollution in an area. The practice of bottom loading makes the efficient recovery of petroleum vapours easier compared to top loading installations. A recovery of 99% of the vapours can be achieved in a safe manner. Avoidance of product contamination: during top loading, the manholes on the top of the tank truck are open, and easily contamination can take place (rain, dust, loose items, etc.). In bottom loading there is no open manhole, but a closed system during loading. Faster truck loading: several factors combine to make bottom loading a much faster method of filling a truck than top loading. First, the operator does not have to go the top of the tank truck to open the man hole and put the loading arm in its loading position. Manoeuvring bottom loading arms towards the tank truck adaptors is easier and much faster. Also under bottom loading system, more compartments can be safely filled simultaneously. Therefore, loading rates are much higher than in top loading. For example, top loading rates are in the range of 1100 1500 LPM, whereas for bottom loading, rates are in the range of 2100 2800 LPM. Less expensive loading islands: bottom loading islands are significantly less expensive to build and maintain than top loading islands. The walkway and overhead loading structure associated with top loading are eliminated. The savings can be quite substantial when the time comes to replace loading islands. Safer: with bottom loading by USA API and European CEN regulations, all fuel tankers should be equipped with electronic overfill prevention sensors. The pre set meter act as primary overfill prevention system. The electronic overfill prevention system serves as secondary safety system with one electronic sensor on top of each truck compartment. The electronic systems are 100% fail safe and self checking. Each loading Island should have an overfill prevention and grounding monitor as one unit, which is connected to all the sensors on the truck by one cable connection. By making this single connection overfill and grounding protection is done. The rack monitor acts as an output relay to terminal pre set and/or automation system. Among other equipment, which is specified in the API Recommended Practice 1004, loading arms are the most important feature in the total set up of an API bottom loading island. The general characteristics of bottom loading arms are similar to those found in top loading arms. Swivel joints with piping, elbows and flanges are used in both type of arms. The major difference is found in the fact that the top loading arms are equipped with a shut off valve, whereas the bottom loading arms are equipped with a dry disconnect coupler at the outlet of the arm. This API coupler is designed to match the configuration of the API adaptor, which is mounted onto the truck. A handle installed onto this coupler is used to activate the API adaptor. The API coupler must meet certain size and design criteria in order to fall within the specifications of the API 1004 RP. These criteria ensure that if a loading arm is equipped with any API coupler, any tank truck with an API adaptor will be compatible. As for API bottom loading systems, the loading arms are designed in a way that the required working envelop for the couplers can always be fulfilled. This working envelope, in which the adaptors of the tank truck are positioned, is described in the API 1004 RP. Regardless which tank truck is coming to the bottom loading terminal, as long as the truck is equipped according API, the loading arms can be connected to all the adaptors, and simultaneously. Another important advantage of bottom loading is that by installing the loading arms according to the API configuration and equipping it with flexible hose, a so called “cross over” is possible. Cross over gives the possibility to load different compartments with different petroleum products simultaneously, which is therefore the major reason to use hoses for bottom loading arms, in stead of rigid loading arms. Tankers should be tested to conform with ADR Appendix B.1a section 5 marg 211 150 and 211 151. The manhole is equipped with a lockable PAF (Pressure Activated Fillcover), which is the third security after the 601000S-3" and the Pressure-vacuum valve. Vapour valve should be installed in the (manhole) base-cover. Bottom valve (EN certified) will be installed at the bottom side of the tank-truck. The bottom valves come standard with air-connection and will open at 4-bar pressure. The VFC is the basic unit to control your PNEUMATIC BOTTOM and VAPOR valves on the tank truck. It gives you the possibility to open and close the bottom valves separately, as well as the safety to close the valves quickly by pressing the STOP button or actuate the interlock. The VAPOR valves are configured to open sequentially, directly after actuating the system. Air supply with a pressure of 4M> up to 8 bars enters the system through a FR unit (Filter Regulator). This FR unit is adjusted with a pressure setting of 5M> bars. The key bottom loading and offloading valve is the API RP-1 004 adapter designed to handle loading rates of 2.400 l/p.m. This valve is designed to conform with API and EU (CEN) standards at a working pressure of 5 bars. Interlock valve, vapour line valve and overfill prevention systems are also installed.