Loading Operations January 1995 TNRCC Rule 116.111(3) in Regulation VI requires that Best Available Control Technology (BACT) be applied to all facilities that must obtain a permit. BACT determinations are made on a case-by-case basis. Current BACT guidelines for loading operations: Accepted collection efficiencies (vapor collected to BACT control device) are as follows: Unenhanced Loading 65% Enhanced Loading 85% Annual Leak Checking* 95% Semi-Annual Leak Checking 97.5% Vacuum Loading 100% * Leak checking as required by New Source Performance Standards (NSPS) Subpart XX Definitions Unenhanced and enhanced loading are not BACT for compounds with vapor pressure greater than 0.5 psia. They are a way of decreasing loading losses if the off property impacts are too high. Unenhanced Loading- Loading loss emissions are sent to a control device, however, the trucks are not leak checked. Enhanced Loading- Loading loss emissions are sent to a control device, however, the trucks are not leak checked. A positive pressure of +3 to +5 inches of water is not exceeded in the truck cavity. This can be maintained by using a blower. Vacuum Loading- Hard-piped loading maintaining a vacuum of less than -1.5 inches of water in the truck cavity. Each application containing vacuum loading will be looked at individually. The pressure in the truck must never become neutral or positive when vacuum loading. Loading fugitive emissions - Uncollected loading emissions are called loading fugitives. These differ from process fugitives which are emissions that escape from valves, pumps, and any type of connections in the piping. The control device may be a flare, an incinerator, a carbon adsorption system or a scrubber. An approved flare has 98 percent destruction efficiency. An approved incinerator has 99.9 percent destruction efficiency. The recovery efficiency of a carbon adsorption system will be evaluated on a case-by-case basis; the Texas Natural Resource Conservation Commission (TNRCC) would like to see <100 ppm organic escaping the bed. Scrubber efficiency is estimated by the applicant. Scrubbers are usually used to control inorganics. The applicant may refer to the standardization packages for flares, absorber units, carbon absorption systems, and fugitive sources for methods of calculating these emissions. There are many emission sources to consider when loading chemicals. Uncontrolled loading fugitives, process fugitives from piping and components, tank emissions, and emissions from the control device that is controlling the collected loading emissions must all be considered. Process fugitive emissions are emissions that result from leaking valves, pumps, flanges, and compressors. Fugitive emissions from equipment and piping that is associated with the loading procedure must be accounted for in the project. Loading Operations Tank truck loading operations can be subdivided into three general categories: atmospheric trucks, pressure trucks used in atmospheric service, and pressure trucks. A. When loading compounds with a vapor pressure >0.5 psia, the collected emissions must be routed to a control device with a minimum of 98 percent destruction efficiency or 95 percent removal efficiency. The BACT for atmospheric type tank trucks consists of annual leak checking according to NSPS Subpart XX standards (which provides for a 95 percent collection efficiency of loading emissions) for compounds with a vapor pressure greater than 0.5 psia. Splash loading is not BACT. Submerged or bottom loading is required. Even though trucks loading chemicals other than gasoline are not subject to the NSPS subpart, the leak testing requirements outlined in Subpart XX are used as a BACT leak-testing benchmark for atmospheric trucks. Trucks which contain compounds with vapor pressures less than 0.5 psia are not required to be controlled; however, impact review does still apply. There may be cases where trucks handling material less than 0.5 psia may need to be controlled because of unacceptable off property impacts. If off-property impacts are found to be unacceptable, the applicant may decide to either leak test two times per year (which would provide for a 97.5 percent collection efficiency) or proceed with a vacuum loading type system (100 percent collection). B. In some cases, applicants may use pressurized trucks in atmospheric type loading situations (for example, a pressure truck used to transport Jet A or gasoline). It is possible for the applicant to obtain 100 percent collection efficiency in terms of estimating emissions if the following is applied: 1. Pressure truck certification: Is the pressure truck certified? Most pressure trucks are required to undergo DOT testing in order to maintain their pressure rating. If the truck is not pressure certified, a 100 percent collection efficiency should not be allowed (unless vacuum loading is being used). 2. Are pressure rated connections being used? A complete description of the loading and vapor recovery connections must be provided for a determination of collection efficiency. Loading into a pressurized truck without using pressure-stressed type connections cannot be given 100 percent collection efficiency. The efficiency will be determined on a case-by-case basis. 3. A 100 percent collection efficiency can be given to those applicants that are loading a pressurized material into tank trucks designed to handle a pressure of 15 psig or greater. Materials loaded into these types of tanks tend to be vapor at atmospheric temperature and pressure (the trucks are specifically designed for this type of service). NOTE: Recent permitting experience has indicated that not all pressure trucks are operated in a leak-free manner. Some trucks are equipped with what is known as a spew gauge. This is not considered to be BACT. A spew gauge is a method of determining the liquid level inside a tank truck. If a truck is equipped with a spew gauge, the vapor tightness of the tank truck is compromised during the loading operation. Although the tank truck may be tested and pressure certified to operate at 15 psig or greater, the spew gauge will still allow emissions to the atmosphere. The truck is no longer vapor tight, and the loading operation itself is no longer BACT. Depressurizations of trucks must be routed to a control device. Hoses used during loading must be purged and are not allowed to drip liquid. Spills must be properly attended to.