BOTTOM-LOADING dry disconnect equipment standards for MC306 and DOT406 vehicles seem frozen in the spotlight since their inception in the 1960s. But the time has arrived to update the American Petroleum Institute (API) Recommended Practice 1004 (RP1004) under which the equipment is standardized. API is forming a task force to revise RP1004, says Prentiss Searles, the API official organizing the study group in Washington, DC.

The association is seeking volunteers from all segments of the industry who would be willing to serve with the group. Al Mosser, a senior standards engineer at Chevron, has agreed to serve as chairman, according to Searles.

The revision process, expected to be completed within two years, will include an opportunity for public comment after the task force has made its recommendations and before they are adopted, says Searles.

Earlier task forces have reviewed the standards and offered changes throughout the years. The current project will be the eighth since the first edition of RP1004 was published in 1967 after bottom loading was mandated by the Department of Transportation (DOT). Shortly after the DOT mandate, the API Transportation Department determined that uniform standards should be adopted for tank vehicle bottom-loading equipment.

Safety and environmental damage were the catalyst for concerns. By 1961, a committee was at work on the project to produce an adapter that would be interchangeable for all loading and unloading purposes involving petroleum fuels. The result of the effort was RP1004 and the subsequent equipment that meets the standard.

Safe Practices Safe loading practices are top priority for companies, but there are additional financial considerations. Managers know that failure to conform to the environmental laws can be costly in fines and legal expenses. They also have the business acumen to look seriously at any product loss as a major hit to the bottom line.

"Before bottom loading was adopted, there was a series of terminal accidents when fuel was top loaded at fast velocities through open manholes," says Kevin Fitzmartin of Emco Wheaton. "A phenomenon that could be seen would happen at night. There would be what looked like a ring of fire on top of gasoline being loaded. It was caused by an electrostatic charge. If trailers weren't grounded properly, there could be an explosion. Vapors in the air could be ignited by even a spark from a hot brake shoe.

"Other dangers involving top loading procedures occurred when drivers fell off the tops of trucks just from being complacent. There also was an economic value to the development of the hardware because major oil companies were looking for a faster terminal turnaround. At about the same time, environmental concerns were just getting fired up. The petroleum industry attracted criticism from environmental advocacy groups because the major oil companies had such a high profile."

During this period, several companies designed dry break connectors for petroleum use, but they were not standardized until RP1004 was published. "Establishing the standard is probably why the rest of the world has gone to bottom loading," says Fitzmartin.

Ken Toma, tank trailer manager for EBW Inc, also remembers what it was like before bottom loading was mandated and system standards were developed. The major oil companies were growing alarmed about personnel loading product at the top of the tank trailers. "The oil companies wanted to keep people on the ground as much as possible," he says.

Not only was it unsafe to have people climbing to and standing on the top, there was always the danger of product spilling onto the person loading the fuel. At the very least, managers knew the job was time-consuming and inefficient, Toma recalls.

David Lusby, vice-president for Fort Vale, notes that efficiency was improved when product could be unloaded in less time at service stations or convenience stores. Because the equipment had gone from three-inch lines in top loading vehicles to four-inch lines in bottom loading, product was moved faster.

Standard in Place With the API standard in place, manufacturers began producing the necessary equipment, offering their own versions to meet the demands of individual carriers and loading racks, but sticking to the standard.

They were following the information from API, which includes: "This recommended practice covers required and recommended features of the following aspects of tank trailer and truck bottom loading and vapor recovery: "(a) The configuration and operation of four-inch (101.6-millimeter) adapters for bottom loading. "(b) Tank vehicles equipped for bottom loading or vapor recovery. "(c) Secondary shutoff control systems. "(d) Loading installations equipped for bottom loading or vapor recovery."

Among the API required features for bottom loading are basic configurations for mating adapters and couplers. In the open position, the adapter must have a clear and unobstructed opening two inches in depth, measured from the outer face or closure of the valve. If a poppet device is used, the adapter poppet must have a travel of two inches, measured from the sealing surface. The front face of the adapter poppet must be flat within 0.004 inch, excluding the corner radius. No fastening device shall protrude above the general plate of the adapter face.

If an interlock control is installed on the adapter, the dimension must conform to those listed by API.

The primary liquid control must be by means of the set stop meter on the loading island or a self-contained system on the tank vehicle. The coupler may be opened for loading by manual or automatic means. The adapter may be operated by mechanical or other means, but it must be capable of being operated by the hydraulic force of the liquid being loaded, according to the RP1004 information.

Mating action must be of the push type, with provision for locking without rotating the loading coupler body. Coupling range must permit mating of the coupler to the adapter in any position in a range of 360 degrees, without any coupler contacting an adjacent adapter spaced on 10-inch centers. The mating section must be designed to limit the entrapment of liquid to not more than two cubic centimeters. A safety interlock or two-step action must be provided on the coupler to prevent any liquid flow while coupling or uncoupling.

Research and Development Don Kilgore, North American sales manager for Liquip Sales Ply Limited (Liquip), notes that an Italian manufacturer, Thieme, produced the first automatic coupler. Soon, other companies were following suit as a result of their own research and development.

"There are several features that apply to all automatic couplers, Kilgore says. "The trend in the industry is to incorporate more latching mechanisms, or fingers, into the coupler. Historically, three have been the standard, but by increasing the number of fingers, the stability between the coupler and tank truck adapter is increased. This reduces the amount of deflection between the poppets of each component and reduces the amount of product that becomes trapped between each valve. It also limits the amount of movement between the components, which reduces wear."

When bottom-loading adapters were implemented, product spillage was reduced to minute amounts, says Dave Huffman of Civacon. "API adapters function as dry disconnects," he points out. "Under typical conditions, the product flows without problems. But if the connection is broken, the valves close automatically."

The API RP1004 calls for the adapter to be "designed for a working pressure of 75 pounds per square inch at 1 1/2 times the working pressure."

At the same time, with equipment underneath the tank trailer or truck, personnel are no longer required to continually climb ladders and maneuver loading equipment into place on top. In addition, the API adapter standard recommends that adapters be as compact as practicable for adequate design, and that the adapter in combination with the coupler allow enough room between mountings for operators to work with heavy gloves.

The standard also recommends that the adapter be as short as practicable and its weight as low as feasible. API recommends the adapters should be installed "on centers that are not more than four feet above grade when the vehicle tank is empty and not less than 1.5 feet when the tank is full." All of that means that, in practice, loading is safer and more efficient, and vehicles return to the road faster, saving money and improving delivery schedules.

Chemical Uses However, safe and efficient delivery of product is not limited to petroleum fuels transportation. The chemical industry has the same concerns for safety and efficiency during loading, but the API recommended practice does not apply. A few companies are building terminal loading racks at chemical facilities to accommodate bottom-loading vehicles.

As a result, there is speculation that loading equipment standards will eventually be set for the chemical industry just as they are for petroleum fuels, although what association or agency would develop them is also speculation.

While petroleum loading arms and lines on tank trailers are four-inch, most chemicals are loaded with three-inch loading arms into tank trailers with three-inch lines. Few chemicals are bottom loaded, says Fitzmartin.

Dry disconnect equipment used with chemicals typically is made of stainless steel, says Huffman. He also noted that the equipment is used in some chemical operations to maintain closed-loop loading and unloading procedures. Two connections, one for vapor and one for liquid, are used most commonly with rail cars, but occasionally they are installed on tank trailers. Dry disconnects also are used with IBCs.

Bob Boggan, at Aeroquip Corporation, said because of the various concerns about personnel safety and environment protection, the chemical industry is moving toward zero leakage tolerance. To meet that goal, dry break fittings must handle high pressures, high temperatures, and harsh chemicals.

Zero leakage tolerance benefits a company's bottom line, says Scott McDonald of Banjo Corp. He notes that many chemicals are extremely expensive, and companies don't want to lose a drop.

Dry disconnect hardware used in the chemical industry varies in size, based on desired flow and other considerations. For railroad cars, adapters have to meet specifications required by that industry, says Dan Christian at Victaulic Company of America.

In operations where designs are not specified, the customer or end user decides what equipment will be chosen, he adds. For tank trucks and trailers that are loading atterminals with varying size equipment, the carrier generally is responsible for providing the appropriate adapters.

Maintenance Procedures Whether dry disconnect equipment is used in transporting petroleum or chemical products, it requires certain maintenance procedures. However, the primary focus for inspections and maintenance lies in the many different types of seals that are used according to the product.

Kilgore notes that with petroleum products, the additive blends that are used by different refiners can impact seals, causing more wear in some instances than others.

Toma says scheduled maintenance can ensure that gasket and seals are replaced at appropriate times. McDonald suggests that the equipment be flushed out after each use.

"Keep the dry break fittings clean," agrees Huffman. "If they are not used for some time, they should be flushed out with an appropriate cleaner." He noted that kits are available to rebuild some seals.

Fitzmartin notes that tank trailers have to be inspected annually, which means the dry disconnects will also be included. "Most terminals have their own internal written procedures for maintenance, and some do a really good job," he adds. "The need for examination depends on the amount of volume that is passing through the equipment.

"Whoever is doing the loading and unloading should watch for leaks and monitor ambient temperatures and vapor pressures."

Seals may last for three or four years, says Boggan. Dust caps can be placed over valves to keep dirt out and protect the equipment from being struck by flying objects such as rocks. Lockout features are also available for valve handles that will protect the equipment from tampering.

As for future prospects regarding dry disconnects, the task force to revise RP1004 is expected to complete its job within two years.

In addition, industry trends are being evaluated and customers are being briefed on how to align their operations to meet government regulations, says Boggan.

Other impacts on the industry are related to transportation growth internationally and how that market growth will be met. In Europe, environmental concerns are growing just as they are in the United States.

Another issue that involves the tank truck industry is the debate on petroleum product wetlines. If wetlines are forbidden by the Department of Transportation, the rule will have a dramatic effect, says Fitzmartin. "The API adapter would have to come right out of the skin of the trailer. I don't know how else they would do it."

Toma noted that this is already the case in some aircraft - the connections come directly out of the skin underneath the wing. One component on the underside is an adapter.

In addition, safety factors now built in to much of the tank trailer equipment would have to be redesigned, Fitzmartin points out. If lines are dry, a minute leak of vapor into a line is much more dangerous than liquid, he says. Options might include keeping lines flooded with nitrogen to be later released. Whatever the outcome, there are many considerations involved.

Meanwhile, dry disconnect equipment used in bulk transportation will continue to be viewed in ways to improve its use and to protect workers and the environment.