WITH the Environmental Protection Agency (EPA) leaning hard on chemical loading racks, tank truck fleets and shippers are under increasing pressure to provide closed-loop transfer systems. Fortunately, the industry is well positioned to meet the challenge.
An update on the regulatory push for chemical vapor recovery was delivered by John Freiler, Girard Equipment Inc, during the 2002 Cargo Tank Maintenance Seminar November 4-6 in Chicago, Illinois. He also discussed the basic design characteristics of the chemical vapor recovery systems now on the market.
An EPA proposed rule entitled “National Emission Standards for Hazardous Air Pollutants: Organic Liquids Distribution (non-Gasoline)” would require chemical loading racks to significantly reduce vapor emissions. Tank trailer operators will have a direct role in any chemical vapor recovery effort.
Freiler pointed out that the EPA proposal would affect both new and used MC307 and DOT407 chemical trailers, which could bring about an extensive retrofit effort. New chemical tank trailers are built with vapor recovery systems in mind, and the Truck Trailer Manufacturers Association (TTMA) has a recommended practice for new installation. Older equipment presents some challenges and is not covered by the current TTMA recommended practice. A retrofit RP is being developed.
The EPA proposal would also call for greater scrutiny of chemical cargo tanks equipped with vapor recovery systems. Like gasoline trailers, chemical tankers probably would have to be tested for leak tightness using EPA's Method 27 or a similar process, according to Freiler.
Turning back to older cargo tanks, Freiler described a four-step retrofit process that consists of the following: checking for outlets that meet the basic needs of a vapor-recovery system, verifying that adequate overturn protection is in place, determining specific system requirements, and choosing a particular system.
In most cases, a three-inch outlet will be needed on top of the cargo tank. Preferably, it should be off the manlid and should be unneeded for any other use. “If an outlet isn't already available, you may have to send the trailer to a code shop for installation of a new outlet,” he said. “Another option would be to modify existing hardware on top of the tank to free up an outlet.”
Vapor recovery hardware must be protected by the trailer overturn devices, according to federal cargo tank requirements. Overturn modifications may be necessary because vapor recovery hardware may have a relatively high profile.
“For maximum visibility, you'll want the vapor recovery valve to be as high as possible without going above the overturn protection,” he said. “With the basics out of the way, the tank operator needs to decide on a specific vapor recovery system.
“Will the system be used frequently or only sporadically? Do you want to use the system for air injection? Do you have an existing hydraulic system? Do you need any extras such as brake interlocks or electronic position readouts? Do you want a system that will keep operators off the top of the tank?”
A bare-bones system may be enough. This is nothing more than a ball valve and quick coupling. On the plus side, it is inexpensive and simple to operate. The disadvantage is that an operator must climb on the tank with a vapor hose and manually activate the valve.
Next in complexity is the piped manual system. It still uses a ball valve, but the vapor line can be permanently attached and runs down the side of the tank. Actuation can be accomplished with or without top access.
The top-of-the-line approach is a hydraulically operated system that is equivalent to vapor recovery on a new cargo tank. It uses bottom outlet hydraulics and is fully operational from the ground. Customized vapor recovery systems also can be designed for retrofit on acid trailers and other equipment that requires unusual connections or different line sizes.
Regardless of configuration, tank operators must ensure that the vapor recovery system includes a good vacuum breaker, according to Freiler. The system and piping must be cleanable and capable of being disassembled. Pressure gauges must be a part of any system to help ensure that operators don't open a pressurized line. If piping extends outside crash protection, it must have a shear section.