Enhanced safety can be achieved through a variety of vapor recovery/pressure systems, according to Adrian Nistler, project engineer at Polar Tank Trailer.
Nistler said the Cargo Tank Risk Management Committee (CTRMC) promotes the use of vapor recovery systems and the uniformity of systems that enhances safety and keeps workers off of tanks.
A minimal system, with a manually operated ball valve and quick coupling in the spill dam area, is beneficial because it captures harmful vapors during the loading process, according to Nistler, who spoke the National Tank Truck Carriers 2012 Tank Truck Show & Maintenance Seminar. The biggest safety concern with this arrangement is that the operator must go on top of tank with a hose.
A piped manual system, with a ball valve and a line running to ground, is beneficial because it captures harmful vapors during loading the process and the operator is not required to connect a hose on top of the tank. But the safety concern is that the operator still must go on top of the tank with this system.
A hydraulic/air operated system, with a hydraulic top valve or air top valve with a line running to the ground, captures harmful vapors during the loading process, and the operator is not required to go on top of tank. Vapor recovery can be used as a vent instead of open manhole unloading.
The safety concern is that the vapor recovery line should be clean and residue-free to keep from contaminating product in the tank.
Combined with a pressure system, with a pressurizing line from the front of the trailer, tee’d into the vapor recovery line, it can capture harmful vapors during the loading process, and the operator is not required to go on top of the tank during loading, during an open manhole, or during pressurized unloading.
The safety concern is that the vapor recovery line should be clean and residue-free to keep from contaminating product in the tank.
Truck Trailer Manufacturers Association (TTMA) publications on vapor recovery:
• RP 102: Vapor Recovery Line Configurations for DOT 407 and DOT 412 Cargo Tanks.
• TB 122: Operation of Typical Vapor Recovery Lines (VRL) on DOT 407 and DOT 412 Cargo Tanks.
• TB 123: Vapor Recovery Retrofit of MC 307 and MC 312 Cargo Tanks.