MC330/331 owners meeting HM-225 mandate
Feb 1, 2002 12:00 PM
OPERATORS of propane transports appear to be meeting the requirements of HM-225 without a great deal of difficulty. The phase-in period provides an adequate time frame for compliance, and technology is catching up with the regulatory requirements.
A progress report on HM-225 was provided during the Cargo Tank Maintenance Seminar October 30 in Chicago, Illinois. Rich Willard, Keehn Service Corporation; Tom Wise, Smart Hose Fluid Systems; Sean Darrah, Base Engineering; and Tom Nelson, DJT Products, made presentations.
A negotiated rulemaking, HM-225 was initiated by the Research and Special Programs Administration (RSPA) in an effort to address what the agency considered to be serious safety issues with MC330/331 pressure vessels. The cargo tanks are used to transport cargoes such as propane, sulfur dioxide, anhydrous ammonia, and nitrous oxide.
A series of compliance dates for the rule started in 1999, at which time operators of MC330/331 pressure vessels were required to begin inspecting and testing product hoses and hose hardware. Record keeping requirements for the tests and inspections took effect in 2000. Tank operators also were required to have operating procedures in place for loading and unloading product.
“The only real problem we've seen with the hose requirements is that protective coverings sometimes make it difficult to fully inspect a hose,” Rich Willard said. “In addition, hose identification numbers sometimes rub off or disappear.”
Since July 2001, passive shutdown systems have been required on new pressure vessels. These devices must be capable of automatically shutting off the flow of product without the need for human intervention within 20 seconds of an unintentional release caused by the complete separation of a liquid delivery hose.
Trailers in metered delivery service must have the same sort of remote shutdown system that is mandated on bobtails. A query system is required with the remote shutdown if the hoses and other delivery equipment will be obscured from the operator during unloading.
Shutdown system retrofits also were to begin no later than July 2001. Passive system retrofits are to be done at the time of the next pressure test, and the process is to be finished by July 1, 2006. Retrofits of remote shutdown systems for pressure vessels in metered delivery service also began with the first pressure test after July 1, 2001, and are to be completed by July 1, 2003.
“The remote shutdown systems are getting better,” Willard said. “Early systems had problems and didn't comply with distance requirements, especially in out-of-sight conditions. We're still seeing warranty issues with remote control systems. It seems it is always the installer's fault.”
One of the biggest concerns for operators of MC330/331 trailers in metered service is whether they need both remote control and passive shutdown systems. Willard suggested that issue has not been adequately answered by RSPA.
“One thing that does seem certain is that dedicated tractors will be almost a must with trailers that have remote shutdown systems,” he said. “We can foresee challenges in instances where owner-operators and other contractors pull shipper-supplied trailers.”
Setting aside the concerns about remote shutdown systems, Willard said that passive shutdown systems would suffice for the vast majority of MC330/331 trailers operating in the United States. At least three products are available giving operators a couple of ways to approach the issue.
One of the first passive shutdown products on the market was a hose-based system. “We felt that this industry was ripe for a new approach to hose technology when we developed Smart-Hose,” said Tom Wise. “This is not a leak-prevention device. Contained in the product hose, this system shuts off the product flow in both directions upon hose and coupling separation, catastrophic hose rupture, or hose stretching.”
The Smart-Hose hardware can be used with any hose — rubber, metal, or Teflon. Most importantly, the hardware can be reused in a new hose. Smart-Hose is available through Goodyear hose outlets.
Base Engineering Inc developed an electronically controlled system for passive shutdown on transports. The modular system can be installed in about two hours. It uses a pressure transducer for leak detection and is activated by a brake interlock.
Hoses, fittings, and piping are constantly monitored, according to Sean Darrah. If a product leak is detected, the Base system responds in half a second to close the internal valve. The tractor engine also can be stopped and the PTO disengaged. A fail-safe feature will close the internal valve with a loss of power or release of the trailer parking brakes.
An optional attendance timer is available. A 30-second warning will sound followed by delivery shut down. Darrah said this feature helps ensure operator attendance during loading and unloading.
Air is the key to the passive shutdown system from DJT Products. The system has been operating in the field for three years, according to Tom Nelson. It is easy to install, taking four to five hours the first time. After that, installation can be done in as little as an hour or two.
The DJT system consists of a Line Break Detector (LBD) that uses a mechanical sensor to monitor pressure in the discharge line of the pumping system. Under normal operating conditions the line pressure will always rise as product is transferred to the receiving vessel. When the line is filled with liquid or when the product pump is started, the line pressure must rise above 25 PSIG (1.7 Bar). A sensing piston moves a sliding cam, setting the LBD air circuit and signaling the operator that the minimum sensing pressure has been reached.
If the pressure in the discharge line should fall more than 14-40 psi, the spring inside the LBD will push the sensing piston back, along with the sliding cam assembly. This action shifts a mechanical air valve, which in turn trips the air circuit and vents all air pressure connected, to the emergency shutoff operator (ESO). The ESO closes all of the manually opened shutoff valves connected to it directly or with cables and linkages.
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