Tuesday, August 26, 2008

Toronto Propane Fire Follow-up

In yesterday’s blog reviewing recent chemical incidents (see: “Chemical Incident Review 8-25-08”) I mentioned that it “is unlikely that it was caused by a legitimate transfer operation”. Well it seems that the accuracy of that observation would hinge on what is a ‘legitimate transfer’. Recent news reports indicated that just before the first explosion there was a propane transfer conducted by company personnel; a transfer prohibited under Ontario safety regulations


Additional follow up information was also included in a Toronto Star article. The city will be inspecting 580 homes in the area for blast related damage and asbestos contamination. It is not clear from the article where the asbestos came from. The City of Toronto expects to spend about $1.5 million (Canadian Dollars) in site and neighborhood cleanup. A suit against Sunrise Propane to recover those costs is likely.


Fixed Facility Transfers


In the way I used the term in my blog, this would have to be considered a ‘legitimate transfer’. In the way that government officials look at propane transfer operations it seems that it was an illegal transfer. The reason for that is that the transfer was taking place from one truck to another truck. Ontario safety rules require that bulk propane transfers take place between a fixed storage tank and a vehicle mounted tank and specifically prohibit truck-to-truck transfers. Both articles note that the Ontario Technical Standards and Safety Authority (TSSA) had previously cited the Sunrise Propane site for such transfers.


Neither article explains the reason for the regulations, other than saying that it reduces the possibility of leaks and fires. Without having seen the actual regulations, I can guess the reasoning. If the Ontario regulators also require high-flow cutoff valves on their propane storage tanks, such valves can greatly reduce the volume of product loss during a hose or connection failure. Without a requirement to have such valves on the storage tanks, there is no reason why a tank-to-truck transfer would be inherently safer than a truck-to-truck transfer.


High-Flow Cutoff Valves


These valves are safety devices that are placed between the tank and the main discharge valve on the tank. They include a flow meter that detects the rate of chemical movement through the discharge line. If the flow exceeds a pre-set value, indicating a large leak, the valve automatically closes, shutting off the flow to the leak.


Without such a valve in place, a human operator has to be present at the transfer, notice the leak, move to the valve control, and close the valve. In the event of a hose or line failure, that operator is in a high risk environment and may have to risk his life to close the valve. Officially, no company is going to ask, or in most cases even allow, an operator to take that risk.


Tank wagons and railcars are not equipped with high-flow cutoff valves fora variety of reasons. Facilities that handle high numbers of hazmat loadings may put such a valve on their permanent loading/unloading lines so that a valve very near the end of the line that connects to the mobile tank is controlled in the same manner. This limits the amount of unprotected line to the small amount between the valve and the mobile tank. Then frequent inspections are done on that short section of line to detect potential failures before they occur.


The United States Chemical Safety Board has recommended that OSHA require such valves on all fixed tanks used to store PIH chemicals, chlorine in particular. To the best of my knowledge, OSHA has yet to do so.


High-Flow Cutoff Valves as Security Devices


There is also a security aspect to the high-flow cut off valve. One of the easiest types of attacks to execute against a high-risk chemical facility containing release COI is for an insider to walk over to the bottom valve on a release COI storage tank and open the valve. Wearing suitable protective gear, the insider would just walk away and join the facility evacuation. A properly installed high-flow cutoff valve would make such an attack much more difficult.


The same relatively simple, stand-alone control system that operates the valve could also be programmed to sound a warning (a pre-set verbal notification over a PA system or plant radio system would work well). It could also initiate various release mitigation measures such as fire suppression systems.


As with all security and safety systems, high-flow cutoff valves must be appropriately designed, installed and maintained to be effective. They certainly should be considered for all facilities with storage tanks containing release-toxic or release-flammable chemicals of interest.

No comments:

/* Use this with templates/template-twocol.html */