Responding to a rail transportation incident is unlike most other hazmat responses. For instance, rail incidents often occur at the most inopportune locations, such as precisely equidistant from the two closest crossings surrounded by woods, swampy areas, or other relatively impenetrable terrain. Such situations call for inventive solutions to extending the working time of our personnel at the scene and reducing the burden of transporting oftentimes-heavy equipment by using all-terrain vehicles for transporting personnel and equipment; or carts to haul equipment to and from the scene.
Once we arrive at the railcar or railcars themselves, a utility rope with equipment bag attached will enable the hoisting of equipment and will reduce the number of trips up and down the side of the railcar. The placement of a ground ladder for access to elevated levels will also reduce the fall hazard presented by the integrated railcar ladder present on a tank car — which is angled itself to conform to the curvature of the railcar — and can provide the sole means of access when a tank car is overturned or the integrated ladder is compromised. To further reduce the fall hazards presented on the confined top platform of a rail tank car, fall protection harnesses that can fit over hazmat PPE are available.
Fixing the Leak
Let’s now say that you have been dispatched to a general service rail tank car that is leaking product. What are some of the likely locations of leaks, and how do we fix them? In terms of leak locations, we may encounter a rail tank car in which the tank itself is compromised in a derailment, a leaking bottom valve; a leaking siphon tube valve or vapor valve, a leaking manway seal; a pressure relief vent or valve that is activating; or condensation or steam discharging from heater coil piping. As we always say in hazmat response, try the simplest actions first to resolve the situation. Just as the “try before you pry” axiom applies to forcible entry situations in fire fighting, it is highly embarrassing to perform detailed response measures on a tank car while in actuality simply closing a valve would have worked — and of course the other personnel on the call will never continue to ride you about that!
In responses involving a leaking manway seal, the relatively easy mitigation measure of replacing the seal on the 18” to 22” opening — 10” fill holes on some acid cars — will “save the day.” When fittings have loosened, tightening the appropriate nuts or bolts will sometimes stop, or at a minimum slow the leak. As rail tank cars are very rugged, we often state that there are three different levels of tightness: tight (using a wrench), damn tight (using a bigger wrench), and railroad tight (using a big big wrench with a cheater bar for leverage).
Likewise, if the pressure relief vent on a general service rail tank car has ruptured due to the sloshing of product inside the car — and not over pressurization — the high technology method of placing a tennis ball on the top of the vent opening and securing the lid of the vent over the ball often serves as a great interim measure, with the long-term fix of replacing the rupture disc hopefully following.
In instances involving the compromised tank of a general service tank car, “old school” methods using plugs, wedges, and sealing material often work well, with newer technology equipment such as magnetic patches working in an equally efficient manner. In one training exercise with a ruptured general service tank car, our team almost stopped the “unstoppable” leak by employing a magnetic patch, a raincoat, and the lid off of a plastic five-gallon bucket. I will leave it to the reader’s imagination to formulate that mental picture.
Sometimes a “leak” really isn’t a leak at all, such as one incident I responded to in which there appeared to be a liquid leak from the underside of a TDI (toluene diisocyanate) rail tank car that turned out to actually be condensation dripping from a heater coil fitting.
Pressure Rail Tank Car Response Considerations
When we are dealing with a possible over pressurization due to product reaction, heating, or reduction in volume of a railcar; or a dent, gouge, or other compromise in the tank car itself in any type of rail car, it is imperative that we determine the pressure inside the tank car to determine product pressure trends and the relative safety of the environment. For instance, we can utilize a pressure gauge with pipe extension that attaches to, ideally, the vapor valve of a chlorine railcar or a gauge screwed into the one-quarter inch threaded port of the sample line of an anhydrous ammonia, LP gas, or other railcar for just that purpose.
In responses involving chlorine railcars, the standardization of valves and fittings on such rolling stock is a big benefit. As we addressed the new “enhanced fittings” chlorine railcars in an earlier discussion, we will concentrate in this discussion on the “traditional” chlorine railcars. Such cars have a single protective housing atop the railcar, with four valves and a pressure relief valve inside. The two valves in line with the length of the car are the liquid valves— think of the “L” in length signifying liquid — and the transversely mounted valves are the vapor valves. The pressure relief valve (PRV) is located in the center between the four valves, with a frangible disc located above the valve for chlorine service. We should also remember that if a chlorine railcar has rolled over and is even slightly inverted, the vapor lines become liquid lines and vice versa.
If we have a leak from a liquid or vapor valve, we should first try closing the valve. If the leak is from the base of the valve, we may try tightening the nuts or bolts on the base of the valve to a “railroad tight” level. We may even be presented with a leak from the valve packing, in which the packing may be tightened or even replaced — with proper training. If a leak from the top section of a valve is encountered, we may screw the plug in the valve opening and open the valve fully, which will “back seat” the valve and seal off the top leak. If the product is not over pressurizing and we have a pressure relief valve that is sticking open, we may even “persuade” the sticking valve with a rubber mallet. If the above measures fail, we may then progress to the “when all else fails” method of installing a Chlorine “C” Kit on the leaking valve or PRV.
The standardization of the chlorine railcars mentioned above spills over into the realm of the Chlorine “C” Kit. Although the “C” Kit is employed for use on chlorine railcars to contain valve or PRV leaks, we must remember to take regular pressure readings of our product and we should also be cognizant of the fact that when we apply a “C” Kit we are containing product under pressure — with associated dangers — and once installed the kit will be traveling to the location at which the car will be off-loaded.
The “C” Kit is comprised of a strongback with hooks that fit into holes in the protective housing of the railcar, bonnets — with gaskets — that fit over either a valve or the pressure relief valve, and associated tools and appliances. To install the Kit, scrape or clean with a wire brush the surface within the protective housing to which the gasket mates. The relief valve on the appropriate bonnet is opened — a very important step to prevent injury — and the bonnet with gasket installed is placed over the leaking valve or PRV. The strongback is placed over the bonnet, and the hardware is tightened down. The relief valve on the bonnet is then closed and the area is checked for leaks with a spray bottle containing ammonia.
Other types of pressure tank cars are less standardized than chlorine cars, however we can still develop an appropriate knowledge base for response considerations nonetheless. Such cars may contain pressure relief valves; liquid and vapor valves (liquid valves in line with the length of the railcar) sample lines (used to draw samples of product), thermometer wells (closed tubes filled with antifreeze to allow the insertion of a thermometer to determine the temperature of product), and gauging devices (used to determine the level of liquid product). Much of the same techniques used on chlorine railcars can be used on leaks from the liquid and vapor valves; and PRVs on such cars.
As stated earlier, sample lines may be used as an attachment point for a pressure gauge to allow for monitoring of internal pressure. Thermometer wells should not present a leakage problem, as the fixtures consist of a closed tube. The caps on thermometer wells do have an important safety feature though, as they are designed to allow a release of pressure prior to the full disengagement of the threads to indicate a fracture in the well itself and allow the cap to be re-tightened.
Gauging devices may consist of a slip-tube style gauge (not to be used after April 2014) or a magnetic gauge. Slip tube style gauges, are a “spitter” gauge in which the packing nut is loosened, a fitting is loosened at the top of the gauge tube and the tube is raised and then lowered until liquid emanates from the fitting, thereby displaying the liquid level present inside the railcar.
The majority of leaks from slip tube gauging devices arises from the packing area and can be mitigated by tightening the packing nut or replacing the packing. Magnetic gauges use a ball-type float with a magnet that engages a magnet on the gauge rod inside the gauge tube. Just as with a thermometer well, the likelihood of a leak is very remote. Likewise, the cap is designed to release pressure as an indicator if a leak is present as the cap is unscrewed.
As stated earlier, we use a Chlorine “C” Kit to cap stubborn leaks on chlorine railcars. For other pressure rail tank cars (e.g. anhydrous ammonia, ethylene oxide, and propylene oxide), stubborn leaks from valves or PRVs can be contained with a Midland Kit. The Midland Kit is similar to a Chlorine “C” Kit, however it is comprised of a beam-type strongback and “U”-shaped devices that pin to the strongback instead of hooks for securing to the protective housing of the railcar. The bonnets are similar in configuration also and are equipped with a relief valve. Personnel should ensure that the bonnet gasket is compatible with the product involved.
In terms of mitigation techniques, properly trained response personnel may also perform some relatively intricate techniques to resolve the situation at hand. Rail tank cars containing flammable product may be flared, a process in which hoses and a vent stack are connected to a vapor valve (to reduce pressure) or a liquid valve (to remove product) and the product is then burned. Pressure rail tank cars containing certain products can be hot tapped to allow for the off loading of product, a process in which a certified welder welds a fitting with a ball valve to the car. A bit with a collar is then threaded onto the fitting, and a hole is then drilled through the shell of the railcar. The bit is then backed out and the ball valve is closed. An off-loading valve and fitting affixed to the main fitting is then used to off-load product. Cleanup companies usually perform the hot tap procedure.
One of the most spectacular methods of mitigation occurs in instances in which a general service railcar containing a flammable liquid has derailed in a remote area and the product cannot be successfully off-loaded. Certain cleanup companies may then dig a pit below one end of the railcar, place a shaped explosive charge on the outside of the car over the liquid space, and place lit flares in the pit. Flares are then placed in the air on long sticks closely proximate to the other end of the railcar, a shaped charge is placed on the exterior of the railcar above the vapor space, and the flares are lit. After all personnel are removed to a safe area, the vapor space charge is detonated and the vapors exiting the railcar begin to burn. The liquid space charge is then detonated and the liquid fills the pit and burns. The product is allowed to burn as long as possible so that the greatest amount of product is consumed.
As can be witnessed in our above conversation, the tactics utilized for the mitigation of railroad hazmat incidents can range from the very simple to the complex. As hazmat technicians we must constantly train for such incidents so that if the time comes to perform such actions as applying a Chlorine “C” Kit atop a pressure rail tank car at 2:00 a.m. one morning, we can do so safely and effectively. We must also remember to keep safety at the forefront of our operations, remembering that when we are operating at a rail transportation incident we are dealing with massive cars and car components; possible products under pressure, and a generally unforgiving environment.
As always, be safe out there and be sure to visit the North Carolina Association of Hazardous Materials Responders website at www.nchazmat.com.
Glenn Clapp is Past President of the North Carolina Association of Hazardous Materials Responders and is a Fire Training Commander (Special Operations) for the High Point Fire Department. He is a Technician-Level Hazmat Instructor, a Law Enforcement Hazmat Instructor, and is a Certified Hazardous Materials Manager and Certified Fire Protection Specialist.