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9/30/2008

In today's manufacturing environment, loss prevention is crucial. Keeping your employees safe and your assets secure allows you to operate a successful business. I have extensive expertise in the petroleum industry and know first hand the tips and techniques necessary to avoid personal injury or asset loss specific to heated asphalt storage tanks. It is vital to understand the sources of risk and then the inspection and maintenance required to counter these risks.
The majority of research material published around asphalt loss prevention has been focused on Cleveland Open Cup Flash or PM Closed Cup Flash results. As the use of hot asphalt has increased over the last century, studies have shown that inconsistent crude streams, improper cracking of crude oil and cross contamination are the major causes for low flash points. Within a storage tank however, it should be known that thermal degradation of heated asphalt along with internal oxidation and refluxing within the tank can cause a change in flash and atmospheric properties also. Although many times thermal oxidation results in only minimal change in the flash point of asphalt, if another element, like coke, is present it can cause other issues.
In simple terms thermal oxidation or coking is the oxidation of heated asphalt caused by oxygen being present in a heated petroleum tank. Coke is found regularly on the roof and roof truss. This is a good place for the oils to collect and start the oxidation process.
Coke is a natural place for the lighter hydrocarbons to collect. Coke is inherently porous, so as the light hydrocarbons, either from contaminated flux or thermal oxidation, saturate the coke and you have the fuel side of the fire triangle.
For a tank loss prevention system to work properly, you must have a good air sweep across the atmosphere of the tank. That is, about 50-100 SCFM of fresh air flow sweeping the asphalt fumes from the atmosphere and exiting the tank through an environmental system. This catch-22 is the root of many issues within the asphalt manufacturing and storage industry. With the presences or potential presence of asphalt coke on the rafters inside the tank (fuel) along with the heated material within the tank (ignition & fuel), we then add oxygen performing the air sweep. You have now created the potential for an fire or explosion within the tank.
The best way to combat the chance of a fire within an asphalt tank is to put in place a proper loss prevention system. That system should include regular monitoring of the atmosphere (Oxygen and Lower Explosive Limit). This can't be left to one person to manage, as this needs to have a back up system. For that system a database for entry and history is essential. This enables the reference, or double check, of the atmospheric testing to be done by a second person. A reference guide and training needs to be present for the employee performing the testing and the employees potentially affected. Your employees need to understand the impact on the system and what to look for.
Next is a tank cleaning schedule. It is good to clean your storage tanks on a regular basis. I personally use a tier system for the cleaning schedule. Finished oxidized material tanks get cleaned annually, flux storage tanks are every three to five years, cooling tanks and every three years and large cooler tanks are every ten years. This cost of safety and asset utilization, should be built in to your operating expense.
Maintenance is the next step to your loss prevention system working properly. Preventative maintenance on all parts of your new safety system needs to be assessed and scheduled. Maintenance employees should know and understand the potential exposure they have. Your maintenance staff will also need to understand the integral parts of the system, how the air sweep operates, how clean is clean in the tank, your environmental system and it's requirements.

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