Code vs. Non-Code Tanks: Variation in Materials & Construction Processes

The manufacturing processes differ and the costs of construction vary significantly depending on which type of vacuum tank you order.

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QUESTION: What are the differences between a code and a non-code vacuum tank?

Tad Boomer
Atlanta, Ga.

ANSWER: Very good question. There is a fundamental difference between code and non-code tanks. A code tank can be used to vacuum hazardous materials, such as chemicals and liquids deemed to be hazardous by the U.S. Environmental Protection Agency. Trucks carrying these tanks are often found in the oilfields sucking up various oils and chemicals. Then again, the code tank can be used for the liquids and materials that a non-code tank can pick up. The code tank is built to the ASME (American Society of Mechanical Engineers) code.

The non-code vacuum tank can only be used to carry non-hazardous liquids and materials. It cannot be used to haul hazardous materials.

As you might expect, they are designed and built differently.

NON-CODE BASICS

For a non-code tank, manufacturers can build whatever they think will work when combined with accessories and equipment specified by the customer. No outside authorities will inspect or verify how the tank was built. The manufacturer is responsible for the construction and for any warranties offered.

During construction, the manufacturer rolls a shell into a circle and attaches flanged and dished heads, then installs the primary shut-off and the openings for intake and exhaust as needed. The tank is put on skids for truck-mounting and the tank construction is essentially complete. 

Overall, a non-code tank is basically anything a manufacturer feels safe building.

CODE IS MORE COMPLEX

The code tank is a different beast from the start. First, the builder must be a certified member of the ASME organization, which requires following an expensive process. A required inspection proves the shop can build pressure and vacuum equipment and a detailed quality control manual must be furnished and approved by ASME.

Then the builder must register with an insurance company, such as Hartford or Commercial Union. They insure that the tank is built to the ASME Code. The entire process is time-consuming and costly. ASME certification costs $12,000 to $20,000 and lasts three years, when the process begins again.

Assuming the manufacturer is a member and gets the order to build a code tank, here is what the build process entails:

First the manufacturer secures a drawing with the design and a complete bill of materials to be used. This means documenting the entire process in a file. Then the materials are ordered and certified papers are delivered showing the type of steel and fittings to be used for the tank. The drawing will show how welds will be performed and the beveling required on the steel where the welds will go.

The manufacturer must determine if the welds will be X-rayed. By choosing to be X-rayed, the welds must have 100 percent coverage. Another cost is incurred to hire the mobile X-ray provider. If the choice is to go with 70 percent or more coverage along the welds, the manufacturer is required to buy thicker steel. The engineer specifies the thickness of steel that will work best, both for X-rayed and non-X-rayed tanks. The non-X-rayed tank is always made of heavier materials.

Before construction begins, a registered engineer must do the math to prove the tank materials can handle the required pressure and/or vacuum. These calculations are also included in the tank file. This cost is paid by the manufacturer; bigger shops have an engineer in-house and small shops may not.

EXPENSIVE PROCESS

At this point, the manufacturer has expended a lot of money and time and hasn’t started construction. Building the code tank requires certified welders on the job. If non-certified welders do some of the work, the tank is voided and the project must start over. 

The design is approved by the customer and the manufacturer can get to work on the tank. At various points during construction, the X-ray is done if needed. When the tank is complete, the insurance inspector gets involved. The inspector typically travels to the manufacturing facility, another cost paid by the builder. When the insurance agent signs off on the tank, it is deemed safe and can be insured.

Code tanks require rollover protection, usually consisting of rolled pipes in the shape of an inverted U. And they usually have vented fill caps in case the materials inside could build pressure.

A code tank requires a lot of bureaucracy and expense, but is very safe. That doesn’t mean the non-code tank is any less safe, however. That depends on the thoroughness of the manufacturing process and if the tank is used under the appropriate applications.



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