FAQ's
Why put fins into viscous service? We always use bare tube.
When heating a viscous product the challenge is to get the heat through the pipe and into the product. Viscous products generally have poor thermal coefficients. This means that the heat passes through the metal well, but then has a hard time getting into the product. Heat coming into the metal pipe but not being able to be transferred out of the metal causes the metal temperature to rise. Fins provide greater metal surface area, maximizing the amount of area in contact with the viscous product, allowing it to maximize the heat flow into the product.
Do the fins get “coked up”?
No. Coking is a function of temperature. The greater the temperature, the greater the likelihood of coking. By allowing the heat to flow out of the metal better, the metal stays at a cooler temperature, minimizing the tendency to coke.
How about fin fouling?
What many people think of as “coking” is really “fouling”. Almost any surface can get fouled when exposed to high particulate loading if not properly designed. It is important to specify the nature of the service as accurately as possible. The more that we know in the design stage about the tendency of the operation to foul, the more we can avoid fouling. With the proper fin spacing, fouling is not a factor.
Does it matter what type of fins are used?
Absolutely! Fins must always be oriented in the direction of the flow. In the case of natural convection tank heating, the flow is defined by the natural convection currents. As the heating coil delivers heat to the tank product, that material will rise, forming a convection current vertically upward from the heater. This means that the fins must be in a vertical orientation, so horizontal pipes must have helical fins. Conversely, in a suction heater or vertical pipe arrangement, such as the suction of a barge, longitudinal fins are optimal.
We use solid, not cut or serrated fins. Our fins are a minimum of 0.05” thick (18 gauge) and are always welded full width and full length to the pipe. We never use a “muff” fin, nor do we use tension wound or “L footed” fins for tank heating applications, as any inconsistency in the fin-to-pipe attachment will lead to thermal and/or mechanical failure.
What are the main advantages of using finned pipe instead of bare pipe?
Finned pipe typically has up to 4-10 times the surface area per linear foot as compared with bare pipe. Although the relationship is not completely linear, it is typical to require 1/3 to 1/6 as much finned pipe as bare pipe. When considering 3-6 times more bare pipe you are typically also considering 3-6 times more welds and taking up 3-6 times more of the surface area of the tank floor. Because shop welds are typically more controllable than field welds, and API-653 floor testing is much easier with significantly less floor space taken up by tank coils, the benefits of finned pipe coils multiplies.
So why doesn’t everyone use finned pipe for viscous product heating?
Frankly, a lot of people have gotten “burned” by installing the wrong finned surface. They may have experienced heavy fouling. They may have experienced the fins separating from the pipes and ending up in the tank suction. These problems first show up in reduced heating performance and have led some operators to avoid fins all together. Truly, though, the right finning in the right application will greatly improve the durability, serviceability, and heating performance of a viscous product tank.
When heating a viscous product the challenge is to get the heat through the pipe and into the product. Viscous products generally have poor thermal coefficients. This means that the heat passes through the metal well, but then has a hard time getting into the product. Heat coming into the metal pipe but not being able to be transferred out of the metal causes the metal temperature to rise. Fins provide greater metal surface area, maximizing the amount of area in contact with the viscous product, allowing it to maximize the heat flow into the product.
Do the fins get “coked up”?
No. Coking is a function of temperature. The greater the temperature, the greater the likelihood of coking. By allowing the heat to flow out of the metal better, the metal stays at a cooler temperature, minimizing the tendency to coke.
How about fin fouling?
What many people think of as “coking” is really “fouling”. Almost any surface can get fouled when exposed to high particulate loading if not properly designed. It is important to specify the nature of the service as accurately as possible. The more that we know in the design stage about the tendency of the operation to foul, the more we can avoid fouling. With the proper fin spacing, fouling is not a factor.
Does it matter what type of fins are used?
Absolutely! Fins must always be oriented in the direction of the flow. In the case of natural convection tank heating, the flow is defined by the natural convection currents. As the heating coil delivers heat to the tank product, that material will rise, forming a convection current vertically upward from the heater. This means that the fins must be in a vertical orientation, so horizontal pipes must have helical fins. Conversely, in a suction heater or vertical pipe arrangement, such as the suction of a barge, longitudinal fins are optimal.
We use solid, not cut or serrated fins. Our fins are a minimum of 0.05” thick (18 gauge) and are always welded full width and full length to the pipe. We never use a “muff” fin, nor do we use tension wound or “L footed” fins for tank heating applications, as any inconsistency in the fin-to-pipe attachment will lead to thermal and/or mechanical failure.
What are the main advantages of using finned pipe instead of bare pipe?
Finned pipe typically has up to 4-10 times the surface area per linear foot as compared with bare pipe. Although the relationship is not completely linear, it is typical to require 1/3 to 1/6 as much finned pipe as bare pipe. When considering 3-6 times more bare pipe you are typically also considering 3-6 times more welds and taking up 3-6 times more of the surface area of the tank floor. Because shop welds are typically more controllable than field welds, and API-653 floor testing is much easier with significantly less floor space taken up by tank coils, the benefits of finned pipe coils multiplies.
So why doesn’t everyone use finned pipe for viscous product heating?
Frankly, a lot of people have gotten “burned” by installing the wrong finned surface. They may have experienced heavy fouling. They may have experienced the fins separating from the pipes and ending up in the tank suction. These problems first show up in reduced heating performance and have led some operators to avoid fins all together. Truly, though, the right finning in the right application will greatly improve the durability, serviceability, and heating performance of a viscous product tank.