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Tanks are a vital part of so many processes and many of them need to be heated. There are almost as many ways to heat a tank as there are types of tanks. Steam coils, heat transfer systems, direct immersion, tank wraps or heat trace; the list goes on and on. Knowing that there are many different types of heat that can be effectively applied would drastically improve the best selection for your application. 

What are the different types of tank heaters?

Today, we are going to discuss several different methods that can be used to heat a tank that you may have not known about in the past. Steam trace is one exception. We won’t talk about that one much because we don’t sell steam trace systems. They’ve been around for over 100 years, and everyone pretty much knows about them. Comparing steam trace to steam engine locomotives is a pretty good comparison when you see some of the new technology available.

All tank heating systems technically are not really heating a tank. They are heating the product in the tank. Tank heating systems use either a direct or indirect method of heating that product. 

• Direct is when a heater is directly placed into the liquid from outside the tank, and heats that tank content. 
• Indirect is when product is pumped into a coil system and is not in direct contact with the tank product. Heat is transferred to the process through an exchanger or coil system. 

We will take a look at several modern effective methods to heat a tank directly or indirectly.

Direct Tank Heating

Examples of direct tank heating systems include flanged or screw plug heaters, pipe insert heater, side arm heaters or DHG systems.

Flanged immersion/screw plug or pipe insert heaters are installed into a tank, and directly contact the liquid. The interface or connection point between the heater and tank is generally a pressure rated flange or NPT connection. Heater temperature control is done by way of a sensor placed in the tank liquid, and that sensor notifies a temperature controller so that it can decide to add or not add heat. These heaters often utilize a heater sheath overtemp sensor that watches the surface of that heater so that it does not overheat or cause damage to the tank contents. 

Below are several examples of direct tank heaters:

• Flange Immersion Tank Heater
• Pipe Insert Heater
• Side Arm Circulation Heater
• DHG Heater

Indirect Heating

Many times it is not possible or effective to use a direct heater due to equipment internal to the tank like mixers, or the need to contain the liquid by way of a double wall construction.  Indirect heat relies on the tubes or tank wall to transfer heat to the tank contents to either maintain their temperature or heat them up. With this in mind, it is important to consider how well your tank wall or the coils used will transfer heat to your process.  

A good example would be if we were going to install square tank pad heaters on the side of the tank to keep that tank at temperature. Attaching that tank pad heater to the tank, we rely on the tank wall that it is attached to to transfer the heat to the tank product. Steel for example is a very common product to make tank walls out of. Steel has a specific heat of .12, which is very poor at conducting heat. Be sure to allow for low heat transfer of steel when taking into account heat transfer.

Below are a few examples of an indirect heater:

• Heat Trace
• Heated Blankets
• Glycol/water or hot oil heat transfer systems

How do I select the right industrial heating solution?

Powerblanket was created to understand and solve heating issues relating to total temperature control. If you’re ready to make a selection, talk to our process heating engineers about which heater control panels might be a good fit for your heating processes.

Tank heating systems are often critical to most industrial applications, particularly with temperature control maintenance. For example, caustic tanks provide critical feedstock to refineries, chemical plants and processes. Biodiesel feedstocks such as vegetable oils, animal fats, palm oils or even jatropha will solidify at relatively normal ambient temperatures, requiring process temperature maintenance to ensure product quality. Keeping this product warm is vital to keep processes running efficiently and preventing product spoilage.

Electric tank heating systems can be designed to heat up tank contents from a lower to a higher temperature, or they can be designed to simply maintain a temperature once it is reached. 

Process Temperature Control

Many products and material arrive on site preheated from its source of delivery. Knowing what your products can tolerate on the low end of heat is critical. Spoilage will lead to longer production times and higher costs on your end. How low can you go before the product cannot be used in your processes?

It’s good practice to have a plan for both how you intend to warm up materials and how you intend on maintaining a consistent temperature. These process temperature maintenance plans are generally composed of two items: insulation and heating equipment. 

Insulation

Thermal insulation is an important component of a temperature maintenance system. The type of insulation and its thickness plays a key role in keeping heat at a stable level within your processes. 

Heater selection

Heater selection is also a factor. Tank heat can be maintained by heat trace, steam coils, heating pads or immersion heaters. Each has their own specific advantages for your application and should be a part of your process temperature maintenance plan.

Tank Heat Up

Tanks will often hold product that need to be heated up. A new load of product that is below the desired temperature for tank contents could be dumped in and, as a result, lower the average temperature. Just as with tank maintenance applications, the thermal insulation system is critical so that you don’t lose what you already have. All methods of heat up must provide dependable heat up.

Of primary consideration is how quickly you want to heat a tank to temperature. If you go too quickly with the wrong heating system, products can become burned or cook themselves onto the heating system.

Since it will take 8-10x as much thermal energy to heat product in a tank up to temperature, compared to maintaining temperature, you should also consider using higher 3 phase voltage. In the U.S., most heating systems are available in 480V 3 phase. This will drastically reduce your amperage requirements which will translate into much lower costs than if using lower single phase voltages.

Heater Types and Placement

As previously stated, your process temperature maintenance plan needs to be specific and use the right type of heater that best fits your processes. Common heater types used to heat up a tank are heat trace, steam coils, heating pads (for smaller systems), and immersion heaters that are specifically designed for tank heating.

Sensor placement in tank heaters should be carefully considered when designing a system.  Level controllers should be interlocked with the heater control panel to shut the heater down in low level conditions. Heater over temperature sensors should be installed on the heater sheath when using an immersion heater so that the heater is not allowed to run up to a high temperature, as this could cause damage to the tank or its contents. 

Finally, the main temperature sensor that regulates the heater must be placed at or just above the heat source. Placing it up high in the tank or far away from the heater will not allow the heater to perform as intended.

Control Panels and Wireless Systems

Control panels should be designed to allow for interface with the tank level, temperature systems, and remote plant control monitoring systems. Modern advances have allowed for a much wider acceptance of wireless communication systems as well. Both temperature and level information can be transferred to the heater panel wirelessly. Data transfer from the control panel to the plant-wide control system will allow tank heating systems to report to the proper personnel regarding performance and reliability.

Create a Heat Plan

Powerblanket can help you decide on a heat plan that meets your temperature-specific needs. Our team of thermal engineers are always available to talk over options and choose what is best for your processes. Reach out to us here.