Votator Scrape Surface Heat Exchangers- Tube Materials & Selection Criteria

At Triplex, things seem to come in waves. And the last few weeks seem to have been nothing but Votator. Whether it’s new units, aftermarket parts, or equipment service, Triplex is your one stop shop for all things Votator Scrape Surface Heat Exchanger. Carrying on the Votator theme, for our first post of 2023, we wanted to provide an overview of the different tube materials available for Votator IIs. So let’s get started.

When sizing and selecting a Votator, the first thing we want to do is take a close look the product our end user is heating or cooling. While understanding the product important when selecting any piece of process equipment, it’s even more important when selecting a Votator.

When choosing a Votator, we often start with considering the tube material. This will determine our heat transfer coefficients and impact sizing (either the length of the unit we select or the number of tubes needed to do the duty).

Votator II is available in 6 different tube materials- chrome plated nickel, chrome plated carbon steel, stainless steel, chrome plated stainless steel, duplex stainless steel, and chrome plated duplex stainless steel.

Probably the most common tube we see is chrome plated nickel. This is the most thermally efficient tube available, especially when compared to a stainless-steel tube, yielding the fewest tubes needed for an application. Common product applications for chrome-plated nickel applications include peanut butter, shortening, margarine, cookie cream, and mechanically deboned meat.

While chrome plated nickel tubes are a great balance of cost and performance, the material is not well suited for highly acidic products or applications where will be using strong chemicals to CIP. In fact, we don’t want to use any chrome plated tube material ins aggressive CIP applications as the chrome can delaminate from the tube.

The next material we have is chrome plated carbon steel. I know what you’re thinking- carbon steel? In a food processing facility? Won’t that rust? Typically, yes, it would, but because the carbon steel tubes are chrome plated, the chrome prevents rusting when exposed to oil-based products or products with little water reactivity. Product applications from chrome plated carbon steel tubes include peanut butter, shortening, and margarine. Bottom line here is carbon steel tubes give us high thermal conductivity at a reduced cost when water is not present.

Next, we have stainless steel tubes. Stainless tubes offer very good corrosion resistance and compatibility with CIP, making it ideal for products like fruit and vegetable purees and condiments that tend to be acidic in nature. The drawback to stainless is it’s thermal conductivity- stainless tubes are much less efficient than carbon steel or nickel tubes, reducing capacity by approximately 10-15%.

One other advantage to a stainless tube is pressure rating- stainless tubes carry a higher pressure rating than nickel tubes, with stainless being rated at 600 PSI product side and 250 PSI jacket side while nickel is rated for 495 PSI on the product side and 230 PSI on the jacket side. This can be important for refrigeration applications requiring IIAR2-2021 compliance.

And for corrosive or acidic products with abrasives, we’ll opt for a chrome plated stainless steel tube, which is great for products with solids or that may slush freeze, such as icings and frostings.

Finally, when we need to pull out all the stops on hard to handle, corrosive products, we start to look at stainless duplex tubes. These are high salt, low pH applications that are very aggressive on stainless steel. Duplex steels are called “duplex” because their metallurgical structure consists of two phases- an austenite phase and a ferrite phase in roughly equal proportions. The duplex stainless steel family does a great job combining corrosion resistance with high strength and ease of fabrication.

What this means for a Votator tube is we’re able to manufacture efficient, thin-walled tubes with greater thermal and mechanical and corrosion performance vs. stainless steel. Duplex tubes, as you might imagine, come with a higher price tag than the other materials, but quickly provide ROI when used with the products for which they are intended.

And for high salt, low pH products that have solids, SPXFlow also offers a chromed plated duplex tube.

As you can see, when sizing and selecting a Votator, it’s critical we understand the nature of the product so we can identify the best tube material for your application. And after reading through this post you still have questions about which tube material is right for you, you can check out our tube selection guide here or contact a Triplex Sales Engineer today!

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