A California-based company specializing in nutritional drinks such as teas, extracts, cultured beverages and specialty yogurts required sanitary shell-and-tube heat exchangers for a critical product cooling application. The manufacturer’s proprietary blends of products are consumed directly from the packaging or mixed in smoothies, desserts and cocktails. As is the case in most food processing applications where living cultures and temperature-sensitive ingredients exist, the heating and cooling of the products must be closely monitored and controlled. Too much heat can jeopardize the cultures and potentially change flavors and consistency. Too little cooling before bottling can lead to extended fermentation and shorter product shelf life.
The nutritional drinks manufacturer needed to cool a product stream flowing at 50 gal/min from 90°F (32°C) to a temperature just above freezing using a recirculated loop of 20 percent glycol and water at 28°F (-2.2°C). Close approach temperatures between the utility inlet at 28°F and the desired product temperature of 34°F (1.1°C) added complexity.
Typically, this approach would be a good fit for a plate-and-frame exchanger. For the nutritional drinks manufacturer, however, the viscous nature of the product made the risk of fouling too great to use a plate-and-frame unit. The processor would only consider a sanitary exchanger capable of clean-in-place (CIP) washdown. Other requirements included a maintenance-friendly design that would not require tearing down the complete exchanger to dislodge fouled product. Fouling from the product, if not removed, could jeopardize quality and potentially introduce cross-contamination from batch to batch.
U-tube style exchangers with double tubesheet design prevent cross-contamination from product in the tubes and utility fluids in the shell.
The management team from the nutritional drinks manufacturer approached their installation contractor, Stu Levenshus with MD Stainless, about finding sanitary shell-and-tube heat exchangers for this critical product cooling application. Levenshus contacted Wisconsin-based Enerquip LLC, a shell-and-tube heat exchanger manufacturer, to develop a shell-and-tube solution that avoid these risks for the processor.
The first design approach was a single, large exchanger design with multiple tube passes and a removable sanitary tube bundle. After evaluating the initial design, the team determined that — given the weight of the single exchanger, plant space limitations, installation location off the ground, and the single exchanger’s limited cooling utility — a split design was a better choice. The exchanger manufacturer adjusted the heat exchange system design to incorporate two, six-pass units coupled together in series using counter-current utility flow.
Although the two-exchanger design made the installation more complicated for the process and utility piping, the approach simplified removal of the tube bundles for routine maintenance. It also made the equipment easier to clean via a CIP system.
An added benefit of the two-exchanger design was redundancy. It provided the ability to reduce product flow and use only one exchanger for lighter cooling duties or during maintenance.
Radiused machined pockets and weep holes for draining were employed to prevent product from building up and fouling in the channels.
Healthy Products Require Sanitary Equipment Features
The nutritional drinks manufacturer had built its reputation on healthy products that improve the lives of its customers. As a result, it wanted to proactively control the risk of contamination of its products.
To address these objectives, the heat exchanger manufacturer incorporated many best practices for sanitary processing into the design of the process coolers. For instance, sanitary tri-clamp connections were incorporated into the heat exchangers. In addition, 316L stainless steel was used for all product-contact parts, and bright annealed tubes were polished to a food-grade 32Ra finish. A double tubesheet design — common in pharmaceutical-grade heat exchangers — was used to ensure that no utility fluids can come in contact with product streams or product surfaces. Also, the bonnets were designed with weep slots to make them fully drainable. Finally, all machined pockets were radiused so that no product could hold up in them and cause contamination.
The removable tube bundles allow the nutritional drinks manufacturer to remove and inspect the exchangers periodically during preventive and maintenance shutdowns. The bundles also are replaceable. Finally, after pressure testing the heat exchangers and bundles for safety according to ASME code, the equipment manufacturer cleaned and passivated the product-contact surfaces according to the latest bioprocessing equipment (BPE) standards. Such techniques make the exchangers more resistant to corrosion.
According to Levenshus, the cooling system installer, the design and the function of the exchangers are a success. “My customer is happy, I’m happy. We’ll be purchasing more cooler sets in the coming years.”
The cooling exchangers performed as planned the first time they were started up, Levenshus noted. No adjustments to the cooling utilities were needed, and the exchangers met the cooling and sanitary requirements to protect the quality of the products. PC