Automatically Dosing Sulfurous Acid Solution In-Line Using TCW’s Peristaltic Dosing System. 

Ragazzini Rotho PSF Peristaltic Dosing PumpA customer approached TCW requesting that we use our dosing equipment to find a simpler way to add H2SO3 in-line to freshly destemmed and crushed grapes. They wanted a system that would automatically sulfite the grapes as they pumped them from their destemmer to their tanks. This customer is a well-known, high-end winery that produces several hundred thousand cases per year, and has a strong focus on biodynamic farming and environmental responsibility. 

The customer, a large well known winery group, also has a Ragazzini Rotho MS3T peristaltic must pump on site which they are very satisfied with because of its simple operation, rugged construction, and easy maintenance. They wanted to dose H2SO3 directly into the outlet of their larger Ragazzini must pump as it transfers grapes from a destemmer to their tanks, eliminating the need to adjust sulfite levels in their tanks — a sometimes dangerous task, which can result in uneven or heterogeneous distribution.

The customer owns an H2SO3 dosing system and was concerned about overrunning the production with sulfurous acid solution. The equipment is from another manufacturer that uses inert gas to pressurize a small vessel and push H2SO3 in controlled one-shot doses. This application calls for continuous low-level dosing rather than single “shots” of sulfurous acid. With their one-shot doser there was too great a possibility of over-dosing sulfurous acid solution if the operator accidentally triggered it too many times.

The Assignment

The customer engaged TCW to provide a solution that met the following criteria:

1. It must be rugged and cart-mounted for easy use and transportability in an outdoor winery with uneven surfaces.

2. If they need to stop the must pump, the doser should stop as well. I.e. the dosing system should be synchronized with the must pump.

3. It must be accurate. This customer’s wines adhere to strict protocols regarding sulfite levels that cannot be exceeded.

4. It should be able to dose a specific volume, similar to their existing dosing system. For example, the user should be able to say they want to dose 150 ml and have the pump stop automatically once that volume has been reached.

5. It should be able to dose for a set length of time at a given flow rate. For example, 50 ml per minute for 20 minutes, and stop once the time has elapsed.

6. It should be easy to use by operators with a wide variety of technological skill levels.

They additionally expressed a desire to have this new dosing system be capable of replacing the aforementioned barrel dosing system, which they expressed dissatisfaction with because it often required repair with expensive parts. The parts are susceptible to greater wear than usually because of the exposure to sulfurous acid, particularly the valve and the flow meter. When these break, they must be replaced at a significant cost, well over $1,000.

Because the Ragazzini produces a known volume with each rotation, no expensive flow meters are required. Likewise, the pumped material is not under pressure, as with the old system, so no valves are required. The pump is, itself, a kind of valve. Furthermore, Ragazzini peristaltic pumps only have one common wear part: the peristaltic tube, which has good compatibility with H2SO3, is relatively inexpensive (about $150 as of the time of writing), and typically lasts years without needing to be replaced.

The Result

TCW used our existing capabilities and equipment to design a dosing system that exceeded the customer’s expectations.

The dosing system utilized Ragazzini’s Rotho PSF3S peristaltic pump, the smallest pump Ragazzini manufactures. The PSF3S offers flow rates from 7 to 83 ml per minute, well within the customer’s desired specs, so we knew it would pose no risk of over-dosing the grapes with H2SO3.

• The system employs a clear, intuitive touchscreen interface that lets the operator select the mode: time dose, volume dose, or manual operation.

• Users can set the total amount they want to dispense, hit start, and walk away, assured that the job will be completed.

• The pump is capable of operation with a remote control. This allows the dosing system to be used for barrel additions. The operator can place the system’s output hose into a barrel, tap a button on the remote, and the pump will begin operation remotely. Once complete, they can transfer the hose to the next barrel and repeat the operation.

The customer was thrilled with the final product, stating: "The doser works perfectly. Exactly what we needed. We took a video of the whole setup with the must pump and the doser in action and sent it to the ops team for the whole company. They really liked it and now there’s high interest in doing something similar for our other facilities.”

They were particularly happy that the system’s final price was several thousand dollars less than their existing dosing system, in spite of offering more features.

Conclusion

The TCW Dosing System is the ideal solution for commercial wineries seeking to make dosing more efficient, safer, and less error-prone. Ragazzini peristaltic dosing pumps are extremely robust and gentle, allowing them to be used to dose abrasive fining agents, acidic compounds, or even delicate enzymes and ingredients. Contact us at sales@tcwequipment.com so that we can work with you to design a dosing system for your facility.

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