Sterilizing Canned Foods and Beverages: Hydrostatic Cookers
If your company is in food and beverage manufacturing, you know the requirements of in-can sterilization. This is usually done in high volume operations with a continuous cooker process using either a hydrostatic (vertical) cooker or a rotary (horizontal) Cooker.
Here is a profile of the Hydrostatic Cooker process and what engineers need to focus on for a successful installation, whether it’s a new machine or a rebuild.
Benefits of Hydrostatic Cookers
The Hydrostatic Cooker offers many benefits to manufacturers:
- Because it is vertical, it has a smaller footprint than other options;
- It can offer a very flexible process to meet product requirements, such as handling multiple can sizes, handling sensitive product that requires a very still process, product runs that require different sterilization times and temperatures, and properly cooling products that may have significantly different thermal properties;
- Hydrostatic Cookers are also very energy efficient, which can reduce manufacturing costs.
The key to maximizing these benefits is a properly designed process and a control system that provides good temperature and speed control, reliability, traceability, and is easy to maintain. How is this accomplished? Let’s start with the basics of how the process works.
In-Can Sterilization Using the Hydrostatic Cooker
A Hydrostatic Cooker is built with multiple towers. While there can be multiple configurations to meet specific product requirements, at a minimum this will include an Infeed Tower, a Steam Tower, an Exit Tower, and a Cooling Tower.
The Infeed and Exit towers are filled with water and controlled to a specified level. This creates a seal to hold saturated steam inside the steam tower and these are referred to as the Infeed Hydroleg and the Exit Hydroleg. The pressure of the saturated steam inside the Steam Tower determines the process temperature of the cooker.
A chain then carries the canned product through the Steam Tower at a fixed speed based on the desired process time. The Infeed Hydroleg is also used to slowly bring the canned product up to temperature, so the temperature of the water in this leg is controlled to a specified temperature. The Exit Hydroleg is also controlled to a specified temperature to slowly bring the canned product down in temperature.
Once cans come out of the Exit Hydroleg, they need to be brought down in temperature to allow for labeling or bright can stacking. It is critical that cans are brought down in temperature slowly and consistently to avoid multiple issues that can cause can damage. This is accomplished by tightly controlling the temperature of the cooling water sprays and by assuring that cans are not submerged in cooling water while they’re still hot.
Based on the thermal properties of the canned product and the required process speeds, Hydrostatic Cookers may require a pre-heat leg, multiple steam towers, a pressurized cooling section, and multiple atmospheric cooling sections. The flow rate and temperature of water in the Infeed Hydroleg, Exit Hydroleg, and Cooling Sections are obviously critical to the ability of the process to meet product requirements.
Why Upfront Process Planning is Essential for Success
So how can you be sure that your Hydrostatic Cooker installation, whether a new machine or a rebuild, will be a successful project that maximizes the benefits of the process? How can you avoid making mistakes during installation that can cause major problems during the life-cycle of the machine? And since this is a large installation, how can you minimize the impact of construction on your facility, reduce schedule changes, and minimize the cost of field changes?
The answer is simple: Take the time upfront to engineer a solid solution. If your project is a new machine, this seems obvious. But this also applies to rebuilds, since relying on old drawings or basing decisions on what’s there now may lead to problems.
Matrix Technologies, Inc. has extensive food and beverage engineering experience, including new installations, full rebuilds, and system upgrades of Hydrostatic Cookers. We’ve found that it’s essential to create a clear definition of the process requirements, whether you’re planning a new machine or a rebuild.
To engineer a proper solution, you need to know such specific numbers as:
- Temperature of the steam dome;
- Process time;
- Cans per minute;
- Temperature of cans coming from your filling operation;
- Required temperature of cans as they discharge from the cooker;
- And the weight and thermal load of the various products that you plan on running.
Other Factors to Consider in Planning
Remember, there’s much more to a Hydrostatic Cooker than the towers. You have to provide for conveyance of cans into and out of the machine, so be sure to include this in your plan.
If this is a rebuild, don’t take the conveyance systems for granted. Will the existing equipment be able to reliably handle the required cans per minute without can damage? Are there areas for improvement? Don’t forget about utility systems; proper design of utility systems will go a long way in helping maintain your investment in a Hydrostatic Cooker.
Other important factors include:
- How will the chain links be lubricated?
- How will you control the injection of chemicals needed for water treatment?
- How will you protect equipment and personnel from the high air temperatures produced in the area of the cooker?
How 3D Laser Scanning Can Help Avoid Field Changes
Upfront engineering should also include audits of the existing physical space where the Hydrostatic Cooker will be installed. This should encompass information on existing structural and mechanical components as well as electrical conduit runs.
The best way to avoid costly field changes is to make sure all possible pipe interferences are factored in. A 3D laser scanning survey of your facility can provide critical information on existing infrastructure that will allow engineers to create 3D models for equipment placement, piping, and conduit. These models can also be used to make sure operators and maintenance personnel have safe access to the equipment they need to operate and service.
Designing the System for Effective Operation
The control system should be designed to provide reliable, consistent operation of the Hydrostatic Cooker process. This includes controlling multiple PID control loops where the process variable of many of the loops has a physical effect on others.
For example, an increase in the Steam Tower temperature means raising the setpoint for the steam pressure control loop. When the pressure of the steam goes up, this causes the water level at the steam/water interface in both the Infeed and Exit Hydrolegs to lower as the level on the atmospheric side increases. These loops must be designed to work together to keep the process balanced.
Also, due to the nature of the process, programming must be both robust and accessible to maintenance personnel for troubleshooting. In addition, the system needs to be designed to meet government regulations related to the product being run. This could include both USDA and FDA standards and may include electronic record rules as dictated by 21 CFR Part 11.
The construction phase can present many challenges as well. By taking the time to produce a solid engineered design upfront, many of the obstacles that come with installing such a large system can be avoided. But, as with all large projects, having a knowledgeable construction manager is vital to keep different construction disciplines working safely and on schedule.
Matrix Technologies is one of the largest independent process design, industrial automation engineering, and manufacturing operations management companies in North America. As a full-service engineering firm, we manage complete turnkey projects that include site prep, building design, mechanical, electrical, controls, programming, and construction management. To learn more about our food and beverage manufacturing experience contact Greg Pfleghaar.
© Matrix Technologies, Inc.
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