Heat Transfer Rolls & Effects of Temperature
As we learned in How to Maintain Heat Transfer Rolls, Part 1 the primary goal in designing heat transfer rolls is to transfer heat from the web to the roll or from the roll to the web. Part 1 also defined the importance of using proper fluids, periodic cleaning, and flushing of your heat transfer rolls. In Part 2, we will define best practices for storing your heat transfer rolls and the importance of remembering rust inhibitors.
Heat Transfer Rolls – Storage Guidelines
Precautions should always be taken when a heat transfer roll is put into storage as there is a high risk of internal and external corrosion. There are a few key-points to consider while storing a heat transfer roll:
- Corrosion develops when a heat transfer roll is stored with fluid inside it and vented to the open air.
- Determining whether all fluid is removed from a heat transfer roll and the inside is dry is very difficult.
- High-humidity environments can still lead to corrosion.
- When moisture settles and corrosion develops, it will affect the heat transfer and roll balance.
- Acid cleaning after storage may or may not be able to remove corrosion and scale
- Coating the heat transfer roll with rust-preventative oil and a rust-preventative wrap will help to safeguard the exterior surfaces.
- Protective films such as VCI (vapor corrosion inhibitor) can be used in place of oil coatings.
Remember the Rust Inhibitors
Heat transfer rolls are usually manufactured using carbon steel, thus acid solutions will not damage its internal parts or surfaces. Effective flushing agents for heat transfer rolls often include corrosion & rust inhibitors. Manufacturers of acid solutions include Ohio Valley Chemical Corporation and Chemetall North America/ Albemarle Company. Your heat transfer roll provider may recommend additional sources.
Seven Tips for Avoiding Heat Transfer Roll Corrosion:
- Drain all fluid before storing a heat transfer roll.
- Fill the heat transfer with a rust inhibitor solution or biodegradable antifreeze.
- Do not use water. Water does not have the chemical ability to prevent corrosion that a rust inhibitor solution or biodegradable antifreeze does.
- Cap-off the ends to retain the fluid and eliminate air. Most ends of heat transfer rolls are threaded, so pipe plugs are often used as caps.
- Rotate the roll to ensure coating all internal surfaces.
- Use proper corrosion protection on the roll exterior based on the type and length of storage. Be advised that even chrome plated surfaces may require some level of corrosion protection depending on conditions.
- Store the heat transfer roll in a dry and safe location with reasonably consistent temperature.
While proper maintenance and storage can prolong heat transfer roll performance, sometimes a roll simply needs to be serviced by its manufacturer. Many heat transfer roll manufacturers will perform the service of roll acid flushing. Depending on the application and roll specifications roll refurbishing may also include surface regrinding, re-shelling or re-plating. In some cases building-up or re-machining the journals may be needed.
Conclusion
The mishaps of heat transfer roll corrosion from improper storage can be avoided with a little preventative maintenance and proper storage. Maintenance of your heat transfer rolls will be achieved using best practices for storage:
- Proper fluid
- Proper cleaning/flushing
- Proper storage inside and out
Following the best practices will help lead to the effective exchange of heat energy and better web heating or cooling. Unwanted downtime, lost productivity and refurbishing costs or replacement costs will also be avoided.