Heat Exchanger and Plate’s Compatibility
Plate-and-frame heat exchangers (PHE’s) are designed with the purpose of meeting specific needs. As they meet those needs, the exchangers need to properly handle water treatment chemicals, since they (the exchangers) frequently interact with water from cooling towers. If there is an issue within the cooling tower and stronger chemicals are needed to fix that issue, contact the manufacturer to ensure that the plates and gaskets can function properly with those chemicals.
When it comes time to service or maintain your heat exchanger, it is important to know your equipment. Consider keeping record of the following:
- The Make and Model Number
- How many plates and gaskets the unit contains
- What spare parts you have in inventory
- When the unit was last serviced
You should receive the total dimension of the plate from the manufacturer. This dimension will rely on the number of plates in the unit. To figure a plate’s dimension, you can measure from the inside of the head to the inside of the follower. If the dimension is off, tighten the unit to restore the original dimension. Once again, the dimension should be checked at least once a year. (To better understand why checking the dimension is so important, see the “Heat Exchanger Leaks” section below of “What to Avoid…”)
Note: If the plates are added or removed, the dimension changes as well.
What to Avoid…
Heat Exchanger Leaks
If a heat exchanger’s frame begins to break down, the PHE can begin to leak, and these leaks are difficult to stop once they start. To prevent this issue, check the dimension of the plate pack on an annual basis. The original dimension must remain the same since a PHE is adjusted to that specific dimension (instead of being adjusted to a torque specification). In addition, to prevent the heat exchanger from leaking, check the frame and tie-bars periodically to ensure that they remain in solid condition.
For safety purposes, do not go beyond the pressure limits of the heat exchanger’s rating. To avoid these pressure spikes, refrain from quickly closing the valve and avoid water hammering. To further the safety of your employees and to protect equipment, take the necessary steps to guard the heat exchanger. Failure to protect the exchanger could cause the unit to blow a gasket which is a safety hazard, as well as an equipment hazard. As a standard of operation, do not let the pressure fluctuate more than 150 psig/min and the temperature more than 20oF/min (11oC/min).
How to Plan…
A plate and frame heat exchanger can easily adapt to new requirements, making it a flexible piece of equipment. You can customize PHE’s by adding or removing plates within the frame, which allows the unit to accomplish different tasks. By planning ahead of time, this adaptability of the PHE allows you to purchase what you need for the current task, knowing that you can adjust for future projects.
Remember, though, that factors such as velocity and turbulence affect the efficiency of a unit. For example, if a plate exchanger size goes beyond the needs of a particular task, plate fouling is more likely, as the velocity will decrease.
In a study conducted several years ago by Industry Weekly, the issue of unexpected downtime proved to be a theme among many manufacturing companies. In fact, the study showed that 30% of manufacturers encountered unplanned downtime at least once every three months. Companies with a minimum of $1 billion in revenue were more prone to these periods of inactivity.
Originally, there was an average of four incidents of unplanned downtime per year, but that number has jumped to a disconcerting seven. By calculating your TDC per occurrence, you can know how much each of these incidents cost. For example, if your TDC is a modest $20K (a low estimate), you will lose $80,000 in revenue on an annual basis, and that is gauged by the minimum number of occurrences. To avoid wasting revenue, know your TDC and develop a plan to prevent and eliminate costly downtime.