In a factory, you may sometimes encounter an awkward situation:
You turn on a tap or open a sampling port, expecting clear, odorless water, but suddenly a strange, unpleasant smell fills the air.
Is it a fishy smell? A rotten egg smell? Or the smell of burnt rubber?
At that moment, an operator's first reaction is usually, "Has the water quality changed?"
But water quality is not necessarily the only culprit.
As an essential passageway for fluids, a plate heat exchanger can also turn a tank of clean water into foul-smelling water when something goes wrong.
Let's put on our detective hats and track down the source of that strange odor!
1. The Most Dangerous Warning Sign: Internal Leakage and Cross-Contamination
Of all the possible causes of unpleasant odors, this is the most serious one, with potentially severe consequences.
Suppose one side of the plate heat exchanger carries domestic hot water, while the other side carries industrial circulating water containing various chemicals, such as biocides and scale inhibitors, which may have strong odors.
If the plates develop corrosion perforations or cracks, contaminated water may leak into the clean water supply.
In this case, the unpleasant smell may actually come from industrial treatment chemicals or contaminated water.
What does it smell like?
It may resemble the smell of chemical solutions.
If this happens, shut down the equipment immediately! Continuing to use or drink the contaminated water could pose a serious health risk.
2. The Most Disgusting Cause: Bacterial Growth
If your plate heat exchanger operates at relatively low temperatures for extended periods, such as 30–40°C, and the water flows relatively slowly, it can become an ideal breeding ground for bacteria and algae.
Microorganisms can multiply rapidly on the plate surfaces, forming a slippery layer of biological sludge known as biofilm.
When this biofilm dies and decomposes, it can release an unpleasant fishy, foul, or rotten odor.
What does it smell like?
It may smell like a stagnant ditch or rotting fish.
If you disassemble the equipment for inspection, you may find green growth or black sludge covering the plates.
3. The Smell of New Gaskets
If you have just replaced the sealing gaskets or purchased a brand-new plate heat exchanger, the odor may simply be coming from the rubber.
The gaskets used in plate heat exchangers are made of rubber materials, such as EPDM or NBR.
At elevated temperatures, volatile substances in the rubber may be released, producing an odor similar to burnt rubber.
What does it smell like?
It may resemble the smell of burning tires.
This situation does not necessarily indicate a serious problem. The odor may gradually dissipate after a period of operation.
However, if the smell is particularly strong, irritating, and persistent, the gaskets may be made from poor-quality materials.
4. Stagnant Water in Dead Zones
The structure of a plate heat exchanger is complex, and certain areas may experience poor fluid circulation.
If the equipment has been shut down for a long time and the water inside has not been completely drained, residual water trapped in these areas can become stagnant.
Over time, the stagnant water may undergo microbial decomposition and deteriorate. When the equipment is started again, the accumulated stale, foul odor may be released all at once.
How can you recognize this problem?
The odor is particularly strong when the equipment first starts up but gradually fades after the water has circulated for a while.
Final Thoughts
An unpleasant odor coming from a plate heat exchanger is never something to ignore.
It could be a warning sign of internal leakage or an indication of a hygiene problem.
If you notice an unusual smell, don't simply put up with it.
First, check for internal leakage. Then investigate possible bacterial growth. Finally, inspect the gaskets and consider whether stagnant water has accumulated inside the equipment.
Only by identifying the source of the odor can you restore clean, fresh-smelling water.
