- Rob Meurs, 12/06/19
Why does a cold glass of beer get wet on the outside, especially on hot summer days? This is due to the contrast between the cool liquid and the warmer air that surrounds it. Warm air contains much more moisture than cold air. As the air touches the cold glass it cools down, contracts and releases its moisture, which collects in the droplets you find on the outside of your glass.
What about the topic at hand? Well, the cool water running through the chilled water pipes has the same temperature as freshly tapped beer, or six degrees Celsius. Now imagine what happens if these pipes lie unprotected in a room-temperature environment of 21°C and a relative humidity of 50%. That’s right, you get condensation, which is why water pipes need to be insulated.
Cross-section chilled water pipe
It is absolutely crucial that the insulation be airtight. There can be no contact with the surrounding air. But insulation can be fragile and a small mistake easily made, such as a strip that’s not properly glued together or a part damaged during operations on board. AC rooms can be crowded, and with all the people running in and out there’s big potential for damage.
The thing about condensation is that it never stops. The water just keeps on dripping, minute after minute, day after day, year after year. Sometimes the source is easy to locate – like when there is only one set of pipes running above the ceiling. But there are places where the deck is crammed with pipes, ducts and hoses. Furthermore, a damp spot in your ceiling doesn’t necessarily mean the leakage is directly above it.
And sometimes, even though you know that everything is properly insulated without any gaps or damage, there is still condensation leakage. In such cases, there’s a good chance there’s a cold bridge somewhere. This occurs when a solid material is in direct contact with a source of cold – for example, a steel bracket mounted on a chilled water pipe. Steel is an excellent conductor of temperature, so it can lead the cold far out of the reach of the insulations. Once this comes in touch with the outside atmosphere, condensation droplets start to form on the steel.
Situation with cold bridge
The importance of insulating chilled water pipes is one of the most underestimated topics we face. The ease with which on-board insulation can be damaged is also disturbing. Insulating pipes and appendages is a delicate job. It mustn’t be rushed and it requires patience and concentration. It’s just like your cold beer: you don’t want to see it ruined.