TESTING TUBE AND SHELL CONDENSERS
In order to test tube and shell condensers with ultrasound, we must first understand how they work. These condensers come in all sizes and shapes, but the principle is the same. The product is run through the shell side and the water is run through the tube side. The water flowing through the tubes carries the heat away, allowing the boiling product to condense back into a liquid, or in some cases just cool down to a desired temperature.
As you can see in the first picture, water enters the condenser through the large pipe on the end, where the green circle is. It then travels through tubes running the length of the condenser and exits through the other end. This condenser was approximately 40 feet long.
The product enters the condenser through the pipe that we see in the center of the picture, circled in yellow. Between these two entry points there is a thick plate that is called a tube sheet.
The water and the product never actually contact each other but the heat is drawn away by the flow of water through the tubes that are running through the product.
This large plate over the end of the condenser in the second picture is called the head plate. There is one on each end of the condenser. We remove these head plates so we can get to the tube sheet for testing. That's where we will find any leak in the tubes in this condenser. The head plates are very heavy and have to be removed with a crane or other device designed for lifting.
The tube sheet is positioned between the product and water entry and exit points on each end of the condenser. It also holds the ends of all the tubes. You can see it in the third and fourth photographs.
After the head has been removed and the water box has been tested for safe entry, we will proceed to enter for testing. Here we can see the ends of the tubes that run the full length of this condenser. This is also called the water box. The water comes in here and runs through the tubes and out the other end taking the heat with it. If one of these tubes springs a leak then the product is leaked into the water, because it is under higher pressure than the water. In this particular case it was propane, so the vapor cloud above the cooling tower was not all steam; it was partially leaking propane being carried to the tower by the water.
This is where we check for leaks. These tubes are about ½ inch in diameter. There are approximately 2200 of them. To test each one individually from both ends would take forever. In this case we pressurize the shell side, which makes it easy to hear the leaking tube. These higher pressure usually only needs to be approximately 25 to 30 psi.
After the water box has been cleared by operations and all safety measures are in place we actually get into the water box and listen for the leak with the UE SYSTEMS ULTRAPROBE 10000.
Once inside the water box, using the gross to fine method, we can determine where the leak is. At 25 to 30 psi differential it is very easy to find these leaks. After we have located the general area of the leak then a plastic funnel can be used to pinpoint the leak. Placing the end of the funnel inside the tube, we use the rubber focusing module to check inside the funnel and hear the leak. Then we check outside and all around the funnel. If we hear the leak inside the funnel and hear no leaks outside, we know we've found it. Ultrasound will not penetrate a solid, so it cannot get outside the funnel. This indicates to me that I have located the exact tube that is leaking.
The leaky tube is usually plugged on both ends taking it completely out of operation, and the unit can be reassembled and put back on line. We have found condensers with only one tube leaking, and we have found them with several tubes that leak, so we're sure to check them all closely.
This entire operation took about 4 hours from start to finish.