Abstract:
A heat exchanger leak detector employs a bubble detector to detect gas pressure build up in a heat exchanger second side from leakage of pressurized gas introduced in a heat exchanger first side.

Description:
BACKGROUND 
     1. Field of the Invention 
     This invention relates to detection of leaks in heat exchangers, and more specifically to visible detection of a leak from one heat exchanger side to the other heat exchanger side using gas pressure build-up to create bubbles in a liquid outside the heat exchanger. 
     2. Prior Art 
     Heat exchangers comprise a first side, sometimes referred to as a product side, and a second side, sometimes referred to as a media side, in close contact with the first side. Plate heat exchangers that comprise a number of plates closely packed in series with fluids flowing through them while maintaining the two sides separate. Plate heat exchangers are commonly used in food processing where it is imperative that the fluids from the two sides remain separate, that is, that there are no leaks between the two heat exchanger sides that could cause cross contamination. Cross contamination occurs when a crack or pinhole develops, allowing fluids on one side to pass from one side into the other side and mix with fluids on that side usually assisted by a pressure difference that exists between the two sides. Because contamination can have serious consequences, it is routine to check the plates for any defect that may result in a leak. 
     Checking for defects usually involves removing a plate and testing it apart from the heat exchanger. Disassembly of the heat exchanger is time consuming and interrupts its use. The need remains for a device and method that can perform a quick and easy test on a heat exchanger in place without removal and disassembly of the heat exchanger to minimize interruption of use of the heat exchanger. 
     SUMMARY OF THE INVENTION 
     This object is achieved in a heat exchanger leak detector that employs a bubble detector to detect gas pressure build up in a heat exchanger&#39;s second side from leakage of pressurized gas introduced in a heat exchanger&#39;s first side. 
     The detector employs a U-shaped container for receiving a liquid, such as water, a modified plug adapted to connect to an exchanger port, and a tube running between them providing fluid communication between the modified plug and the container. 
     When there is a leak in the heat exchanger, air pressure from the heat exchanger first side passes through the leak into the heat exchanger&#39;s second side, which pressure passes through the tube into water in the U-shaped container. When gas pressure builds up over the head in the tube portion that is below water level is discharged from the tube&#39;s second end and into the water forming bubbles of the gas to rise in the water from the tube&#39;s second end, providing a visual indicator of gas build up. 
     The top of the container is typically closed. Therefore gas released from the bubbles causes a pressure build-up in the container above the water. When pressure builds up above the water, a water level difference between the two container legs follows, creating a further visible indicator of the leak 
     The device is adapted for use outside the exchanger system as a simple and temporary leak detector. Thus, it may be used with any heat exchanger design by simply connecting the detector to a port on one side of the heat exchanger, supplying air pressure to a port on the other side and sealing all remaining ports. It is then easily removed for normal operation of the heat exchanger. Because air can be used to pressurize the first side of the heat exchanger and water can be used in the container, the detector is inexpensive to use and quick to install. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the heat exchanger leak detector of the present invention. 
         FIG. 2  is a side view of the heat exchanger leak detector of  FIG. 1 , shown connected to a heat exchanger port and with bubbles visible in water in the first leg of the U-shaped container. 
         FIG. 3  is a perspective view of the heat exchanger leak detector of  FIG. 1  shown connected to a port on one side of the heat exchanger and pressurized gas supplied to a port on the other side of the heat exchanger with other heat exchanger ports capped. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The gas leak detector  10  of the present invention for use with a heat exchanger  100  comprises a modified port plug  12  adapted to fit in a first heat exchanger port  102  that provides access to a heat exchanger&#39;s first side (not shown), with a hole  14  through the modified plug  12 . A second port plug  15  connects to second heat exchanger port  104  to which a supply of pressurized air  106  is connected. The second heat exchanger port  104  provides access to a heat exchanger second side (not shown). A tube  16  extends from the hole  14  into a container  17  that can be filled with a liquid  18 , typically water. 
     The container  17  is a generally U-shaped with first and second legs  20 ,  22  extending upward from a bottom  24 . The first leg  20  connects to the modified plug  12  with an air tight seal. The tube  16  extends from the modified plug  12  into the first leg  20  of the U-shaped container  17  to a tube end position  26  below a position  28  to which water, or other equivalent liquid, is filled during use. The second leg  22  is typically open to the atmosphere to allow the water level to adjust without pressure in the second leg  22 . It also may be closed to create a difference in water level in the two legs  20 ,  22  when the first leg  20  is pressurized by air from the heat exchanger&#39;s second side in the instance that pressurized air passes through a leak between the heat exchanger&#39;s first and second sides, in which case a fill port is provided in the container into which the liquid can be poured into and out of the container  16 . 
     In operation, all pipes and hoses are removed from the heat exchanger to be tested. Other ports  107 ,  107 ′ of from each of the first and second sides of the heat exchanger  100  are capped. The leak detector modified plug  12  is secured with an air tight seal in the first heat exchanger port  102  of the heat exchanger&#39;s second side. Air pressure is supplied to the second heat exchanger port  104  and the U-shaped container  17  is filled with water to a suitable level above the end  30  of the tube  16 . At least the first leg  20  of the container  17  is clear for visible inspection of the water. After a period of time, if there is a leak bubbles  108  will appear in the water as air pressurizes the second side of the heat exchanger  100  through the leak which bubbles are visible through the container  17 . 
     If the bubble test does not quickly disclose a leak, the detector is left for a longer period of time to allow gas to be released from bubbles over that longer time which accumulates and pressurizes the first leg  20  above the water level, which causes a difference in water level between the container&#39;s first and second legs  20 ,  22 , which is a more sensitive indicator of a leak.