Fluid leak detector
BACKGROUND OF THE INVENTION 
     This invention relates to fluid flow monitoring systems, and more particularly to a system for detecting a leak in a conduit or the like to receive the flow of a fluid. 
     In the past, a pneumatic or hydraulic type bridge has been provided with a differential pressure unit (DPU) to indicate the constituent in a mixture removed by a scrubber or the viscosity of a fluid. For example, see U.S. Pat. No. 2,449,067 issued Sept. 14, 1948. However, these types of equipments are not employed in monitoring systems to determine the failure of fluid conduits or the like. 
     SUMMARY OF THE INVENTION 
     In accordance with the leak detector of the present invention, apparatus is provided comprising a system having first, second, third and fourth legs to carry a fluid, an inlet, an outlet, said first and second legs being connected in succession from said inlet to said outlet, said third and fourth legs being connected in succession from said inlet to said outlet, one of said first and second legs being an adjustable valve, said third and fourth legs providing constrictions, a DPU connected from the junction of said first and second legs to the junction of said third and fourth legs, and an indicator connected from said DPU to indicate the differential pressure sensed thereby. 
     In accordance with the foregoing, the DPU indicator will show a pressure difference if the first leg leaks. The first leg may thus include the cooling coils of a furnace, if desired. 
     The above-described and other advantages of the present invention will be better understood from the following detailed description when considered in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings which are to be regarded as merely illustrative, the FIGURE is a diagrammatic view of a fluid leak detector. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A leak detector constructed in accordance with the present invention is indicated at 10 in the FIGURE including a fluid inlet 11, a fluid outlet 12, a first leg including furnace cooling coils 13, a second leg including a needle valve 14, needle valve 14 having a knurled knob 15 to adjust the pressure drop across needle valve 14, third and fourth legs including orifices 16 and 17, a DPU 18 connected from between the junction of coils 13 and needle valve 14 to between the junction of orifices 16 and 17. The DPU 18 is conventional and has a conventional rotatable output shaft 19 to operate an indicator 20. 
     Circulation means 21 may be other furnace apparatus to circulate a fluid in the direction of arrows 22, 23, 24 and 25. 
     OPERATION 
     In the operation of the leak detector 10 shown in the FIGURE, needle valve knob 15 is turned until indicator 20 shows some known value -- preferably zero. Thus, if later on a leak should develop in coils 13, such a leak will be shown on indicator 20. 
     The flow resistance through the orifices 16 and 17 is greater than that through coils 13 and needle valve 14. For example, the volume flow rate through coils 13 is about 10 times that through orifice 16.