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Ultrasound in Leak Detection

Ultrasound in Leak Detection. Leaks Pressure Vacuum Steam Valves Hydraulic Electrical. Rolling Elements Bearings Gearboxes Sheaves Couplings Pumps. Passive Ultrasound Sources. Leaks. Definition.

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Ultrasound in Leak Detection

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  1. Ultrasound in Leak Detection Training Level 1 Version 2.0

  2. Leaks Pressure Vacuum Steam Valves Hydraulic Electrical Rolling Elements Bearings Gearboxes Sheaves Couplings Pumps Passive Ultrasound Sources Certification Training Level 1 Version 2.0

  3. Leaks Definition Leaks happen when a fluid, gas or liquid goes from a high pressure to a low pressure medium through a hole that is not supposed to exist, usually accompanied by irreversible lost of material and / or energy P1 P2 P1>P2 Certification Training Level 1 Version 2.0

  4. Introduction Reasons for leak detection • Safety • Explosions – Combustible fluids • Poison – Toxic/Corrosive gases • Economic • Avoid material loss from leakage • Efficient energy management • Maintain efficient and reliable processes • Quality control • Maintenance management • Detect faulty components • Decrease warranty cost Certification Training Level 1 Version 2.0

  5. Pressure - Vacuum Comparing methods for leak detection • Immersion or dunk method • Chemical trace • Chemical penetration • Gas sniffing • Airborne ultrasound • Soap method • Pressure decay • Search gas tracer probe • Water Tunnel Certification Training Level 1 Version 2.0

  6. Airborne Pressure Vacuum Steam traps Electrical Structure borne Vacuum Valves & Steam traps Hydraulic Introduction Medium of Transport Certification Training Level 1 Version 2.0

  7. Leaks External leaks pressure and vacuum leaks Certification Training Level 1 Version 2.0

  8. Pressure - Vacuum Understanding the turbulence When a fluid moves from a high pressure zone to a low pressure zone, friction between fluid molecules and medium molecules generate ultrasonic waves Certification Training Level 1 Version 2.0

  9. Pressure - Vacuum What is the cost of air? Air is free, compressed air is not Certification Training Level 1 Version 2.0

  10. Cost to compress 1 CFM of air • Assumptions • Motor service Factor = 110% • Power Factor = 0.9 • A typical compressor produce 4 CFM per 1 HP • 1 HP = 110% x 0.746 KW/0.9 = 0.912 KW • This means that produce 1 CFM = 0.228 kW • With a cost of 0.06 $/kW/hr : 1 CFM = $0.0137/hr • the 1 CFM in 8000 hr operations hours cost a year: • 1 CFM x 8000 hr x 0.0137 $/hr = $109.6 Certification Training Level 1 Version 2.0

  11. Pressure - Vacuum Assuming energy cost 5 cents per Kw-h, and 365 operation days Certification Training Level 1 Version 2.0

  12. Pressure - Vacuum Leak factor factors affecting leaks • Pressure differential • Orifice size and shape • Fluid viscosity Certification Training Level 1 Version 2.0

  13. Pressure - Vacuum Procedure for leak detection Certification Training Level 1 Version 2.0

  14. Pressure - Vacuum General considerations • Safety • Know the system • Select most suitable collector and accessories • Plan the inspection • Execute the inspection • Document and report findings • Take action Certification Training Level 1 Version 2.0

  15. Pressure - Vacuum Safety There is no single rule of thumb for leak inspection safety. Each and every circumstance can be different so SDT encourages the Inspector to seek advice and guidance from qualified safety personnel in each facility. All safety procedures must be followed and every risk must be avoided. Certification Training Level 1 Version 2.0

  16. Pressure - Vacuum Know the system • Get updated layouts and blueprints of the air system • Identify flow direction – supply / demand • Identify system components • Identify consumption points – general demand and point demand by users Certification Training Level 1 Version 2.0

  17. Pressure - Vacuum Know the system Certification Training Level 1 Version 2.0

  18. Pressure - Vacuum Select the right equipment 1. Ultrasonic detector with tuneable frequency, accessories, batteries fully charged 2. Surfactant to intensify acoustic signal (to detect very small leaks) 3. Paper to record leaks 4. Tags to identify leaks 5. Flashlight, blueprints / Layouts 6. Thick fabric to shield and isolate leaks Certification Training Level 1 Version 2.0

  19. Pressure - Vacuum Planning the inspection • Define route to follow from the layouts or blueprints • Identify points most likely to have leaks accessories (lubricators, filters, pipe unions, valves etc.) accessories threaded – welded, pneumatic tools • Select most appropriate sensors • Prepare a list with required information • Coordinate with floor supervisors for the best time to do the inspection – maximum pressure in the lines (low demand) Certification Training Level 1 Version 2.0

  20. Pressure - Vacuum Execute the inspection End End use points Begin Compressors Certification Training Level 1 Version 2.0

  21. Leak Detection Managing the inspection area 1. Shielding Technique Place a barrier between different ultrasound sources 2. Positioning Look for the best body/sensor position 3. Covering Place a barrier around the inspection point to block other competing ultrasounds 4. Managing Reflection Large leaks reflecting off of hard surfaces may create false positives Certification Training Level 1 Version 2.0

  22. Leak Detection Managing the inspection area Shielding Technique Blocking a known source Enables inspector to hear additional leaks in near vicinity Use a cloth, a rag, a piece of foam, or even a gloved hand (gloved for safety) Certification Training Level 1 Version 2.0

  23. Leak Detection Managing the inspection area Positioning Using the body to block a known source of competing ultrasound Enables inspector to find additional leaks Certification Training Level 1 Version 2.0

  24. Leak Detection Managing the inspection area Covering Minimizing the inspection area Blocks all competing ultrasounds Especially useful finding vacuum leaks Certification Training Level 1 Version 2.0

  25. Leak Detection Managing the inspection area Managing Reflection Ultrasonic energy reflects more than it absorbs Ultrasound from turbulence reflects off hard surfaces Sometimes, it seems as though a leak is coming from a brick wall! Follow the angle to the source Certification Training Level 1 Version 2.0

  26. Leak Detection Leak Detection Techniques Special situations when pressure is not feasible Threshold Leaks (= 10-2 std – cc/sec, 10 psi) At this level very little ultrasonic disturbance reaches the detector. Using the Acoustic Leak Magnifier the signal is intensified. Un pressurized Systems A bi sonic transmitter is used Certification Training Level 1 Version 2.0

  27. Leak Detection Documentation and reporting • When a leak is found it must be identified, and if possible, quantify the air loss using: • Mass flow sensor • Graph Intensity versus volume • Sizing orifice (formula) • Use a tag to identify the leak position • Document a leak report Certification Training Level 1 Version 2.0

  28. Leak Detection Documentation examples Certification Training Level 1 Version 2.0

  29. Leak Detection Take action “It is often noted that finding a leak never saved a dime and no truer words can be spoken on the subject of ultrasonic compressed air leak detection. As satisfying as it may be to spend 8 hours identifying 100’s of compressed air leaks, there is no payback in wrapping a yellow ribbon around a leaking pipe fitting. It has to be fixed to save “ Dan Durbin, Chief Engineer, Anheuser-Busch, St. Louis, Missouri $ Costs Certification Training Level 1 Version 2.0

  30. Valve InspectionUsing Ultrasound Certification Training Level 1 Version 2.0

  31. Valves Two ways to check 1. Contact the valve and listen 2. Do a comparison method before and after the valve Certification Training Level 1 Version 2.0

  32. Easy as A B C • Checking valve for flow • Upstream and downstream • Works for any gas or liquid

  33. Hydraulic Systems Benefits • Find internal leaks and passing valves • Find cavitation • Perform inspection without disassembly • Save time Use contact sensor Certification Training Level 1 Version 2.0

  34. Hydraulic Systems Example Cavitation in a pump Certification Training Level 1 Version 2.0

  35. Steam Traps and Ultrasound Certification Training Level 1 Version 2.0

  36. Steam Traps What is steam? it is vaporised water produced by adding heat energy to its boiling point, then more energy is given to change water to steam without further increasing the temperature + 970 BTU + 142 BTU 1 lb. water at 70 oF 1 lb. water at 212 oF 1 lb. steam at 212 oF Certification Training Level 1 Version 2.0

  37. Steam Traps Properties of saturated steam Certification Training Level 1 Version 2.0

  38. Steam Traps Steam application Heating • Industrial • Home Industrial processes • Distillation • Humidification Cleaning Certification Training Level 1 Version 2.0

  39. Steam Traps What is a steam trap? It is an automatic valve that opens for condensate, air and carbon dioxide (CO2) and closes for steam Certification Training Level 1 Version 2.0

  40. Steam Traps How steam traps operate Velocity Density Temperature Certification Training Level 1 Version 2.0

  41. Steam Traps Effects of air in heating system • Occupies precious space in the steam line • Air/steam mix has less calorific energy to transfer • Insulating property of air acts as heat transfer barrier Certification Training Level 1 Version 2.0

  42. Steam Traps Temperature reduction caused by air Certification Training Level 1 Version 2.0

  43. Steam Traps Effects of CO2 in a heating system CO2 enters the system as carbonates from the feed water, a few ppm stays after the DI plant and mixes with the cooled condensate to form carbonic acid which is highly corrosive. Certification Training Level 1 Version 2.0

  44. Steam Traps Effects of condensate in a heating system Dramatic decrease in heat transfer capability of system Occurrence of water hammer in steam lines Certification Training Level 1 Version 2.0

  45. Steam Traps Efficient heating system Air, CO2 and condensate are removed as quickly and as completely as possible Steam traps do the job! Certification Training Level 1 Version 2.0

  46. Steam Traps Inverted bucket Operation: Density How it works Uses the difference in density between condensate and steam. When steam is predominant the trap is closed When condensate is predominant the trap is open Usual failure mode Open Certification Training Level 1 Version 2.0

  47. Steam Traps Float and thermostatic Operation: Temp./Density How its works Float traps work on the basis of the difference in density between steam and condensate. A thermostatic element opens a valve when the trap cools to a specified temperature Usual failure mode Closed Certification Training Level 1 Version 2.0

  48. Steam Traps Thermostatic Operation: Temperature How its works The float operates on the basis of a difference between steam and condensate Usual failure mode Open Certification Training Level 1 Version 2.0

  49. Steam Traps Visual inspection Venting live steam to the atmosphere Can pose safety issues Certification Training Level 1 Version 2.0

  50. Steam Traps Ultrasonic inspection Allows one to hear inside the trap Certification Training Level 1 Version 2.0

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