Use of Vacuum for Prevention of Leaks. Wayne Geyer Steel Tank Institute

Transcription

1 Use of Vacuum for Prevention of Leaks Wayne Geyer Steel Tank Institute

2 Choose the False Statement 1. A perfect vacuum is a space void of all air 2. Perfect vacuum exists only in outer space 3. Pressures below atmospheric pressure are considered to be under negative pressure, or vacuum 4. 1 Atmospheric pressure = 760 Torr (mm) = kpa = 14.7 psi = HG 5. Low vacuum is measured in Inches of Hg

3 Barometers Measure Atmospheric Pressure At atmospheric pressure, h = HG or 780 mm

4 Choose the False Statement 1. A typical vacuum cleaner can pull 600 Torr (-11.6 Hg ) vacuum with molecules of air remaining in every cubic centimeter of space 2. Rule of thumb: 1 psi = 2 HG 3. Vacuum is an unproven test method 4. UST manufacturers have applied vacuum to the interstice of double wall tanks to test both walls for nearly 20 years 5. Continuous vacuum is a new leak detection method in the United States

5 True or False 1. The longer the tank holds the vacuum originally established within the interstice, the greater the proof of integrity of both walls even better than a 5 psi soap solution test. Select the Right Answer The vacuum can change over time due to a. Temperature change b.atmospheric changes c. Outgassing d.improper threaded joint connections e All of the above

6 1) Precision Interstitial Vacuum Monitor Ken Wilcox Associates ( System performs post installation tank tightness test prior to adding product System conducts vacuum test on interstice between secondary contained tank walls Minimum initial vacuum is 13 HG Tank is declared tight when vacuum loss does not exceed 5 5 HG AND.

7 1) Precision Interstitial Vacuum Monitor KWA ( Leak Threshold: 0.1 gph Certification 0.1 gph leak rate with PD = 100% & PFA < 0.5% Applicable to: gas, diesel, fuel oil, water Tank Capacity: 50,000 gallons Test Period 12 hours for tanks < 10,000 gallons 24 hours for tanks 10,000 50,000 gallons

8 2) Interstitial Vacuum Monitor for Liquid Leaks Ken Wilcox Associates ( Leak Threshold Tank is considered tight at a point in time when a 14 HG vacuum is established and tested for a specified period of time for a given tank size Vacuum loss no greater than 5 HG With gasoline: 0.4 hr 3.7 hr With diesel: 5 hr hr Certification for tank size up to 20,000 gallons 0.1 gph leak rate with PD = 100% & PFA < 0.5%

9 Continuous Vacuum Systems Introduced into the United States from Germany Prevents releases into environment without size limitations 24/7 AB 2481 in California mandated continuous leak detection systems July 1, 2003 Interstice must be maintained under constant vacuum or pressure to detect a breach in the primary or secondary containment before the liquid or vapor of the stored substance is released to the environment North Carolina introduced similar regulation in November 2007 for tanks only, not pipe

10 How Does the Continuous Vacuum Method Work?

11 Disclaimer Several continuous vacuum systems have been tested and certified by KWA Some systems use a vacuum pump to maintain vacuum over operating life Some systems use the submersible turbine pump to maintain vacuum over operating life (not for suction system) STI is not endorsing any system

12 STP Method Photos Courtesy of Franklin Fueling

13 UNTERDRUCK - LECKANZEIGER TYP 08 / PTB Nr. III B / S 1500 B auj ahr: Fabr. Nr.: Alarmfall: Wartung: Achtung: Leistungsdaten: Externe Schaltleistung, Klemmleiste K, Klemmen AS: 230 V - 50 Hz - 42 W 230 V - 50 Hz; max. 50 VA Plombe am Alarmschalter entfernen, akustisches Signal abstellen und Installationsfirma benachrichtigen. Der Leckanzeiger ist einmal jährlich vom zuständigen Fachbetrieb auf Funktionsfähigkeit und Betriebssicherheit zu pr üfen. Für Behälter bi s 2,0 m Durchmesser Betrieb Alarm Saugen Auspuff M essen Vacuum Method for tanks with a leak in the inner wall Sicherungsgerätebau GmbH, Siegen VL - H2 / 1. A leak occurs in the inner wall of tank. Liquid enters the interstitial space. 2. Vacuum drops, pump is switched on to build up vacuum in interstitial space again. 3. More liquid enters interstitial space. 4. Pump is repeatedly switching on and off. 5. Liquid is filling interstitial space. 6. Liquid stop valve closes and pump is separated from the interstitial space. Now pump can not produce any more vacuum. 7. More liquid enters measuring line which results in a vacuum drop down to alarm pressure. 8. Optical and acoustical alarms are triggered. Leak detector Measuring line Exhaust line Suction line Liquid stop valve Tank with interstital space

14 Vaccum Method for Piping with a Leak in Pipe 1. A leak occurs in piping. 2. Liquid fills interstitial space. VL-HFw2 3. Pump is repeatedly switched on and off. 4. Liquid reaches liquid stop valve. Now pump can not produce any more vacuum. 5. More liquid enters measuring line which causes vacuum drop down to alarm pressure. 6. Optical and acoustical alarms are triggered. h <= 3 m Liquid stop valve Suction line Measuring line T - joint

15 Vacuum Method Leak In Outer Wall of Tank or Piping Air Enters Interstitial Space From Outer Wall Vacuum Pump Attempts to Maintain Vacuum in Interstitial Space Vacuum Drops to Alarm Pressure Optical and Acoustic Alarms Are Triggered

16 Vacuum Method Leak in Both Inner and Outer Wall of Tank or Piping Product Enters Interstitial Space From Inner Wall While Air Enters Interstitial Space From Outer Wall Vacuum Drops to Alarm Pressure Optical and Acoustic Alarms Are Triggered before a release of product can occur unless the failure is catastrophic

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21 Items to Consider Training & Education Owners Distributors & Installers Manufacturers Availability Cost Factors Complexity, Alarms, etc. Alternatives (liquid sensors, etc.)