TEST GRAVITY VALVE
Problem description
  • Separated primary and secondary vacuum to prevent spoiling the ring
    vacuum with out gassing of electronics and cables, etc.
  • The foil needs to be thin to reduce multiple scattering
  • Protection against deformation and rupture because off pressure
    differences that can occur

    • Vacuum system
    Vacuum system of test setup
    Gravity Valve
    		 
    (december, 2001)
    Gravity valve response 
  • Conditions during the gravity valve response measurement:

    • The dedicated turbo pump for gravity valve is 
switched off

    • Only one vacuum is pumped or vented the other follows 
because of gas flow through the gravity valve
    

  • Response pressure of the gravity valve

    • 2.5 mbar (primary > secondary)

    • 1.5 mbar (secondary > primary)
    • Controlled evacuation 
  • Membrane switches control the differential pressure between primary
 and secondary vacuum via a PLC by opening/closing electric valves

  • The maximum differential pressure is set at 5 mbar

  • The delay time of the valves is 0.5 seconds (closed state)

  • The gravity valve is switched off

  • The settings of the needle valves are frozen during the operation

  • The evacuation of the primary vacuum limits the pump down velocity


    • Controlled venting
    		 
    Evacuation-2
It is possible to evacuate and 
vent with the membrane switches set
at a maximum pressure difference of 2 mbar

    Conclusions 
  • All measurements indicate that the gravity controlled valve works okay

    • It opens at extremely low differential pressures

    • Leak rate during normal operation needs to be determined

    • Response of the gravity valve to leaks has to be investigated 

  • The controlled evacuation and venting procedures work fine

    • It is possible to evacuate and vent with a maximum pressure difference of 2 mbar
    		•