Commissioning steps for gamma level sensor.pdf

Pentax Gama Ray level switch for detection of cyclone jam Commissioning steps for gamma level sensor: Observations and settings:1. Check the dose rate near detector with source ‘ON’ with radiation servey meter, it should be 0.4mR/hr to 1mR/hr 2. Detector supply at PLS-100 monitor across DP+, DNa. Without detector: 11.90VDC (12V approx) b. With detector: 10.70VDC (approx) 3. Detector current should be in cetween 25 to 40 mA max. If detector current is very less than 25mA and high than 40 mA then detector may be faulty. 4. With detector in connection check /set ‘sensitivity’ across the test points TP15(+) and TP(-). It should be around 500 mV and can be set by sensitivity pot on PLS100 monitor card. (To get the consistant pulses from detector) 5. Keep ‘cal’pot clockwise minimum and observ the gamma counts on display, original gamma counts should be 25 to 35 gamma counts, check this counts with DIV JP1 to JP3 jumpers(DIV 4,2,1). (At first installation this jumper should be at divide by 4 or2) 6. With ‘CAL’ pot, by rotating it in anticlockwise direction increase the sample time (sample time is time between the two readings on gamma counts display) from 25/35 counts to 80/100 counts. Sample time should be 3 to 4 secs. For setting the gamma counts with cal pot source should be in ON condition. 7. On gamma count disply you will find that the counts varies between 80 to 100 counts that is beacause the gamma rays emmission is the random process as we measure the dose rate unit is mR/h. 8. Level indication LED and level indicator across over the counts are less than 20 counts (set by JP-9). 9. Make off the source and observe the counts on display that comes down to 00,01,02,03, this time LEVEL LED will be ON and level relay changes its status. (NC to NO & NO to NC). This condition can called as cyclone jam.

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10. On gamma counts seven segment display reading shows reading upto 99 and if count reading exceeds 99 then OVF LED will turn ON which indicates the actual gamma counts equal to 99 plus the actual counts on the display. Please note that the OVF LED is only for the indication of display overflow above 100 and not the material overflow. 11. Make ON the source and observe the gamma counts on display which should again vary from 80 to 100 counts, LEVEL LED is OFF and level realy is normal(ie system is normal)

12. If the gamma counts on display shows 00 counts for more than two miniutes then system LED and System relay will triggered and if such condition continues for longer preiod then check the detector supply, current and sensitivity. 13. If the water circulation of detector water jacket fails , the temperature of detector goes beyond 55 degC then the temperature circuit of detector will triggered and on PLS-100 monitor OVF LED, SYS LED and TEMP LED will be on and system relay will be triggered. And if such condition is continued for longer period then detector will get damaged. In this case if cyclone jam occures then level indication will not work. Hence for trouble free operation of the system water circulation is must. 14. System operaiton can be checked by putting source ON and OFF. Source off condition is as good as cyclone jam.