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NFPA 20 11.4.2 Tank Level Indication

Question asked by cupton on Jul 24, 2017
Latest reply on Jul 25, 2017 by cdafd

I have a few questions in regards to diesel storage tank level indications for a fire water pump.  


  • For a Diesel driven fire water pump, states "Means other than sight tubes for continuous indicating of the amount of fuel in each storage tank shall be provided".  What is the definition of a sight tube?  And, what is the intent of this statement.  To me it means another means of measuring the level like using some other technology, like radar, to provide a continuous level reading.    


  • states " A fuel level indicator shall be provided to activate at the two-thirds tank level."  What is the intent of this statement?


  • states "The low fuel level condition shall initiate a supervisory signal".  Is the low fuel level closer to the bottom 10% of the tank?  Or is it at the 2/3rds mark as defined by the previous statement?  What would be the purpose of the supervisory signal?  Other sections define the supervisory signals as low fuel pressure.  


However, Appendix Figure A.11.4.4 shows a level indicator and a low level switch on the storage tank.  If I understand the picture, then one local gauge and a level switch (one for high, one for 2/3s, and another at low?).  Is this correct?



Aaron F.