40 extends in a radially inward direction to form a half ring 80 that forms one half of the obstruction 82 and the shell 42 extends in a radially inward direction to form an opposing half ring 82 that forms the other half of the obstruction 82 the diameter of the opening 50 is slightly greater than the outer diameter of the conduit 12 but less than the outer diameter of the dust cap 14 therefore when the shells 40 and 42 unite in the protector 39 s closed state the protector 20 cannot be pulled away from the inlet fill connection as the inner annular shoulder 15 of the dust cap 14 abuts the annular obstruction that is formed from the half rings 80 and 82 as depicted in fig5 the inner diameter of the collar formed from the shells 40 and 42 is sufficient to accommodate the outer diameter of the dust cap 14 as depicted in fig5 the protector 20 includes a closed end 52 that prevents access to the dust cap 14 from the protector 39 s far end i e the end of the protector 20 farthest from the gas supply system 10 the closed end 52 also prevents an unauthorized person from sliding the protector 20 along the conduit 12 toward the gas supply system 10 and over the dust cap 14 for purposes of gaining access to the inlet fill connection in some embodiments of the invention the closed end 52 is formed from a circular end cap of the shell 40 in this manner.