TESTING FOR CONDUCTIVITY
When testing a hose, swivel, breakaway coupling and/or nozzle at a service station, it is recommended that a megohmmeter be used. A megohmmeter is capable of generating test voltages significantly higher, 100 – 1000 Vdc., than that of the typical inexpensive multimeter. When selecting a megohmmeter it must be able to apply a test voltage of 500 Vdc. and be capable of measuring resistance in the 500,000, ohm range (0.5 Mohm). For accuracy, a digital megohmmeter is probably best unless an analog meter is found which has a resistance range from 0-5 Mohms, at 500 Vdc. test voltage.
WARNING: FOLLOW THE METER MANUFACTURER’S INSTRUCTIONS FOR PROPER EQUIPMENT OPERATION REGARDING POTENTIAL SHOCK HAZARDS.
TOTAL RESISTANCE MEASUREMENT (Nozzle to Dispenser)
A quick and easy method to check the maximum allowable resistance is as follows:
1. Connect one test lead of the megohmmeter to a dispenser ground.
2. Attach the other test lead to the nozzle spout and take your reading.
(An example: There is a 1 ft. whip hose, breakaway coupling, 12 ft. long hose, swivel, and a nozzle in the measuring path. The maximum cumulative resistance possible is 3 x 500,000 = 1,500,000 ohms for the breakaway coupling, swivel, and nozzle plus 70,000 ohms/ft x 13 ft total hose length = 910,000 ohms for a total of 2,410,000 ohms or 2.41 Mohms.) If your reading is less than the additive resistance, the path is considered conductive.If your reading is greater than the maximum accumulative allowable resistance then you need to determine which component or components are causing the resistance reading to be high (See Component Resistance Measurement below).
COMPONENT RESISTANCE MEASUREMENT
A method to isolate a nonconductive component is as follows:
1. Connect the megohmmeter test leads on each end of the part to be measured. If a nozzle, swivel, or breakaway coupling measures greater than 500,000 ohms or a hose measures greater than 70,000 ohms/ft at 500 Vdc. the component is defective and needs replacement.
2. If every component has a resistance measurement below the ranges listed above but the overall resistance is greater than the accumulative allowable, check the joints. It may be necessary to disassemble and clean the joints.
3. If any components were replaced or joints cleaned, retest for conductivity once reassembled.
It is recommended that the proper megohmmeter be used for all continuity testing. Using incorrect test equipment and methods can result in unnecessary component replacement expense. See Husky Technical Bulletin STBCONDUCT Rev. 2 or visit www.husky.com for more information.
Form No. TEST RESIST (Rev. 2, 2/1/18)