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How to determine voltage for Holiday Test
- Thread starter zibaeng
- Start date
We have a shop Holiday procedure for polyethylene coating that reads:
Dry film Mils Voltage
8 to 11 1,700
12 to 15 2,200
16 to 20 2,700
21 to 40 3,200
41 to 55 4,200
You first need to find out what the min required thickness is and set your Holiday tester accordingly. Note that Holiday is a destructive test. Do not keep going over the same area or your coating will be ruined. Also as mentioned by Stanweld you should always find out from the coating supplier what the specific voltage requirements for their product is. This only gets you in the ballpark.
Dry film Mils Voltage
8 to 11 1,700
12 to 15 2,200
16 to 20 2,700
21 to 40 3,200
41 to 55 4,200
You first need to find out what the min required thickness is and set your Holiday tester accordingly. Note that Holiday is a destructive test. Do not keep going over the same area or your coating will be ruined. Also as mentioned by Stanweld you should always find out from the coating supplier what the specific voltage requirements for their product is. This only gets you in the ballpark.
Ask the pipe coating. Make a test mock-up of the coating at the minimum thickness acceptable, then start cranking up the voltage until you get 'breakthrough' - sparking on unblemished areas. This is the 'insulation breakdown' voltage, and is destructive. You need to keep all testing at no more than 75% of this voltage.
Now, make a very small pinhole in a untested area of the mock-up with the heaviest acceptable coating, and drop you voltage to about 500V per mil, and keep raising the voltage until you get the first indication of sparking/'jeeping'. This is the minimum, acceptable testing voltage.
Pick a standardized test voltage somewhere between the minimum found and 75% of the 'breakdown' voltage. Rules-of-thumb are only starting points. Don't use them without experimental testing on the actual 'stuff', either by the manufacturer or by you.
Now, make a very small pinhole in a untested area of the mock-up with the heaviest acceptable coating, and drop you voltage to about 500V per mil, and keep raising the voltage until you get the first indication of sparking/'jeeping'. This is the minimum, acceptable testing voltage.
Pick a standardized test voltage somewhere between the minimum found and 75% of the 'breakdown' voltage. Rules-of-thumb are only starting points. Don't use them without experimental testing on the actual 'stuff', either by the manufacturer or by you.
The two main players in the Holiday Detector business are The K_B Bird Dog and the Detectors made by Tinker & Razo. K-B makes the familiar wand type seen in a lot of ads while Tinker & Razor make several models from th the low voltage 67.5 V to the 35,000 volt sparker.
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