Dielectric Union Failure

A dielectric union pipe fitting is designed to hold two types of metal pipe together without actually soldering them.

Dielectric union failure.

It is a voltage which a dielectric material insulator will withstand without breaking down. It is the highest voltage at which the specific insulation will not break down. All insulating materials undergo breakdown when the electric field caused by an applied voltage exceeds the material s dielectric strength. They seem to think that the main failure mode is overtightening of the union which results in metal metal contact and galvanic corrosion.

View entire discussion 7 comments more. Plumbing codes in all states require the use of dielectric unions when connecting dissimilar metals. They are ideal for use in air and water conditioners hot water storage tanks processing tanks and steam gas and water piping. Metallographic examination revealed evidence of severe stress corrosion cracking within the brass as well as dealloying on the surface.

Persistent failures leakage were observed in the brass portion of dielectric unions after a relatively short service period. Dielectric unions are use to join pipes made from dissimilar metals to avoid electrolysis which leads to corrosion and pipe failure. A dielectric class 3000 union with a dielectric coated a105 carbon steel tailpiece that is 3 4 female npt with a 304 stainless 1 2 male npt threadpiece teflon o ring is coded as follows. With a copper and an iron pipe this is necessary as the combination of metals under solder could produce galvanization leading to corrosion and failure of the pipe.

Slow degradation failures are characterized by a gradual increase of leakage current against stress time until a failure criterion is reached 100µa in this study. What is electric strength. This union is made from galvanized steel and lead free brass. This is the failure of an insulator due to the voltage impressed across it.

Evaluations using stress calculations and the dynamics of freezing water indicated that the unions were not overtightened during. This is nearly the same as dielectric withstand. Each includes a union nut 2 tailpieces and a gasket. Its only intended use is to break continuity.

Failure is the over firing of the dielectric resulting in the formation of a low resistance batio. To order call 800 769 0503. We explain the effect of galvanic corrosion at copper to steel pipe connections and we include notes on the recommendation for a jumper wire across dielectric fittings or. Electrical breakdown or dielectric breakdown is a process that occurs when an electrical insulating material subjected to a high enough voltage suddenly becomes an electrical conductor and electric current flows through it.

This failure mode is unique for bme capacitors that normally were.