Oil Breakdown & Tube Arcing

Dielectric (Oil) Leak: The dielectric, usually oxidization inhibited transformer oil, must provide high voltage insulation to prevent arcing from all high voltage surfaces. If oil leaks develop that usually means air also leaks in to the housing and if the air enters the high voltage field area it will cause an arc-over. If arcing continues, carbon from disintegration of the oil will begin to coat surfaces and they cannot be restored.

The oil used contains absorbed gasses which must be removed by vacuum treating to prevent their release in the housing. Such treating increases the dielectric strength as measured in units of volts per distance. Typical values are in excess of 30 kilovolts per inch. An important consideration is the materials used inside the housing, usually plastic insulators. These can leach plasticizers or other chemicals which can dissolve in the oil and degrade the dielectric strength. Temperature enhances the leaching. Care must be exercised to test materials used in the housing, even for new manufacturing lots of these parts.

Oil is commonly used as a coolant and lubricant in various electrical equipment, including X-ray tubes. However, over time, the oil can break down and degrade the dielectric strength of the equipment.

Dielectric strength is a measure of the ability of a material to insulate electrically. A material with a high dielectric strength can withstand a large amount of electrical voltage before breaking down and allowing current to pass through.

When oil is used as a coolant and lubricant in electrical equipment, it can come into contact with various contaminants such as dust, metal particles, and water. These contaminants can cause the oil to degrade and break down over time. As the oil breaks down, it can lose its insulating properties and become conductive, reducing the dielectric strength of the equipment.

Additionally, as the oil ages, it can also form sludge or varnish, which can also reduce the dielectric strength of the equipment. The sludge and varnish can accumulate on the surfaces of the equipment, insulating them and reducing the ability of the equipment to dissipate heat.

Furthermore, the oil's viscosity can change over time due to thermal and mechanical stress, making it less effective as a lubricant and coolant, which can lead to more wear and tear on the equipment, and thus reducing the dielectric strength of the equipment.

To avoid the breakdown of oil and the reduction of dielectric strength, it is important to regularly maintain and replace the oil. This includes regularly checking for contaminants, changing the oil at regular intervals, and monitoring the viscosity of the oil.