Questions

• Can electrodes be repaired
• Can I receive a shock from the system after the unit has been stopped
• How can I determine if there is a failure with a roll covering or electrode
• How long should an electrode last
• What considerations are important for installation of proper exhaust systems
• What Information should be provided when calling for parts, service or technical assistance
• What is the correct electrode air gap
• Why are the electrodes failing
• Why is only part of the electrode discharging corona
• Why isn't corona present across the full length of the electrode
• Will a system from another location work on my line
• With summer approaching what can I do to ensure optimum performance from the treater

Answers

If the ceramic is broken or pin-holed, the electrode is not repairable. If the high voltage lead or mounting tabs are broken or damaged and the ceramic tube is complete, the electrode can be repaired. Credit may apply for useable length of ceramic.

Yes, but the shock is a result of stored electrical energy in the form of static present on the material. Once the corona treating system power supply is de-energized, all power to the electrodes is removed. It is quite common to experience static buildup and discharge in the process of converting films. There are many factors besides a corona treater that can contribute to static buildup. The simple movement of a substrate over a roll will create static. If a roll is not turning...or is turning at a slower speed than the substrate is traveling at...static creation will be accelerated. Environmental conditions such as temperature and the dew point of the air are also factors that can contribute to static build up. There are many commercially available devices to reduce or eliminate static build up.

Enercon has a device in stock specifically to test for dielectric failures. The instrument, our part number LM4039-01, consists of a transformer and probe to generate approximately 10 KV - 48 KV from a 115 VAC, 50/60 Hz input. The probe is hand-held and generates high voltage at the tip. The tip consists of a 3 - 4" length of wire, which is passed over the area to be tested. If the dielectric is failed, it will generate a direct arc through the failure. If the dielectric is good, a corona will develop.

With proper cooling and handling, a ceramic electrode should and will provide years of continued service. The key to longevity is cooling. Overheating is the number one cause for electrode failure, followed by physical damage. As long as the ceramic dielectric function of the electrode is in tact, the electrode will provide identical performance day to day, year to year. The ceramic provides the dielectric, or buffer, which prevents a direct arc to ground.

Each system requires a specific exhaust air volume and static pressure to ensure that electrodes are cooled properly, and that the ozone produced by the corona discharge is removed. Specific system exhaust requirements are stated on the station Installation Drawing (ID). Ductwork diameter should be sized to minimize losses for the volume of airflow required. Other factors to consider are minimizing the length of run and the number of bends, or directional changes necessary to route the air outdoors. If there are any concerns about the ductwork, please contact Enercon Industries service department to review the installation.

It is good practice to have the model or serial number of the unit available when calling for parts or service. This information helps our engineers and Customer Service Team to rapidly provide assistance, and ensure the parts are correct for the specific system in question. The system serial number is located on the red Enercon Industries label placed inside the power supply cabinet door, on the station, or on top of the high voltage transformer.

The electrode air gap can vary between 0.040" – 0.100," depending on the material in the system; but, the gap must be consistent across all electrodes. The recommended gap is 0.060." However, if the material is relatively thick, or if a potential splice results in a tail or splice of greater thickness, then increasing the gap is acceptable.

The minimum air gap is 0.040." If the distance between the electrodes and the ground roll is less, the cooling air required to ensure the temperatures of the electrodes do not exceed safe operating temperatures will be restricted.

The proper gapping procedure can be found in the station manual. If you need an air gap gauge, please contact us to receive one at no charge.

Electrode failures are usually a result of either physical contact, or inadequate cooling. Each type of failure exhibits specific tell-tale signs as to the cause. Physical damage, seemingly obvious, may not be so in all cases. Upon close examination however, usually hairline fractures are visible emanating from the area of impact. Also, the more common sign is the electrode is fractured around the circumference of the tube, not along the length.

Failures that result due to heat as a consequence of inadequate cooling are usually focused or form a pin point, hence the term pinhole type failure. The electrode heat results in a mechanical failure of the ceramic dielectric. These type failures usually result in a specific or concentrated failure point due to heat build up. Cooling related failures that occur where the cooling passages are blocked off are easily understood. Electrode failure near severely carbon tracked insulating shroud, or near the edge of the web are also a result of heat related failure. In both cases, the impedance of the carbon tracked shroud, or the open area outside the web path is less than the impedance offered to the overall length of the electrode, resulting in a greater amount of energy discharged in the smaller area. A breakdown or pin-hole in the dielectric occurs.

There are a few reasons for inconsistent corona, all of which are a result of higher impedance presented to the corona discharge between the electrode and ground roll. To identify causes for inconsistent corona, it is helpful to understand the principle of corona discharge. Corona treatment is simply an electrical circuit. The electrical discharge will seek the path of least resistance, or impedance.

In most corona treating systems, high voltage is applied to the electrode which is suspended over a grounded roll. There is a dielectric covering either on the electrode, the ground roll or both. The dielectric covering can consist of ceramic, silicone, hypalan, epoxy or glass. The dielectric strength of these materials vary and establish the number of electrodes required, or the roll size necessary to safely handle the amount of power discharged. The dielectric material thickness is relatively constant and generally the gauge or thickness of material is also relatively constant, offering consistent impedance to the high voltage discharge to the ground.

Although dirty electrodes or ground roll surfaces can affect the dielectric and affect the corona, the amount is usually insignificant. The major variable that affects the circuit is the distance that must be ionized in the air gap. Air is an extremely good insulator and offers high impedance to corona. The primary reason for variations in corona discharge is due to discrepancies in the air gap between the electrodes and ground roll. At lower power levels, the energy necessary to ionize the air gap will discharge to the path of least resistance, offered by an electrode, or section of an electrode that is closer to the ground roll.

Inconsistent or less than full corona discharge from the electrode to the ground roll is due to uneven electrode air gap. Corona discharge seeks the path of least resistance from the electrode to the ground roll. Uneven air gap results in increased dielectric offered to ground. The standard recommended electrode air gap is 0.060" or 1.5 mm. Contact us for a free gap gauge.

Each corona system is sized according to the specific material to be treated and with the desired performance results based on the customer’s specific required parameters. The power available for each system is predetermined by the materials it is intended to be used with. In order for the system to perform, difficult to treat material or operation at extremely high line speeds will require higher available power capacity.

System design is developed from a few basic fundamental parameters: web width, line speed and required treat levels. Ground roll coverings and electrode type dictate the physical size and number of assemblies required to apply the necessary energy to the material width at the required line speeds to achieve the desired treatment.

Of course cost is always a consideration, but performance and treatment requirements ultimately play a major role in the decision. The type of ceramic electrode: round, rectangular or PV, stainless steel tube, segment, or finned aluminum all have a maximum amount of energy (in Watts) that can be discharged per linear inch. The type roll covering: epoxy, bonded silicone, silicone sleeve or ceramic have a specific amount of surface area necessary per kilowatt of power to safely operate. Provided with the line specific parameters of material, treat width, line speed and application required treat levels, the system’s remaining size factors are derived. The roll diameter is determined by the type roll covering used or if added spacing is require for electrode assembly placement around the ground roll. The electrode type is generally a customer specification, but can be dictated by the type of material treated (i.e. a metal electrode cannot be used to treat conductive substrates).

Many manufactures of films are consolidating or re-using "moth-balled" equipment. In some cases, this practice is possible. However, it is important to understand that the original material specifications determined the design of that treating system. Often the "shelved" unit may not fit the specification needs for the application.

The majority of corona treating system problems are a direct result of station failure. Problems in the power supply usually are the ultimate result of station breakdown. Dirt, moisture accumulation and film residue create a destructive combination resulting in high voltage breakdown. Blocked cooling paths, dirty electrodes, and build-up on electrode insulators and high voltage component supports all are potential points of failure. The best action to ensure reliability is keeping these areas clean.