SYLGARD High Voltage Insulator Coating. A guide to proper application

Transcription

1 SYLGARD High Voltage Insulator Coating A guide to proper application

2 A Ready-to-Use Coating SYLGARD High Voltage Insulator Coating (HVIC) is a one-component, ready to use silicone elastomer dispersion designed for use on high voltage insulators to prevent flashover and arcing, especially in severely contaminated environments. SYLGARD HVIC: Has the longest proven RTV coating field performance Resists airborne contaminates Remains virtually maintenance-free Is cost effective Is spray applied with no mess & good finish Use SYLGARD HVIC: As a protective coating - for glass and porcelain insulators, lightning arresters, bushings and post insulators. Against dampness and pollution where applying SYLGARD HVIC overcomes flashover problems On polymer insulator surfaces after priming and special surface preparation. Use this application guide to get consistent high-quality results for your high voltage insulation application projects. Follow these guidelines for best results: Clean all surfaces of dust, grease and wax If washing is first required, use non-soapy detergents, rinse surfaces well and allow them to dry. If the insulators have previously been coated with silicone compounds or other types of greases, first clean off the old compound. If the old grease does not come off easily by hand, try using diesel or paraffin diluted with an emulsifiable degreasing fluid. Remove the final grease film with a non-polar solvent and clean the insulator surface with isopropyl alcohol immediately prior to application of SYLGARD HVIC. Do not use soaps, which act as release agents and make good adhesion impossible. Check temperature and humidity when applying Because SYLGARD HVIC is a one-part room temperature vulcanising material, moisture causes it to cure. When humidity is relatively high, cure is faster. Both temperature and humidity affect tack free and cure times. When temperature and humidity are high, tack free and cure times are shorter, while when temperature and humidity are low, tack free and cure times are longer. For maximum protection, apply a total dry thickness of 0.5 mm - SYLGARD HVIC is normally applied in two to three coats, depending upon the method and equipment used. - For maximum protection and life expectancy, a total dry thickness of 0.5 mm (0.020 in) is recommended. - Measure thickness using a wet film thickness gauge. Please note that 0.7 mm (0.28 in) of wet film is required for 0.5 mm (0.20 in) of cured SYLGARD HVIC. - Cured or dry film thickness can be measured with an ultrasonic thickness gauge. Choose SYLGARD HVIC for high reliability and low lifetime running costs 1998, 2001 Dow Corning Corporation. All rights reserved.

3 œ Œ Applying SYLGARD HVIC A variety of application methods are possible, depending on your needs. Apply by spraying, brushing or dipping. Spraying is the most common method. Setting up the spray equipment À à Use dry air or nitrogen Uncoated insulator Õ Air to atomise at gun Spray gun HVIC line SYLGARD Coated insulator SYLGARD HVIC Spray setup 1 kilogram of SYLGARD HVIC covers m2 of insulator surface - 1 kilogram of SYLGARD HVIC as supplied will cover m 2 of insulator surface at a cured thickness of 0.5 mm. (1 lb covers 744 in 2 at 0.20 in thickness). - This coverage excludes losses resulting from material left in the container and spray equipment, together with losses from over-spray. - For application by inexperienced sprayers, or onto insulators with small diameters where over-spray is likely, it is recommended that a 15% wastage factor be used in quantity calculations. (So, 1 kg of SYLGARD HVIC will coat 0.9 m 2 of insulator surface.) Dilute properly for easy application - Before use, thoroughly agitate SYLGARD HVIC on a paint shaker or a can roller to ensure uniformity. - Thinning may be required, depending on the application equipment to be used and the humidity and temperature conditions. - Some diluting may even be required for brush application. - To dilute, use a high flash point (40 C or above) naphtha spirit solvent similar to solvent 360 from shell oil or white spirit. - Add the solvent in small amounts and mix thoroughly at each step. The final mixture must be homogeneous. Compressor Pump Always wear gloves when mixing. First agitate thoroughly in a pail or separate container. Then dilute by slowly adding solvent in small amounts. Make sure the final mixture has uniform thinness. Connect the airline from the compressor to the spray pump air inlet. Connect hose lines from the air outlet À and the SYLGARD HVIC outlet à on the pump to the spray gun. Adjust compressor and pump settings Õ so that fluid comes out of the gun nozzle when trigger is pressed. Close the airadjusting valve Œ situated either in the gun handle or at the pump air regulator module. Screw gun spray pattern adjustment œ all the way in, and then back out 1/2 to 3/4 of a turn. Turn the SYLGARD HVIC volume adjustment valve all the way in, and then, with pressure on the trigger, turn slowly out again until SYLGARD HVIC spray just emits from the nozzle. Open the air adjusting valve Œ to give suitable atomisation of the SYLGARD HVIC. Use this setting for the initial coat on the insulator. When spraying additional coats, you will need to adjust the valves to get a larger volume spray pattern and for more SYLGARD HVIC. When spraying SYLGARD HVIC, always wear eye protection and rubber gloves. If spraying inside, or in a locaiton with poor ventilation, you should also use respirators along with safety glasses. only one application gives a long-lasting maintenance free solution.

4 Applying the first coating Applying SYLGARD HVIC with spray equipment. Apply first coating in a thin layer. This will ensure a build-up without any runs or streaks. The first coat can run easily, so apply a light flash coat first. Allow first coat to dry for minutes. When first coat becomes tacky, apply subsequent coats. Applying 2nd & 3rd coatings After the first coating, the next coatings should be applied whilst the surface is tacky (wet-on-wet), and can be applied more thickly. Spray in a long, slow arc motion until ripples appear in the coating surface. When this happens, move on to another part of the insulator. Do NOT continue to spray after rippling to avoid runs. Spray until pail is empty, or, for continuous spraying, top up pail with SYLGARD HVIC and solvent mixture that has been prepared in a separate container. Equipment clean up Clean spray equipment and hoses so that SYLGARD HVIC does not cure in the gun, pump or hoses and cause blockages. Follow the steps below: Fill the pump pail 1/4 full with solvent. Open both spray gun control valves Œœ to allow free fluid and airflow. Spray the atomised solvent through the hoses and gun for a few seconds. Then, close the air valve Œ on the spray gun handle, and spray the remaining solvent un-atomised through the system. Blend saved solvent with SYLGARD HVIC for the next operation Remove pail, wipe out with a clean cloth. Add more clean solvent, and spray again through the system and save for next time. During the second cleaning, unscrew the gun nozzle and spray the solvent through the nozzle holes in both directions. Pour away any remaining solvent from the pail and wipe dry with a clean cloth. Spray equipment options Various types of spraying equipment can be used: Air-assisted airless spray sets give the best finish with the air atomisation of the product. Airless equipment can also be used to minimise over-spray losses and gives a higher build-up per gun pass. For small quantity applications, it is also possible to use siphon type spray equipment, but more coats are required to achieve the 0.5 mm thickness and the material would need significant thinning. Notes: Cured thickness should be around 0.5 mm +/ mm and 0.7 mm uncured. Check this during spraying using a wet film gauge If an insulator has numerous skirts, it may not be possible to get the full 0.5 mm thickness on the underside. In such cases, make sure that at least one good coat is applied so that the insulator base colour is not visible. Coated surfaces can be touched or will be tack-free in about 30 minutes. A full, final cure usually takes 8 hours.

5 Using air assisted-airless spray equipment: Use a Graco Monarch or similar air powered 5:1 to 10:1 ratio divorced pump (or similar) with wetted parts manufactured from stainless steel/ptfe. Mount the spray set on a twowheeled mobile trolley. Fit the fluid inlet of the pump with a flexible suction hose, complete with a rigid riser tube. The pump air motor is completed with a twin air regulator module to facilitate control of pump operating pressure and gun atomising pressure. Connect air atomising regulator to a brass manifold fitted with 4 manual isolation valves. Fit the fluid outlet of the pump with an inline filter assembly, complete with fluid dump valve and a connecting hose to a brass manifold fitted with 4 manually operated material isolation valves. Each of the 4 material isolation valves is suitable for connecting air and fluid hose kits (say 20 metres long). Each hose kit terminates with an air spray gun similar to the Graco type 800 with a 1.5 mm diameter nozzle set-up. This set-up allows the use of up to 4 spray guns from the same pump (could run 3 guns at height of 15/20 metres or 4 guns at ground level). Use a portable air compressor to operate the spray pump. The compressor should be rated at 7 bar (100 psi) with a free air delivery of 1.5 cubic metres per minute (50 cfm) for 2 guns and 2.25 cubic metres per minute (80 cfm) for 4 guns. Brushing Use a soft-bristled brush to apply SYLGARD HVIC. If more than one coat is required, dilute the product so that the brush will not pull the surface skin on the first coat. Clean the brush frequently. Brushing does not usually give a smooth finish, but it does provide the same electrical benefits as spraying. Dip coating Good results can be obtained by dip coating for factory application. Be sure to rotate the insulator to achieve uniform thickness and prevent drips. Touch-up procedure ensures uniform coating Use a foam pad or brush to touch up or remove drips and to repair surface flaws or damaged coating. Re-coating procedure Clean the entire insulator with a solution of isopropyl alcohol diluted with 50% clean water. If the adherence and thickness of the original coating is little affected, the entire insulator can be over-coated with an additional coat of new SYLGARD HVIC if necessary. The dry film thickness of the additional coat would be around 0.25 mm. Coating surfaces of polymer insulators It is also possible to coat the surfaces of polymer insulators with SYLGARD HVIC. Clean the surfaces of such insulators, and apply DOW CORNING 1200 OS primer, or DOW CORNING HV1860/120 primer or low VOC 5200 primer before coating to ensure good adhesion. See specific primer data sheets for full primer application details. Service life projection & assessment The service life of SYLGARD HVIC depends upon the severity of the contamination, insulator design and the degree of electrical stress. In addition key elements will have been good application with the correct application controls (cleaning and correct thickness). On the basis of Dow Corning's experience over the last 25 years, we have found that many installations provide excellent service for up to 10 years and beyond. However, the length of the service life will be dependent upon the factors detailed above. Thin or bare spots indicate that the coating is approaching the end of its useful life. Loss of hydrophobicity could be another indicator. Increases in leakage current could indicate that the coating may need a clean and possibly an overcoat. Safety requirements Because SYLGARD HVIC is combustible, do not use conventional application methods near or on energised electrical equipment. Do not apply SYLGARD HVIC under energised conditions. Use material safety data sheets (MSDS) to carefully review all the required safety precautions for handling SYLGARD HVIC and DOW CORNING primers.

6 Dow Corning Product Lines for the Electrical Power Industry Dow Corning provides a series of cost-effective silicone insulation options for protecting electrical systems. These are designed to reduce arcing, tracking and flashovers to improve your system reliability and lower maintenance costs. Other Dow Corning electrical products for original equipment manufacture and maintenance include: Full range of silicone rubbers specially designed for high performance composite line insulators, above and below ground system components and substation components. Sealants and adhesives for site maintenance and gaskets Lubricants for circuit breakers and switchgear Dielectric compounds Varnishes and resins Insulation repair and enhancement for underground electrical cable Silicone transformer fluids For more than 50 years, our high performance silicone solutions have supported the electrical industry so rely on Dow Corning s complete product line that s backed by long-term proven performance and full technical support. Your Global Connection Asia Dow Corning Asia Ltd. - Japan Tel.: Dow Corning Asia - Singapore Tel.: Australia & New Zealand Dow Corning Australia Pty. Ltd. Tel.: North America Dow Corning Corporation World Headquarters Tel.: South America Dow Corning do Brasil Tel.: Europe Dow Corning Europe Tel.: +32 (0) LIMITED WARRANTY INFORMATION - PLEASE READ CAREFULLY The information contained herein is offered in good faith and is believed to be accurate. However, because conditions and methods of use of our products are beyond our control, this information should not be used in substitution for customer's tests to ensure that Dow Corning's products are safe, effective, and fully satisfactory for the intended end use. Suggestions of use shall not be taken as inducements to infringe any patent. Dow Corning's sole warranty is that the product will meet the Dow Corning sales specifications in effect at the time of shipment. Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted. WE HELP YOU INVENT THE FUTURE. DOW CORNING SPECIFICALLY DISCLAIMS ANY OTHER EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY. DOW CORNING DISCLAIMS LIABILITY FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES. Dow Corning and SYLGARD are registered trademarks of Dow Corning Corporation. TM WE HELP YOU INVENT THE FUTURE is a trademark of Dow Corning Corporation. 1998, 2001 Dow Corning Corporation. All rights reserved." Form No