Rodurflex FAQs
• Are Rodurflex products Rural Utility Service (RUS) approved?
• Are Rodurflex insulators suitable for applications using high temperature conductors?
• Freight Considerations and Unloading Expectations
• Performance in Various Contaminated Applications
Are Rodurflex products Rural Utility Service (RUS) approved?
Lapp is continuously working with the RUS department of the USDA to ensure that our products are acceptable to Municipal and Co-op customers. The RUS electric department has reviewed the Rodurflex designs features and benefits and have confirmed that there is no restriction to member companies purchasing Rodurflex products. This has been verified in the form of multiple purchases from RUS member companies, Tri-State G&T and Western Farmers Electric Coop.
With regard to Rodurflex polymer insulators, RUS does not have a formal approval or approval process for high voltage polymer insulators. The largest polymer insulator class requiring formal approval with RUS is the 35 kV distribution dead-end polymer insulator.
The varying manufacturing processes and customer-specific engineered designs applied to transmission polymer insulators prevent a commoditized type of design approval typically associated with distribution type insulators. When applications exceed the 35 kV range, RUS provides their stakeholders with three items to assist in insulator selection, ensuring a certain degree of quality and consistency between manufacturers as well as installation applications. Lapp is able to help provide interface between the end user and RUS, should there be any questions regarding the ability of our insulators to comply with these requirements.
1) ANSI C29 – compliance with ANSI C29.11 (composite testing) & C29.12 (composite suspensions) are required. Lapp confirms that we meet these requirements. Internet links to both specifications are provided below should you wish to review them.
• www.nema.org/stds/c29-11.cfm
• www.nema.org/stds/c29-12.cfm
2) RUS Bulletin 1724E-220 – This comprehensive bulletin is provided as both an educational tool, as well as a recommended specification to member companies. Member companies are free to use as much or as little of this typical specification as is necessary. Experience reviewing RUS influenced specifications dictates that member companies will use anywhere from one paragraph to the entire document. Lapp confirms that Rodurflex insulators comply with 1724E-220 with very few comments. If you wish to review this bulletin it is available through the USDA website at the following link. www.usda.gov/rus/electric/pubs/1724e-220.pdf
3) RUS Bulletin 1724E-200 - This is the design manual for high voltage transmission lines providing the parameters which transmission construction must meet in order for line approval by RUS. Chapter 8 in this document discusses insulator applications, encompassing both porcelain and polymer units, and specifies application parameters rather than specific unit approval. Lapp has the capabilities to supply Rodurflex units which are in compliance to this specification. This bulletin is also available for through the USDA website at the following link. www.usda.gov/rus/electric/pubs/1724e-200.pdf
Are Rodurflex insulators suitable for applications using high temperature conductors?
When applying an insulator with high temperature conductors, it is critical that the
insulator maintain its mechanical strength under a sustained and continuous high
temperature. The mechanical strength of Rodurflex insulators is based upon the integrity of the FRP rod and the crimping of end fittings onto the FRP rod. The failure point of the insulator under high temperature is when the FRP rod reaches the Glass Transition point (Tg) where the rod loses its elastic property and mechanical strength. At this temperature, the crimping strength between the end fitting hardware and the FRP rod can be compromised. This compromise can
directly affect the mechanical strength of an insulator, and lead to a line drop.
The suitability of the insulators in this application is dependant upon the core of
the FRP rod not reaching Tg. For FRP rod the Tg is typically between 110 and 140 degree C.
CIGRE has performed thermal imaging of polymer insulators under high temperature conditions and has determined that under normal hardware configurations, that the hardware connectors serve as a heat radiator and prevent the insulators from reaching Tg. This testing has been performed up to 216 degree C without insulators experiencing a core temperature rise that will compromise the integrity of the insulator. This testing verifies suitability of Rodurflex insulators in high temperature conductor applications up to 216 degree C (~420 degree F)
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Freight Considerations and Unloading Expectations
Rodurflex insulators fall under the same freight policies as Lapp porcelain insulators, including published freight minimums as designated by region.
When considering freight minimums, it is important to note that Rodurflex orders can be combined with distribution pins, spools, dead ends, guy strains, line posts and porcelain transmission bells to achieve freight minimums.
Standard shipping is performed in closed vans for both LTL and full truckload shipments. The use of flatbed / side load trailers requires a price adder to cover additional freight costs. In the event customers require flat bed deliveries, please contact your customer service representative for price adders prior to shipment.
When Rodurflex insulators arrive at their final destination, packaging will be tailored on pallets of 4ft , 6ft and 8ft depending upon insulator length. It is important that customers have the capability to handle up to 8ft pallets, with weights up to 2000 lbs at the delivery point. Order specific packaging dimensions can be supplied upon request.
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Performance in Various Contaminated Applications
One of the inherent advantages of Rodurflex silicone composite insulators is superior contamination performance when compared to porcelain and glass insulators. This contamination performance is attributed to the Hydrophobic Transfer Mechanism(HTM) of the silicone rubber, which allows for transfer of the
water repellency of silicone to the pollution layer on the surface of the insulator.
When considering Rodurflex insulators for contaminated environments, effectiveness in the application should be considered prior to material selection.
| Contamination | HTM Effectiveness |
|---|---|
| Iron oxide (Weathering Steel) | very good |
| Sand | very good |
| Salt | very good |
| Coal | very good |
| Industrial emissions | very good |
| Bird deification | very good |
| Cement | moderate |
| Bentonite | moderate |
| Layered clay | moderate |
| Algae | poor |
| Fungus | poor |
| Mold/biological Growth | poor |
This is considered representative of Rodurflex insulators and should not be considered universal for competitor’s designs, as HTM can vary significantly based upon material selection criteria, insulator design parameters and aging
performance.