How does the mechanical strength of HDPE insulators compare to porcelain with regards to turning angles (transverse loading)?

Our HDPE insulators exceed ANSI cantilever requirements of 3,000 lbs.  Porcelain versions have not always met this criteria as confirmed by independent lab testing (NEETRAC).

What protection is recommended in both equipment and overhead distribution lines in lightning prone areas?

Do you see any increase in rates of failure as conductor size increases?

In over 50 years of experience, there is no correlation to conductor size and failure rates. Most failures occur as a result of an over-voltage event, such as lightning, or a fault-current event, such as prolonged line-to-line or line-to-ground contact.

How do you define "high" lightning areas?

We use the NASA data, which identifies areas with historic frequency of lightning strikes.

Is there a difference in performance between post insulators and pin insulators?

Inherent in the design, the resultant performance of line post insulators provide greater flashover, impulse and puncture performance.

What is your standard warranty on insulators?

Hendrix polymer pin insulators are Guaranteed for Life.

What is the maximum conductor angle that can be applied to a polymer pin insulator?

While Hendrix does not stipulate maximum allowable angles, the tested cantilever ratings of all our insulators exceed the ratings of most mounting hardware (cross arm pins, ridge pins, etc).

What is the material compound used in the polymer insulators?

95% of the material in a Hendrix insulator is 100% virgin high density polyethylene, with the balance a proprietary blend for UV resistance, track resistance, manufacturability, and color.

How do your HDPE pin-type insulators compare to Radio Freed (i.e. black top) porcelain insulators?

Radio Freed porcelain insulators have a semi-conductive coating on the top portion and pin hole threads to mitigate electrical discharge at air gaps which cause radio interference (RIV). HDPE insulators fill the thread well with non-conductive mastic to eliminate air gaps with the mounting pin thereby reducing the chance for electrical discharge and RIV noise.

For coastal environments, would you recommend a higher Class insulator than for inland applications?

With porcelain insulators it is common practice to use higher-class insulators than used inland for the same distribution system voltage levels.  The porcelain surface is hydrophilic and small amounts of contamination, coupled with fog, mist or light rain can lead to frequent tracking, discharge and flashover at relatively low voltage levels.  So application of porcelain insulators with higher leakage and flashover ratings made practical sense to reduce flashover incidence and related damage.
 
Polyethylene insulators are hydrophobic and non-polar, naturally repelling water and surface contaminants, making them less prone to flashover in coastal applications than their porcelain counterparts.  Higher class HPI insulators may be used to further increase flashover withstand capability, but may lead to a higher rate of puncture in areas with high lightning densities.

Why should porcelain insulators not be used with tree wire or covered conductor?

There is a dielectric incompatibility between the materials which creates high electrical stress at the interface.  Porcelain has a dielectric constant in the range of 6 to 8, while Polyethylene is 2.2 to 2.4.  Over time, the electrical stress at the interface can lead to destructive discharge and tracking, causing conductor covering erosion and puncture. 
Porcelain insulators with a Radio-Free semi-conducting coating create even higher electrical stress at the covered conductor interface and should be avoided.

Will cyclic changes in temperature loosen the hand tight insulators?

No. In actuality, the conductor and tie (or Vise jaw) will hold the insulator in place to prevent any rotation. Hendrix polymer pin insulators are installed in all 7 continents and all 50 states in the U.S.

Do you have statistics on the failure rate of porcelain vs. polyethylene type insulators?

The failure rate of polyethylene insulators is less than one-tenth of one percent (0.1%). We do not have data on porcelain.

Does Hendrix recycle insulators and how is this different from porcelain?

HDPE is 100% recyclable. It is the same as a #2 rated plastic (i.e. milk cartons, water bottles). Porcelain has no redeemable after life except as landfill. When broken, it is a sharp and dangerous by-product.

Do you have a comparative type test certificate of Porcelain and Polyethylene Insulators?

Reference NEETRAC Distribution Insulator Performance Evaluation, baseline project no. 07-146, dated March 2010. NEETRAC compared 8 porcelain pins with Hendrix, and the results are clear.Hendrix out-performed all the porcelain by a wide margin.

How easy are poly insulators cleaned vs. porcelain?

Polyethylene is a naturally hydrophobic, non-porous material lending to easy natural cleaning via normal rainfall. Porcelain relies on the glazing to seal and protect from the elements. Any breakdown in this protection can lead to contamination buildup and ultimate failure.The hydrophobicity of polyethylene is much greater than that of porcelain.

How do Vise Tops compare with tie tops in the event of a large limb falling on wire. i.e. breaking arms or causing wire to break?

Vise Tops will provide adequate grip the on conductor to varying degrees depending on wire size and type. Many users prefer the Vise Top for the benefit of being able to easily re-sag the line in the event of unintended loading rather than complete damage to the cross arm and pole. We can supply grip strength information on the Vise Tops.

Does the Vise-Top insulator damage the covering of covered conductor?

No.The first generation Vise Top and new Universal Vise Top insulators with plastic and composite inserts, respectively are specifically designed to maximize performance without damage to covered conductors.

Has there been independent lab testing on porcelain insulators to ANSI standards?

Yes. NEETRAC performed a comprehensive test comparing porcelain pin insulators to polymer pin insulators in 2010. The polymer pin insulators outperformed the porcelain by far.

Do you make a post insulator in this technology?

Yes, we offer line post insulators for a range of distribution systems.  You can find them in our catalog and website, www.HendrixHPI.com.

How easy is it to remove/replace eyebolts on Vise Top insulators. Why is there a shearing eyebolt on the Vise Top insulators?

After a Vise Top insulator is installed, there remains a hex bolt head that allows bolt removal/replacement with a standard socket or wrench. The shear bolts allows for the proper and consistent amount of tightening while allowing indication of completed installation.

Why are there different “Neck Sizes” and what are the differences between them?

Neck sizes on Medium Voltage Distribution Tie Top Pin Insulators were historically developed by NEMA (National Electrical Manufacturers Association) and then presented, accepted, and set as an industry standard by ANSI (American National Standards Institute). The neck sizes are classified as “C”, “F”, and “J”and the basic difference between them is the radius of the “Saddle” and the diameter of the Neck itself. 

What is the recommended installation procedure for an HPI Insulator?

HPI pin insulator installation should always be done by hand.  Proper installation is accomplished by turning the insulator on the mounting pin until it engages the internal mastic.  The lineman will feel an increase in resistance as the insulator contacts and compresses the mastic.  Align the insulator’s top saddle with some small forward or reverse rotation.  Care should be taken not to over-tighten. Tools are not recommended.

Can the HPI be “over-tightened”?

The insulator is properly seated when the mounting pin contacts and compresses the mastic within the threaded cavity.  At this point, the lineman will feel an increase in resistance due to the compressed mastic.  Excessive turning of the insulator on the mounting pin can cause damage to the insulator threads or neck area.

Can the linemen use a wrench to tighten HPI insulators?

NO – A wrench of any style should never be used on an insulator

What is the purpose of the “Mastic” in the top of the threaded area?

The purpose of the mastic in the threaded area of the insulator is simply to eliminate air space and reduce RIV (Radio Interference Voltage).

Does the top of the cross arm pin or pole top pin have to make contact and compress the Mastic?

To eliminate all the air space between the threads of the cross arm pin and the mastic – Yes – we recommend that the insulator be threaded down on the pin until positive contact is made.

Can all types of Bare Wire Conductors be used on Hendrix Polyethylene Insulators?

YES – all types of Bare Conductors (aluminum, alloys, copper, etc) and/or Covered Conductors can be used on HPI Insulators without concerns.

What types of conductor “ties” can be used with HPI Insulators?

Conductor Ties of any design and/or material can be used with HPI Insulators – preformed style, bare hand ties (copper or aluminum), covered hand ties, “jelly jar” style, or any other conductor tie style that is available.