INTRODUCTION | DESIGN FEATURES | WHY US?

DESIGN FEATURES

The shed profile with its spacing and shed overhang ensure effective performance under all weather conditions for the end user.

Portland Cement Assembly: The end caps of the Station Post Insulators are made of Malleable Cast Iron. Which have an excellent track record of performance in the field. Metal parts (end caps) are hot dip galvanized to exceed the relevant ANSI standards. The Top and Bottom metal parts (end caps) are treated internally with bituminous coatings. The coatings help distribute mechanical stresses and alleviate stresses induced by expansion and contraction. They also help balance the coefficient of expansion of Porcelain, Cement and the Ferrous Casting. Further these coatings act as a barrier to prevent Chemical reactions between the Zinc in the galvanized metal parts and the Cement in the joint. The sanded potion at both ends of the Porcelain Body strengthens the interface between the Porcelain and the Cement. Assembly is performed on jigs to ensure concentricity and parallelism. Special Portland Cement duly tested and properly stored is used for cementing by the injection method.

Bolt holes of the Top cap are aligned with the bolt holes of the bottom cap. All bolt holes conform to ANSI / IEC / BS specifications.

Proper sizes and quantities of galvanized bolts, lock washers and hex nuts necessary for assembly are supplied with each unit for intermediate connection. The metal parts are properly designed and the contoured end caps and cement are cleaned and trimmed off so as to ensure trouble free performance.

The porcelain surfaces are covered with a smooth glaze, which increases the strength of the porcelain, provides a pleasing appearance with profiles facilitating very good self cleaning and washing by rain and wind.

The standard color is gray glaze- ANSI 70, and RAL 8016 chocolate brown or sky tone gray can also be supplied on specific request.

Every post insulator has a logo, year of manufacture and Serial. Number on the top shed. The serial number marked with the actual date of manufacture provide complete traceability to our customers.

Routine Testing per standards:

The quality control measures adopted in the entire manufacturing process beginning with mixing of the porcelain ingredients and up to the end with proof test of the finished insulators ensure performance reliability in service.

There are series of tests before assembly such as dimensional check on porcelain, straightness, uniformity of sanding, smoothness of glaze, cracks and other external surface imperfections.

The Porcelain shells, are 100% ultrasonically tested for physical homogeneity before assembly.

After assembly and proper curing the post insulators are subjected to Mechanical proof tests as per relevant standards.

The complete Quality Assurance Manual is available for inspection by the customer for review.

Normally the maximum working load of the insulator is 40% of the cantilever failing load for the station post insulators. The maximum working load in tension, compression and torsion is 50% of the rated value. These are as per national safety code of ANSI C2-1990, Rule 277.

While designing, the resultant load from combined load should be considered for evaluating loading conditions.

When the formula given in ANSI standard C37.32.1972 is used to determine the short circuit forces on post insulators, the maximum recommended working load can be extended to 100% of their rated values. However, it is acknowledged that this extension is allowed only because the forces calculated are generally accepted to be at least 2.5 times greater than the actual developed system forces.

When using newer and more realistic techniques for calculating the short duration forces, such as those created by system faults or earthquakes, it is recommended that 40% of the rated cantilever or 50% of the rated tension, compression or torsion values should not be exceeded.

We provide different sizes for mechanical strength and creepage distances. Station post insulators for almost all the applications are available for voltage range from 33 KV to 550 KV and maximum mechanical properties. For most Voltage classes, we supply standard, high strength and extra high strength designs.