Bolt Type Tension Clamp

Description

Tension Clamp

The Bolted Type Dead End Tension Clamp is one type of single tension hardware fitting, it is mainly used on the overhead transmission lines or distribution lines. The tension clamp is also called dead end strain clamp or quadrant strain clamp, it is one kind of transmission line clamp.

Because the shape of the tension clamp is like a guy, some customers call it guy type or bolt type. According to the conductor diameter, there are different series of bolted type tension clamp such as NLL-1, NLL-2, NLL-3, NLL-4.

The NLL series of bolt type dead end clamp the main body is made from material high strength aluminum alloy which meets the requirements of standard specification in the latest issue of BS.

The bolt type of tension clamp is suitable for aerial lines up to 35kv. Quan Pham Industry bolt type tension clamp is intended for use with ACSR or all-aluminum conductors.

Some clients ask NLL series of bolt type together with the armor tape or special liners to protect the conductor from damage. According to the material, there is another series of NLD-1, NLD-2, NLD-3, NLD-4. NLD series is produced from high strength malleable iron.

NLD series tension clamp is used with aluminum-clad steel conductor. When it is used on the aluminum conductor, it usually assembled with liners.

The above is only introduced the main body of the tension clamp. There are U bolt, nut, and washers required for fasten the conductors into the gun bodies.

NLL Series of Bolt Type Tension Clamp

NLD Series of Bolt Type Tension Clamp

Design of Clamp

• bolted, quadrant type, with a clevis end fitting, used for termination aluminum or aluminum alloy conductors. Appearance is similar to Figure 1 below.
• Nominal groove angle of 60 as detailed in Figure 1.
• High strength aluminum alloy clamp body.
• Steel U-bolts, each fitted with two hex nuts, two flat round washers, and two lock washers.
• All steel components, except those made of stainless steel, to be hot-dip galvanized in accordance with BS EN ISO 1461:2009 or ASTM A153/153M.

Figure 1: Typical Bolted Dead and Clamp

• To accommodate and secure a range of bare overhead line conductors with diameters detailed in Columns 2 and typical wire size in Columns 3 and 4 of Table 1.
• Number of U-bolts provided to secure the conductor in the groove the clamp as stated in Table 1, Columns 5.
• Dimensions of clevis and coupling pin in accordance with Table 1.
• Ultimate tensile strength of clamp assembly in accordance with Column 6 of Table 1.

Table 1: Parameters of the Overhead Line Dead-end Clamp

• Ultimate tensile strength of pulling the eye to be greater than or equal to 60﹪ of the ultimate tensile strength of the whole clamp assembly.
• A split pin made of cold drawn bronze, brass or stainless steel is to be provided to secure the coupling pin in place.
• The minimum failing load of the coupling pin corresponds to the ultimate tensile strength of the whole clamp assembly.
• Clamp assembly to be free from cracks and other visible defects, with no sharp edges and burrs. Leading edge of the contact surface near the pulling eye to be flared to minimize damage to the conductor.

Customized Markings

The dead end clamp can be legibly and durably marked, in any words with the following:

• Customs’ identification mark or symbol;
• Tensile strength of the clamp;
• The conductor diameter range.

This specification references the following standards:

BS EN ISO 1461:2009- Hot dip galvanized coatings on fabricated iron and steel articles. Specifications and test methods

ASTM A153/153M- Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware

IEC 60471：1977- Dimensions of clevis and tongue couplings of string insulator units

This specification was informed by the following standard:

BS 3288-2:2009-Insulator and conductor fittings for overhead power lines.