Expulsion Drop-Out Fuse Barrel Inspection and Fuse Rating Requirements
Purpose
The purpose of this instruction is to provide all Horizon Power Workers the minimum inspection
and fuse rating requirements for Drop-Out Expulsion Fuses (DOF).
Safety
Before commencement of work, a risk assessment must be carried out using the Risk Analysis
Procedure (OSH-3.6-1-02), to identify and document the hazards and risks associated with the
task and ensure appropriate control measures are implemented.
It is important that, appropriate control measures must be identified, documented and implemented
in order to control hazards to As Low as Reasonable Practicable (ALARP).
Instruction
DOF’s have a limited life span and must be checked for serviceability prior to their installation by
using a Wear Rod. (See Fig. 1)
The Wear Rod measures the diameter and length of the DOF barrel insert and the inside diameter
of the DOF barrel.
Wear Rod
The wear rod is used to find out whether the barrel has any abnormalities, for example, the fuse
element may not clear and the barrel may not drop away, causing extensive damage to the fuse
barrel.
A flash over may result, shorting out the adjacent phases and tripping the feeder.
When using the wear rod, the operator should check the following:
• Its 500 mm length must pass down the barrel
• Its 13.5 mm diameter section is used to check the diameter of the inner tube at the
expulsion end. The rod should not penetrate the inner tube
• The 5 mm notch from one end is used to check the shrinkage of the inner tube. The
shrinkage should not exceed this distance
• The fuse barrel must be replaced if any of these tests cannot be correctly performed