Projects

Client:

Hillside Aluminum Smelter

Project Destination:

Plant A 801
Main Warehouse
9 West Central Arterial
Richards Bay

Specifications:

A 150 kA electrical switch (Isolator) (according to the supplier, MERSEN, the biggest switch in the world). The weight of the switch, frame included is estimated 3.3 – 3.5 tons.
Physical material of the switch and its contacts are aluminum.

Project incentive:

The switch was opened while power was still flowing through it, a safety mechanism accordingly activated resulting in burned contact points.

Project description:

1.    The design and manufacturing of a contact mounting system to hold the contacts in place while welding them to the switch.


2.    The design, manufacture and fitting of a custom frame to the switch to keep the parts together (until plant installation is complete) and

for transformational purposes (to the plant itself).

3.    We also received specifications from the manufacturer (Mersen) to work towards in re-furbishing the switch.

 

Calibration of the welder.

 

Procedures and stages:

Phase 1:
First the burnt contacts had to be removed and the surface where the contacts were to be mounted had to be cleaned thoroughly.
The Aluminum robotic welder (which we already have in house) had to be set up according to the welding specifications for the contact positions (which first had to be spot welded at intervals to prevent warping). Special training had to be done to be able to control the aluminum welder properly.

The welding process uses Tungsten Inert Gas, so a lot of safety precautions had to be taken during the setup and welding itself.
The process entailed that to secure it properly several runs of welding had to be made, on each of the contacts on both sides of the switch.
During the welding and handling process a lot of care had to be taken about the actual contact point of the aluminum contact, because it is made of silver and is a very small contact area, any scratches would have compromised the conductivity.

Purpose of frame:
The switch did not have a mounting structure, and because it works in very close tolerances Powerbars and Control cc had to reassemble the switch and all its mechanisms, thus designing a frame to keep all the parts in place. By designing this frame an improvement on the system as a whole was also accomplished, and accordingly its final installation could be done accurately.

Phase 2:
The switch was prepared for transport by making the movable parts secure and installing locking mechanisms to prevent the contacts from touching each other. 
Thick masking tape was stuck onto the contact parts to prevent contamination by for example dust, air, oil and water (during the journey) and also corrosion, because for the time being the switch is going into storage as a spare.

Secured moveable switch parts with wooden blocks (left), taped contacts (middle), locked activation mechanism (right).


The final phase of the project:
The last phase of this project was the preparation for transportation:
The goal was to get switch to Richards Bay in the same condition we had it set up in die workshop.
We foresaw some possible installation problems and thus included in the design hoisting parts, so that the whole assembled switch can be installed without dismantling again.

The installation would thus be a type of ‘plug and play’ scenario.
The frame’s design is so versatile that once the switch has been installed and the bus bars have been welded  to it, the option to remove the frame again presents itself.

 

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