Modern Mining April 2018

MODULAR PLANTS

application and house whatever equipment is required. E-Houses come in various shapes and sizes and can vary depending on the application. Some look like normal prefab- ricated buildings while others form part of a mobile machine, for example on a stacker or a reclaimer. E-Houses are fully customised and particu- larly expensive due to labour-intensive steel fabrication. They can also be costly to transport and often need to be moved via abnormal load trucks and placed on special vessels for sea freighting, which takes time and costs money. When it comes to E-Houses, the end-user would be advised to consider whether this is the correct solution, given the costs of logistics and erection. The modular substation is a much larger substation that may consist of two or more containerised substation sections or

the container as a standard are removed and replaced with metal clad flooring. Wooden floors are a severe fire risk, as even a small electrical fault can generate massive amounts of heat which could potentially set the entire container alight, compromising the entire oper- ation and capital investment. As a minimum, a simple fire detection system should be installed that can detect smoke within the substation. It is extremely important to shut down any air conditioning or HVAC systems in the event of a fire, as these will fuel the fire to the extent that the entire substation could burn down in a matter of minutes. The risk posed by arc flash and high fault currents should also be considered. Arc flash is one of the hot topics in industry and has recently been added as a consideration to the Mine Health and Safety Act in South Africa. The Act now calls for the employer to consider the risk and potential incident energy that could be emitted by a potential arc flash and the potential danger therefrom. With that being said, the most important question to ask is, “what happens if things go bang”? It is critical that the electrical engineer- ing team and mobile substation manufacturer have the answers to this very important ques- tion. My advice is to only make use of fully type-tested equipment which has been tested in accordance with the latest SANS/IEC stan- dards. In addition, the installation must be carried out within the guidelines provided in the OEM manuals. The installation of fully type-tested equip- ment ensures that – in the event of an arc flash incident – the potentially fatal hot metallic gases and excess pressure are diverted away from personnel and equipment and out of the mobile substation in a controlled manner,

An example of arc ventila- tion ducting. This ensures that arc flash is directed out of the container safely.

E-House sections which have been joined together to create a much larger substation. These are ultimately used where time constraints are a major factor or where the conditions on site are too extreme for civil works. These units are typically constructed in a convenient location, tested and cold commis- sioned, broken up into multiple sections and then

Safety should always be the most important consideration when it comes to the design and selection

re-assembled on site. A typical example of a modular substation could be a 12 m and a 6 m container that are placed in line with each other having inter- leading doors or, alternatively, are joined completely on site, with a bus-trunking join- ing the busbars of two sections of an MV or LV board – this is a relatively cost effective way of getting a board that is too big for a 12 m container into one complete substation. There are many different modular substations and versions but, since they are all transported in modules or sections, we would consider them to be ‘modular substations’. There are several factors to consider when choosing a mobile substation for an application. Safety should always be the most important consideration when it comes to the design and selection of a mobile substation, as it is an area of fatal risk if the engineering and design does not address safety considerations adequately. To reduce the risk of fire, one needs to ensure that the standard wooden floors that come with

of a mobile substation.

feature

April 2018  MODERN MINING  43