Product category:
Industrial Drives/Controls
News Release from: Siemens Large Drives | Subject: Containerisation
Edited by the Engineeringtalk Editorial
Team on 16 July 2002
Hostile environment no bar to drives
Copntainerisation is a novel solution to the problem of operating variable speed drives in extreme conditions.
Variable speed drives (VSDs) are widely recognised as being an efficient way of reducing the energy consumption of electric motors and, as such, are an extremely cost-effective investment Indeed, the value of the energy savings will often far-outweigh the initial purchase price of the drive system
This article was originally published on Engineeringtalk on 15 Jul 2002 at 8.00am (UK)
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VSDs are therefore increasingly being specified both for new projects and for retrofitting to existing plant.
For most applications it is a relatively straightforward task to install a drive, but it has to be remembered that these are highly sophisticated and relatively delicate electronic devices.
For this reason, installing a drive in hostile environments - perhaps where the atmosphere is aggressive or where temperature extremes are encountered - is anything but straightforward.
This is especially true for large drives in excess of, say, 250kW where the physical size of the convertor and transformer add to the difficulties.
A typical drive may have a quoted operating temperature range of +5 to +40C, whereas the ambient temperature in a Siberian oil field may be as low as -55C and the desert could easily reach +50C.
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Even in temperate regions, it may be necessary to install a drive in a chemical plant where no 'clean' switchroom is available, meaning that the sensitive electronics of the convertor must be protected from the aggressive atmosphere by some other means.
Large drives are often installed in isolated locations, in which case an additional requirement might be for protection against tampering and vandalism, as well as protecting authorised personnel from the potential electrical hazards presented by the drive.
When drives are retrofitted to existing plant there is often only a limited window of opportunity - perhaps to coincide with a planned shutdown - during which the drive has to be installed and commissioned.
It is therefore desirable to minimise the amount of site work required and to have as much of the equipment pretested as possible.
The issues outlined above are relevant to a great many industries worldwide, including oil and gas production, petrochemicals, chemicals, water, and sewerage treatment.
And with an accelerating interest in the use of VSDs to reduce energy consumption, many organisations are seeking ways to overcome the operational challenges presented by harsh environments.
A solution that has been successfully implemented on numerous occasions by Siemens Large Drives Division is known as containerisation.
The basis of this approach is to take an ISO standard freight container and install the convertor, transformer and other associated equipment inside, together with any heating and/or cooling and atmospheric control system necessary to provide the drive with an appropriate operating environment, protected from the hostile conditions outside.
The containers - similar to those seen on lorries throughout the country - are robust structures fabricated from corrugated steel, measuring 6.1m (or 12.2m) long by 2.4m wide and 2.6m high (or 2.9m high for the 12.2m version).
Standardised fittings on the exterior mean that the containers can easily be carried by road, rail or sea, which has proved to be an added benefit for Siemens customers in terms of ease and cost of transportation.
Depending on the project specification, the container is usually segregated so that, for example, there are separate compartments for the transformer, convertor, auxiliary equipment and a control room for use by the operator.
Not only does this keep the low voltage and high voltage safely separated, but it also assists with maintaining the required temperatures for the various compartments.
VSDs always generate heat, so an important part of each project is the cooling.
In some applications, such as in the desert, there will be no external water supply, so it is necessary to use a proprietary closed-loop air conditioning system.
Elsewhere, it may be better to use closed-loop cooling with de-ionised water, and a water-water heat exchanger that utilises an external 'raw' water supply.
Furthermore, some applications will only require cooling, but others may need a combination of cooling and heating in order to provide satisfactory conditions all year round.
Whatever the solution employed, the result is that the drive components can operate in what, for them, are ideal conditions, regardless of the environment outside the container.
But the advantages of containerisation do not end there.
Because all of the components are precabled, they can also be tested together prior to the drive leaving the factory.
This saves time on-site and helps to ensure that the drive will work 'right first time'.
Furthermore, the fact that much of the cabling is already completed means that there is less to do on-site, so saving valuable time.
All of this is particularly relevant to retrofit applications where there may be only a limited time for installation and commissioning - and huge cost penalties can arise if the planned shutdown has to be extended.
Provided that suitable access controls are fitted, the complete container can be extremely well protected from intruders, and access to high voltage areas can be restricted to protect personnel who may have legitimate reasons for working on the container.
As has already been mentioned, utilising standard ISO dimensions means that transportation is simple and less costly than it might be for nonstandard shaped or sized equipment.
On the other hand, if the standard dimensions need to be modified - as happened when drives needed to be transported through tunnels on the trans-Siberian railway - Siemens can simply take account of this at the design stage and produce a suitably adapted container.
Often with retrofit applications there is no existing switchroom in which to install the drive.
Siemens has found that to supply a container is far cheaper than to construct a brick/concrete structure of a similar size, which leads to a further cost saving for the customer.
This was particularly beneficial for a 690V; 500kW convertor and motor supplied for a multiphase pump being installed at the desert.
Since this was a remote pilot site there was no existing infrastructure and constructing a new switchroom was out of the question.
Containerisation was therefore an elegant solution to what could have been a difficult installation.
Because of the way the containerisation concept incorporates climate control for the drives, there is now virtually nowhere on the planet that a drive could not be installed.
The only proviso is that there must be access so that the container can be delivered, which implies that suitable roads and cranage access must be available.
But then again, if 'the sky's the limit' for the transportation budget, there is always the helicopter option.
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