Sandy Thomas looks at the problems encountered when using to foot switches in tough marine environments.
In oil and gas terminals, foot switches are used to operate machinery such as capstans, barriers and anchors/winches. However, footswitches used in the marine environment are often unreliable, especially when used to control the capstans, which are generally situated on exposed and wash-down areas.
The existing footswitches available on the market incorporate moving parts which in use are exposed to water, weather, strong sunlight, sun and dust/grit. They are often treated roughly with poor or no maintenance, and in ore, coal and other facilities that produce abrasive materials, these footswitches can fail in a matter of days.
Strainstall has used its experience in sensor design to produce the Strainstall Rugged Footswitch, which has been manufactured with no moving parts, and so is suited for use in adverse and hazardous conditions.
Applying load to the pedal in the normal way causes stress in the element, and the resulting strain is sensed by in-built strain gauges.
The electrical signal from the strain gauges is monitored and provides switch operation. In addition to its uses to provide a simple on/off function, by utilising a suitable signal conditioner, the unit can also be used to provide a variable output. This would allow it to be used for speed control of electric motors, for example.
The footswitch has a very stable housing, manufactured entirely in stainless steel, including marine grade high tensile stainless steel for the element, is fully sealed to IP67/68 standard and includes a protected signal cable.
This enables the footswitch to be used in Hazardous Gas Atmospheres when connected in an approved manner for Zone 1 and 2 applications. It has been granted ATEX/IECEx Certification, which allows for simpler and cheaper installation as it does not require any other safety interface.
One of the major benefits of this type of footswitch is that, because it has no moving parts, it requires no maintenance, which provides significant cost savings over the life of the system.
Rugged Footswitch benefits:
* Durable and rugged construction.
* Suitable for use in hazardous areas.
* Sealed against dust and water to IP67.
* Ideal for harsh environments.
* Maintenance free.
* Manufactured from marine grade stainless steel.
* Provides cost savings.
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Sandy Thomas is Marine Director, Strainstall UK Ltd, Cowes, Isle of Wight, UK. www.strainstall.com
Fig. 1. The Strainstall Rugged Footswitch, which has been manufactured with no moving parts.