Industrial springs are often seen as just a component or forming part of a sub-assembly. For the potential user or equipment designer, there appears to be a simple choice to start the selection process.
“There are, essentially, just two ways for customers to look for and select the appropriate spring for his or her job,” says Nick Goss of Goss Springs. “Either they look in a standard spring catalogue and select the spring that most closely meets their requirements, if possible; or they turn to a specialist manufacturer, like ourselves, for example, who will offer a complete design advisory service.”
The type of application that the spring is to be used in will determine life expectancy and performance. “Generally, the more expensive the material we use, the longer the life of the component,” explains Goss. “A typical application for a compression spring in an engine valve might involve 8,000 cycles per minute and the best material to guarantee this sort of performance is chrome silicon.”
In the extreme environment of the offshore industry, Inconel is usually the material of choice. Inconel alloys are oxidation and corrosion resistant, and well suited for service in extreme environments. When heated, Inconel forms a thick, stable, oxide layer, protecting the surface from further attack.
ALWAYS READY
A spring design may be required for an application that might not be in use constantly, but must be ready to work when called upon. There are many applications where the spring will be held and stored for long periods of time, usually in a compressed state and here a high tensile spring or stainless steel will be selected. To illustrate this case, without putting too fine a point on it, the compression spring deployed in an aircraft ejector seat mechanism has to work – just that one time.
Adds Nick Goss: “However, for many standard duties, the spring, which is storing energy, is produced from range 3 music wire or high tensile stainless steel. In operation, the material is subject to degrees of stress and therefore must be highly tensile.
“A standard stainless steel will operate in conditions of up to 300 degrees C. Some grades of stainless steel, though, have restricted environmental operating conditions. The basic ‘music wire’ used for producing springs is available in different grades; type 302 stainless should not be used in conditions where acids are present and is thus unsuitable for applications processing citrus fruits where instead type 316 should be used.”
In the medical industry, components are often made from platinum, iridium or gold. Especially in applications involving sub-cutaneous sites, the material must be resistant to the corrosive effects of blood.
A readily worked alloy, platinum–iridium is much harder, stiffer and more resistant to chemicals than pure platinum, which is relatively soft. Platinum–iridium is also very resistant to high-temperature electric sparks and is widely used for electrical contacts.
