Piggy in the Middle

Thursday 17th April 2014
Piggy in the Middle

The Spring Challenge.

This application was for a constant force compression spring to connect two pipeline "PIGS" together. (A pipeline pig is a machine that enters into the actual pipeline from an offshore oil rig supplying oil or gas to the mainland.) As the pig moves along with the flow of oil or gas, the pig records data, such as the condition and reliability of the pipe wall. Originally, a traditional wire wound spring was used for this connection, but the long term compression forces caused performance deterioration. The readings from the PIGS were becoming more and more unreliable as pulsing shock-waves in the pipeline hit the PIGS along their journey. The spring also needed guaranteed flat end surfaces and the piano wire material was corroding in the hostile atmosphere. Reliability of the wound spring was also poor.

The Machined Spring Solution.

The customer gave ABSSAC the overall dimensions, as these parameters were finite. Next the desired axial spring rate was supplied.  Using Finite element analysis, Abssac could tune the geometry of the machined spring to guarantee the desired spring rate, but also look at the resonant frequency of the spring system to try and counteract the pulsing shock-waves.

Abssac supplied a machined spring with guaranteed flat end surfaces as well as precision tolerances on the overall length, outside and inside diameter. An exact compression spring was supplied in a material that gave much better resistance to the corrosive atmosphere. Our customer reported "PIG" reading accuracy had increased by 50% using the machined spring product.

For further details on the machined spring product, please call us on 01386 421005 or look at the machined spring web page

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