Creep


When metals get hot, over a certain threshold temperatures depending on metal type, they literally begin to move. Very, very, slowly in many cases, hence the name ‘creep.’

 

Lead for example will creep at room temperature and there are examples on historic buildings where old lead plumbing has slowly bowed over several centuries of use!

 

Away from lead piping however, other metals are also at risk. Carbon steel has a threshold temperature just over 400°C.

More exotic materials can cope with higher temperatures but are often more expensive, so designers select material depending on the severity of temperature service.

 

Items designed to code, think steam HP pipework for example, often enter service with the caveat that they have limited service life – typically 100,000 hrs (approximately 11.5 years of continuous service).

 

The reason being is that as creep damage accumulates, tiny cracks begin to form and propagate within the material. This weakens and finally fails the component under load.

Axiom mechanical has a wide range of experience in helping Clients manage the creep life of components, from:

 

  • Examining operating temperature data to assess how much creep life is left.
  • Identifying and Specifying key areas for replication assessment – a method for looking to see if creep cracks are forming.
  • Organising and specifying criteria for the post exposure testing of materials.

 

We have saved Clients hundreds of thousands of pounds of new capital expense by redefining rates of creep life usage and extending out service life.