WHAT IS LRE?: A LOW RESIDUAL ELEMENTS DEFINITION & OVERVIEW

September 11, 2019

LRE is an acronym that stands for “low residual elements,” which are any elements that have not been added to any material on purpose. Often, these undesirable elements are difficult to remove by standard metallurgical processes, making them even more troublesome.

When undesirable residual elements occur in steel (or any other materials, for that matter), they can have potentially negative effects on the material’s mechanical properties.

Unfortunately, there’s no way to completely prevent the presence of these lingering, unwanted elements, as any steel-making process will inevitably result in some amount of LRE.

So, these remaining elements are clearly unavoidable and undesirable. But, exactly why are these residual elements so undesirable?

HYDROGEN STRESS CRACKING, BRITTLE FRACTURING & MORE: THE COMPLICATIONS OF UNCHECKED LRE

The simple answer to this question is that many residual elements have the potential to negatively influence processing conditions and outputs on various mechanical properties.

As a result, there’s a continuous need for fabricators to identify and quantify the extent of the effects of low residual elements in order to keep them under control and within acceptable limits.

Otherwise, any number of issues can be incurred, including:

Hydrogen Stress Cracking

Residual elements in the presence of caustic fluids plus moisture can cause hydrogen stress corrosion cracking, which can occur quickly, depending on the temperature and pressure of line application.

Hydrogen stress cracking is a form of hydrogen embrittlement (i.e., a decrease in a material’s ductility or durability) that occurs when corrosion occurs.

These sources of this corrosion might include everything from acid-induced damage to the accidental ingress of hydrogen – and much more.

Left unchecked, hydrogen stress corrosion cracking can also lead to even more complex issues, including brittle fracturing.

Brittle Fracturing

When enough corrosion impacts the materials, even the hardest steels or other materials can be penetrated. This penetration, in turn, causes brittle fracturing, which is the rapid cracking of any type of material or equipment under stress.

These cracks typically occur so abruptly and often without any warning signs, preliminary deformations, or subsequent time for prevention before it actually occurs.

Brittle fracturing can be quite a nuisance for manufacturers and fabricators across industries.

It’s important to go back to the root of the problem – low residual elements – and attempt to control them as much as possible before they lead to more serious and difficult to remedy material failures.

PROACTIVE STEPS FOR MONITORING & REDUCING LRE

As world-leading leading fabricators of custom piping materials, pressure vessels, and modular skids, our team at Globe LLC goes above and beyond to ensure proper stress corrosion cracking, brittle fracturing, and hydrogen embrittlement prevention practices are in place.

Some of the hydrogen stress cracking, brittle fracturing, and hydrogen embrittlement prevention practices that our project managers enforce on a day-to-day basis include:

• Specialized LRE-watch jobs designed to eliminate error pulling material.
• Separating material ordering and processing from regular CS to improve quality control.
• Adding identification information of LRE materials at the time of cutting. Cut sheets are printed on orange paper, and the shop foreman is then responsible for communicating the need for LRE material control to others in the facility. In addition, the cutters will be able to confirm LRE through the orange identification papers.
• All warehouse materials that come into contact with any fluid service are required to meet LRE requirements for valve body and bonnet, pipe, flanges, fittings, and so on.
  
  

The above is just a small sample of the many ways Globe LLC minimizes the presence of low residual elements, which leads to smoother operations and more reliable products for our customers and clients.

WANT TO LEARN MORE ABOUT HYDROGEN STRESS CORROSION CRACKING & PREVENTION?

If you’d like to speak directly with a Globe representative about any of the above matters or to speak about a project or product you’d like to engage in or have fabricated, we’d love to hear from you.



Feel free to contact us today!