Erosion Corrosion of CS Pipe in Limestone Slurry 1

[749KDV]

Does anyone know, or have reference to, the erosion corrosion rate of a straight section of CS A106 GrB pipe under a limestone slurry service? The velocity of the slurry is 8 fps with a 44 micron limestone particle size. I am trying to justify, or prohibit, the use of straight sections of CS pipe for this application. The driving force for using the unprotected steel pipe is cost savings. Of course for bends and certain straight sections (15D-20D) after bends, a basalt lined pipe will be used.

Test data would be most helpful.

Thank you.

 

[corrosionman]

749kdv Your own experiences are probably the best judge of how abrasive is the slurry, but there is lots of evidence that polythene pipe can greatly out perform cs with slurries. You might even find it is very ok even for the bends.
Call me if you want convincing DW

 

[749KDV]

Corrosionman, Thanks for your response. I agree with your assesment regarding the use of PP for this type application, and I have specified it in the past for underground routing. Unfortunately, not all engineers agree with us. This system will be run above ground and it has been determined that a basalt lined pipe would be better suited due to various construction and pipe support issues. In order to save money, our partners are trying to skimp by stating that straight sections of the piping run need not be basalt lined. I am tasked to provide a technical basis (by calculation) to show that although an economic analysis may prove that using unprotected steel pipe for straight sections will reduce upfront capital cost, periodic replacement of these sections due to erosion in this type of abrasive service will, in the course of a 20 year design life of the system, prove that it is NOT the best decision. What it comes down to is the all too familar argument with the "bean counters" that spending more money initially, will save money through the years. It is tough to collect erosion data on unprotected steel pipe ~other than bends~ and that's where my efforts have proved futile. My gut feel is that it is the wrong decision, however, without a sound technical basis to disprove their decision, I will be forced to accept it.

 

[corrosionman]

If the straight lenghts are not lined but the bends are, do you have a step in diameter at the junctions ? This would be disasterous. If not, can you get a steel pipe whose inner dia will exactly match the inner dia of Basalt pipe ? This will lead to non standard flanges . Do you have any branches or small dia instrument tapping points to cause problems, and is your system at ambient temp. Basalt has a high expansion thermal factor which will "move" the liners every temp change. Have you considered cast iron as a possible material. Is your slurry corrosive in any way. many people confuse corrosion with erosion. The steel gets a veneer of rust, which is soft and easily polished off by slurry so exposing new clean steel which easily rusts so gets polished off and so on. this is why very often plastics can massively outlast steel - - not stronger or tougher just that it does not form rust. You would find rubber lining costs half what you will pay for basalt. Cheers DW

 

[stanier]

Slurry Systems Handbook by Abulnaga reports Phil Venton's work on the Gladstone pipeline. Expected rates of corrosion erosion were 0.076 mm/year whereas field results were 0.25mm per year. Phil's work is reported in the BHRA proceedings.

Venton, P. B. 1982. The Gladstone Pipeline. Working paper A-4, BHRA Group, Hydrotransport 8.