In general, mining companies have a poor track record of delivering projects on time or on budget. Today, for the first time, I heard about the McNulty Curve; a graph which predicts the level of pain that companies will endure when ramping up a project.
Some previous studies on project cost overruns highlighted a few key reasons for process plant failure (defined as major cost over-run or inability to achieve design capacity):
- insufficient effort was devoted to understanding process chemistry
- insufficient continuous pilot-scale testing was conducted
- the plant lacked parallel process streams and/or in-line spare equipment units
- the design incorporated sequential unit operations that either
werefirst-of-a-kind or the largest ever built or both
Terry McNulty advanced this concept and derived ramp up curves for various types of processes. He defined the types as follows:
- Series 1
- The owners relied on mature technology.
- Standard types of equipment were selected.
- Thorough pilot-scale testing was done on potentially risky unit operations.
- Series 2
- If the technology was licensed, the project was one of the first licensees.
- Some equipment was a prototype in size or application.
- Pilot-scale testing was incomplete or was conducted on non-representative samples.
- Process conditions were unusually severe or corrosive.
- Non-innovative parts of the flowsheet received inadequate attention
- Series 3
- There was very limited pilot-scale testing and important steps were ignored.
- Feed characteristics such as mineralogy were poorly understood.
- During process development, product quality received little attention.
- There were serious design flaws.
- Engineering, design, and construction were on a “fast track” with inadequate planning to offset added risk.
- Series 4
- If continuous tests were run, they were only to make the product.
- Equipment was downsized or design criteria were compromised to reduce cost overruns.
- The flowsheet was unusually complex with prototype equipment in two or more unit operations.
- Process chemistry was poorly understood.
McNulty highlights a few other factors that were correlated with project over runs, some of which are particularly relevant for the mining industry.
- Corporate management had a promotional or overly aggressive attitude.
- The owners had very little day-to-day engineering input.
- Driving forces underlying the project were ill-conceived.
- The ore receiving and preparation areas received little attention.
- Translation of the
testworkto design criteria was flawed.
Sources: Most of this information was from a paper called Minimization of Delays in Plant Startups. It can be found here: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.126.1359&rep=rep1&type=pdf#page=119