I even have a thermal mug and a sweatshirt with it printed on them.
So why did title this blog backwards? Well to understand that let me start with some background.
For those not familiar with the concept, it’s meant to be a clever way to say that motivation will only get you so far. Every year millions of people create their new year resolutions to lose weight or make some other kind of change to their lives. And here we are 3 months into the new year and the motivation to do those things is not as strong as the desire to eat that cake or skip the gym and sleep in.
This is when the discipline to follow a plan comes in. Motivation can often wain, being strong some days and feeling paper thin others, so you must rely on the disciple to follow the plan to get you thru to your goal.
This concept is perfect for many of us to set and achieve goals……….
………. but it’s not the best plan for everything.
A recent project that I worked on is a perfect illustration of when motivation can be more helpful then pure discipline.
The project was an acoustic analysis of a fluid pumping system. Specifically, the study was to be performed per API 674 Annex C Approach 2. More commonly called a DA2 study.
So, what was the problem you ask?
As with many projects, the piping layout had already been designed before the request was made to perform the DA2. This meant there were many things that they would not, or could not, modify to address the results of the study.
The initial study, which met the API pulsation limits, required a very large pulsation control device along with multiple high-pressure drop office plates in the system.
After numerous iterations back and forth with the customer I eventually came up with a solution that could fit within their design. However, it still showed high pulsation levels above the API defined limits for the given pipe size. This is when motivation becomes more important than discipline.
Looking only at the pulsations in the system is a valid way to evaluate a design and experience has shown that if the pulsations are below the API limits the system has a high probability of running without issue. But it is only part of the picture needed to evaluate how the overall system will perform.
In this situation I often look for guidance from Dr. Walter W. von Nimitz, PhD of South West Research from his paper “Pulsation and Vibration Control Requirements in the Design of Reciprocating Compressor and Pump Installations”.
“Pulsations as such do not cause piping failures; however, they can couple to the piping at closed ends of a line, bends, restrictions, etc., to produce acoustical shaking forces.”
In other words, the pulsations themselves do not directly affect the piping but they can interact with the piping to induce shaking forces. I touched on this in “The Layman’s Guide To Acoustical Analysis – Pt2 Noise”.
Now I do need to add a caveat here to make sure there is no misunderstanding. The pulsation levels in the system can’t just be ignored by focusing on shaking forces. The pulsations in the system ARE directly responsible for cavitation in a suction system (assuming there is sufficient NPSHa at the pump inlet) and premature activation of relief valves. There could also be other process items that are adversely affected by the pressure variations such as some types of flow meter.
If the pulsations are causing issues such as cavitation or tripping relief valves, then I go back to the drawing board. Do not pass go and do not collect your $200 because in these cases the pulsations must be addressed even if the shaking forces are very low.
Now for the system in question the pulsations were over the API defined limits however I had plenty of margin against cavitation and any other unwanted effects, so I switched my focus to the induced shaking forces. As Dr. von Nimitz had stated the damage to the piping is a result of the shaking forces that strain the metal causing fatigue or wear damage leading to catastrophic failure. And the ultimate goal of this particular study was to protect the piping from damage while ensuring everything ran without issue.
By following API (discipline) but layering that with engineering experience and judgement (motivation) I created a solution that met the customer requirements. Looking at the motivation for what was needed, and not just working to meet a defined limit, the customer now has a system that will run effectively and efficiently for a very long time without an unneeded outlay of money and time.