"Here at the plant, reliability is right behind safety and environmental stewardship in terms of importance. We all take great pride in our reliability indictors, such as MTBR. We believe we are the industry leaders in reliability," he boasted. As he finished his statement, we walked up to the facility's pride and joy-a 250 hp, horizontal, between bearing pump that transferred finished gasoline to storage. It had never failed.
The first thing I noticed was the pump was so quiet it did not sound like it was even running, and there were no signs of any spills on the pump or baseplate. The suction and discharge pressure gauges showed no signs of pulsations or cavitation. As I placed my hand on one of the bearing housings, I felt virtually no vibration.
"To handle varying production rates, this pump has a variable speed drive and a spillback line to ensure it always runs at the best efficiency point," the proud operator stated as he pointed to the pump's spillback control valve.
Everything about the installation was impressive: There were more than 10 pipe diameters of straight suction piping, ample casing and piping venting valves. Even accelerometers were permanently mounted on every bearing to provide continuous vibration monitoring.
Looking across the pump-alley, I watched another operator start a pump. He carefully checked that it was adequately vented, checked the seal pot and seal flush flowmeter, and waited by the pump after it started to ensure all was well before walking away.
"This was all too good to be true. These guys are doing everything right," I thought. It was then that I heard the plant siren signaling a problem. I remembered from the safety video that I was supposed to be escorted by my host to a safe location. But my operator was nowhere in sight, and my feet felt so heavy I could barely walk. The siren kept blaring until I realized the siren was actually my alarm clock. It was all a dream; there really was no perfect pump installation. Alas, I had to go back to my real world of misapplied pumps, overworked operators and underfunded pump installations.
In Search of the Perfect Pump Installation
I recently saw a TV commercial for an air conditioning system, which stated, "The most important day of an air conditioning system's life is the day it is installed." I have thought about this often and decided it is not true for pumps. There are many important days in a pump's life. Here are the days I think are truly critical to maintain a near perfect pump installation:
- The day the process engineer specifies the pump's hydraulic requirements
- The day the pump specifications are written
- The day the pump is selected
- The day the mechanical seal is selected
- The day the piping and control system are designed
- The day the pump is installed
Additionally, to reap the benefits of a near perfect pump installation, also be aware of these important days:
- Every day it is repaired
- Every day it is started
In reality, a perfect pump installation can never exist. Process engineers never know exactly what flow range or pressure rise will be required during the pump's life. Processes tend to evolve due to market forces and technological improvements, forcing pumps to operate away from their sweet spots. Also, pump manufacturers do not always have the right pump for the application. To make things worse, tight project economics can severely limit the level of design features the installation is allowed.
Thinking about all these selection forces and considerations can give a pump user a severe case of anxiety. How can we ever hope to obtain a (near) perfect pump installation? There is no definitive answer to this impossible question. All I can provide are a few guidelines based on many years of experience in the pump trenches:
- Have the process engineer specify the possible range of flow and head requirements, not just maximums. Minimum flow rates for start-ups or other special conditions may require spillback lines or variable speed drives for pump protection.
- Have the process engineer specify the possible range of process temperatures and if the stream is expected to be dirty or corrosive. This input will allow for a suitable mechanical seal selection and flushing plan.
- Follow the PIP guidelines when designing the pump's piping system.
- Select a control system that allows the pump to operate at the lowest stress level, i.e., near the BEP most of the time. Beware of temperature and level controls that can force the pump to operate well away from the pump's BEP.
- Diligently follow PIP installation guidelines to ensure the pump is rigidly grouted in and installed with low stress.
After the pump has been purchased and installed, remember that the road to pump reliability must run through the training department. Train operators to understand what pump reliability is about and how to put the knowledge into practice. Operators need to understand that every start-up, shut-down and inspection is an opportunity to improve the process' reliability.
The same also goes for mechanics. Instill in them that they are not just part changers; they are also reliability technicians. Every pump failure and subsequent repair is an opportunity for improvement. Frequent discussions between the operators, mechanics and machinery engineers should be encouraged as a means of solving problems related to detrimental operating and repair practices.
I will leave you with this quote attributed to Admiral Hyman G. Rickoever, U.S. Navy, known as the "Father of the Nuclear Navy": "The devil is in the details, but so is salvation."
Details matter, especially during the most crucial days of a pump's life. Remember that pump reliability is everyone's job, not just the machinery engineer's.
If you have a pump installation you think is near perfect or perfect, let me know. Tell me what its MTBF is and why you think the installation is noteworthy. I will share your story in my column.
