OK, I confess to being an engineer in my core when I was explaining to my son the other day how the heart is a reciprocating pump. The systolic and diastolic pressures are the high and low-pressure peaks based on the heart’s expansion/contraction cycle. Blood pressure is one diagnostic indicator on the health of the heart and circulatory system.
What prompted me to remember all this was a presentation I’m looking at by Emerson’s Tim Olsen. You may recall Tim from his successful election to the position of 2nd Vice Chair for the AIChE Fuels & Petrochemicals Division (FPD). The subject of the presentation is pump health monitoring.
Thankfully, Tim did not take this heart analogy path we find ourselves on in this post. Typically, a process pump failure will cause a process upset and loss of production. If the pump is pumping flammable or hazardous substances and has a seal failure, safety, health, and environmental issues may occur. Having a spare in-line pump does not prevent unexpected failures that may result in conditions requiring prompt operator attention.
Without monitoring, pump seal failures often appear to be sudden and indicated by spills, vapor clouds, or fires. Today, for most process pumps, warnings come from periodic manual vibration measurement. Tim shares that most refiners monitor their critical pumps, perhaps 5% of all the pumps. The definition of what is critical is likely similar across refiners, but there will be differences.
Both safety and economic reasons are considered when identifying critical pumps. Every pump, critical or not, can cause pains such as process upsets and increased maintenance costs. For this reason, pump health monitoring may be warranted on many “non-critical” pumps. In the case of refiners, Tim cites a pump failure example, which can lead to insufficient fractionator reflux causing column overhead system over-pressuring. This in turn leads to the lifting of a relief valve to flare.
Tim recommends adding wireless measurements in places where existing diagnostic instrumentation is not present. He has observed three key areas that refiners are looking at pump monitoring capabilities: alkylation units, critical workhorse units like the crude unit, fluid catalytic cracking (FCC), and hydrocracker, as well as those applications with a history of unexpected pump failures.
Continuous vibration monitoring is important to identify and prevent root causes of seal failure from occurring. Some causes of this vibration include poor shaft alignment, worn bearings, loose pump mounts, broken foundation mounting bolts, cracked foundation, cracked or damaged impeller, and cavitation. This excessive vibration increases the wear on the pump’s mechanical seal leading to failure.
Replacing the field operator or maintenance technician’s manual spot measurements with continuous measurements provides the information to predict when failures will likely occur to allow maintenance to be performed before a failure occurs. This information can be historized and trended and made available in real-time to both console operators and maintenance departments. Wireless vibration transmitters form the heart of a health monitoring solution that is secure and easy to implement.
Tim makes the point that that having pump health monitoring is like adding sets of eyes continuously focused on these pumps, providing operators the opportunity to take corrective action before the pump failure. This early warning can help avoid the associated health, safety, and environmental impacts.
Pump health monitoring as part of an overall predictive maintenance program can deliver financial returns. In a Chemical Processing article, More-intelligent devices help plants get smarter, Emerson’s Doug White noted:
Actual implementations of predictive maintenance have led to significant gains… Potential production from existing equipment typically increases 1-3% because of fewer unscheduled shutdowns, while unplanned maintenance costs decrease 10-30%. The return on investment can be among the highest of any possible plant expenditure…
Although this may admittedly be a stretch, the cost of pump health monitoring is perhaps like the cost of good nutrition and exercise for maintaining a healthy heart.