Industry Insight 5 Factors in Determining Overall Pump Life-Cycle Costs
Everyone focuses first and foremost on purchase price when estimating pump life-cycle costs, but there are other optimisable costs that will help moderate pump-related expenses.
Facility managers who rely on industrial pumps for the various liquid-transfer duties in their manufacturing processes can be excused if they occasionally think that once the pump has been purchased, the majority of the heavy lifting has been completed. It is easy to see why this mindset might become prevalent. After all, identifying the right pump for the right process requires a lot of time and due diligence, from performance reviews to cost estimates, to even soliciting opinions from other manufacturers.
In reality, studies of different types of manufacturing operations have indicated that, when all is said and done, the purchase price of a pump will only be 10 % to 15 % of its total life-cycle cost, with “life-cycle cost” defined by The Hydraulic Institute as the “total lifetime cost to purchase, install, operate, maintain and dispose of the pump.”
Based on that definition, the reality is that cutting a check for the purchase price of the pump is only the first of many potential expenses that will be incurred over the pump’s operational lifetime, which – if the operator is fortunate – can be as long as 20 years or more. Hand in hand with that, pumps are said to account for between 20 % and 25 % of the energy usage in a manufacturing operation. Therefore, it is imperative that facility operators analyse their pre-buy research not only from an initial-cost perspective, but also from a total life-cycle cost viewpoint.
To do that, there are five cost factors to consider when attempting to arrive at a trustworthy figure for what a pump’s total life-cycle cost may be. Let’s take a closer look at all five:
1. Capital Cost
As mentioned, capital expenditure – or Capex – in the amount of money paid to actually purchase the pump is the first and most obvious life-cycle cost. But identifying and optimising that Capex cost involves much more than comparing and contrasting price tags.
The first consideration should be identifying the pumping technology that best suits the needs of your liquid-transfer processes. Usually, this comes down to a choice between positive displacement (PD) and centrifugal-style pumps, with the type of technology that is ultimately chosen having huge implications regarding the total life-cycle cost of the pump.
In many instances, final pump selection can come down to an either/or choice:
• If a PD pump is chosen, will its operation require the use of a gear reducer or speed-reduction device? If it will, that is an added upfront cost that must be considered since centrifugal pumps do not need speed reducers.
• There have been a number of significant advances recently in the development of leak-free or seal-less pumps. These types of pumps, however, are generally more expensive than sealed pumps, but on the other hand, an inventory of replacement seals will not need to be purchased, stocked and tracked.
• Within the PD realm, air-operated double-diaphragm (AODD) pumps are a unique technology in that they do not need a traditional electric or fuel-powered motor to operate and have no couplings or seals that need to be maintained or replaced. The only daily operational cost is paying for a supply of air, but this means that the facility must be able to accommodate that capability. AODD pumps also do have a number of wear parts that will need to be monitored, including their diaphragms, balls and valve seats.
Particular to the chemical-manufacturing industry, over the years centrifugal pumps have become the default liquid-transfer technology in many of the world’s chemical-processing systems. Because of this, many chemical processors will always choose a centrifugal pump because they know how they operate, are familiar with their benefits and are confident they will get the job done, no questions asked.
The problem with this mindset is that it means that many chemical-processing systems have been designed around the needs of the pump, rather than the needs of the system. For example, design engineers will design their systems so that raw materials can be blended or heated in a way that their viscosity is brought to a level that enables them to be handled by a centrifugal pump. In this case, they are reconditioning the material to fit the need of the pump, regardless of any potential life-cycle cost impact.
The operator, in addition to getting the viscosity to a centrifugal-friendly level, must also ensure that the pump continues to operate at its Best Efficiency Point (BEP), generally believed to be a window in which the pump operates at 80 % to 110 % efficiency levels. Any time spent operating outside the BEP can result in shaft deflection that will place higher loads on the pump’s bearings and mechanical seal, which can damage the pump’s casing, impeller and back plate. This domino effect will lead to higher maintenance and part-replacement costs that – teamed with the costs required to actually keep the pump operating at its BEP – will increase total life-cycle costs.
2. Installation Costs
Determining installation costs and their eventual effect on total life-cycle expenses requires a total overview of the pumping operation. Some questions to consider include:
• Will any modification to the pumping system be needed when the new pump is introduced or can it just be plugged into the existing infrastructure?
• Will new or modified connections to the process piping, electrical wiring and instrumentation, and auxiliary systems and utilities be needed?
• Are there any special weight considerations that could lead to the need for a special foundational platform, i.e. a baseplate?
• Will any boring into the existing foundation, or the pouring of a new foundation, be required?
This last question is the one that can have the biggest effect on total life-cycle costs. Some pump technologies are easy to install; for instance, AODD pumps that need only an air and discharge hose to be hooked to them before they are asked to do their jobs, even if that job demands that the pump operate underwater.
Vertical pumps, on the other hand, are typically less expensive than some other styles, but they sometimes need extensive foundation work that could require boring as much as 30 feet (10 meters) into the ground just to install the pump. Again, this can prompt the facility operator to employ some comparative if/then thinking: “If I want to use a more economical vertical pump, then it will cost quite a bit in installation costs.” By taking that into consideration and reviewing all of the possible alternatives, that if/then statement can be turned into: “If I use a more expensive multi-phase pump, then I will have lower installation costs.”
Another area of consideration during pump installation is alignment. Simply put, pumps that are not aligned properly with the motor – and many often aren’t – can lead to quicker part wear that can result in inefficient operation and pump failure. There are now some pump technologies that can be pre-aligned as they are manufactured through the use of an adapter, which eliminates the need to align the pump on-site, along with any costs associated with that alignment process.
A final expense within the installation-cost realm is commissioning costs. These are the fees that must be paid to have the installation reviewed to ensure that it satisfies all of the parameters for proper installation and safe operation. Only after this review has been performed and sign-off received will the facility manager be able to flip the switch and begin operating the pump.
In the end, it all comes down to each individual facility’s needs, wants and economic considerations, with all of the spokes in the installation-cost wheel playing a part in determining total life-cycle costs.
3. Operating Costs
The most obvious cost here is acquiring the energy – generally electricity, fuel or air – that is needed to power the pump. Here again, the style and operational capabilities of the pump technology play a notable role. For example, when contemplating a pump that operates via a motor that is 50 horsepower or lower, energy efficiency should not be a top-of-mind consideration for the operator. However, energy efficiency becomes a critical concern when the motor is 100 horsepower or larger, especially when those heavy-duty motors are featured on pumps that perform continuous-duty pumping operations.
Again, a comparison between PD and centrifugal-style pumps is in order:
• Typically, a PD pump motor is sized according to the bypass valve set point. This optimises the motor sizing so that it is close to the actual operating points and limits the energy consumed while still enabling it to achieve desired flow rates regardless of temperature, pressure or viscosity changes during the pumping process.
• Centrifugal pumps, on the other hand, are often not protected with bypass valves. Instead, centrifugal pump motors are sized according to the runout power. This essentially oversizes the motor “just in case” the pump operates at runout. In reality, most centrifugal pumps don’t operate at runout, meaning that the cost for a larger motor is often a needless expense.
Another cost to focus on when considering life-cycle operating expenses is the cost of any ancillary liquids needed to heat, cool or lubricate the pump during its operation. For instance, sealed pumps can require a water “quench,” a process in which tap water is injected into the seal gland as a way to cool and clean the seal faces. This water is usually introduced into the pump at very low volumes, sometimes even lower than a dripping water faucet, but if 10 pumps require this treatment and they operate for 8,000 hours a year each, the costs for that water can quickly escalate. This expense is not needed with seal-less pumps.
Operating costs also contain a human element in the form of labour costs. These costs can fluctuate widely depending on the complexity of the pumping system itself. A system that regularly handles hazardous or explosive materials requires closer monitoring than one that only transfers benign materials. Though there has been growth in next-generation remote Cloud-based pump-monitoring systems and equipment in recent years, most manufacturing facilities still rely on first-hand on-site observation of the pumps to determine if they are meeting the parameters of any and all required performance indicators.