Consulting-Specifying Engineer - October 2008 - (Page 85)

Equipment Lifecycles Specifying pumps the smart way By reviewing the lifecycle cost analysis of a pump, an engineer can make better decisions on behalf of the building owner. BY STAN KUTIN, Commercial HVAC Pumps, ITT, Morton Grove, Ill. Engineers in charge of very large projects routinely have used a lifecycle cost analysis (LCA) to help decide among the alternatives available to them. Wise decisions in expensive, long-lived projects are well worth the additional data collection, estimations, and calculations required by LCA. In contrast, engineers who specify pumps for building service have traditionally not used LCA. All too often, they used a simple payback period analysis, or even worse, they went along with a general contractor’s choice of the pump with the lowest initial cost. However, LCA concepts are not difficult to understand or apply, and they can help an engineer make better decisions on behalf of the building owner. Simply stated, the lifecycle cost is the sum of all costs associated with owning the pump over its service life. LCC = Ci + Cin + Ce + Co + Cm + Cd + Cenv + Cdis Impeller Bearing, seal, shaft Coupler Discharge flange Where: LCC = Lifecycle cost Ci = Initial cost, including the pump and fittings Cin = Installation, commissioning, training costs Ce = Energy cost over the pump’s service life Co = Operations, labor costs Cm = Routine maintenance and repair Cd = Costs incurred due to pump downtime Cenv = Cost of remediating or preventing environmental damage Cdis = Disposal cost Centrifugal pumps tend to have a long service life, so the time value of the cost elements must be considered; most analyses calculate the net present value at some assumed interest rate. The LCA is a simple spreadsheet exercise. The real difficulty lies in estimating the cost elements. Routine maintenance and downtime costs are difficult to estimate, unless there is a similar system already in operation and its maintenance history is available. Changes in energy cost over the next 10 to 20 years are hard to predict, and for smaller, less expensive systems the LCA may seem like “overkill.” Despite this, incorporating LCA ideas into the pump selection process will make for better choices. Pump selection Proper selection of a centrifugal pump is the first step toward equipment longevity, but it’s not that easy. The design flow and head requirements of a system are obtained from estimations, rules of thumb, and safety factors, which often result in excess flows. On occasion, systems are not built as designed, creating either insufficient or excess flows. The actual flow rate of the system determines where the Suction flange Base Vertical split-case double-suction pumps are designed for simplified service. (Bell & Gossett Series VSX) Consulting-Specifying Engineer • OCTOBER 2008 85

Table of Contents Feed for the Digital Edition of Consulting-Specifying Engineer - October 2008

Consulting-Specifying Engineer - October 2008 Contents Viewpoint Letters News M/E Roundtable Cities Under One Roof Eight Design Tips for Integration Is 'Green' Really New? Down the Drain Product of the Year Awards Codes & Standards Case Study New Products Equipment Lifecycles Advertiser Index Green Space

Consulting-Specifying Engineer - October 2008

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