Life Cycle Cost & Reliability For Process Equipment (Page 10 of 22) in pdf

Step 5: Gather cost estimates and cost models.

This section is complicated because cost details are assembled. Of course the more thorough the

collection process, the better the LCC model—however for brevity, the details have been shortened

with enough just information described to show the trends.

Case 1: Fix when broken: Use the following details in Table 1 gathered from plant experience an

presented in a Weibull analysis format describing the predominate failure mode (no effort is made to

describe common cause failures, rare events, or mixed failure modes, etc.). Use an accounting principle

that costs will follow activity—in this case, costs will follow failure activity.

Capital cost are US$18,000, and lost gross margin occurs at US$10,000/hour when the process is

down for repairs. Annual power cost for running the pump is US$165/yr per horsepower. The plant

incurs 1.6 power outages each year for an average downtime of 0.5 hours, and this cost is charged into

plant overhead rather than to individual pieces of equipment. Annual power costs are: (US$165/hp-

yr)*(100 hp) = US$16,500 as shown in Table 1.

Pump seals have Weibull values: (shape factor) β = 1.4, and (characteristic life) η = 4.5 years. When

seal failure occurs, 8 hours of downtime is also lost production time at US$10,000/hour when the

process is down for repairs. Maintenance crew costs for labor, incidental materials, and expense are

US$100/hr (i.e., two people at US$50/hr each). Seal replacement costs are US$2,500/seal. Seal

transportation costs are usually expedited and cost US$75 per incident. Find the annual pump seal

costs (including lost production time for seal failures) by simulation as shown in Table 1. In a similar

fashion, other component cost calculations are summarized in Table 1 along with other routine costs for

PM and PdM efforts.

Maintenance visits the pump monthly for routine PM inspection, lube oil addition/change out, and

emissions tests. Maintenance cost is US$50/hour for labor, incidental materials, and expense with 1

hour on the average charged per visit.

No failure times are incurred during this activity.

Annual maintenance PM costs are: (12 visits*1hr/visit)*US$50/hr = US$600 shown in Table 1.

Operations visits the pump once per week for routine PM inspection and vibration logging. Operations

cost is US$35/hour for labor and expense, with 0.2 hours charged for each visit. Annual operations

PM costs are: (52 visits*0.2hr/visit)*US$35/hr = US$364 shown in Table 1.

The Vibration Department receives vibration data from operations by e-mail and scans the data weekly

for abnormalities.

Surveillance cost is US$50/hour for labor and expense, and on the

average, 0.2 hours is charged for each weekly visit. Annual Vibrations Department PM costs are: (52

visits*0.2hr/visit)*US$50/hr = US$520 as shown in Table 1.

Maintenance and operations conduct a joint tail-gate training session on good maintenance and

operation practices for this pump once per year. Three people from Maintenance attend at US$50/hr-

person

and

three

people

from

Operations

attend

US$35/hr-person—the

training

session consumes an elapsed time of 0.5 hours. Annual training costs are: (0.5 hr * (3people*US$50

+3people*US$35)) = US$128 as shown in Table 1.

Life Cycle Cost & Reliability For Process Equipment Page 10

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