Justifying Preventive Maintenance


How often do you experience unscheduled downtime?  What are the causes?

Example Recommendations

AR 3504: Institute A Preventive Maintenance Program for CNC Machines   

Annual Savings




CO2  (lb)




Overtime Labor

745 hours


Maintenance Cost

621 hours


Replacement Parts



2,800 pieces







Management estimates that the three CNC machines must be run overtime about 2,070 hours per year and that about 60% of this is due to machine breakdowns. In addition, present inventory levels are inflated 35% to compensate for breakdowns.


In order to reduce lost production time, repair, maintenance and inventory costs due to machine breakdown, we recommend implementing a preventative maintenance (PM) program.

Estimated Savings


Management reports that each of the three CNC machines is run during overtime hours for about 10 hours per week plus about 13 hours per weekend for 30 weeks per year.  Thus, the annual overtime is about:

Management reports that the regular hourly wage and benefit package is about $10 per hour and overtime is about $15 per hour. If so, the annual overtime operator labor cost is about:

Management estimates that about 60% of the overtime is related to machine breakdowns and that a preventive maintenance program could reduce machine breakdowns by 60%.  Thus, the annual overtime labor savings due to a PM program would be about:

$31,050 /year x 60% x 60% = $11,178 /year

Replacement Parts

Preventative maintenance would also reduce the cost of replacement parts.  We estimate that the amount spent on replacement parts for the three CNC machines would be reduced by at least $500 per month due to a PM program.  Thus, the replacement part savings would be about:

Maintenance and Repair Labor

As calculated before, the annual overtime was about 2,070 hours per year, and management estimates that about 60% of this overtime is due to machine breakdowns.  Assuming that a machine is put back into production as soon as it is fixed, the time spent repairing broken CNC machines is about:

2,070 hours/year x 60% = 1,242 hours/year

Management estimated that the time required to implement an effective PM program would be about:

However, this is more than the current time spent repairing the machines. Preventative maintenance programs have repeatedly been shown to reduce, not inflate, repair time.  Thus, we estimate that the time required to implement an effective PM program would be about half the current downtime maintenance:

1,242 hours/year x 50% = 621 hours/year

Assuming that a skilled craftsman earns $15 per hour, the labor savings would be about:

(1,242 hours/year – 621 hours/year) x $15 /hour = $9,315 /year


In addition, management reports current inventory levels are 35% higher than necessary to compensate for maintenance breakdown.  Current inventory is about 8,000 parts and each part costs about $3.50.  The value of inventory held due to machine breakdown is about:

8,000 pieces x $3.50 /piece x 35% = $9,800

If this amount were invested in the company or elsewhere at a 15% to yield, the additional revenue would be about:

$9,800 x 15%/year = $ 1,470 /year

Total savings would be about:

$11,178 /year + $6,000 /year + $9,315 /year + $1,470 /year = $27,963 /year

Estimated Implementation Cost and Simple Payback

There is no implementation cost; hence the payback is immediate.

AR 3354: Purchase Screenless Extruder Head for Extruder #1

Annual Savings




CO2  (lb)




Net Revenue Gain

120,000 lbs


Maintenance Labor

360 hours





33 months


Management estimates that Extruder #1 is down for about ten hours per month to change the screen/filter in the head of the extruder.   This downtime could be eliminated by purchasing and installing a screenless die. According to maintenance personnel, a screenless die costs about $90,000.


To reduce downtime, we recommend purchasing a modified screenless die that would not require periodic cleaning. This would add about 10 hours of production per month and reduce maintenance labor costs.

Estimated Savings

To estimate savings, we seek to estimate the total costs associated with the current operation, in which the extruder is down for 10 hours per month, and the total costs associated with the recommendedoperation, in which the extruder is operational for 10 more hours per month.  The savings would be the difference between costs in the current and recommended operations.


We assuming that the die change requires a three-person maintenance crew.  Management reports that the average cost of labor is about $15 per hour including benefits.  If so, the cost of maintenancelabor for change-outs is about:

10 hours/month x 3 persons x $15 /hour-person x 12 months/year = $5,400 /year

We assume that when the extruder die is being changed, the three regular operators are assigned to other duties in the plant.  Thus, the cost of operator labor is about:

10 hours/month x 3 persons x $15 /hour-person x 12 months/year = $5,400 /year

There are no material costs during the 10 hours per month that the extruder is down.  However, there are depreciation and overhead costs. We estimate that these costs are about $10,800 annually.  (Our rationale for this number, $10,800, will be described in the next section).  The total cost of the present operation (including labor, materials, overhead and depreciation) is about:

$5,400 + $5,400 +$0 + $10,800 = $21,600 /year


By changing to a screenless die, maintenance costs would be eliminated.  Operator labor costs, depreciation costs and overhead costs would remain the same. In addtion, running the extruder would now require materials.  According to management, the production rate for this extruder is about 1,000 pounds per hour and the production cost of styrofoam (which includes labor, materials, overhead and depreciation) is about $0.45 per pound.  Management estimates that about 70% of the production cost is for materials.  Thus, the cost of material now that the extruder is operational would be about:

10 hours/month x 1,000 lb/hr x $0.45 /lb x 12 month/year x 70% = $37,800 /year

The total production cost if the extruder were operational for 10 more hours per month would be about:

$5,400 /year + $10,800 /year + $37,800 /year = $54,000 /year

Note that $54,000 per year for an additional 120,000 pounds of material per year equates to the $0.45 per pound that management estimated as the production cost of the material:

$54,000 /year / 120,000 pounds/year = $0.45 /pound

Thus, overhead and depreciation must equal the difference between the total production cost and the cost of labor and materials:

$54,000 /year – [$5,400 /year + $37,800 /year] = $10,800 /year

Assuming a 20% profit margin, the revenue generated from this product would be about:

$54,000 /year x 120% = $64,800 /year

Thus, the net cost if the extruder were operational for 10 more hours per month would be about:

$54,000 /year –  $64,800 /year = -$10,800 /year

Note that a negative net cost is a net increase in revenue.


The savings are the difference between the costs in the current and recommended scenarios:

$21,600 /year – (-$10,800 /year) = $32,400 /year

Estimated Implementation Cost

According to maintenance personnel, a screenless die costs about $90,000.

Estimated Simple Payback

$90,000 / $32,400 /year x 12 months/year = 33 months

AR 5:  Upgrade Coolant Systems For Machining Tools








3,240 gal; $29,970

270 gal; $2,498

2,970 gal; $27,472


64,800 gal; $23,040

5,400 gal; $1,920

59,400 gal; $21,120

Labor Cost








Implementation Cost


Simple Payback

17 months


 Machining coolants are an important component of metal working operations. Coolants improve machinability, increase productivity, and extent tool life by cooling and lubricating the work piece and cutting tool. When performing these functions, the coolant becomes contaminated with tramp oil, chips and fines, dissolved salts, and bacteria, and eventually must be replaced.  The frequency of replacement can be minimized by controlling the amount and resident time of contaminants in the coolant.

The maintenance director felt that the average frequency of coolant replacement could be reduced from about every two weeks to about every six months if the residence time of the contaminants in the coolant could be substantially reduced.  After researching the issue and discussing it with experts in the field, we agree with his assessment.  This recommendation illustrates the savings potential for upgrading the current coolant circulation equipment on each machine.  Further technical assistance for reducing & recycling waste machining and grinding coolants is available through MnTAP at (612)-627-4646 or (800)-247-0015.  In addition, the US Environmental Protection Agency has published “Guides to Pollution Prevention : The Fabricated Metal Products Recovery” (EPA/625/7-90/006) which is also a valuable reference.


 Contaminant resident time in the coolant could be substantially and cost-effectively reduced by adding the following equipment to the metal working machines:

    1. Pre-settling tank before the coolant reservoir

    2. Filtration unit between pre-settling tank and coolant reservoir.  The filtration unit could be pressure and vacuum filtration, diatomaceous earth filtration, or magnetic filtration.

    3. Bacteria inhibitant, such as chemical pasteurization and low speed centrifuging or aeration, in the holding tank.

         The current and recommended coolant circulation systems are shown schematically below.  The key idea is to reduce the contact time between coolant and contaminant.  In the system below, this is achieved by a pre-settling tank which catches the heavier chips and filtration before the coolant enters the holding tank.

Estimated Savings


The cost of coolant for the machine shop is about:

270 gal/container x $9.25/gal x 12 containers/yr = $29,970 /yr

A 1,400 gallon spent coolant tank is emptied 7 times a month by Environmental Recovery.  Assuming 1,200 gallons of spent coolant are removed each time, the  annual amount of spent coolant removed is about:

1,200 gal/tank x 7 tanks/month x 12 months/yr = 100,800 gal/yr

Assuming that the final mixture is 19 parts water and 1 part coolant, the total spent coolant from the machine shop is about:

270 gal cool/tank x 12 tanks/yr x 20 gal(water&coolant)/gal coolant = 64,800 gal/yr

Thus, about (64,800 gal/yr / 100,800 gal/yr = ) 64% of the total disposal cost is attributable to the machine shop.

The total disposal cost for spent coolant is about:

$3,000 /month x 12 months/yr = $36,000 /yr

The total cost of coolant disposal for the machining shop is about:

$36,000 x 64% = $23,040 /yr

The labor cost of cleaning and replacing coolant is about:

45 machines x 8 hr/machine x 25 times/yr x $20 /hr = $180,000 /yr

The total cost is thus about:

$29,970 /yr + $23,040 /yr + $180,000 /yr = $233,010 /yr


The new system would require replacing the coolant and cleaning the tanks every 6 months instead of every two weeks.  Coolant and cleaning costs would be reduced to about one twelfth of the present costs.

$233,010 /yr  /12 = $19,418 /yr

In addition, we estimate that it would take about 2 hours each week to remove chips from the settling tank and service the new equipment.

45 machines x 2 hr/machine x 50 times/yr x $20 /hr = $90,000 /yr

The total costs associated with the new system would therefore be about:

$19,418 /yr + $90,000 /yr = $109,418 /yr

Savings (Present – Recommended)

Total savings = $233,010 /yr – $109,418 /yr = $123,592 /yr

Implementation Cost

$4,000 /machine x 45 machines = $180,000

Simple Payback

SP = $180,000 / $123,592 /yr x 12 months/yr =  17 months

AR 6:  Consolidate Coolant Systems For Grinders























Implementation Cost


Simple Payback

8 months


      In the metal working shop, concentrated coolant is mixed with water in a central location and piped to individual machines.  This ensures that the proper concentration of coolant is being used by each machine.  In the grinding shop, 8 grinders use the same type of coolant.  However, each operator mixes his own coolant.  Although the recommended concentration is 5% coolant to 95% water, operators reportably use imprecise methods of mixing such as adding coolant “till it looks pink”. Overly diluted or concentrated coolant can reduce tool life, adversely affect product quality and increase coolant and coolant disposal costs.  In addition,  in the current arrangement each machine must be individually cleaned when the coolant is replaced.  The maintenance director suggested that a central coolant loop for the 8 grinders using the same coolant would alleviate many of these problems.


      We agree with the maintenance director and recommend establishing a central coolant loop for the 8 grinders using the same coolant.  This will ensure better control of coolant concentration and reduce coolant, disposal, operating and maintenance costs.  The central coolant loop should be equipped with a contaminant control system similar to that described in AR 1.

Estimated Savings

      The estimated savings below consider only savings from reduced coolant and cleaning costs.  Other savings from  increased operator productivity and product quality and machine lifetime may also be significant.


According to management, the total cost of trimsol is $33,565 per year.  In AR 1, we estimated that the machine shop uses $29,970 per year worth of trimsol.  Thus, the cost of trimsol used in the grinding shop is about:

$33,565 /yr – $29,970 /yr = $3,595 /yr

According to management, the cost of other the two types of coolant used in the grinding shop is about $17,140 per year.  Thus, the cost of all coolant used in the grinding shop is about:

$3,595 /yr + $17,140 /yr = $20,735 /yr

In AR 1, we estimated that the grinding shop produces about 36% of the spent coolant.  Thus, the disposal cost for the grinding shop coolant is about:

$36,000 /yr x 36% = $12,960 /yr

The labor cost for thoroughly cleaning the grinders and replacing coolant is about:

8 machines x 4 hr/machine x 2 times/yr x $20 /hr = $1,280 /yr

The total annual cost of coolants, disposal and cleaning is about:

$20,735 /yr + $12,960 /yr + $1,280 /yr = $34,975 /yr


As in AR 1, we estimate that an upgraded coolant cleaning system would dramatically decrease the frequency that the coolant must be replaced.  Assuming that coolant use could be reduced to one eighth of current use, the cost of coolant and disposal would now be about:

($20,735 /yr + $12,960 /yr) / 8 = $4,212 /yr

We estimate that the cost of cleaning one central coolant loop would be about:

8 hr x 2 times/yr x $20 /hr = $320 /yr

Therefore, the total cost would be about:

$4,212 /yr + $320 /yr = $4,532 /yr

Savings (Present – Recommended)

Total savings = $34,975 /yr – $4,532 /yr =  $30,433 /yr

Estimated Implementation Cost


Estimated Simple Payback

SP = $20,000 / $30,433 /yr x 12 months/yr =  8 months

AR  14:  Devise and Implement a Preventive Maintenance System



Annual Savings


576 hr/yr

288 hr/yr

288 hr; $4,320

Debris Maintenance

1,800 hr/yr

900 hr/yr

900 hr; $13,500

Coolant Maintenance

200 hr/yr

100 hr/yr

100 hr; $1,500

Scrap Remachining

540 hr/yr

270 hr/yr

270 hr; $4,050

Coolant Fluid

15,750 gal/yr

7,875 gal/yr

7,875 gal; $2,764



Implementation Cost:


Simple Payback:



This is a productivity driven operation and high production levels must be maintained.  Such optimum production levels are difficult to achieve without a preventative maintenance in place.  The assessment team found a variety of problems related to the lack of a preventative maintenance program.  As a case study, we analyzed the Copelandā machining cell to illustrate some of the savings opportunities frompreventative maintenance. These results may be generalized and applied throughout the facility.

Operators reported that daily cleaning and maintenance of the machines is often neglected. Maintenance is scheduled every Thursday, but other problems often require attention and the maintenance is not performed.  According to operators, most cleaning and maintenance occurs after a machine breaks down. Operators cite a direct correlation between the buildup of debris and machine failure.

Productivity driven facilities, such as yours, should prevent problems rather than just respond to problems as they arise.  Quality Control, maintenance, and the operators all agree a preventative maintenance program and better personnel training would drastically improve productivity and quality.  More importantly, these changes would  decrease downtime and related costs.


We recommend devising and implementing a preventative maintenance program.  This program should define and track specific daily, weekly, and long term maintenance requirements.  We estimate an immediate payback.

Estimated Savings

The estimated costs and savings are based upon figures agreed upon by quality control, maintenance, and the machine operators.


The downtime for the Copelandā machining cell for repairing failed machines is about:

2 day/mo x 24 hr/day x 12 mo/yr = 576 hr/yr

Filings and shavings collect in bottom of these machines.  With proper maintenance, these filings are removed by an automated collector.  However when left to accumulate, the machines must be shut down to remove the debris.  The downtime for this cleaning is about:

2 hr/wk x 6 machines x 3 shifts x 50 wk/yr = 1800 hr/yr

The debris accumulation also prevents collectors from sealing properly.  Coolant leaks through these gaps and the time required to clean leaking coolant and add extra coolant is about:

4 hr/wk x 50 wk/yr = 200 hr/yr

Assuming that 25% of the makeup coolant is leaked, the cost of makeup coolant fluid is about:

30 gal/day x 25% leakage x 6 machines x 7 day/wk x 50 wk/yr = 15,750 gal/yr

15,750 gal/yr x 5% coolant concentrate x $7.02/ gal = $5,528 /yr

Quality control estimates 30% of the 50 scrap parts per month result from the excess debris in the machines, while each part requires 30 minutes to rework.  The time required to remachine defective parts is about:

50 parts/mo x 6 machines x 30% x 0.5 hr/part x 12 mo/yr = 540 hr/yr

We estimate a comprehensive preventative maintenance and personnel training program would decrease the current costs by approximately 50%.  Savings from higher moral and a cleaner work environment are intangible, but will also contribute to productivity.  Assuming the average cost of wages and benefits is about $15 per hour, the total savings, including coolant and salary, would be about:

[(576 + 1,800 + 200 + 540) hr/yr x $15 /hr + $5,528 /yr] x 50% =  $26,134 /yr

The payback would be immediate.

AR 15:  Implement a Preventive Maintenance Program



Annual Savings

Defect rate

47,040 Cylinders

39,984 Cylinders

7,339 Cylinders; $28,224

Production downtime

1,572 hr/yr

1,336 hr/yr

236 hr; $5,189

Debris maintenance

300 hr/yr

75 hr/yr

225 hr; $4,950

Tracking replacement

5,000 rollers/yr

1,000 rollers/yr

4,000 rollers/yr; $5,200

Tracking downtime

300 hr/yr

100 hr/yr

200 hr/yr; $4,400

Coolant maintenance

200 hr/yr

50 hr/yr

150 hr; $3,300

Coolant replacement

203 gal/yr

0 gal/yr

203 gal; $1,422

Net for cylinder cells

$52,882 /yr

Net for all production lines


Implementation Cost:


Simple Payback:

3 months


On the day of our plant visit, the cylinder and the journal lines were the only two lines available for observation because the bracket line had run out of castings and production on the Mitsubishi line was intermittent.  Because of this, we took a detailed look at the cylinder machining operation to see if we could identify any productivity issues.  We then extrapolated our findings to the entire plant.

High production levels are critical in the cylinder machining operation. Because of the emphasis on production, operators report that daily cleaning and maintenance of the machines is consistently neglected and that no regular maintenance schedule exists.   According to operators, cleaning and maintenance typically occur only after a machine breaks down.  In addition, large quantities of debris are produced.

Based on our observations and discussions with operators, we believe that production could be increased if a preventative maintenance program were implemented.  In this analysis, we attempt to quantify the savings that we believe would result from a successful preventative maintenance program.  In virtually all cases, facility personnel agreed that a preventative maintenance program would help correct the issues we identified.


We recommend devising and implementing a preventative maintenance program.  This program should define and track specific daily, weekly, and long term maintenance requirements and responsibilities.  In addition, you may want to commission a more detailed study of productivity issues in this cell and in the plant.

Estimated Savings

The estimated costs below are based upon figures agreed upon by management, maintenance, and/or the machine operators.

Management reports that the current defect rate for this facility is about 2.4% and the lost cost per cylinder is about $4.00 ($7.00 selling price – $3.00 purchase price).  The major causes of defective pieces are broken tooling 27%, oversized holes 16%, machine damage 8%, surface scratches and misloads 5%, material handling 40% and other 4%. Broken tooling, oversized holes, machine damage, and surface scratches account for 56% of the total scrap rate and are all associated with excessive chips.  For example, excess chips cause tools to wear out ahead of schedule and increase the frequency of broken tools.

We believe that a preventive maintenance program with regular chip collection would reduce the defect rate.  The defect rate associated with excess chips is about:

2.4% total defect rate x 56% associated with excess chips  = 1.34%

The number of cylinders lost to problems associated with defective chips is about:

70,000 cylinders/wk x 50 wk/yr x 1.34% chip related defect rate  = 47,040 cylinders/yr

If this defect rate were reduced by 15% by a preventive maintenance program with better chip removal, the savings would be about:

47,040 cylinders/yr x $4 /cylinder x 15% reduction = $28,224 /yr

Assuming 15 operators work in the cylinder cells for 7,800 hours per year, the labor savings associated with reducing the defect rate would be about:

15 operators x 7,800 hr/yr x 1.34% chip related defect rate x $22 /hr x 15% reduction = $5,189 /yr

Filings and shavings are collected in bottom of these machines.  With proper maintenance, an automated collector removes these filings.  However when left to accumulate, the machines must be shut down to remove this debris.  Assuming that a preventative maintenance program would reduce this downtime by 75%, the labor savings would be about:

2 hr/wk/shift x 3 shifts x 50 wk/yr x $22 /hr x 75% reduction = $4,950 /yr

Excessive debris causes excess chip collection in the cylinders, which in turn causes unnecessary wear and tear on the roller track.  Roller track sections must be replaced at a rate of about 2.5 sections per week, which totals about 5,000 rollers per year. According to maintenance, with proper maintenance the number of sections could reasonably be reduced to one-half section each week.  This would reduce roller replacements by about 80%.  The roller purchase cost savings would be about:

5,000 roller/yr x $1.30 /roller x 80% reduction = $5,200 /yr

Currently, about two hours are required to replace each roller section.  In addition, the machines are down for an additional hour whenever a roller section is being replaced.  The labor savings associated with reduced roller replacements would be about:

(2.5 – 0.5) replacement sections/wk x (2 hr/section + 1 hr related downtime) x 50 wk/yr x $22 /hr = $4,400 /yr

Excess debris accumulation also prevents collectors from sealing properly.  Coolant leaks through these gaps and must be cleaned and replaced.  This takes about 4 hours per week.  Assuming 75% of this time could be eliminated, the savings associated with reducing coolant leaks would be about:

4 hr/wk x 50 wk/yr x $22 /hr x 75% = $3,300 /yr

About 50 gallons per day of coolant solution is leaked.  Coolant costs about $7 per gallon and is mixed with water at a rate of about 20 parts water to 1 part coolant.  Assuming that this leakage would be reduced by about 25%, the coolant purchase cost savings would be about:

50 gal/day x 6.5 day/wk x 50 wk/yr x 5% coolant concentrate x $7 /gal x 25% = $1,421 /yr

The total savings identified above for the cylinder cell operation would be about:

$28,224 /yr + $5,189 /yr + $5,148 /yr + $4,400 /yr + $5,200 /yr + $3,300 /yr + $1,421 /yr =  $52,882 /yr

Other savings from higher moral and a cleaner work environment are intangible, but will also contribute to productivity.

It appears that similar productivity issues also plaque the remaining lines. In particular, the journal line appeared to have more maintenance-related problems than the cylinder cell operation.  We recommend devising and implementing a preventative maintenance program for all production lines in the facility.  If similar problems could be corrected on the other three lines, the total savings resulting from a plant-wide preventive maintenance program would be about:

$52,882 /line/yr x 4 product lines =  $211,528 /yr

Estimated Implementation Cost

The additional cost of implementing a PM program would be minor because most of the actual maintenance work is already being done; it is just being done after rather than before production delays.  A PM program would, however, require some additional effort to develop and manage the program.  Based on our experience, we believe that a single person could manage an effective preventative maintenance program.  A production engineering position is currently unfilled and in the budget.  Perhaps this individual could be responsible for implementing and maintaining the PM program.  We estimate that the total salary and benefits associated with the position would be about $50,000 per year.

Estimated Simple Payback

SP = $50,000 / $211,528 /yr x 12 mo/yr = 3 months

AR 3554: Replace Plaster Mixer

Annual Savings




CO2  (lb)







3,340 lbs


Production Labor

1,200 hours





   17 months

Analysis and Recommendation

The current plaster mixer was installed in 1942.  Management is considering replacing the plaster mixer with a new portable unit to reduce maintenance, repair, labor, spillage and transportation costs.  Based on the following analysis, we believe that it would indeed be cost effective to replace the plaster mixer.

Estimated Savings

Maintenance management reports that they spend about $4,000 on parts and labor to repair the plaster mixer each year. In addition, management estimates that lost product due to spillage from the transportation of mixed plaster is about 2% of each batch mixed.  The plant mixes about 167,000 pounds of plaster each year at a cost of  $0.09 per pound.  The total cost of lost product is about:

2% x 167,000 lb x $0.09 /lb = $300 /yr

Management reports that employees spend about 4 hours per day mixing and/or transporting plaster through the plant.   Management estimates wages and benefits are about $18 per hour.  Straight time labor cost is about:

$18 /hr x 4 hrs/day x 5 days/week x 50 weeks/year = $18,000 /yr

In addition, management states that 4 hours per week of overtime are required to mix and or transport totes of plaster.  Management estimates wages and benefits for overtime are about $27 per hour.  Overtime labor cost is about:

$27 /hr x 4 hrs/week x 50 weeks/year = $5,400 /yr

The total savings would be about:

4,000 /yr + $300 /yr + $18,000 /yr + $5,400 /yr = $27,700 /yr

Estimated Implementation Cost

Management estimates the equipment and installation cost of a new portable plaster mixer would be about $40,000

Estimated Simple Payback

$40,000 / $27,700 /yr x 12 months/yr  =  17 months

AR 3554:  Replace Bulk Sand Delivery System

Annual Savings




CO2  (lb)







12 hours



775 hours





37 months

Analysis and Recommendation

Management is considering replacing the current bulk sand delivery system because it requires excessive maintenance and is placed at the opposite end of the plant from the primary processes which it serves.  We estimated the savings associated with replacing the sand delivery system and locating it at the other end of the plant.  Based on the following analysis, we recommend replacing the system to increase productivity and reduce maintenance costs.

Estimated Savings

Maintenance management reports that they spend about $3,700 on parts and labor to repair the bulk delivery system each year.  In addition, maintenance also spends about $2,000 to clean the system each year.  The total annual maintenance cost is about:

$3,700 /yr + $2,000 /yr = $5,700 /yr

Management estimates that lost production due to maintenance downtime of the bulk sand delivery system is 12  hours per year.  Management estimates that overhead, labor and overtime cost to cover this downtime is $75 per hour.  The total cost of lost production is about:

$75 /hr x 12 hrs/year = $900 /yr

Management reports that a lift truck operator spends about 2 hours per day transporting bulk sand across the plant.   Management estimates wages and benefits are about $18 per hour.  The straight time labor cost is about:

$18 /hr x 2 hrs/day x 5 days/week x 50 weeks/year = $9,000 /yr

In addition, management states that one hour of overtime is required to transport bulk sand one day per week.  Management estimates wages and benefits for overtime are about $27 /hour.  The overtime labor cost is about:

$27 /hr x 1 hr/week x 50 weeks/year = $1,350 /yr

In addition, management estimates that it takes about 1.5 hours per day, 3 days per week to mix and unload the bulk delivery system.  The labor cost of mixing and unloading is about:

$18 /hr x 1.5 hrs/day x 3 days/week x 50 weeks/year = $4,050 /yr

All of these costs would be eliminated by purchasing a new bulk sand system and locating it at the other end of the plant.  The total savings would be about:

$5,700 /yr + 900 /yr + 9,000 /yr + $1,350 /yr + $4,050 /yr  = $21,000 /yr

Estimated Implementation Cost

Management estimates the total cost to purchase and install the new bulk system would be about $64,000.

Estimated Simple Payback

$64,000/ $20,600 /yr x 12 months/yr  =  37 months

Preventative Maintenance of HVAC&R Systems

For Preventive Maintenance of HVAC&R
Fix the Problem – Don’t Treat the Symptoms

Lawrence R. Grzyll, M.S., ChE., and Robert P. Scaringe, Ph.D., P.E.
Mainstream Engineering Corporation
Rockledge, Florida 32955


If you complain to your doctor about a terrible pain, hopefully your doctor does not simply provide you with a painkiller but instead tries to find the cause of the pain and treat the cause. Rather than treat the symptoms, you want your doctor to attempt to fix the underlying cause of the problem. Pain from an appendicitis attack requires more than pain killer, it requires an operation to fix the problem. Similarly, if your car muffler fails you hope the mechanic’s solution is not to just turn the radio up louder. In these vastly different examples the message is clear, treat the underlying problem, not just the symptom of the problem.

The same message applies to air conditioning and refrigeration systems. If you are just changing a failed compressor without attempting to rectify the underlying problem that caused the failure, or simply recharging the system with out fixing the leak, you’re no better than the doctor that gives pain killers to the appendicitis victim or the mechanic that turns the radio up louder to fix the muffler problem! Don’t you think that the equipment owner would pay more to fix the underlying problem, and avoid the future hassle associated with another failure? If you fixed the underlying cause of the problem, don’t you think the equipment owner would call you back, instead of just calling the next contractor in the yellow pages?

One of your goals as a contractor is to change your role from one who is simply called on the hottest day of the year (when the system has failed) to one who is building a relationship with your customers. You want to get the equipment owner to look at the value of the service received, and not simply settle on the lowest price for the specific job. Many technicians that are reading this may be saying, “I deal with residential customers and all they care about is lowest price!” This is not necessarily true, because by and large these same residential customers bring their car to a “dealership” rather than the local independent mechanic and pay much higher hourly labor rates. Many times the equipment owner does not see a difference in the quality of the service so they select the lowest cost “supplier.” The focus of this article is to suggest ways to build relationships with your customers and improve the perceived value of your service. Use this article as the first step in developing your own preventative maintenance program for your customers. “Preseason Tune-Ups” must do more than simply hose off the condenser coils, change the filters, and connect the gauges for a few minutes. The equipment owner’s view of a preseason tune-up is a service to get the system running right, and an attempt to solve problems before the system fails. This article will focus on just a few of the common failure items you should be investigating as part of your PM program.

Lets look at issues that can cause system failure.

1. compressor failure

2. relay (electronics) failure

3. system leaks,

4. refrigerant contamination

Compressor Failure

Today’s compressors are amazingly reliable considering their duty cycle and their cost. High head pressure, low charge (loss of motor cooling and lubrication), and acid formation are about the only ways to keep them from running for more than 8,000 hours (assuming a 30% summer duty cycle and assuming 5 months/year operation that means more than 7 years of operation). Some technicians want the compressor to fail, since they believe that is where the money is, and that they make their best money on change-outs. However, more and more technicians are beginning to realize that a consistent flow of maintenance and tune up money from a loyal customer actually makes more money in the long run. In addition, when that customer finally does change their system out or replace a critical component, they are less likely to shop based on price. This is the scenario that appears to be true, as evidenced by the dramatic increase in service contracts and system insurance/maintenance programs. If an owner’s system fails and he does not know you, then why should he call you, or pay more for your service? In this case, clearly you are competing solely on price with everybody in the yellow pages.

So how do we keep the compressor running? There are several preventative maintenance measures that can be performed to help ensure long compressor life.

Always check for acid in the system as part of every tune-up and service call. This is a moneymaker for you and a money saving investment for the equipment owner. A QwikCheck“ refrigerant acid test is inexpensive and takes less than 10 seconds to use in the field. If acid is detected, use QwikShot“ along with a filter/dryer change to remove the acid without leaving any residue (don’t use an acid neutralizer, since the neutralization process forms corrosive salts and water as byproducts). If the refrigerant is acid free, check for moisture. If you don’t have a sight-glass with a moisture indicator, try Mainstream’s new QwikLook‘ moisture indicator. It attaches to the service valve and checks for excessive moisture levels.

Check to see if the wire leads to the compressor are tight and clean. A loose or dirty spade connector will arc causing pitting and other damage to the spade. If the wire leads are dirty, clean them with some fine grit sandpaper or steel wool. If the wire leads are loose or damaged, reattach the compressor lead wires with a QwikLug‘ wire terminal adapter. Check the run and common wire leads, since these typically fail before the start winding lead. If only one lead looks bad, consider changing all the leads, since the others may be very close to failing as well. There is nothing worse than a system failing a few weeks after you performed a preventative maintenance service. If the original three (run, start, common) female spade connectors attaching the wire leads to the compressor are tight, you may want to cover these spade terminal connectors with an oxide inhibiting compound, which is available at most electrical supply houses and can help prolong the life of the original spade connectors.

Assuming you have already checked the system pressures and the refrigerant’s condition and charge, you may want to suggest the equipment owner install high and low pressure safety switches. Pressure switches are easily connected and disconnected from the system service valves. Because they have a valve-core depressor built-into the attachment, they are quick to connect and can be removed as needed to attach a manifold gauge set. Operating at high head pressure due to a failed condenser fan motor or clogged condenser can cause compressor failure. A high-pressure shut off avoids this potential problem. Low-pressure operation means the compressor is operating without proper cooling and/or lubrication flow, and could cause air and moisture to contaminate the system from any leaks on the low side of the system. If the equipment owner does not elect to purchase these high and low pressure safety switches, instruct them that when the system fails to turn the unit off until you can get there to repair it. Explain how operating the system in a failed state could damage the equipment.

Check the evaporator, filter, and condensate-pan for scum and biological growth. Besides reducing the airflow through the system (and potentially clogging the drain line), an accumulation on the evaporator will raise the compressor pressure ratio, making the compressor work harder (and lowering the performance). Use a time-release pan cleaner such as QwikTreat‘ to keep the pan and drain line clear. Clean the evaporator and inlet airflow passage. Change the filter, if needed. Likewise a restricted condenser airflow passage will also increase compressor pressure ratio, shorten compressor life, and reduce system performance. These coils are easy to clean. During your service call or tune-up, check the exterior condition of the compressor and filter/dryer. These housings can easily rust in humid environments. A can of paint or rust proofing can slow the corrosion process and extend the life of the unit. Of course, be sure to inform the equipment owner about the rust proofing service you have performed. One other potential problem is a corroded condenser fan. Spending it’s life in a humid environment causes the motor shaft to rust, and when the rusted shaft surface contacts the permanently lubricated bearings in the fan motor, it significantly shortens the life of the bearing. A light coat of spray-on lubricant on the fan motor shaft and other critical rust areas will extend the life significantly. Also, check to see that the female spade connectors on the capacitors are not damaged or corroded.


A recent article on preventative maintenance suggested waxing the outside of the unit to prevent rust and make the exterior look new, since image is key in the service business. Some technicians do this to help prevent severe rusting and to make the unit look better after they leave. The key is to provide a service that the customer feels was valuable and worth the investment.

Relay Failures

The next possible failure mode is the electrical circuit. Check the status of the contacts on the relay. If the relay contacts are pitted, the relay should be replaced, not simply cleaned. Once pitted, the surface will quickly degrade after a clean-up, since the hard coat on the contact has been removed. If they are severely pitted, try to determine if the pitting is due to age or if the unit is cycling repeatedly for some reason. Safety controls (low pressure, high pressure, case temperature, motor current, or thermostat anticipators) could be causing the short-cycling. You should resolve this problem, because if the unit is short-cycling, the compressor will fail sooner rather than later. If you just performed apreventative maintenance service and the compressor does fail, I doubt the customer will call you back. For air conditioning/heating applications, suggest a setback thermostat. They can save the equipment owner on energy bills and pay for themselves. You might consider offering to install one.

System Leaks

There is no requirement by the EPA to fix minor leaks, however the EPA requires the repair of substantial leaks on any system that is normally charged with more the 50 pounds of refrigerant. A substantial leak is defined by the EPA as 35% loss of charge per year for industrial process and commercial refrigeration systems. For all other systems, a 15% loss of charge per year is considered substantial. In fact, many technicians will tell you that they routinely make a few bucks on every service call by topping off the system. It may be better customer service, however, to find the leak. Wouldn’t you like to be the technician that fixed the leak that had been plaguing the owner for years?


When looking for a leak, the first thing to check for is oil residue, since this is an indication of a leak. At the leak, refrigerant and entrained oil leaks out of the system. While the refrigerant will vaporize, the oil remains at the area of the leak sometimes leaving a residue that is clearly noticeable. The longer the system has been leaking the larger the residue, unless it has been cleaned off for some reason. Electronic refrigerant leak detectors are ideal for quickly finding or confirming the location of a leak, however they are sometimes ineffective at identifying the exact location of very small leaks. It is only for these very small leaks that the use of an ultraviolet (UV) leak detector is suggested. The use of a UV leak detection approach requires the introduction of a fluorescent fluid or dye into the system. Since sufficient time must be provided for the UV fluid to mix with the oil, circulate through the system, and accumulate at the leak, it is typically a leak detection approach that is started on one service call and completed at a subsequent service call. Like the oil, the UV fluid will accumulate at a leak. When illuminated with a UV light (black light), the UV fluid/oil mixture, which has accumulated at the leak, will fluoresces making the residue easier to see than simply an ordinary oil residue. QwikFind‘ fluid is the only UV fluid on the market that is not a dye. QwikFind is a blend of anti-wear and anti-oxidant additives that naturally fluoresce, and are used by many oil manufacturers to improve the lubrication qualities of their oil.

Refrigerant Contamination

The last potential deathblow to your system, which is by no means insignificant, is refrigerant contamination. One quick, easy, and admittedly crude check for non-condensable gasses is to compare the measured high-side pressure with the saturation pressure at the condenser coil temperature. If the refrigerant charge is correct, then saturated conditions exist in the condenser. By comparing the saturation pressure to the actual high-side pressure, you can determine if there are any non-condensable gasses present in significant quantities in the refrigerant. Non-condensable gasses will raise the actual pressure above the saturation pressure. However, this method requires an accurate measurement of condensing refrigerant temperature so that the saturation pressure can be determined from a saturation pressure/temperature chart, and it requires an actual condenser pressure measurement. Typically, a pressure more than 20 psi above the saturation pressure does indicate that a non-condensable gas problem may exist. If non-condensable gases are trapped in the system, recovering vapor from the condenser should remove these non-condensable gasses and reduce the pressure discrepancy. To detect small quantities of non-condensable gas requires detailed laboratory analysis and is not justifiable except in larger systems.

Check the system for acid and treat the system if acid is detected. Treatment for acid will also remove any trapped moisture so there is no need to test for moisture, if acid is detected. If acid is not detected, go the next step and check for moisture. Moisture accelerates the formation of acids, and can form ice, which can clog an expansion device and lead to recurring problems. You need to monitor the system for moisture. On many residential installations, the installer may not have installed a sight glass in order to save money on the initial installation. Retrofitting a sight-glass is probably not practical, due to the excessive cost associated with recovering refrigerant and recharging the system. In these cases, consider installing a QwikLook moisture indicator. QwikLook is a moisture indicator that installs in minutes to the low-side service valve and is perfect for those installations that don’t have an inline moisture indicator.

The failure to adequately evacuate lines sets before connecting them and the moisture trapped in open oil containers can lead to significant moisture levels in systems. The potential problem with moisture has changed dramatically with POE oils because they are extremely hygroscopic (meaning they absorb moisture). When the oil container is open, air fills the space above the oil in the partially filled container and the moisture in the air will be absorbed into the oil. A final comment on impurities is in order.

a) Never put any water-based cleaners or flushes into a refrigeration system. If you introduce any water-based additive into a system, you need to evacuate the system to below 29 inches of mercury vacuum and assure that the entire system is heated above 75F for any water removal. However this does not assure timely water removal, for that you need warmer temperatures and deeper vacuums.

b) Keep the system sealed when ever practical.

c) Always pull a deep vacuum before charging. On a R-22 system with a volume of 10 cubic feet, the difference in evacuating from 10 to 25 inches of mercury vacuum means that after recharging the non-condensable gas level drops from 14 % non-condensables (by volume) to 3.5 % (calculations assume ideal behavior, 70F ambient, 5 cubic inch vapor volume). An evacuation to 28 inches of mercury would drop the non-condensable gas concentration after recharging with R-22 to 1.4%. The ARI standard for non-condensables is 1.5% (by volume).


Equipment owners do look at the value of the service received, but when the value is perceived to be identical, they pick the lowest cost supplier. You should convince them that the services you provide really are different, and you provide more value. This can be accomplished by doing a more thorough and complete job, by fixing the problem, and solving the underlying cause of the problem.

Preventive Maintenance for Health and Safety

Preventive Maintenance Role in Health and Safety

Preventive Maintenance

  • Maintaining equipment service records
  • Scheduling replacement of components at the end of their useful service life
  • Acquiring and maintaining inventories of:
    • least reliable components
    • critical components
    • components scheduled for replacements
  • Replacing service-prone equipment with more reliable performers

By introducing the element of planning into your maintenance function, you are likely to reduce your repair and manpower requirements.

Exploratory maintenance to anticipate and prevent breakdowns. Diagnostic measures to analyze your plant requirements include:

Operating and performing specifications of equipment

Past experience with components:

  • inspection records
  • servicing records
  • replacement frequency
  • inspected component failures

Regularly scheduled lubrication program:

  • identify lubrication points on equipment
  • colour code in order to identify
  • lubrication frequency
  • consult manufacturer and accepted industry
  • best practices to establish schedule

Why Preventive Maintenance?

Preventive maintenance is predetermined work performed to a schedule with the aim of preventing the wear and tear or sudden failure of equipment components. Preventive maintenance helps to:

  • Protect assets and prolong the useful life of production equipment
  • Improve system reliability
  • Decrease cost of replacement
  • Decreases system downtime
  • Reduce injury

Mechanical, process or control equipment failure can have adverse results in both human and economic terms. In addition to down time and the costs involved to repair and/or replace equipment parts or components, there is the risk of injury to operators, and of acute exposures to chemical and/or physical agents.

Preventive maintenance, therefore, is a very important ongoing accident prevention activity, which you should integrate into your operations/product manufacturing process.

What is Involved?

To be effective, your preventive maintenance function should incorporate the following elements:

  • Planned replacements of components designed around the following:
  • Reliability of components (equipment failure is usually caused by its least reliable component)
    • check manufacturer’s information
    • check accepted industry best practices

Developing a Preventive Maintenance Program for Water Systems

By Billy Byars

Maintenance of Water System

An important aspect of any effective and efficient water service organization is a preventive maintenance program. The objectives of a maintenance program should be to eliminate the interruption of service caused by equipment failure and to extend the service life of all equipment for as long as practically possible and economically feasible. With this in mind, a good maintenance program will consist of a preventive maintenance plan, a general maintenance plan, an emergency maintenance plan, and a program evaluation. While each of these program topics will be discussed separately below, it is important to remember the effectiveness of the overall maintenance program will be determined by how closely each plan fits together.

Preventive maintenance provides a water system with three basic benefits: (1) better service to all customers, (2) increased equipment service life, and (3) efficient use of resources. A preventive maintenance plan can be established by the use of planned work orders, planned work schedules and an evaluation process for all water system equipment. The use of planned work orders is an integral part of any preventive maintenance plan. Planned works orders should include the complete procedures to be performed, the total manpower (number of personnel, skill type, and total time) needed, and a list of materials required for the each preventive maintenance job. Compiling all planned work orders in an organized work schedule provides an efficient way of using the resources available to the water system, completing the work in a timely manner, and producing a framework for quality maintenance records. Equipment evaluation is one area overlooked when discussing a preventive maintenance plan. In order to evaluate the effectiveness of any preventive maintenance plan, a benchmark of the existing conditions of all equipment is required. When preventive maintenance work is completed, the water system should have the ability to evaluate equipment performance on both a short term and long term basis. Also, the preventive maintenance work itself can be evaluated to better improve the individual components of the plan. Preventative maintenance can be considered a time efficient and cost effective way of maintaining a water system. Scheduled preventative maintenance can lower total maintenance costs by allowing the system to purchase quality materials when time is available to obtain the best price. Scheduled preventative maintenance can be time efficient by the productive use of manpower and work schedules to complete the work while retaining some control over both the maintenance and operation of the equipment.

General maintenance is usually the largest component of any maintenance program. A general maintenance plan can be established by developing planned work orders, prioritizing work within daily, weekly, and monthly schedules, developing a material purchasing system, and evaluating the overall performance of all general maintenance work. As with the preventive maintenance plan, the use of planned work orders is vital to an effective general maintenance plan. Planning work in advance can assure that proper procedures are followed by each staff member, correct materials and supplies are available to complete the work, and a record of the completed work is available for filing in project and equipment files. Reviewing planned work orders will provide the water system with a means of fine tuning their general maintenance plan. Another key is a prioritized work schedule. Prioritizing work on a daily, weekly, and monthly basis creates a productive working environment for personnel. This results in more maintenance being completed at a much lower overall cost. Efficient maintenance requires that adequate materials and supplies be available for use at a moment’s notice. It is important that water systems realize the need for developing a material purchasing system. This system would include a complete material and supply inventory, standardized purchasing procedures, and a tracking method of all materials used by the water system. It is important to have a centralized area designated for the storage of all materials and supplies used by the water system. An evaluation process should be developed to determine the overall performance of all maintenance work along with its effectiveness over the service life of the equipment. Changes in the types of procedures and materials used can be detected and corrected during the evaluation process. Also, the efficiency of a water system’s use of resources and manpower as they pertain to the general maintenance plan can be determined.

An emergency maintenance plan is an invaluable component of most maintenance programs. This specialized plan will save both time and money when utilized properly. The foundation in developing an emergency plan is knowing the capabilities and limitations of the water system’s staff and resources. The next step is to formulate contingencies for all types of emergencies that your water system has encountered in the past or could encounter in the future. It is important to be as specific as possible in identifying the many emergencies that could occur. Finally, a comprehensive list of consulting engineers, contractors, technical sales representatives, and material supply companies should be developed. This list should contain information as to the contact people, phone numbers (business and emergency), and the specific time and reasons each would be contacted. This contact list and a material/supply inventory list should be updated as often as possible and readily available for use at any time. Experience and planning are the keys to assuring the emergency maintenance plan operates properly. When the dust has settled and normal operation has resumed, a comprehensive evaluation of all actions taken as a part of the emergency plan should occur in a timely manner. At this point, evaluating the actions taken will hopefully result in a better emergency plan and, thus, an improved response to the next emergency.

The final component of a comprehensive maintenance program is a program evaluation. The only way to improve a water system’s maintenance program is to periodically evaluate it to ensure the main objectives of eliminating the interruption of service caused by equipment failure and extending the service life of all equipment for as long as practically possible and economically feasible are being met. By applying the knowledge and experience gained from successful and unsuccessful maintenance work along with proper planning and training, the evaluation process will improve the overall maintenance program by strengthening the individual preventive, general, and emergency plans. As more evaluations are conducted, the water system will find itself gaining more experience, performing improved maintenance work, increasing the service life of all equipment, benefiting from more productive work, saving more money, and providing the best possible water service to the customers.

Preventive Maintenance of a Compressed Air System

How to maintain a compressed air system
Compressed Air System

So you need todevelop a preventive maintenance strategy for compressed air systems?

All components in a compressed air system should be maintained in accordance with the manufacturers’ specifications. Manufacturers provide inspection, maintenance, and service schedules that should be strictly followed.

Because the manufacturer-specified intervals are intended primarily to protect the equipment rather than optimize system efficiency, in many cases, it is advisable to perform maintenance on compressed air equipment more frequently

One way to tell if a compressed air system is well maintained and operating efficiently is to periodically baseline its power consumption, pressure, airflow, and temperature. If power use for a given pressure and flow rate increases, the system’s efficiency is declining. Base lining the system will also indicate whether the compressor is operating at full capacity, and if that capacity is decreasing over time. On new systems, specifications should be recorded when the system is first installed and is operating properly. Types of Maintenance Maintaining an air compressor system requires caring for the equipment, paying attention to changes and trends, and responding promptly to maintain operating reliability and efficiency.

To assure the maximum performance and service life of your compressor, a routine maintenance schedule should be developed. Time frames may need to be shortened in harsher environments. Proper maintenance requires daily, weekly, monthly, quarterly, semi-annual, and annual procedures. Please refer to the Compressed Air System Best Practices Manual for the types of procedures that are relevant to the compressors and components in your system. Excellent maintenance is the key to good reliability of a compressed air system; reduced energy costs are an important and measurable by-product.

The benefits of good preventive maintenance far outweigh the costs and efforts involved and strategic maintenance planning are essential to a good PM system. Good maintenance can save time, reduce operating costs, and improve plant manufacturing efficiency and product quality