Archive | March, 2007

565

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March 1, 2007
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Lube Oil Varnish Control

Lube oil varnish is the largest problem facing the lube oil used in combustion turbines.

Varnish forms because of lube oil degradation, largely from the extreme temperatures and oxygen existing in combustion turbines. Varnish buildup causes excessive wear on parts, can lead to bearing failures and can cause critical components—such as servomechanisms—to seize. These failures are costly, not only because of the repair expenses, but also because of the off line lost revenue.

What is varnish and where does it come from?
Varnish results in a thin film deposit often found on bearings, servo-valves, and other metal surfaces. The film is made up of soft insolubles that fail to be removed by full flow filtration.

Thanks to advancements in high temperature-resistant materials, modern combustion turbines are able to operate at very high firing temperatures. This, in turn, causes high bearing compartment temperatures.

As the lube oil flows into and around the bearings, it gets hot and mixes with air in the bearing compartments. Each time the lube oil passes through a hot bearing compartment, it oxides a little. This oxidation causes the early depletion of antioxidant additives, and leads to the formation of insolubles, which are the beginnings of varnish.

These early insolubles are soft and do not have a definite shape, so the full flow filtration systems on combustion turbines cannot remove them.

If left in the lube oil, the insolubles will eventually stick to metal surfaces. Since most large combustion turbines also use their lube oil system to operate servomechanisms for fuel valves and variable vane actuators, filming can occur on these components and cause them to stick, malfunction, and eventually result in the engine tripping off line. Furthermore, varnish films will cause excessive wear to bearings, resulting in early bearing failures and unexpected maintenance requirements.

While oil degradation is the primary cause of varnish, oil degradation itself is caused by several factors. Poor filtration will allow particulates, wear particles and water to build up and contaminate the oil. Oxidation, high temperatures, and moisture will cause the depletion of antioxidant additives. All of these factors degrade the oil and allow insolubles to form. Furthermore, it has been found that wear debris—especially of the sub-micron size—acts as a catalyst for varnish formation.

0307_solution_spotlight_img1Do you have a varnish problem?
All large combustion turbines with non-synthetic lubricating oil are vulnerable to varnish. As oil degrades, varnish is bound to form. The real question is, “when will the problem hit?”

How can you control varnish? 
Varnish is composed of insolubles that have no fixed shape, so they simply “squeeze” through conventional filters, rendering the filters useless for varnish control. As a result, other filtration methods must be used. Current marketed varnish treatments are expensive, demand consistent maintenance, and are prone to expensive malfunctions. Products currently on the market include electrostatic precipitation systems and edge filtration units.

Electrostatic precipitation requires the use of complex and expensive components including PLCs. They also require high-voltage electricity to create positive and negative charges to particulates in the oil. These systems can cause breakdown of some additives. Meanwhile, edge filtration methods have a very limited amount of filter surface area at the edge of the discs. As a result, they have low flow rates and are prone to clogging in applications when filming occurs, as is the situation with varnish in the lube oil.

Are there other options?
According to Seaworthy Industrial Systems (SIS), its varnish removal system (see Fig. 1) has no PLCs, no high voltage and no complexity. It offers especially high flow rates and varnish capacity and is not susceptible to clogging.

This organic filtration system operates as a 3-micron mechanical filter and as an adsorbent/absorbent filter that literally draws the varnish out of the lube oil and holds it within the element to be discarded when the elements are changed. These filters operate in another unique way; they do not accumulate any static charge so that there is no Electrostatic Spark Discharge (ESD) to further degrade the lube oil.

The system also incorporates magnetic filtration utilizing high strength, rare-earth, magnetic technology to remove the ferritic wear particles that act as catalytic particles that accelerate the degradation of the lube oil and its additives.

How does it work? 
The Seaworthy system is designed to act in a side stream (kidney loop) configuration. Once connected to the oil reservoir, it is turned on and left on. With only a circulation pump and filter assembly, there is very little chance of error and no need for constant maintenance or expensive service technicians.

The system’s depth filtration elements capture varnish, insolubles, particulate matter and water, while its added magnetic filtration catches wear particles of all sizes.

When first started, the filtration system begins to filter the lube oil, ridding it of varnish, particulates and water. Depending upon the severity of the turbine’s varnish condition, the now-clean lube oil will begin to dilute the varnish film on the turbine’s metal surfaces, drawing it back into the lube oil. Once again, the system removes that varnish from the oil. This cycle continues to “self-clean” the entire turbine lube oil system.

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For systems without varnish, or for those that are now “clean” from the foregoing process, the Seaworthy works to ensure that varnish buildup does not occur. This is accomplished by filtering the insolubles from the oil before they reach high enough concentrations at which varnish forms, while simultaneously using magnetic filtration to capture wear debris which would otherwise act as a catalyst for varnish formation.

How well does it work?
Seaworthy notes that field tests performed by a large U.S. utility company (see Fig. 2) showed that in the first 20 days of operation, its filtration system reduced the lube oil varnish potential rating (VPR) by 24%—thus improving an “abnormal” varnish level to “acceptable.”

Seaworthy Industrial Systems, Inc. Centerbrook, CT

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4475

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March 1, 2007
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Constant Level Oilers: Best Practices For Optimal Lubrication

Constant level oilers have been utilized on process pumps and other rotating equipment for more than half a century. Although some oiler designs haven’t changed much over time, others have become more advanced—as have the equipment and applications they serve.

Regardless of the types of oilers in your plant, you’re counting on them to maintain proper levels of lubrication—however and wherever they are deployed. That’s why proper selection, installation and maintenance of these devices should be an utmost concern. By taking steps to eliminate additional points of contamination ingression and avoid installation and application errors with your constant level oilers, you can ensure both proper quality and quantity of the lubrication they supply.

0307_lubrication_img1The right amount and condition
The right condition and the right amount are two critical elements of lubrication. The right condition refers to the quality of oil—specifically oil that is contaminant free. Having the proper quantity of contaminated oil is no better than having an insufficient quantity of contaminant-free oil. Having the proper quantity of oil would be considered more important than maintaining the quality of the oil, but both have significant impact on the life of the lubricant and component being lubricated. Oil sump lubrication doesn’t require that a specific level be maintained for proper bearing load—only that oil levels do not reach critically low or high points (Fig. 1).

In a low-level operating condition, the bearing will not receive enough lubricant necessary for proper film strength—a precursor to surface contact, skidding and possible catastrophic failure. Without enough oil to prevent friction, thermal runaway can happen quickly to a steel bearing. As the temperature of the bearing increases, the ball and race both expand, which creates an even tighter fit. This further increases the temperature, and the cycle continues to a rapid, catastrophic failure.

In a high-level operating condition, churning of the lubricant will occur, accelerating the oxidation rate as a result of excessive air and elevated temperatures. It is a common mistake to believe that more is better—especially when it comes to oil sump lubrication. Too much oil can affect the operation of oil rings, flingers and direct bearing contact. Leaking seals are another result of high lubricant levels.

Solving the problem
Maintaining the proper quantity of lubricant is perhaps the easiest means of increasing lubrication life and effectiveness. Consult with your equipment manufacturer for recommended oil levels, optimum lubricating equipment and preferred practices. For direct contact lubrication, such as in rolling element bearing applications, the ball at the deepest point of submersion in a static condition should not be submerged more than one-half the diameter.

The constant level oiler (Fig. 2) continues to be one of the most widely used methods of maintaining the proper level lubricant in a bearing housing. These devices replenish oil lost by leakage through seals, vents and various connections and plugs in the bearing housing. Once the proper level has been set, replacing the oil in the reservoir is the only required maintenance.

Constant level oilers have a “control point” that must align with the proper oil level of the equipment. The device is installed on the equipment and oil is filled to the predetermined level. All constant level oilers require air to function properly. Consequently, if the oil level within the sump lowers, the seal at the control point is broken, allowing air to enter the reservoir and displace the oil until the seal is reestablished. As long as a constant level oiler is set correctly and there is oil in the its reservoir, the equipment will always have the optimum oil level within the sump.

Vented & non-vented designs
Constant level oilers can be put into two categories: vented and non-vented. As mentioned previously, all oilers require air to function properly.

  • In vented types, the air comes from the surrounding atmosphere.
  • In non-vented types, the air necessary for proper operation is the same air found within the sump.

Vented oilers, which entered the marketplace over 60 years ago, still are the most used type today. That’s because they provide great value in maintaining proper oil levels and extending equipment life. It is important to note that vented oilers will provide the proper quantity of oil, but not necessarily proper quality, as they can be a source of contamination ingression.

0307_lubrication_img2-1

Pressure differentials between the equipment housing and surrounding atmosphere is a leading cause of contamination ingression. In outdoor applications, for example, or where housing temperature fluctuations occur during frequent on/off running conditions or process fluid temperature changes, air flow over the equipment create this atmospheric exchange as pressure is equalized. During this air exchange, contamination from the surrounding environment is “breathed” into the oil sump.

Non-vented oilers do not exchange air with the atmosphere. One common non-vented model uses a pressure balance line that connects the air within the oiler base to the air within the sump (Fig. 3). Non-vented types of oilers operate under the same principle as vented. Their “control point” is set to align with the desired oil level and if it lowers, air enters the reservoir displacing the oil until the seal is re-established.

Proper specification
Determining which type of oiler to use for an application requires consideration of the surrounding environment, type of seals and design of the housing, including port locations and vents. In highly contaminated environments, it is recommended that a non-vented type of oiler be installed to minimize particulate and moisture ingression. Other sources of ingression are through seals and vents located on the top of the housing.

Certain types of seals are better at preventing ingression than others. Spending money to upgrade seals to prevent contamination ingression and oil leakage will not be as effective if vented types of oilers are used. The ideal configuration for oil sump housing lubrication is to eliminate the potential for contamination ingression by “closing” up the sump. Some seals are not capable of handling the pressures due to equalization and would require an expansion chamber. An expansion chamber has a rolling diaphragm that expands as the air within the sump heats up minimizing pressure increases (Fig. 4).

Proper installation & maintenance The leading causes of incorrect oil sump levels when using constant level oilers include:

  • Incorrect oiler settings
  • Pressure differential (vented types only)
  • Oiler location
  • Blocked or plugged fittings
  • Improper filling methods

These problems can be overcome, as follows:

0307_lubrication_img2Incorrect oiler settings. . .

Review the instruction sheets provided with the oiler for better understanding of how to adjust and set the device for proper use. Understanding where the control point is can greatly reduce problems associated with high and low oil levels. On adjustable-type oilers, knowing the adjustment parameters relative to the port and oil level are equally important.

A vertical stem pipe is used on the most commonly used vented type of oiler. This stem pipe serves two purposes: (1) it sets the level via wing nuts; and (2) it breaks any meniscus that may form due to surface tension. Many users throw this stem pipe away, which could prevent feeding or cause a low oil level condition with only the set screw supporting the upper casting. State-of-the-art non-vented oilers offer easier installation methods with outside adjustment and visual verification of proper settings that can be done via a sight gauge.

Pressure differential (vented types only). . .
Airflow across equipment housings generated by fans, blowers and even the equipment motor can be sufficient to create pressure differential between the bearing housing and the oiler reservoir, thus causing the oiler to feed so much that it reaches an overfill condition. As discussed previously, equipment operating temperature changes also can create pressure differentials.

Pressure increases/decreases can be controlled by closing the housing through the use of non-vented oilers, replacement of vents with expansion chambers and proper seal selection.

Oiler location. . .
Location of a constant level oiler relative to shaft rotation can affect how the device dispenses. The recommended placement is on the side of the equipment facing the direction of the shaft rotation at the bottom when using the side mount. Oil is pushed up into the reservoir versus being pulled away—which can cause feeding and an overfill condition (Fig. 5).

0307_lubrication_img3Blocked or plugged fittings. . .
It is important to check the connection fitting between the oiler and the housing to verify that there is no blockage. When oil becomes oxidized or contaminated, it can plug this fitting. If this situation occurs, the device will not feed and the level can become low. It’s easy to check for blockages and/or plugs by removing the oiler during oil changes and looking at the fitting opening.

Improper filling methods. . .
When filling through the top of the equipment, knowing the required oil volume is necessary to achieve the preset level. If the oil quantity is known, then this method is considered to be a safe filling procedure. More times than not, however, the quantity is unknown and new oil is haphazardly filled through the top, using a sight gauge to determine the level. Unfortunately, this results in a high fluid level because of residual lubricant draining from the internal components such as a shaft or gear.

Proper filling can be achieved through the surge body when a sight gauge is present. The sight gauge provides a visual aid for achieving the predetermined fluid level in the sump. Filling without a sight gauge can cause overfilling of the oil sump and surge body. An indication of overfilling will become evident if fluid begins flowing from the surge body once the reservoir is replaced. To adjust for overfilling, drain the lubricant from the sump until the constant level oiler begins feeding, and reaches the preset level.

Excessive refilling of the reservoir also will have a negative effect on the oil level. Each time the reservoir is removed and replaced, a small amount of lubricant is added to the oil sump level. Over time, this chain of events will increase the fluid level. To minimize unnecessary filling, refill the reservoir only when it is half full or less.

In summary
Constant level oilers are an easy and effective method of maintaining proper oil level in equipment. Whether utilizing vented or nonvented types, proper application and installation is critical for ensuring optimum performance of the device and the equipment it protects.

“If it’s not broke, don’t fix it” may apply if oil change intervals of only eight months are acceptable in your plant. On the other hand, if extending oil change intervals is a goal of your lubrication program, standardizing on reliable seals, nonvented oilers, expansion chambers or other types of effective breathers is a best-practice approach you’ll want to seriously consider.

Rojean Thomas is senior technical consultant with Trico Corp., Pewaukee, WI. For more information, telephone: (262) 691-9336 ext. 200; or e-mail:rthomas@tricocorp.com

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March 1, 2007
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Proper Sampling Techniques

0307_collecting_data_img1                                                                                                                                                                                                        Oil analysis is a very powerful technique in a Reliability Centered Maintenance Program. Previous articles in this publication have discussed the use of oil analysis in a condition-based program being both predictive on equipment condition and proactive on lubricant condition. Sampling is the first step—and a key element—in determining oil and equipment conditions. Since bad data may lead to the wrong conclusions and cause either an unnecessary or wrong action, it is critical to sample properly. As an example, let’s say you visit a physician for a blood test to determine your cholesterol level. Clearly, it is going to be very important for the doctor to get a good “representative sample” to make the correct diagnosis. One hour before the exam, however, you eat a double cheeseburger with fries. In all likelihood, your results will come back positive for high cholesterol and the doctor may put you on medication and a strict dietary program. If you’ve not had problems in the past, the correct course of action would be to take another sample. If it is a good representative sample and comes back positive, you can rest assured that your doctor took the right course of action from the outset. On the other hand, if the second blood test comes back negative, there is a possibility that the first sample was not truly “representative”— and that your doctor took the wrong course of action. Our cholesterol test example is very similar to what can happen with oil analysis. If a sample is not taken properly, it may lead to the wrong conclusions. Therefore, you never shut down a piece of equipment based on the results of just one sample. You should always resample when unusual results come back on an oil analysis report.

The main objectives of a sampling program are to:

  • maximize data concentration;
  • minimize outside interferences;
  • sample at proper intervals.

Important considerations in an effective sampling program are:

  • sampling location
  • sampling hardware
  • sample bottles
  • sample procedure

Oil analysis provides the following basic information:

  • oil condition
  • equipment condition
  • contaminant type and amount

0307_collecting_data_img3

Table I summarizes available oil analysis tests and the information they can provide.

Keep in mind that the sampling process is dependent on the objectives for the data. For example, if we only are interested in oil condition, such as viscosity, FTIR and acid #, the sample location and the technique are not as critical as they are when we are analyzing for large wear debris indicating possible catastrophic failure. Hydraulic systems with precise controls—such as servo valves—require very clean oil. Therefore, the particle counts need to be very accurate, requiring a good representative sample of the system.

0307_collecting_data_img2Live zone sampling 
The preferred method is to collect a sample as it is flowing through the system with as much turbulence as possible. The best place to do this is at an elbow or T for good mixing, as illustrated in Fig. 1. The primary location should be within the return line of a circulating system, as shown in Fig. 2.

Many times, if there are a number of components, more than one sample point is needed. The primary sample point identifies any problems in the whole system and is the main return line to the system, which is fed by secondary lines to the main components. If, for instance, a high Fe content is found in the primary line, each of the secondary lines needs to be sampled to identify the component(s) experiencing the problem(s).

0307_collecting_data_img5

Live zone sampling, the preferred sampling method, gives the most representative data in a circulating system. Assume you have a 10,000 gallon turbine oil reservoir and you are trying to identify initial wear of journal bearings that are tin based Babbitt. With emission spectroscopy, you would look for tin and correct the problem before the bearing is wiped. Sampling from the reservoir would dilute the amount of tin to the extent that it could not be identified. The goal is to maximize data concentration, which can be achieved through live zone sampling as close to the bearing as possible, using primary and secondary sample points.

Utilize oil analysis laboratories to assist in installing sample points that should be on all new equipment with circulation systems. You should plan on installing the necessary valves on existing equipment when an outage is scheduled.

Finally, be sure to adhere to the following sampling guidelines:

  • Sample from live fluid zones.
  • Sample from turbulent zones such as elbows.
  • Sample downstream of bearings, gears, pumps, cylinders and actuators.
  • Sample machines during typical working conditions and at normal operating temperatures.

Avoid the following missteps in sampling:

  • Don’t sample from dead pipe legs or hoses.
  • Don’t sample from laminar zones.
  • Don’t sample after filters or from sumps.
  • Don’t sample when machine is cold or not operating.

 

0307_collecting_data_img4Static (reservoir) sampling 
Many samples are taken in static systems by sampling from an oil reservoir. Here, again, it is important to sample from the correct location with the proper procedures. The most common technique is to use a vacuum gun and plastic tubing as illustrated is Fig. 3.

0307_collecting_data_img6

The sample needs to be drawn from the same point every time—as close to the middle of the reservoir near the return line. A good way to do this is to wrap a plastic collecting tube around a steel rod, as shown by the layouts in Fig. 4. To avoid contamination problems, use a new tube for every sample.

0307_collecting_data_img7

A better technique for static (reservoir) sampling is to permantly install a sample tube. Pitot tubes, as shown in Fig. 5, are the best alternative when static sampling. The ideal location is near the return line. In a hydraulic reservoir with baffles, the pitot tube should never be placed after the baffle toward the suction line.

Flushing/bottle cleanliness
Whenever a sample is taken, the lines carrying the fluid must be flushed properly. A minimum of five times the volume line is recommended. As a general rule of thumb, with a 4-ounce sample bottle, use the following procedure, which is courtesy MRT Laboratories.

1/4″ SS tubing = 3/4 bottle/ft of sample line 3/8″ SS tubing = 1 bottle/ft of sample line 1/2″ SS tubing = 2 bottles/ft of sample line

When using carbon steel double the above volumes.

Bottle cleanliness is very important when collecting samples for particle counts. Two types of bottles are used for oil analysis as illustrated in Fig. 6.

The frosted bottle will handle hotter fluids, but the clear PET allows you to see the fluid more clearly. Neither bottle is clean enough when low ISO cleanliness numbers are being measured. Specialized bottles need to be purchased depending on degree of cleanliness required. The following are the bottle cleanliness requirements:

0307_collecting_data_img8

  • Clean maximum 100 particles/ml > 10 micron
  • Super Clean maximum 10 particles/ml > 10 micron
  • Ultra Clean maximum 1 particle/ml > 10 micron

Sample frequency
The most important factor in setting sampling intervals is the criticality of the equipment. For example, there actually are situations where equipment is sampled weekly. Most critical equipment is sampled monthly. The more data points that are available, the better the trend analysis in determining equipment condition. Table II should serve as general guidelines in selecting the correct sampling frequency.

Conclusion
Oil analysis is a critical part of any predictive maintenance program and sampling is a critical component of any oil analysis program.

Consistency in collecting samples is critical to obtaining good data. The same person should collect the sample from the same location every time.

Samples should be labeled properly and sent as soon as possible to the oil analysis laboratory. Training in collecting oil samples is available from oil analysis laboratories and should be utilized.

Never forget that your data is only as good as the person who collects it and your reliability program is only as good as your oil analysis program. It would be better to have no data than to have bad data. That’s because bad data could encourage you to take incorrect action with your equipment.

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March 1, 2007
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Justify Your Equipment Reliability Enhancements

0307_equipment_reliability_img1Mechanical seal optimization and rolling element bearing selection are critical issues for any plant. In this installment, we review case studies and associated cost justifications to learn how making the right decisions regarding these components can pay off. Each of these case studies is thoroughly experience-based—and the upgrades they describe are easy to implement, even on a tight budget.

Bearing housing seal opportunities
Most rolling-element bearings fail to reach their predicted theoretical L-10 life. One of the primary reasons for this life curtailment is contamination of the lubricant. Past practice for protecting bearings from contamination has included the use of lip seals and stationary labyrinth-type seals. These solutions, however, can suffer from short life or simply fail to exclude atmospheric contaminants.

Rotating labyrinth seals represent newer technology. Yet, by definition, even they will always have an airgap—although the airgap dimension varies with design and seal size. Therefore, rotating labyrinth seals will not preclude (at least some) air interchange. In contrast, and like mechanical seals, certain facetype bearing protector seals will prevent this air interchange entirely.

Suppose a facility had identified certain centrifugal pumps that suffered from disappointing bearing life and that these pumps were installed in a contamination- prone environment. It is not difficult to imagine bearings adjacent to steam quench injection points near mechanical seals, or in mining pumps or in areas experiencing sandstorms to be at risk here. Moreover, given source data published in Ref. 1, it is more than reasonable to anticipate a two-fold increase in bearing life with hermetically sealed bearing housings.

0307_equipment_reliability_img2The term “hermetic sealing” is used to indicate no ingress of the ambient environment and no egress of the medium contained in the device or assembly so sealed. Modern mechanical seal technology has led to the development of dual-face magnetic seals (Fig. 1) that can quasi-hermetically (i.e. minimum leakage) seal pump bearing housings, gearboxes and other rotating equipment. Dual-face magnetic seals protect the lubricant and bearings by completely excluding contaminants. With quasi-hermetic seals in place, it is now possible to cost-justify the use of superior synthetic lubricants, and in fact, lower the total cost of operating equipment.

Progressive, reliability-focused equipment users who seek to improve the profitability of their operations employ Life-Cycle Costing (LCC), the conscientious application of which can help operations minimize waste. In the case of dual-face magnetic bearing housing seals applied to gear speed reducers and similar equipment, LCC often will show dramatic savings in operating and maintenance costs.

One of the simplest and most straightforward ways to assess the benefits of dual-face magnetic seals over sealing methods that allow an infl ux of atmospheric contaminants would be to look at a plant’s projected pump failure frequencies and repair costs. The cost of a set of dual-face magnetic seals would be more than offset by the avoidance of a number of bearing-related pump failure incidents. In virtually all cases so examined, upgrading to dual-face magnetic seals will show payback periods of less than six months. As explained
below, using a conservatively projected five-year life for dual-face magnetic bearing housing seals indicates a 16:1 payback.

More elaborate and more precise benefit-to-cost calculations are available and could take many forms. Only one of these, labeled a simplified benefit-tocost calculation, is given here (Ref. 1). It relates to a centrifugal pump that was originally equipped with lip seals (being replaced once per year) and now is being upgraded to five-year life dual-face magnetic seals. The five-year results are shown in Table I.

0307_equipment_reliability_img3

Again, the calculation in Table I covers a five-year life for hermetic sealing with dual-face magnetic seals. As shown, an incremental expenditure of ($640-$70) = $ 570 for dual-face magnetic bearing housing seals would return ($16,138-$5,084) = $11,054 over a five-year period. The payback would be approximately 19:1.

Compared against any other means of sealing, i.e. housing seals that would allow “breathing” (ambient air interchanges), dual-faced magnetic seals win. The potential benefits might favor dual-face magnetic seals even more if a plant were to opt not to replace its lip seals every year. In other words, not replacing lip seals would likely result in more bearing replacements or even total pump overhauls—and in certain cases, unit downtime costs. Likewise, it is noteworthy that studies with lip seals on centrifugal pumps being replaced twice every year show cost breakdowns that again favor dual-face magnetic seals—and do so by greater margins.

Lubricant pump-around (“circulating oil”) opportunities
The best example of a reliability-focused company is one that views every maintenance event as an opportunity to upgrade. The following enhancement case history is actually a hypothetical example of how, upon experiencing failure of oil ring lubricated pillow block bearings, a reliability-focused user would take steps to greatly reduce the risk of future bearing failures. Once a failure event occurs, this reliability-focused user would have a staff member (or staff members) who could immediately and authoritatively determine that upgrading is feasible and cost-justified.

Reliability engineers at such a facility would know that, according to findings published by several prominent bearing manufacturers, jet oil lubrication— as shown in the catalogs of all major bearing manufacturers—is considered the best possible method of applying lubricating oil to rolling element bearings.

0307_equipment_reliability_img4

Jet oil lubrication is unexcelled for rolling element bearings operating at high speeds and heavy loads. The oil jet is directed at the space between the outside diameter of the bearing inner ring and the bore of the cage. For extremely high speeds, means for scavenging the oil should be provided on both sides of the bearing. The oil system may be used to assure free axial fl otation of the bearing cartridge in the housing on a thin pressurized oil film. If axial fl otation is desired, a clearance of 0.001″ (0.025 mm) between the housing and the cartridge is recommended.

A pressurization source is required for the oil, however. Although circulating oil systems can economically provide this pressurization for large pumps, the economics do not favor full-fl edged circulating systems for smaller pumps. This is where small auxiliary gear pumps or inductive pumps merit consideration.

While high-velocity oil jets might be an option in some services, applications with large, heavily loaded, high-speed bearings operating at high temperatures actually may demand their use. In such cases, applying several jets on both sides of the bearing provides more uniform cooling and minimizes the danger of complete lubrication loss from plugging. The oil jet should be directed at the opening between the cage bore and inner ring’s outside diameter (O.D.). Again this is illustrated in the literature of virtually all bearing manufacturers. Adequate scavenging drains must be provided to prevent churning of excess oil after the oil has passed through the bearing. In special cases, scavenging may be required on both sides of the bearing.

Small auxiliary pumps used for jet-oil delivery. . .
Until recently, only large-scale oil mist systems were economically attractive, although smaller units are now available for a variety of stand-alone applications. Where the overall economics or unavailability of compressed air preclude oil mist, jet-oil spray systems are the best solution. As just one of many examples, a novel inductive pump in oil spray units would make this technically advantageous lubricant application method inexpensive, virtually maintenance-free and, thus, highly attractive.

Inductive pumps use electromagnetic force to drive a completely encapsulated internal piston, creating positive piston displacement within a sleeved cylinder. By using one-way check valves, both ends of the piston can be used for simultaneous suction and pumping. Since each stroke displaces a fixed volume, any increment of this volume can be delivered with a high degree of accuracy. One of several small auxiliary pump styles and sizes obtainable in the marketplace today (Ref. 2) can easily pressurize lubricant taken from the bottom of the sump to appropriate spray pressures. Lubricant rates are adjustable from 30 ml/min to 1.5 gpm (~ 6 l/min). Weighing a scant 14 lbs (~6 kg), the 3.25×9.5×4 inch (approximately 83x241x100 mm) unit can be combined with an automotive spin-on filter and an industrial spray nozzle connected to a length of fl exible tubing. Taking suction from the bottom of the bearing housing oil sump, a simple inductive pump is among those that represent a highly effective pump-around system.

Consider a user having to deal with a situation where large pillow block bearings support the shaft of an overhung blower impeller. This could well be a situation where the oil ring option described earlier in this cost justification example might be judged a reliability risk—and where objections might be raised to a conventional continuous lubrication oil system purely on economic grounds. Table II refl ects an estimated incremental cost basis to justify an attractive solution using an inductive pump.

As a result of this analysis, it can be shown that an inductive pump installation would win out on economic grounds and would be technically superior to an oil application strategy depending on oil rings.

References

  1. Bloch, Heinz P. and Alan Budris; (2nd Edition, 2006) Pump User’s Handbook: Life Extension, The Fairmont Press, Inc., Lilburn, GA 30047, ISBN 0-88173-517-5
  2. Technical literature, Inductive Pumps, Inc., www.inductivepump.com

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March 1, 2007
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Lubrication Management & Technology News

LEADERSHIP CHANGE FOR LUBRIZOL ADDITIVES

Val Pakis, who recently served as president and CEO of D.A. Stuart Company, will rejoin Lubrizol as vice president, driveline and industrial additives. In this role, he will focus on continued organic growth, as well as merger and acquisition activity. He also will be responsible for the equipment manufacturer liaison group. Before joining D.A. Stuart in 2000, Pakis had worked at Lubrizol for 20 years in a variety of commercial roles.

APPLICATIONS AVAILABLE FOR NAME AWARD

Applications for the North American Maintenance Excellence (NAME) Award for 2007 are now available for download from the NAME Award Web site (www.nameaward. com), according to the Foundation for Industrial Maintenance Excellence (FIME), administrator of the award. Each year, the award board of directors revises the application as part of its continuous improvement efforts and updates information to keep it current with accepted best practices, reports Richard L. Dunn, FIME executive director.

The 2007 application includes a totally revised section on maintenance storerooms and materials management. This area of maintenance program management has traditionally been a hurdle for maintenance managers, according to Dunn. “Our 2007 revisions should help applicants better understand what constitutes excellence in this important area,” he says.

Long regarded as the most prestigious recognition for industrial maintenance practitioners, the NAME Award program also is an important learning tool for any plant striving for maintenance excellence. “The application requires a plant to conduct a thorough self-audit of its maintenance programs and processes,” Dunn says. “Just completing the application is an important learning experience. And it encourages the maintenance department to reach out to other departments in a cooperative effort. Maintenance people seldom have all the requested information themselves.”

Another benefit to submitting an application for the award is that each applicant receives feedback from the board of directors. “Each application is reviewed question by question by the board of directors,” Dunn explains. “The results of this review are then reported back to each applicant in the form of identified strengths and opportunities as well as important benchmark data. For the $1000 application fee, a maintenance operation can receive a report that would cost many times that amount from a consultant.”

“The NAME Award program isn’t just about winning an impressive trophy,” Dunn says. “It’s more about encouraging best practices in maintenance. We’ve had plants apply several times and never receive the award, but they used the application and our feedback to help them set their agendas for improvement. It was gratifying to us to see how their operations improved from one year to the next,” Dunn says.

Applications for the award are due June 30 each year. The FIME board of directors reviews each one and determines which, if any, qualify as finalists. Each finalist is offered the opportunity for a site visit, which comprises a three or four-day audit by three or four members of the board. The results of the site visit are reported back to the board of directors, who then determine which sites should be honored.

The number of awards presented depends solely on the qualifications of the applying plants–as many as three awards have been presented in a single year. Winners receive extensive feedback and benchmarking information and are invited to serve on the board of directors. The Foundation for Industrial Maintenance Excellence is a not-for-profit group of volunteers comprised of previous NAME Award winners and other knowledgeable maintenance practitioners.

For more information, visit www.nameaward.com or e-mail dunncomm@comcast.net

SMRP LAUNCHES JOINT METRICS EFFORT WITH EUROPEANS

The Society for Maintenance & Reliability Professionals (SMRP) and the European Federation of National Maintenance Societies (EFNMS) have launched a joint activity to compare and document existing indicators for maintenance and reliability performance. This will help maintenance managers understand the indicators and their definitions.

SMRP has defined a number of Best Practice Metrics to measure maintenance performance. The process is ongoing, and metrics are publicly available at www.smrp.org. In 2000, EFNMS defined a set of indicators to measure maintenance performance (see www.efnms.org.). These metrics are now incorporated in the European standard prEN 15341 “Maintenance Key Performance Indicators.” With the increased globalization and with companies acting globally, a common understanding of the indicators to measure maintenance and availability performance is paramount, and there is no doubt that this activity in a short period of time will play a part in a global standard for maintenance indicators. This is highlighted by the fact that COPIMAN (Technical Committee on Maintenance of the Pan American Federation of Engineering Societies) is joining the comparison effort.

The result of the activity will be a document pointing out the similarities and differences in the indicators. The document is in progress, and the first step has been taken to identify the similarities between the EN standard and the SMRP metrics.

For more information, log on to www.smrp.org

TIMKEN AND JOE GIBBS RACING EXTEND NASCAR AGREEMENT

The Timken Company has extended its agreement with Joe Gibbs Racing as an official technical partner of the NASCAR racing organization. Timken will provide product development and technical engineering across Joe Gibbs’ multiple team operations, including the Nextel Cup Series.

The Car of Tomorrow is a NASCAR initiative to improve driver safety, performance, competition and cost-management for the teams. Timken has worked collaboratively with the engineering team at Joe Gibbs Racing to develop and test technologies that improve the car’s powertrain and driveline performance, delivering longer life, improved fuel economy and higher horsepower availability.

“With the Car of Tomorrow design, NASCAR has given us defined parameters within which we can work,” says David Holden, research and development engineer at Joe Gibbs Racing. “That brings more parity to the sport, but it also poses tremendous design challenges for us in terms of loads, stiffness and weight. Fortunately, working with Timken engineers, we are able to accommodate some of those changing conditions and still field very competitive cars.”

COOPER BUSSMANN SPONSORS NASCAR CRAFTSMAN TRUCK

Cooper Bussmann is the new primary sponsor for the #63 NASCAR Craftsman Truck operated by the MB Motorsports race team. This is the first NASCAR Craftsman Truck Series sponsorship for the St. Louis-based corporation. Cooper Bussmann will run a limited number of races, including Dover, Indianapolis, St. Louis, Atlanta and Homestead-Miami.

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Passing The Torch

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Ken Bannister, Contributing Editor

The acquisition and dissemination of knowledge is truly a noble pursuit. I submit the following account of one of my own personal experiences as an example.

I recently was privileged to participate in a very special metal-shaping course with my son. Delivered over several weekends, the sessions introduced us to the world of metal shaping and its mysterious “English Wheel.” (This piece of equipment is known in England as a “raising machine” because it stretches and raises metal into smooth, sensuous, curved shapes.)

During the course, I opted to fabricate a 1/3- size “boat tail” speedster-styled rear fender with multiple compound curves and welds. Incorporating a wheel well sized appropriately to accommodate a clock, it would be, I thought, a unique wall decoration for my shop.

John, our instructor, was a retired metal craftsman in his late 70s, who taught us how to cut, hammer, shape, weld and roll lifeless pieces of steel into metal objects we could be proud of. More importantly, he managed to pass on enough basic skills, tricks of the trade and understanding of hand-tool and English-wheel metal shaping for us to produce, in just a matter of hours, a level of craftsmanship that would have taken him two years of apprenticing to achieve.

During our conversations, John cited his concern over the withering of the maintenance gene pool and today’s “throw-away” society that could care less about his beloved English Wheel. Those, he told us, were the main reasons prompting him to pass on his metal-shaping secrets.

Today’s news is full of forced early retirements in which the most senior of skill sets belonging to job specialists, tradespersons and skilled craftspeople are being erased forever. Unfortunately, many such layoffs are knee-jerk reactions to loss of market share and failing balance sheets that force the highest labor expense out of the door along with the experience and knowledge.

Faced with such a decision, a company often does not exercise good decision-making when it comes to succession planning. As a result, huge voids are created in the company’s asset management capabilities.

One of my a recent consulting assignments involved an automotive assembly plant that cut back its two senior lubrication technicians—and did so without giving any succession training to the remaining junior technician. Five power and free conveyor automatic lubrication systems, dispensing expensive high-temp moly chain oil, ran dry and lost their prime. In an effort to keep the chains lubricated, a junior oiler bypassed the autolubers by placing a drum with an open drip valve pouring oil directly on the chain. This situation went unchanged for over six months—resulting in a lubricant cost well into six figures! That was more than 20 times what it should have cost, all because the junior oiler was not shown what to do, nor did he ask what he should do.

This expensive situation could have been avoided had the company merely contracted with a retired senior lubrication technician to return the day after his retirement began for a short-duration project. Under this arrangement, he could have worked with the replacement staff to document simple—but vital—procedures, tricks and intimate equipment knowledge.

I challenge those of you close to retirement to assure your legacy by “passing the torch.” Work with management in devising a plan to share your knowledge with your successors. I further challenge those in junior positions to step up and ask for that torch. Finally, I challenge management to perform succession planning and create an environment in which the torch can be passed successfully. Our future depends on it. Good Luck!

Ken Bannister is lead partner & principal consultant for Engtech Industries, Inc. Phone: (519) 469-9173; e-mail: kbannister@engtechindustries.com

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Compressed air contamination…Air Dryer and Purification Technology

Knowing the true sources of contamination in compressed air systems and what to do about them can lead to improved operating efficiencies for the equipment and far fewer maintenance headaches for you.

Ask many maintenance engineers what the major contaminant in their compressed air system is, and their answer would be oil. Oil is perceived to be the greatest cause of contamination in these systems because it can be seen emanating from open drain points and exhaust valves. Most of the time, however, what may look like oil actually is oil condensate (oil mixed with water).

In reality, nearly 99.9% of the total liquid contamination found in a compressed air system is water, with oil being only a very small part of the overall problem. A small 100 cfm compressor and refrigeration dryer combination, operating for 4,000 hours in typical northeastern U.S. climate conditions, can produce approximately 2,200 gallons of liquid condensate per year- a staggering amount. Filter systems can remove oil and dust, but well maintained air dryers are required to remove water and adjust humidity levels.

Sources of contamination
Contaminants in the compressed air system generally can be attributed to:

  • The quality of the air drawn into the compressor
  • The operation of the air compressor
  • Compressed air storage devices and distribution systems

Air quality…
Air compressors draw in large amounts of air from the surrounding atmosphere that contains a large number of airborne contaminants, including atmospheric dirt, micro-organisms, oil vapor and water.

In an industrial environment, there are 140 to 150 million particles of dirt in every cubic yard of air. Eighty percent of these particles are too small to be captured by compressor intake filters. Consequently, they pass directly into the compressed air system.

Bacteria and viruses also are brought into the compressed air system. The warm, moist air provides an ideal environment for the growth of micro-organisms. Ambient air typically contains up to 3,850 micro-organisms per cubic yard. If only a few of these bacteria or viruses enter a sterile process or clean production system, enormous damage could result, diminishing product quality or even rendering a product unfit for use and subject to recall.

Air also contains oil in the form of unburned hydrocarbons that are drawn into the compressor intake, as well as vaporized oil from the compression stage of a lubricated compressor. When these vapors cool and condense, they cause the same contamination issues as liquid oil.

Water vapor, condensed water and water aerosols from the atmosphere can wreak havoc on a compressed air system. The air’s ability to hold water vapor is dependent upon its temperature. As the temperature increases, the level of water vapor that is held by the air increases. It takes 7.8 cubic feet of free air to generate 1 cubic foot of compressed air @ 100 PGSI. During compression, air temperature is increased significantly, which allows the air to easily retain incoming moisture. Significant amounts of water, as well as the other previously mentioned contaminants, enter the compressed air system without proper protection.

Air compressor operation…
The air compressor itself can add contamination, from wear and tear particles to coolants and lubricants. Rust and pipe scale can be found in air systems without adequate air dryer systems. Over time, this contamination breaks away and causes damage or blockage in production equipment and may also contaminate final products and processes.

0307_maintenancelog1Almost all air compressors use oil in the compression stage for sealing, lubrication and cooling. Some oil, in liquid or aerosol form, enters the compressed air system and mixes with water vapor, which can cause damage within the system. The amount of oil in the oil/water mixture accounts for less than 0.01% of the overall volume. But it is this resemblance to oil that leads to the mistaken belief that oil is the major contaminant in compressed air systems.

Storage and distribution…
After the compression stage in a system, air is typically cooled to a usable temperature, reducing the air’s ability to retain water vapor. A proportion of the water vapor condenses into liquid water and is removed by a drain fitted to the compressor after-cooler.

Additional condensation, however, occurs in the compressed air system because the air continues to be cooled by the air receiver, piping and the expansion of air in valves, cylinders, tools and machinery. 0307_maintenancelog2Condensed water and water aerosols can cause corrosion to the storage and distribution system, as well as damage to production machinery and an application’s end products. Liquid water also can wash away prelubricants on cylinders and valves, decreasing their operational life. Furthermore, water in a compressed air system reduces production efficiency and increases maintenance costs. Removing liquid water and water vapor from such a system helps ensure that it runs properly and efficiently.

Purification technology overview
Coalescing filters are probably the most important purification equipment in a compressed air system. They are designed to remove aerosols (droplets) of water and oil using mechanical filtration techniques. Coalescing filters have the additional benefit of removing solid particulate to very low levels (as small as 0.01 micron in size). To be effective, they should be installed in pairs. Both filters perform the same function, with the first-a general-purpose filter-used to protect the second-a high-efficiency filter-from bulk contamination. This dual filter installation ensures a continuous supply of high-quality compressed air with low operational costs and minimal maintenance requirements.

0307_maintenancelog3The next component in the compressed air system is the air dryer. Properly maintained air dryers remove moisture from the compressed air system, eliminating condensation in the system’s piping, pneumatic tools and instruments. There are two basic types of air dryers: refrigeration and adsorption (desiccant). A dryer’s efficiency is measured as the dew point, which is the level of dryness in a compressed air system.

Refrigeration dryers (such as the one shown in Fig. 1) cool air to a pressure dew point of 35 F, which is the effective limit on this type of dryer because water freezes at 32 F. This style of dryer is ideal for general industrial applications in light assembly, including those that use air motors, air tools, valves, cylinders and rotary actuators, painting and welding equipment, to name a few. Refrigeration dryers are not suitable for installations where piping is installed in ambient temperatures below the dryer dew point (i.e., systems with outside piping).

Adsorption (desiccant) dryers (like those shown in Fig. 2) pass the air over a regenerative adsorbent material that strips the moisture from the air. These types of dryers are extremely efficient and can provide a pressure dew point as low as -100 F, with a typical range of -40 F. Desiccant dryers remove liquid from the compressed air system through the use of chemical beds. They often are used in cold-weather pneumatic applications, such as mining, agriculture, utilities, pulp and paper and transportation.

It should be noted that refrigeration and adsorption dryers are designed for the removal of water vapor, NOT water in liquid form. To work efficiently, air dryers require the use of coalescing filters installed in front of them in the compressed air system.

Other types of filters include:

  • Adsorption filters-Oil vapor passes through a coalescing filter just as easily as compressed air. These filters, which provide a bed of activated carbon adsorbent, remove oil vapors and provide protection against oil contamination.
  • Dust removal filters-These are used to remove particulates when no liquid is present. They perform to the same level as the system’s coalescing filters.
  • Microbiological (sterile) filters-A sieve retention or membrane filter removes solid particulates and micro-organisms. These filters are often referred to as sterile air filters because they provide sterilized compressed air.

Maintaining compressed air systems To achieve the stringent air quality levels required for today’s production facilities, a compressed air maintenance system must be employed. Air-treatment maintenance should address the complete compressed air system. It is highly recommended that compressed air be treated to a quality level suitable for protecting air receivers and distribution piping prior to entering the distribution system. Maintenance programs should be tailored to the type of compressed air system, size of connecting lines, water capacity, flow capacity (system size), filtration capability, construction material of air dryers (i.e., steel or copper) and safe working pressures. Evaluation of each factor helps ensure proper and economical compressed air system operation. Low-pressure dew points derived from proper maintenance of air dryers and other purification technologies help to prevent corrosion and inhibit the growth of micro-organisms within the compressed air system. Well-maintained air dryers and purification components also help minimize pressure loss in the air system, a major contributor to operational costs, thus reducing energy consumption. Finally, air dryers that are maintained properly have a longer life cycle, reducing production downtime, while contributing to increased output and profitability.

Mark White is a product manager with domnick hunter Ltd., a division of Parker Hannifin. Rick Hand is FRL product manager with Parker Hannifin Corporation. For more information, e-mail: mark.white@parker.com or rhand@parker.com

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March 1, 2007
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The Maintenance/Purchasing Partnership

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Ken Bannister, Contributing Editor

Because of its use of consumable products and need for replacement maintenance repair and overhaul (MRO) inventory items, the Maintenance department must requisition and contract through the Purchasing department on a daily basis. If equipment reliability is to be assured, the direct working relationship between these departments must be a good one built on an understanding of each other’s mandate and clear lines of communication.

The approach toward procuring purchased items varies greatly from organization to organization. Large ones will often support a selfregulated purchasing group; medium to small organizations may rely on Maintenance to perform shared purchasing/expediting duties with a single buyer-or even relinquish all purchasing duties to a contracted third-party inventory-management company. Regardless of the approach, building a workable Maintenance/Purchasing relationship will depend greatly on how well the following types of complaints are managed.

Examining typical complaints from the perspective of both partners leads to the formulation of a workable approach that allows Maintenance to focus on delivering equipment availability and reliability, and Purchasing to focus on procuring products that deliver the best value for the least amount of expenditure.

Typical Complaints #1
Maintenance: “Purchasing never recognizes the urgency of our purchasing needs, requiring us to take our own measures to ensure the part gets here fast enough, especially on a breakdown job when the line is down and we need the parts here now!” Purchasing: “Maintenance always is trying to side-step the procurement process and expedite parts behind our back, often agreeing to outrageous delivery costs to get things here faster.”

Solution…
Unfortunately, many Maintenance organizations are still purchasing items as a direct result of reactive situations. Maintenance departments that actively engage in proactive maintenance strategies (preventive, predictive, condition-based) linked to the planning and scheduling of maintenance events are better able to provide Purchasing with enough lead-time fl exibility to procure the part with the best delivery option (no more expensive air freight or taxi delivery charges).

Clearly defining the role(s) of each department (Maintenance/Purchasing) allows any size organization to map out the procurement business process specific to the organization, as well as set up clear levels of responsibility. Using a template similar to that shown in Fig. 1, both departments meet to discuss which department is best suited to take on what role based on expediency and ability to perform the role. With roles decided, the workfl ow is now diagrammatically mapped indicating the responsible department for each action. This enables both departments to follow a structured approach and commence working trust in one another.

Typical Complaints #2
Maintenance: “Purchasing always buys the cheapest product or service it can find.” Purchasing: “Maintenance doesn’t understand that we have a mandate to continuously reduce purchasing costs.”

Solution…
Establishing MRO-item purchasing programs based on Life-Cycle Costing (LCC) is paramount for reducing downtime costs, equipment repair costs and procurement costs. An LCC program begins with both departments understanding the fundamental difference between price and cost.

When purchasing a replacement MRO item, price is the money paid to receive a quality item FOB (Freight On Board) at your plant, through regular shipping methods.

Cost is attributed to the equation when additional money is spent without value, as depicted in the following scenarios:

0307_communications1

  • Price plus additional money for emergency shipping
  • Price plus additional money spent to administer and wait for the return of defective, inferior quality items
  • Price plus additional money spent for accelerated replacement and incurred downtime costs of less expensive, inferior quality items (lower cost items with lower Mean Time Between Failure [MTBF] life-cycle reliability ratings)

Purchasing the least expensive item may make sense initially when buying on price alone, as indicated in the Fig. 2 examples. Product A, priced at $10, is twice the price of the $5 Product B. Purchasing Product B over A gains an immediate 50% price saving.

However, taking life-cycle expectancy into account changes the scenario considerably.

Product A has a life expectancy of three years, whereas Product B is a lower-quality manufactured part with an expected life expectancy of only one year. Over a three-year period, Product B is changed out three times compared to Product A, which actually increases the purchase price by 50% over the life-cycle of the more expensive part (1 x $10 expenditure vs. 3 x $5 [$15] expenditure).

Furthermore, purchasing the lower-quality Product B incurs two more sets of additional costs associated with downtime of the equipment, maintenance replacement costs, purchasing administration costs, work order administration costs and inventory management costs over the life cycle of Product A.

Working together to understand and make buying decisions based on Life-Cycle Costing dramatically reduces operations, maintenance and purchasing costs.

0307_communications2

Typical complaints #3
Maintenance: “Purchasing never seems to purchase the right part.”

Purchasing:Maintenance never gives us the correct information to order in the correct part.”
Solution… Once again, clear lines of communication are vital to attaining mutually desired outcomes. Setting up a minimum information requirement for the purchase requisition, preceded by a detailed part specification standard, as outlined in the Fig. 1 template, will significantly reduce the chances of an incorrect part purchase.

Typical complaints #4
Maintenance: “We always get blamed for downtime.”
Purchasing: “Downtime is not a purchasing problem.”

Solution…
Downtime is everybody’s problem. This becomes more apparent when a Value Stream Map is created for the organization depicting intra-department input/output relationships. Taking a facilitated approach, both Maintenance and Purchasing must work together to become consistent in their methods of procuring and using parts. We already have seen that purchasing parts based on LCC can signifi- cantly reduce downtime-something that is brought about through understanding and collaboration between Maintenance and Purchasing. Other collaborative acts resulting in cost reduction can include:

  • Initiating a preferred vendor or supplier program based on quality products, service, delivery and reasonable pricing policy
  • Developing a parts specification book based on existing preferred parts and vendors that have historically shown good life-cycle tendencies
  • Involving Purchasing in Maintenance planning and scheduling meetings

Purchasing is a very important part of your equipment maintenance process. Thus, it is well worth the investment to create a cooperative environment between your Maintenance and Purchasing groups.

Ken Bannister is lead partner and principal consultant for Engtech Industries, Inc. Telephone: (519) 469-9173; e-mail: kbannister@engtechindustries.com

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