Archive | July, 2007

358

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July 1, 2007
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Part II: Introduction To Synthetic Lubricants & Their Applications

Part II: Selection

Improved equipment operation and energy savings are two welcome benefits associated with the selection of the correct synthetic for the job.

All synthetics are not alike. Selection should be based on the optimum base stock type for the application. The additive system, which also is very important, imparts unique properties to the finished synthetic lubricant. As a result, there can be major differences in performance for the same synthetic type from different suppliers. Case histories and actual field tests are the best way to select a particular synthetic fluid. There are many applications where mineral oils, because of their cost and performance, are perfectly acceptable. Synthetics are problem solvers to be used in applications where their unique properties are cost-justified under the following conditions:

  • Temperature Extremes—Since synthetics contain no wax they are used at very low temperature conditions. ISO 32 PAO and ISO 32 diesters have pour points > -50 F. They also are effective at temperatures well above 200 F, whereas mineral oils should be limited to a maximum of 200 F and synthetics should be considered at temperatures as low as 180 F.
  • Lower Wear—In general, synthetics provide much higher film strength and lubricity than mineral oils, especially in a high-sliding environment that occurs in worm and hypoid gears.
  • Energy Savings—Some synthetics have low coefficients of friction because of their uniform molecular structure, resulting in significant energy savings in many applications.

0707_formulations_img1Properties & applications of synthetics

Table I illustrates the most common synthetics and their major applications.

Polyalphaolefins (PAO)…
If only one synthetic could be selected in a plant, it would be a PAO. These are the most versatile and most widely used synthetics. They operate over a very wide temperature range, can be produced in a wide viscosity range without changing their basic properties and are compatible with most other lubricant types. Because of their nonpolarity, they have poor additive solubility and cause slight seal shrinkage. Consequently, they must be blended with a polar synthetic such as an ester, which swells seals and gives good additive solubility.

Some of the more common uses for PAOs include:

  • Hot and heavily loaded gear boxes: an EP PAO is used for helical and herringbone gears, while a non-EP ISO 460 is commonly used for worm gears.
  • Rotary screw air compressors: PAOs and polyalkylene glycols (PAGs) are the two most commonly used air compressor oils for extended life service.
  • ISO 68 PAO is used in oil mist lubrication of rolling element pump and motor bearings.
  • PAOs have H1 approval in food plants and are used in a wide range of applications.
  • PAOs are not recommended for high-temperature reciprocating compressors because they can form hard deposits on exhaust valves, thus not allowing them to seat properly.

Diesters…
Diesters are one of the oldest synthetic types—and they are limited in the viscosity ranges produced. The most common ISO VGs are 32, 46, 68, 100 and 150. The viscosity indexes are only high for the ISO 32 while the others are in the 70-100 range, depending on the alcohol and acid used in their manufacture.

The major performance strength for diesters is their excellent solvency minimizing deposit formation. They also have good low-temperature properties and high thermal stability and flash point.

Diesters have a low aniline number and a tendency to swell elastomeric seals. Therefore, resistant seals, such as DuPont Viton, need to be used. Diesters also can hydrolyze in a hot, high-moisture environment—something that
occurs in rotary screw air compressors.

Uses for diesters include:

  • Major application in severe duty reciprocating air and hydrocarbon compressors: diesters’ high thermal stability and excellent solvency will prevent carbon buildup on exhaust valves.
  • The synthetic of choice in air compressors many years ago: diesters are still used, but to a limited extent because of their potential for hydrolyzation. They are blended with mineral oils to form partial synthetics used in air compression and with PAGs for air compression.
  • Diesters are used extensively both in the ISO 68 and 100 viscosity grades for oil mist lubrication of rolling element pump and motor bearings.

Polyol Esters (POE)…
POEs have very high thermal stability allowing them to be used in a very high temperature environment. They also are fire resistant with high flash- and fire-point temperatures. Because they are readily biodegradable, they can be used as hydraulic fluids in environmentally sensitive areas.

The major disadvantage of POEs is their cost. They are 50% more expensive than PAOs, PAGs and diesters. Although they have a tendency to hydrolyze at hightemperature and high-moisture conditions, POEs are more stable than diesters.

Primary uses for POEs include:

  • Aviation and industrial gas turbine applications where the effective operating range is -40 F to 400+ F, with primary viscosity ~27cSt.
  • Extended life fluid for air compressors: rated >12,000 hours and stable at temperatures of 240 F, which is higher than the maximum temperature allowable in a rotary screw air compressor.
  • Fire-resistant hydraulic fluid for underground mining, steel mills and foundries: Factory Mutual approved and MSHA certified; flash point for ISO VG 46 > 510 F and fire point >680 F.
  • Environmentally friendly hydraulic fluids that are readily biodegradable and contain ashless antiwear additives.

Polyalkylene glycols (PAG)…
As discussed in the first article in this series, PAGs are quite versatile. They can be designed to produce a wide variation in water solubility by adjusting the ratio of ethylene and propylene oxide during manufacturing. They have very high viscosity indexes exceeding 250, as well as excellent polarity for metal surfaces that gives them good lubricity. PAGS don’t produce deposits and can be designed to minimize hydrocarbon gas solubility. Their major weakness is compatibility with hydrocarbon lubricants like mineral oils and PAOs. They also shrink many elastomeric seals and attack certain paint types.

Some primary uses for PAGs include:

  • Rotary screw and centrifugal air compressors
  • Enclosed gear boxes in particular worm gears
  • Fire-resistant hydraulic fluids
  • Food grade products ISO VG 150 and higher needing H1 approval
  • Hydrocarbon-flooded rotary screw compressors
  • High-pressure ethylene compressors in HDPE production

Applications
This following list highlights several applications where synthetics provide major cost justifications. Many more applications could have been presented:

  • Air Compressors
    • Rotary Screw
    • Reciprocating
  • Hydrocarbon Compressors
    • Rotary Screw
    • Reciprocating
  • Enclosed Gear Boxes
    • Helical, Herringbone, and Spiral Bevel
    • Worm

Air compression
Rotary screw compressors…

Most of today’s industrial air compressors are rotary screws like that shown in Fig. 1.

0707_formulations_img3In a rotary screw compressor, air is compressed, high temperatures are generated and, along with the moisture that is present, a severe oxidative environment is present for oil. The lubricant in this equipment performs four major functions: cooling, lubricating (bearings, gears and screws), sealing and corrosion prevention. This requires an oxidatively stable lubricant with high VI and good lubricity. Many OEMs have their own fluids—which are mainly synthetics. As shown in Table II, the different lubricants used can be classified based on fluid life.

The expected hours shown in Table II are OEM recommendations on expected life. Depending on the conditions, synthetics may exceed these numbers if the temperature and moisture are lower than normal.

The most common fluids used for air compressors for extended service are ISO VG 46 PAO and PAG/Ester. The esters most commonly used with PAGs are diesters and POEs that swell seals to counteract shrinkage caused by PAG.

POE gives the longest life extension for the fluid and is being used for extendedwarranty applications. Some POEs on the RPVOT test, which is a measure of the oxidative stability of a fluid, give results in excess of 3000 minutes—that’s nearly double the results obtained with PAOs and PAGs. POEs can be used at temperatures up to 240+ F, which is above the shutdown temperature of an air compressor. PAO can handle temperatures up to 220 F and PAGs are lower at 200 F. PAGs have the added advantage of very high viscosity indexes that gives a thicker film at high temperatures which minimizes wear. Furthermore, they don’t form deposits at high temperatures when they oxidize.

Two major cost justification areas for the use of synthetics is in fluid life extension and energy savings. Consider the following case study.

An evaluation was performed on a 300 hp compressor with a 60-gal. sump capacity operating at 180 F. Running mineral oil required change-out every 1000 hours, while a PAO greatly exceeded the OEM recommendation of an 8000-hour change by running 15,000 hours. This resulted in a 67% savings—or more than $1700—in lubricant costs in one year. (Data courtesy of Dr. Ken Hope, Chevron Phillips.)

Energy savings can be significant with air compressors. A number of studies have shown savings between 3-5% with rotary screw compressors. Combining energy savings and longer fluid life, along with less wear and better operation, synthetics make sense for air compression applications.

0707_formulations_img4Reciprocating…
While reciprocating compressors (Fig. 2) are not used much in air compression today, there are still many old compressors working in the industry.

Because of high temperatures, the cylinder region in a reciprocating compressor is the most difficult area to lubricate. One major problem associated with the use of mineral oils for this application is that they form hard deposits when they oxidize and coat the exhaust valves, thus keeping the valves from seating properly. As a result, hot gas is drawn back into the cylinder to be recompressed. This dangerous condition can lead to high heat generation and a possible fire.

The lubricant of choice for reciprocating compressor applications is an ISO 100 or 150 diester with excellent solvency. Fig. 3 shows two actual exhaust valves. The valve on the left had been running for six months on diester. The valve on the right had been running four months on mineral oil. The valve on diester continued to run with no coking, saving over $10,000 in valve replacement costs.

Hydrocarbon compression Rotary screw compressors…
Non-flooded rotary screw compressors running at temperatures below 180 F can use mineral oils without major problems. Users, however, may want to turn to a synthetic like a diester or a PAO for their energy-saving potential. Flooded screw compressors with hydrocarbon gas will quickly lose their viscosity with most mineral oils and synthetics because the gas dissolves in the lubricant, thus lowering the viscosity.

PAGs are the most resistant lubricant to hydrocarbon gas dilution and are recommended for flooded screw compressors. More resistant to dilution than mineral oils, PAGs will, however, be diluted to an extent with hydrocarbon gases, a fact that must be taken into consideration in selecting the initial viscosity to arrive at the correct viscosity at the operating temperature. PAGs have the added advantage of having very high VIs.

0707_formulations_img5Ethylene high-pressure reciprocating compressors…
PAGs are the lubricant of choice for high-pressure ethylene compressors because of their minimal dilution by hydrocarbon gas. The typical viscosity of PAGs used in this application is 270 cSt. The film integrity at a reasonable viscosity is maintained at very high pressures, leading to low lubricant consumption and very low wear rates.

Low-pressure hydrocarbon compressors…
Mineral oils at ISO VG at moderate temperatures have been used successfully. As conditions become more severe, though, synthetics need to be considered. Both PAGs and diesters are good alternatives. PAOs, however, are not recommended because of their tendency to form hard deposits when they oxidize.

Enclosed gearboxes Helical, herringbone and spiral bevel…
Gearboxes experience EHL lubrication through sliding and rolling motion. A key criterion in lubricating gear teeth is to have thick enough film for the high sliding and shock loads. In many cases, EP additives are effective as anti-scuffing agents and are used in many loaded gear reducers. Parallel and right angle shaft gears such as helical, herringbone and spiral bevel are lubricated normally with an ISO VG 220 with EP. Under abnormal conditions, such as high temperatures and high shock loads, an ISO VG PAO with EP is used. Although PAGs can be used, because of their incompatibility problems, PAOs are preferred. Energy savings are more difficult to attain with high-efficiency gears like helicals, herringbones and spiral bevels. Normally, synthetics have shown efficiency improvements of 3% or less. Therefore, the use of synthetics for these gears is not justified by energy savings alone. A better way to justify in these applications is to take into account how dramatically gear performance is improved under difficult load or temperature conditions when synthetics are used.

0707_formulations_img6Worm…
Worm gears (Fig. 4) are highly inefficient. They also are good candidates for synthetics. A worm gear is a right-angle gear with non-intersecting shafts. These units consist of a steel worm and a sacrificial bronze wheel. There is very little rolling motion. Most motion is sliding—which causes the high wear and high heat. Worm gears typically can run 90 F degrees or higher than ambient temperatures. Since EP additives can attack bronze, very few EP gear oils had been used in the past. The only alternative had been to use a compounded high-viscosity mineral gear oil—such as ISO 460—containing animal fat for lubricity to protect the teeth during boundary lubrication. These types of lubricants oxidized quickly at high temperatures and didn’t provide a high level of wear protection.

The two most popular synthetics used in worm applications today are ISO VG 460 PAO and PAG. Each will perform very well. Neither of these synthetics contain EP and they both provide a high film strength and score very high on the FZG test that measures scuffing of gear teeth at different load stages. Mobil SHC 634, which is an ISO 460 PAO with no EP, exceeds 13 stages, the highest level on the test. This results in very low wear rates and energy savings.

Efficiency savings in excess of 7% have been documented. Because of their lower traction coefficient (which is the internal friction in the lubricant) PAGs often provide higher efficiency savings—but PAOs do very well. Temperature drops with a synthetic can be 20-30 F degrees. While PAGs are more common in gearboxes in Europe, more are being used in the United States. A PAG, because of its greater energy efficiency, is a good choice for new gears and can be used on other gears only with the proper flushing procedures. Moreover, PAGs attack some paints. A safer choice to convert a worm gear from mineral to synthetic is to use a PAO.

The following is a case history of the conversion from mineral oil to PAO:

A major can manufacturer used double-enveloping worm gears with an average reduction ratio of 60:1. The company was using a compounded ISO 460 mineral oil. On average, the company was experiencing four gear failures per year, each costing an average of $12,500 to repair. Temperatures typically were 200 F—and in some cases got as high as 215 F. The mineral oil was replaced with an ISO 460 PAO and the failures were eliminated. In fact, to date, 18 months later, there still have been no failures in this equipment. In addition, the average temperature dropped across the worm gears by more than 20 F degrees.

Conclusion
Synthetics are real problem solvers. While they can work well and be cost justified, there are many applications where mineral oils will do just as well. Three applications where synthetics can improve equipment operation and provide major cost savings are air compressors, high-pressure and hot reciprocating compressors and worm gears.

Deciding which synthetic to use is very important. Each candidate will have advantages and disadvantages that need to be considered before a final decision is made.

Keep in mind that the same synthetic type from different manufacturers can give different results. Even though the base stocks may be similar, the additive package may impart different properties from one supplier to another. Make comparisons between the data sheets, but let your final decision rest on field performance. Look at case histories and, if possible, run a carefully controlled plant test where meaningful data can be collected. Even though this will not be possible in some cases, definite equipment improvements can still be observed without rigorous testing and data collection. Be sure to document this data. Since synthetics are more expensive than mineral-based oils, you will want to be very accurate in your cost justifications.

Acknowledgements
The author wishes to thank Tim Taylor of Summit and Dr. Martin Greaves of Dow Chemical for their assistance in the preparation of this article. LMT


Contributing editor Ray Thibault is based in Cypress (Houston), TX. An STLE-Certified Lubrication Specialist and Oil Monitoring Analyst, he conducts extensive training in a number of industries. E-mail: rlthibault@msn.com; or telephone: (281) 257-1526.

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2764

6:00 am
July 1, 2007
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The Fundamentals: How To Write An Effective PM Procedure

Follow these steps in developing the type of world-class document and process that provides real value throughout your operations.

If you want to change your current maintenance reality, you must begin with the basics. One of the cornerstones of a successful maintenance effort is the precise execution of thoughtful, well-written preventive maintenance (PM) procedures. There are several steps that must be followed to ensure that these procedures are as effective as possible.

Step #1: Assessment The first step in the development of an effective PM procedure is to determine the condition of the machine or machine center. You have to know where you are before you can decide where you want to go and how you intend to get there. If the machine is newer equipment, this evaluation should be fairly straightforward. If, however, you are dealing with equipment that has been in service for a period of time or has a history of unreliability, this assessment could be quite a lengthy undertaking. Still, it’s time to invest if you want to leave reactive maintenance behind.

The assessment portion of the project should begin with a thorough cleaning of the machine. Having a clean machine will make the remainder of the assessment process easier to complete. Just as importantly, the machine should be evaluated as it is being cleaned to determine if there are any cleanliness issues that may be leading to or masking failures. Examples of these conditions include build-up or residue on electric motors, excess grease on bearings or other moving parts, oil residue on or below components, damp hoses and accumulated residues that might be indicating or hiding deeper problems. Any discoveries of this nature should be noted so they aren’t overlooked when the PM is written. Machine maintenance is a field that revolves around surprisingly few basics—one of these is that a clean machine runs better and longer.

The work team for the assessment portion of the project should be made up of both Maintenance and Production personnel. These are the people who operate and maintain the machine. They are your experts, and that fact alone should be motivation enough to involve them in the PM development process. The issue of “ownership” is another important reason to include these people. If your hourly professionals are involved in the development of the PM at every step of the process, they will have a vested interest in the success of the finished product. After the cleaning is completed, the next step of the process is to conduct a comprehensive mechanical and electrical assessment. In this portion of the exercise, you are looking for what is going right, as well as for what is going wrong.

  • Fasteners should be checked for torque.
  • Drive belts, chains, sheaves and sprockets should be inspected for wear and alignment.
  • Hydraulic components should be observed for signs of leakage.
  • Pneumatic components should be assessed with ultrasonic equipment if you have it and for audible air leaks if you do not.
  • Bearings should be inspected for signs of lubrication issues.
  • Moving parts should be analyzed for wear. Overall machine alignment should be checked to the extent that you are able.

During this mechanical assessment, notations should be made of any condition that is found to be out of spec—whether you intend to repair it or not. This is also the time to update your bill of material for the machine. Think of these variances as messages from the machine about potential trouble areas. The machine is telling you where your maintenance procedures are adequate and where they are not.

Step #2: Documentation and analysis Once the assessment is complete, you will again need both Maintenance and Production personnel to proceed to the next step. You also will need the maintenance records of the machine, including any documentation on breakdowns or failures. If formal documentation of prior reliability issues is not available, you may need to rely on anecdotal evidence or employee memory. Additionally, you will need all owner’s manuals, drawings and installation documentation.

Once you have gathered the necessary team members and documentation, the task before you is to make a written list of every known machine failure that has occurred in the past, as well as every possible failure that the team can envision occurring in the future. Do not forget to include the potential failures that you discovered during the mechanical and electrical assessments of the machine. If these conditions had gone undiscovered, would they have eventually caused machine failure? This exercise is the first phase of a Failure Modes and Effects Analysis (FMEA)—and, perhaps, the most crucial part of the PM development process.

Conducting the FMEA can be a daunting task. Don’t let it scare you. Just remember that the idea is to try to document what has gone or can go wrong with a machine so that you can put a procedure in place to prevent it from happening again. (A good website to visit on the subject of FMEA development is http://www.isixsigma. com/tt/fmea/) There also are some common-sense tips that can help.

  • First, follow the flow of the work that the machine was designed to do. If you are dealing with a hydraulic system, follow the fluid. If you are looking at a widgetmaker, follow the widget.
  • Do not try to conduct the FMEA in small installments over time. You will lose your train of thought, as well as the brainstorming continuity that is necessary to successfully complete the task.
  • Once you have convened your team, arrange the work schedules so that this group can meet eight hours per day, every day, until the FMEA is finished and the PMs are written.
  • Finally, follow the “likelihoods” when you are listing causes. As an example, a bearing failure could have a cracked machine footing as a root cause, but unless you have seen some indication of structural issues during your machine assessment, there is a low likelihood that this condition is causing your machine to fail.

Incidentally, a failure should be defined as any time that a machine: (1) ceases to do whatever it was designed to do; (2) when you want it to do it; (3) at the rate you desire; (4) at the quality specification you require. This is a very important concept. If a machine has been designed to stamp 500 holes per hour and it can only manage 480 holes per hour, the machine is in failure mode—despite the fact that it is still running and producing product. Likewise, if the machine is managing to stamp 500 holes per hour, but 100 of them are in the wrong place, it is exhibiting a sign of failure.

Step #3: Writing your procedures
Once your FMEA is completed, it’s time for the PM procedures to be written. A good place to begin is by reviewing the owner’s manual and the supporting documents that were provided by the manufacturer when the machine was purchased. You want familiarize yourself with the functions the manufacturer suggests conducting and when. This is especially true if the equipment is a new and just being brought online. If that’s the case, following the manufacturer’s suggested procedures should keep you out of trouble until you develop some machine history of your own to evaluate. Keep in mind that the PM procedures and intervals suggested by an OEM are not in and of themselves the road to machine reliability. Each machine and machine installation is unique—and, manufacturers typically have not operated their products in real-world plant environments before supplying them to you. Most importantly, they have not operated them in your plant, with your personnel, at your rates of production. Thus, your reality will differ greatly from the manual. Through your evaluations and research, you have identified many potential failures that must be guarded against and many repetitive tasks that must be performed. Now you must decide the most effective schedule to complete the tasks.

In most cases, there will be a daily perfunctory or runtime inspection, a weekly mid-level inspection, a monthly major PM, as well as a series of regularly-scheduled procedures that will deal with overhauls, major replacements of wear parts, mandated inspections and the like. Regardless of the CMMS system that you have—or even if you do not have one—remember the following points when writing your PM procedures:

  • Keep it simple and short. You do not want to cut-and-paste your entire FMEA into your PM and print it out once a week with “Perform These Tasks” written across the top. Your millwright will be overwhelmed, and nothing will get done. Rather, the work should be divided into a series of shorter operations, optimally of no more than two hours in length. The millwright will experience a sense of accomplishment and an accompanying morale boost every time he completes one of these shorter pieces of work.
  • Keep it safe. The first language that the millwright encounters as he reads his PM document must refer to the safe performance of the task. Lockout/ tagout and PPE should be specified at this point.
  • Keep it logical. If you are checking bearings, check all of them. If you are checking drive belts, check all of them. Give the millwright the benefit of intuition by grouping similar functions and objects.
  • Solicit input. Construct your PM document so the information that must be recorded on it could only be derived by the actual completion of the PM. If your PM contains a series of check boxes, you will get a series of checks. How, though, would you know if the work were actually performed? If you ask for readings, temperatures and measurements, it will be much more likely that the work you have requested will be performed.
  • Build accountability into the document. To put it simply, when the millwright signs the document, he is signing that the work actually was done…that it was done correctly…that it was done according to specification. A good way to ensure conformity is to randomly assign a supervisor to view the work as it is performed or immediately thereafter. This is the standard you must hold, and your millwrights must understand that this is the level of accountability to which they are being held.

Getting where you want to go If you follow these steps detailed here, you will be on your way to a betterperforming and less-reactive process. Remember, however, that a written PM procedure is a living document. It will change over time based on the machine’s performance and the millwright’s inputs. While you may not get it exactly right the on the first cut, over time, a well-written PM procedure can evolve into a world-class document and process—one that will have transferability and application to the other machines in your operations.

Ray Atkins, CPMM, CMRP, is a veteran maintenance professional with 14 years experience in the lumber industry. He is based in Rome, GA, where he spent the last five years as maintenance superintendent at Temple-Inland’s Rome Lumber facility. He can be reached at raymondlatkins@aol.com

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2063

6:00 am
July 1, 2007
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The Fundamentals: Shaft Seals On Rotary Valves & Airlocks

When it comes to sealing solutions for your bulk handling systems, you may have more options than you thought.

Rotary valves and airlocks are fundamental components in bulk material handling systems. They serve to accurately meter product from storage into a process, as well as to isolate pressure differentials between storage and conveying systems.

The rotary valve is essentially a revolving door, on a horizontal instead of a vertical axis. Situated in the discharge opening of a silo, day bin or other vessel, the upward-facing, wedge-shaped “door” section is filled with process material by gravity. As the section rotates into the circular housing, excess material is scraped away, so that the wedge contains a controlled amount of material.

When the filled wedge section rotates to the opening at the bottom of the valve, a controlled amount of process material will drop into the receiving vessel (which could be a screw feeder or pneumatic conveying or packaging system). Varying the rotational speed of the valve, therefore, alters the rate of flow of material into the downstream system.

A rotary valve consistently delivers a specific amount of material at its discharge.

An airlock is a rotary valve whose vanes fit closely enough to its circular housing to maintain an airtight seal. The airlock then can maintain one pressure on its inlet side and a different pressure or vacuum on its discharge side. Thus, for example, pressure from a pneumatic conveying system on the inlet side of the airlock does not affect a loss-in-weight bagging system on the discharge side. Maintaining pressure differential and a precise quantity of material in each of a rotary valve’s wedge-shaped sections depends upon a tight, accurate fit between the vanes of the valve and the circular housing, and upon properlyfunctioning shaft seals. Both factors exert even greater influence over performance of an airlock.

Sealing options
Several different sealing options are available as standard equipment from different rotary valve and airlock OEMS. Some OEMS take the conventional, 3000-year-old packing and gland follower approach. Some use mid-20th century lip seals. Others incorporate latter-20th century quad seals. Several OEMs are beginning to investigate and use contemporary, contacting face seals. The selected sealing option is fitted into a shallow stuffing box, cast into the endplate of the valve, along with a bearing support.

Packing…
0707_fund_seals1Where packing is used, a simple gland follower is employed to compress the packing. Many different packing styles from many manufacturers are available. Such options include: ptfebased braiding for food grade and chemical environments; ex-foliated graphite yarns for high temperatures; various synthetic fibers braided with ptfe-yarns for abrasion resistance; and graphite braided with various synthetic fibers and or metal filaments to resist corrosion, extrusion and thermal degradation. Packing seals (see Fig. 1) can fail if not regularly attended, and the out-of-the-way locations of airlocks often make packing adjustment diffi- cult or impossible. Once dry product begins leaking between packing and the shaft, abrasive damage can quickly occur, eventually necessitating overhaul of the airlock. By the time leakage is noted, significant damage may have occurred, and any pressure differential across the airlock may have been compromised for a considerable time, sometimes allowing undesired variations in package fill levels.

Lip and quad seals…
0707_fund_seals2Lip seals (see Fig. 2) can lead to the same problems as packing. Lip seals and quad seals use the backup approach for maximizing runtime. By stacking several quad or lip seals in layers, leakage is delayed until the last row is compromised. The components function because the profile of the seal against a rotating shaft generates a vacuum condition at the internal seal location (process side) and a positive pressure on the external side of the lip. The vacuum keeps the process material in.

As the lip wears from contacting the shaft and interfacing with the process material, the vacuum condition degrades, requiring the next ring to seal. This continues through each lip or quad seal until the last seal point fails. All materials and lip configurations are not created equal and some degrade more quickly than others.

0707_fund_seals3Abrasive process material, fine particles and high temperatures are particularly challenging for both lip and quad seal types. The quad seal provides twice the number of contact points per ring (see Fig. 3). This also requires less compressive force against the shaft, resulting in less friction and better wear life. Also, various other lip seal profiles are available with different sealing features.

Sometimes air or inert gas is introduced in an attempt to blow process material away from the seal to prolong service life.

Mechanical seals…0707_fund_seals4

Specialized mechanical seals (see Fig. 4) are available for retrofit in airlocks. These compact, unbalanced, double-faced components can be fitted into the airlock’s packing area and adjusted with the gland follower. They are typically purged with air or inert gas as a barrier fluid for closing seal faces. Careful monitoring of the air/gas pressures can predict product leakage, allowing maintenance personnel with an opportunity to adjust the seals before leakage (and possible shaft damage) can occur.

Unlike packing and lip seals, mechanical seals do not contact the rotating shaft with a non-rotating sealing element. The rotating seal faces are fixed to the shaft, and they seal on a plane that is 90° opposed to the shaft’s axis. This effectively eliminates abrasive wear to the shaft—and in so doing, eliminates the need to replace or resurface a prime overhaul component, saving labor, time and materials during periodic overhauls.

At the same time, this configuration also eliminates abrasive wear of packing or lip seals, and the associated risk of product contamination by seal face detritus. Product purity is more easily maintained. Mechanical seals often require more radial and axial space for installation than lip seals and small-section packings. Consequently, the stuffing box space incorporated in the airlock frame may not be large enough to retrofit a mechanical seal. There are several steps you can take if your stuffing box space proves insufficient.

  • Most airlock end plates are easily removed. If there is sufficient packing box depth, the plate can be chucked and centered in a lathe and the packing radius enlarged.
  • Where there is insufficient packing box depth, the face of the existing box can be faced off in the lathe or milling machine, an extension ring can be centered and welded in place atop the existing box, and the ring and stuffing box i.d. can be re-cut to provide a smooth, consistent bore.
  • Where needed, a larger-diameter gland follower can easily be fabricated from a piece of pipe welded to a steel plate flange, then drilled and machined to suit.

In this way, most rotary valves and airlocks can be retrofitted with mechanical seals in your own plant’s maintenance shop (or in a local machine shop) with little effort.

The true cost of maintenance
The sort of proactive maintenance offered by air-purged contacting face seals can extend the operating life of airlocks between overhauls, minimize product waste and can also aid in predicting maintenance shutdowns.

Airlocks are periodically taken out of service to resurface and machine the vane tips. Some configurations have replaceable vane tips as an integral part of the design. Others are repaired by building up the vanes with weld and re-grinding the tip surface. Replaceable vane tips often are used in highly abrasive wear applications. In non-abrasive applications, seal replacement is the primary maintenance performed between overhauls. Vane tip service and seal and bearing replacement are the main reasons for overhauls which necessitate equipment shutdowns.

To avoid unnecessary shutdowns, the minimum goal for any airlock seal should be to last at least as long as the tips of the vanes. This provides the optimum meantime- to-repair. Ideally, shaft seals should be rebuilt or replaced when the vane tips and body are overhauled. Since the overhaul invariably takes place in the workshop, all maintenance can be performed in a clean, controlled environment, with tools and equipment ready at hand.

Trying to perform seal replacements and other maintenance in the field between overhauls is hard on personnel and, in turn, makes quality workmanship difficult to maintain. This makes mean-time-to-rebuild unpredictable.

The true cost of a single production line shutdown includes the cost of workers idled by the shutdown, product lost before the problem was identified, product not manufactured and product lost while bringing the line back to grade on restart, as well as the actual parts and labor costs associated in the maintenance operation. Taking these factors into consideration, an organization may look on mechanical seals not as a more expensive sealing solution, but as a thrifty investment in reliability. More importantly, when properly maintained and monitored, a mechanical seal’s performance is predictable.

The best sealing option
Any of the sealing options discussed in this article will work reasonably well when sealing non-abrasive materials. Difficulties arise when abrasive materials and very fine materials pass through the rotary valve or airlock.

Materials found in the home building products and mining industries, salts and sugars in the food industry and additives such as TiO2 or starch are all extremely abrasive. Such materials will embed into packing and act as a grinding mechanism, cutting into the shaft and making the rotary valve or airlock unreliable.

Lip and quad seal elastomers also can become abraded, lose their sealing characteristics and begin to cut into the shaft. Face seals can stop shaft damage, redirect wear to a sacrificial component and provide a predictive maintenance mechanism—but at a higher price.

What’s best for your application can best be determined by balancing the purchase cost of any given seal type against the maintenance and downtime costs associated with it.

Paul Wehrle is chief engineer with the MECO Seals Division of Woodex Telephone: (207) 371-2210; e-mail: bird@mecoseal.com

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The Fundamentals: Effects Of Doubling Up On Hearing Protection

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Most end users think OEMs take particular pains to design things that last. That’s true in most cases, but not all.

Will doubling up or wearing dual protection-an earmuff in addition to earplugs– provide added protection against extreme noise levels? The answer is yes, according to a recently released Sound Source™ bulletin from the Bacou-Dalloz Hearing Safety Group-but maybe not as much as you thought.

The new bulletin, Sound Source #11a, “Dual Protection,” is authored by audiologist Brad Witt, the Audiology and Regulatory Affairs Manager for the Hearing Safety Group. He notes that dual protection is not required by OSHA regulations for general industry in the U.S., but is required for mining operations governed by the Mine Safety & Health Administration (MSHA) for noise exposures over 105 dBA (8-hour time-weighted average). Similarly, NIOSH recommends dual protection for any exposures over 100 dBA, and some companies require it for employees with progressive noise-induced hearing loss despite normal protective measures.

There are, however, risks associated with dual protection. “Using earplugs and earmuffs concurrently seriously isolates the wearer,” Witt writes, “so it is warranted only in extreme noise levels.” He also suggests that dual protection may be overused. “When a high attenuation earplug or earmuff is properly fitted and the user is motivated to use it correctly, some hearing professionals say the need for dual protection is rare.”

Obtaining maximum benefit
So how much protection will doubling up provide? “That depends on the fit,” says Witt, “but, it is not simply the combined ratings of the earplug and earmuff. There is a ceiling effect that limits the amount of combined protection. Even if wearing a perfectly fitted earplug and earmuff with ideal attenuation, we would still hear sound transmitted through our bodies and bones to the inner ear.”

The maximum amount of attenuation that can be attained by most people is 35-50 dB, depending on the frequency of the sound.

As for a rule of thumb for estimating the effects of dual protection, OSHA recommends adding 5 dB to the NRR of the higher rated device. “But this,” says Witt, “sacrifices some accuracy. An earmuff typically adds about 4 dB to the NRR of a well-fitted foam earplug, and about 7 dB to a well-fitted pre-molded earplug.” He also says that an earmuff with moderate attenuation provides the same effect as a high-attenuation earmuff when either is worn over a well-fitted earplug.

According to Witt, the key to obtaining maximum benefit from dual protection is proper fit-especially the fit of the earplug. When a poorly fitted earplug is worn with an earmuff, the resulting dual protection is little more than the earmuff alone.

About Bacou-Dalloz
Sound Source, a free periodic publication of the Bacou- Dalloz Hearing Safety Group, addresses questions and topics relating to hearing conservation and hearing protection. Bacou-Dalloz manufactures and markets a comprehensive range of safety products designed to protect people from hazards in the workplace. The Group specializes in head protection equipment (eye and face, respiratory and hearing protection), body protection equipment (clothing, gloves and footwear) and fall protection equipment. These products are sold through a worldwide network of distributor partners for use in all sectors (construction, manufacturing, telecommunications, homeland security, petrochemicals, medical, public services, etc.)

Bacou-Dalloz Hearing Safety Group
San Diego, CA

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Problem Solvers

Pump-Operated Piston Bins

0707_problemsolvers_img1Assmann’s 400-gallon polyethylene, non-pressure piston bins are ideal for transporting and storing viscous products up to 500,000 centipoise. They function via a pump operated system that both fills and discharges through a 3″ bottom valve. Materials are protected from air, moisture, dirt and other contamination in the bin with the use of a sealed and closed-looped system. The products incorporate a durable design, forklift pockets and reusable containers.

Assmann Corporation 
Garrett, IN

 

Food & Pharma Grease

0707_problemsolvers_img3CRC Industries has added Food Grade White Grease for food and pharmaceutical processing applications to its line of NSF Registered products. According to the manufacturer, this high-purity, high-quality synthetic provides advanced lubrication and durability, while protecting against rust, oxidation and wear. Resistant to water, salt spray and detergent, it’s suitable for use in temperatures ranging from 0 to 450 F.

CRC Industries Inc.
Warminster, PA

 

Metalworking Product Catalog

0707_problemsolvers_img2E&R Industrial offers a new master catalog covering over 100,000 MRO and production metalworking products from more than 500 manufacturers. Product categories include cutting tools, abrasives, precision tools, hand and power tools, lubrication, MRO items, machinery and safety supplies.

E&R Industrial 
Sterling Heights, MI

 

 

 

Lube Storage & Dispensing

0707_problemsolvers_img4LubeRite™ Storage and Dispensing Containers from JustRite protect lube oils, hydraulic oils, gear oils, motor oils and coolants from contamination and spills that can lead to machinery downtime. Fully sealed, these containers are available in pump and pouring applications. Pouring applications come in 2-, 5- or 10- quart drums, while pump applications are available in 5- or 10-quart drums. These durable products feature quick fill ports, flip-switch activated breather vents and color-coded identification systems.

JustRite Mfg. Co. L.L.C. 
Des Plaines, IL

 

Multi-Use Wind Power Lubricant

0707_problemsolvers_img5Klüberplex BEM 41-141 from Klüber has been formulated to reduce the use of multiple greases in wind power stations. It uses one special base oil mixture along with a package of additives to overcome the differing demands of individual bearing lubrication points that are prominent in wind power applications. This new lubricant is suited for use on main bearings, generator bearings and pitch and azimuth bearings, all of which are subjected to high stress conditions. Klüber Lubrication

North America L.P. 
Londonderry, NH

 

 

 

Severe Environment Lubrication

0707_problemsolvers_img6The line of Permatex® brand Anti-Seize Lubricants from ITW Devcon are designed for the harshest industrial environments. The lubricants reduce wrench torque and help protect mated metal parts against corrosion, rusting, galling, friction and seizing. The line includes Permatex Anti-Seize Lubricant, Permatex Copper Anti-Seize Lubricant, Permatex Food Grade Anti-Seize Lubricant and Permatex Nickel Anti-Seize Lubricant. Each lubricant can withstand a wide range of temperatures, up to a maximum of 2400 F in the case of the nickel formula.

ITW Devcon
Danvers, MA

 

Preserving Stored Equipment

0707_problemsolvers_img7Royal Purple’s new VP Preservative Oil helps prevent rust and corrosion in stored equipment such as engines, gearboxes and other closed systems. Protection from this vapor phase preservative formulation lasts up to one year or more, depending upon how well sealed the closed system is and how much temperature- induced “breathing” occurs. Additionally, vapors from the oil form a monomolecular layer on all metal surfaces for further protection. VP Preservative Oil is available in 5-gal. pails and 55-gal. drums.

Royal Purple
Porter, TX

 

Oil Filter Crusher

0707_problemsolvers_img8According to Newstripe, its FilterFlat oil filter crusher reduces the cost of filter disposal by up to 80%. After a simple installation and connection to shop air, the economical product converts used oil filters from EPA hazardous material into recyclable metal and oil. And the process takes only 40 to 60 seconds. With a crushing force of 24,000 pounds, this product can handle filters up to 9″ tall and 6.375″ wide.

Newstripe, Inc. 
Aurora, CO

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Solution Spotlight: Meeting Specialized Needs Of Air Compressors

Plant operations rely on proper and consistent performance from air compressors—when compressors fail, production can quickly be brought to a halt. Accurate compressor lubricant selection is essential to prevent lubricant-related issues that could cost a plant considerable downtime. The type of lubricant needed can vary greatly depending on the type of compressor or gas being used, while different gas temperatures and discharge pressures may require different qualities in the oil.

“It is critical to match the proper lubricant with its intended application,” says Bill Stein, a product application specialist with Shell Lubricants. “When developing compressor lubricants, consideration must be given to the fluid type and additives used, as well as the intended use of the product.”

To meet the complex needs of today’s air compressors, Shell is now offering next-generation technology in its line of air-compressor oils: Shell Corena AP, Shell Corena AS and Shell Corena S.

Shell Corena AP Oils
These products are intended for the lubrication of industrial reciprocating air compressors, in particular, those up to and above air discharge temperatures of 220 C (428 F) with continuous high delivery pressures. According to the manufacturer, Shell Corena AP incorporates a combination of specially selected synthetic esters and advanced additive technology. As a result, this product works well in the most demanding of conditions, handling continuous high pressures and high temperatures, where traditional mineral oils are not suitable. A low tendency for deposit build-up helps promote continued high compressor performance over long periods. Moreover, the normal valve maintenance period, typically between 250 and 1000 hours of operation using conventional mineral oils, can be extended to 2000, or even 4000 hours.

Shell Corena AS Oils
These advanced synthetic rotary air compressor oils use a specialized additive technology. Shell Corena AS is capable of giving high performance in oil-flooded air compressors of screw or vane design. It provides effective lubrication, even under severe conditions, to oil-flooded single- and two-stage compressors, in particular those operating with output pressures of greater than 20 bar (290 psi) and with air-discharge temperatures greater than 100 C (212 F)— including intermittent operation under these conditions.

The manufacturer also notes that Shell Corena AS can help increase oil drain intervals significantly compared to conventional mineral oils, where allowed by the manufacturer— up to a maximum of 12,000 hours, even when operating at a continuous maximum discharge air temperature in excess of 100 C (212 F).

Shell Corena S Oils
A premium performance mineral oil, Shell Corena S is suitable for the lubrication of rotary sliding vane and screw air compressors, operating with lower discharge temperatures. Based on a blend of high-viscosity index, Group II paraffinic mineral oils and carefully selected additives, the oil provides thermal stability, good water-shedding properties, good seal compatibility, anti-oxidancy, anti-wear and low oil carryover. In field use, Shell Corena S has demonstrated more than 5000 hours of operation.

Shell Lubricants
Houston, TX

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Mineral-Based Lubricant Exchange

Some of the most crucial issues in lubricant management involve getting the right lubricant to the right place at the right time. On many occasions, getting these things “right” is not particularly problematic. What happens, however, when something does go wrong around your operations? Your inventory control may not have been updated, shipments may have been delayed or other unforeseen circumstances may have caused a critical shortage of lubricant(s) at your site. In these situations, substitutions may have to be made—quickly! How, though, do you fi nd a compatible lubricant substitute?

Lubrication Management & Technology’s “Mineral-Based Lubricant Exchange” guide has been compiled to help you in the event that substitutes must be chosen. The chart on the following pages has been designed as an easy-to-use cross-reference of the products of major lubricant formulators, based on the information they provided to our editors.

Keep in mind that the products shown on our chart are general guidelines for comparison purposes only— they do not infer that performance is interchangeable. If you are considering a lubricant substitution for a specifi c application, you MUST consult the respective formulator(s) to ensure proper performance.

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Notes on using the chart
Viscosity is a widely accepted property for comparing lubricants. It is expressed in several ways: ISO, Saybolt, AGMA and Kinematic. Note that the viscosity equivalents of ISO and Saybolt are what we have used in our chart to compare the various products of the listed formulators. (Refer to Figs. 1 and 2 for a comparison of common viscosities and to see the effect of temperature on viscosity.)

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Analyzing the bigger picture
Although following recommended oil-change and greasing schedules is the usual way of doing business in a facility, this alone will not optimize machine performance and minimize downtime. Regular oil analysis—conducted in-house or by a qualified lab—is another powerful tool to use in enhancing reliability and increasing uptime. Remember that accurate and timely oil analysis can alert personnel to impending lubricant deterioration or machine malfunctioning, and allow them to initiate corrective action—well before an actual failure occurs.

Joe Foszcz is a contributing editor to Lubrication Management & Technology. For more information, e-mail him directly: jfoz@atpnetwork.com

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Perseverance, Surprises and Unintended Consequences

By the time I joined Rentech in 2000, the three Clark TCV 16 engine/compressors compressing hydrogen and nitrogen at our East Dubuque Ammonia Plant had begun experiencing shortened packing life. Packing life on the 4600 psi 3rd and 4th stages—that historically had reached 18 to 24 months—suddenly fell to just three to six months. Excessive ring wear also was observed.

Maintenance personnel at the plant had noticed that the major brand lubricant we were using on these units looked somewhat different than in the past. When questioned about this, the supplier assured us that no changes had been made. As we continued to pursue the problem, the manufacturer later admitted that the formulation had indeed been changed and the diminished performance we were experiencing was unintended and unexpected. Consequently, we began to look for an alternative lubricant.

The first alternative we selected, an independent brand cylinder lubricant, appeared to work well for about a year. Then we encountered another unintended consequence. The oil carried downstream of the compressor was plugging the chillers in the synthesis loop. At that point, we determined that an oil with a lower flock point (temperature at which wax crystals form) was what we really needed.

We opted to go with Royal Purple’s NGL-NS synthetic lubricant as it had no flock point and no sulfur that could poison the process catalyst. After just three weeks, however, we experienced a packing failure on a synthesis loop compressor cylinder. A repetitive failure occurred just four weeks later. In all, we had six packing failures over a twoto- three-month period. Then, the failures stopped—just as suddenly as they had begun.

Interestingly, only the packings on the recirculation cylinders of compressors C & B were failing. We sent samples of the failed packings, along with foreign material found in them, to Royal Purple for analysis. Because the oil travels downstream of the compressor, the supplier attributed the failures to the NGL-NS cleaning out 37 years of “stuff” that had accumulated in the loop. We were advised to persevere with the clean-up and to expect that the failures would eventually stop. They did. Our packing life increased to two years. Subsequently, we also changed packing materials, increasing our current life to four years with expectations of six years life.

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Each of these engines/compressors has two turbochargers. In summer months, these units would experience pre-ignition problems due to low intake air volume. We would have to reduce the load on the engines in order to operate. At some point in the past, as part of a lubricant consolidation program, our plant had elected to lubricate this equipment with the SAE 40 weight gas engine oils used in the compressors. We were looking for a better bearing lubricant for the turbochargers and elected to try Royal Purple’s Parafilm 68. Again, we found ourselves experiencing unintended consequences.

The first unintended consequence was related to the engines being started with compressed air. The air to the engine is automatically shut-off when the turbocharger speed indicates that the engine is running. After changing lubricants, the engines would not start. We determined that the new bearing lubricants had reduced friction in the turbochargers’ bearings so significantly that they were spinning up just on the compressed air, and that they no longer needed engine exhaust gas to do so. We had to reset the air cut-off parameters in order to start the engines.

The second unintended consequence was that the preignition problems in the compressors completely went away. The engines could now be run fully loaded yearround while still maintaining a slight open position of the waste gate valves.

Identifying more opportunities
We operate a 2500 hp Elliott turbo expander in our Nitric Acid Plant that is one of only four ever made and the last still in operation. It operates at 16,000 rpm. This unit has always experienced problems with short bearing life and high vibrations. We thought this resulted from the equipment’s fabricated case coupled with too much overhung mass on the rotor. At times, the unit would shake the floor grating so violently that it hurt your feet to stand on it. Replacement bearings cost $8000 and would have to be replaced twice a year. The bearing alarms were normallyset based on whatever vibration levels existed after a rebuild. In an effort to reduce vibrations and extend bearing life, we elected to change out the ISO 32 turbine oil to Royal Purple Synfilm 32. We expected to see improvement from this oil change due to the much higher film strength of the Royal Purple lubricant and we were not surprised. Immediately after the oil change bearing vibrations went down from 4 mils to 2.7 mils. Bearing life went from six months to 20 months. Recently we had the rotor balanced, which further reduced the vibrations to 1.2 mils—and is expected to extend bearing life even longer.

Based on these successes, we began to look for even more opportunities to improve machine performance with lubricant upgrades.

Single screw compressor… 
We elected to change the oil on a 400 hp Vilter single screw compressor at our two 20,000-ton ammonia storage tanks. This compressor had a number of operational issues. It continually tripped on high temperatures. Valves failed to operate because of oil deposits gumming up the valves. We had excessive make-up oil due to the oil’s inability to readily separate from ammonia. In this application, we elected to change out the factory oil for Royal Purple Uni-Temp 300 refrigeration oil. Based on assurances from Royal Purple that we would also achieve substantial energy savings, we installed data loggers on the compressor to record volts and amps. All of the operational issues with the compressor disappeared and we documented a 9% reduction in power consumption.

Mycom ammonia compressor… 
Shortly thereafter we changed to Royal Purple oil in the Mycom ammonia compressor serving one of our Nitric Acid Plants. All went well for about a year until we got a water leak in the shell and tube heat exchanger, and unintended consequences recurred. The internals in the compressor rusted and took out the bearings. We also found a black residue in the compressor we believe came from the oil. After a second compressor failure using the new oil, we elected to return to the previous oil as it appeared to have a superior ability to handle wet ammonia.

Rotary screw compressors…
Next we elected to change the oil in our three Sullair rotary screw air compressors to Royal Purple Synfilm. For whatever reason, the larger 400 hp compressor was being lubricated by a major brand multi-purpose mineral oil requiring eight oil changes per year. The two 100 hp compressors were lubricated with a factory synthetic oil with annual oil drains. Being a polyalkaline glycol type oil, the factory oil was incompatible with most other lubricants. Thus, it was necessary for Royal Purple to supply its Royal Flush product to flush the old oil from the compressor before adding new oil. In addition to its price advantages, the new oil has reduced discharge temperatures by 12 F degrees and has extended oil drain intervals via oil analysis to 12,000 hours.

4-stage urea plant compressors… 
In April of 2002, we elected to address issues we were having with our two Clark CMB 4-stage compressors in the urea plant. These units, which compress CO2 to 3000 psi, were experiencing excessive cylinder ring wear, packing sealing problems and plugging of the downstream separators. We elected to change the major brand cylinder lubricant to Royal Purple CAP701W ISO 220. This proved to the solution to each of these issues. So again, we looked for other areas where we could improve the performance and reliability of our equipment with lubricant upgrades.

Steam-driven centrifugal compressor… 
We also looked at a steam-driven 5000 hp Allis Chalmers centrifugal compressor in Ammonia Chiller Service. The speed increaser gear box (4900 rpm input/12,800 rpm output) was in high vibration alarm. The turbine and gearbox share a common lube sump containing 1200 gallons of ISO 32 turbine oil, so we could not drain and replace the oil because shutting the turbine down meant shutting the plant down. We decided to drain the turbine oil to the lowest level we thought was safe and then we added six drums of Synfilm 32 to the existing oil (27 ½%) hoping to get enough film strength into the oil to bring the vibrations down. It worked. Vibrations were reduced from 0.2 IPS to 0.17 IPS (a 15% reduction), which was below the alarm limits. We ran the turbine until our next scheduled turnaround. We drained and replaced the major brand turbine oil with Parafilm 32 and have run the turbine and gear box without incident for the past five years.

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This compressor has a separate oil system for the trapped bushing seal that seals the ammonia into the compressor. Feeling good about our successes, we decided to tackle what we believed was a lubricant related seal problem. The major brand ISO 32 R&O oil we had successfully used for years suddenly became unavailable. We were assured that the supplier’s new offering was equally good, but then some of those unintended consequences reared their ugly heads again. What used to be minor carbon deposits found in the seal at turnaround became significant carbon deposits on the seal—which caused premature seal failure and plant shutdown. We consulted with Royal Purple about a replacement oil and began a new round of unintended consequences.

First we tried Synfilm which didn’t separate well enough from ammonia. To overcome this we changed to Uni-Temp, which we knew separated rapidly from ammonia, but its high solvency began to aggressively clean up deposits from the seal system that were carried to the seals—again causing premature seal failure. Finally, we changed to Royal Purple Barrier Fluid FDA 56, which solved the problem once and for all. That’s because this product does not have the cleaning abilities of the Unitemp. In this case, we felt it simply was better to leave whatever “stuff” was in the system alone.

150 pumps… 
We operate over 150 pumps at the East Dubuque Ammonia plant, all of which had been lubricated by an ATF fluid. A little over a year after changing these pumps over to Synfilm, it occurred to us that we had not experienced a single bearing failure since the move. Even now, we seldom see bearing failures on these pumps—the few problems we do have are usually seal failures.

The road to success
Today our plant is running better than at any time in its 40+ year history. Budget trends are down and equipment availability is up. We are currently at two-year turnaround intervals and feel we could easily go to three. Though it may have started as an accidental journey, we have learned that good lubrication is key to reliability and good lubrication begins with optimum lubricant selection. We also learned that solutions are not always obvious and that patience and perseverance are required in order to stay the course to some solutions.

0707_operationsuccess_img3Sometimes we wound up having to take two steps back before being able to take three forward. We also learned that there is no such thing as a magic bullet—or magic oil. For many applications we see no advantage in using anything but traditional lubricants. For many others, the benefits vastly exceed the cost of premium performing lubricants.

One thing is certain, however. We no longer look at lubricants as an expense. Instead we look at lubricant selection as an opportunity to maximize productivity and profits.

Lance Wilkinson is maintenance superintendent/technical manager with Rentech Energy Midwest, in East Dubuque, IL. He has extensive experience in the Petro-Chemical Industry, including 21 years in engineering, seven years as a craftsman and supervisor and three years as a machinist. Wilkinson holds a BSME from the University of Texas at Austin. E-mail:lwilkinson49@sbcglobal.net

 

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