How much do you know about the blending process and its effect on oil cleanliness? Is that where the trouble starts?
There are many different lubricant blenders in the U.S.—some very large and some small. In this series, the general practices of large, major oil company blenders and some of the medium-size specialty lubricant suppliers are examined.
The blending process
The typical flow through a blend plant is characterized by Fig. 1. The process begins with receiving of the base stocks that are shipped to large facilities by pipeline, barge or rail. Smaller facilities receive base stocks by rail or truck.
Base stocks usually are not filtered before being introduced in the blend tank, but there are some exceptions. One blender company filters all base stocks shipped by barge, rail and truck with a 25 micron filter. Additives come in many package styles, including drums, totes and bulk. They typically are not filtered before being introduced in the blending tank. Hydraulic and turbine oils contain less than 1% additives, so cleanliness is not as important as it is for base stocks
Base stock and additives are introduced in the blend tank and mixed together to make the finished product. Cleanliness targets are set by some facilities for turbine, hydraulic and other oils specified by large customers. The first filtration (which typically is a coarse one, perhaps through a bag filter) is from the blend tank to the finished product tank. The final filtration, which is to achieve a specific cleanliness target, is from the finished product tank into a bulk truck for customer or distributor delivery. Finer filtration also is performed from the finished product tank to the packaging operation.
There is a range of lubrication blenders—from those that provide very little to no filtration and no measurement of lubricant cleanliness, to those that have tight cleanliness specifications to meet specific customer needs. Hydraulic and turbine applications usually require cleaner fluids.
The following are examples of companies that have targeted cleanliness levels on oils shipped from their facilities.
- A large major supplier of finished lubricants has established a reasonable target of 19/17/14 for its hydraulic and turbine oils. It normally will achieve a cleanliness level of 2 or more ISO codes below the target. This supplier filters with a sock filter from the blend tank to finished product tank, then uses finer filtration from the finished product tank to a truck or packaging line.
- Another major supplier of finished lubricants has a program for its premium turbine oils. For an additional charge, the turbine oil is guaranteed to have a minimum ISO cleanliness of 18/16/13. (This meets General Electric’s cleanliness specification of 16/13.) This supplier also will guarantee hydraulic oils to an ISO cleanliness of 17/15/11—something that is achieved by having initial filtration with a 13 micron filter going into the product storage tank. This is followed by a 6 micron filtration from the product storage tank to a dedicated tank truck for turbine oils or the drum packaging operation to achieve guaranteed cleanliness targets. In addition, all drums for both the turbine and hydraulic fluids with guaranteed cleanliness are polyethylene plastic to maintain the cleanliness level. In most cases this supplier will be lower than the established cleanliness level.
- A mid-size supplier of specialty lubricants has a guaranteed ISO cleanliness code of 14/13/11 for its ISO 32, 46 and 68 synthetic oils. This is for only plastic-packaged products (in drums, pails and totes). The main filtering step incorporates a product-holding tank with fine offline line recirculation filtration. This company also does bag filtration from the base stock tank to the blending tank. The fluid is recirculated until the required cleanliness level is attained. The plant has stainless steel dedicated piping that helps meet these cleanliness levels.
- Another mid-size supplier of specialty lubricants has a program to supply hydraulic fluid for injection molding machines requiring clean fluid. This company supplies the fluid in plastic containers at a guaranteed ISO Cleanliness Code of 17/15/13.
Clean fluid shipped by the lubrication blender will require less or no filtration when it reaches the end user. Remember, though, there is a cost for fluid cleanliness. Some companies charge $.05 to $.20/gallon, which is well worth the cost to get a guaranteed cleanliness. Many blenders don’t measure fluid cleanliness as it leaves the plant and many do just a very coarse filtration—if any. Fluid cleanliness can vary by one or two ISO codes, depending on how it is measured—whether it is with a portable or online counter or sent to a laboratory for evaluation. (Part III of this series will address online versus laboratory particle counting.)
Do you really know how clean the oil is that you are buying? Is it clean enough for your equipment, especially hydraulics and turbines? With the exception of a few companies, no one publishes data that specifically points to a cleanliness rating for their products. The few that publish this information do so only for specific products. In order to shed more light on the subject through this series of articles, 17 oils were purchased and underwent evaluation for cleanliness and water content along with other oil analysis.
MRT Laboratories of Houston, TX was selected to do all the test work for several reasons, including:
- The lab’s proximity to sample collection, which minimized shipping;
- The authors’ experience with the quality of MRT’s work;
- The fact that this laboratory is ISO 17025-2005 accredited.
The following samples from four of the major lubricant suppliers and one small blender were purchased from Houston-based distributors in five-gallon plastic pails:
- Four ISO 32 turbine oils
- Four ISO 46 hydraulic oils and one ISO 32
- Four ISO 100 R&O circulating oil
- Four ISO EP 220 gear oil
The following tests were performed on the samples:
- Particle counts as expressed as ISO 4406 Cleanliness Code with the use of an
optical blockage counter
- Karl Fisher Water Coulemetrically
- Viscosity @ 40 C
- Acid Number
- Emission Spectroscopy for 24 metals.
The five-gallon plastic pails were delivered sealed to the laboratory. The pails were agitated, and individual samples were taken from the middle of each. A superclean bottle was used and flushed with four ounces of fluid before being filled. The samples were immediately run in the laboratory
It is interesting to note that the only turbine oil packaged by a blender came from Supplier D; this sample was the cleanest of the group. The others had been packaged by the distributor/marketer. All of these oils were clean and very dry. (Product moisture has not been discussed but it is a very important property of a lubricant and should be monitored.)
Supplier E’s product was an off-brand hydraulic oil purchased from an automotive parts store and 30% lower in cost than the premium hydraulic oils purchased through a distributor. There was no viscosity designation on the pail. It was called R&O hydraulic oil. This oil upon evaluation appeared to be used flush oil. It had 24 ppm of iron along with 41 ppm of aluminum. It also contained high levels of silicon, sodium and potassium. This indicated possible coolant contamination. In light of its high particle count and water content, this fluid should not be used in a hydraulic system. How would you know the low quality of such oil unless you ran oil analysis tests? It was observed that the oil was very dark and emitted a pungent odor. Low-viscosity hydraulic oils are not dark in color, nor do they have an odor.
There are many very good lubricants sold by compounder blenders. The evaluation of this low-quality oil should not reflect on the rest of the group. A lesson to be learned from this is that one should buy lubricant from a supplier with whom you are familiar—especially if it is used in a critical application like hydraulics.
Supplier D’s product was the cleanest of the group—and the only one packaged at a lubricant blend plant. The others were packaged by distributors. This is a common practice. Many distributors package their own oils in drums and pails—especially hydraulic and turbine oils. The only other oil that was marginal for a hydraulic system without further filtration was that from Supplier B—it showed a high amount of water and a high particle count, but all other tests revealed it was high-quality oil. The moisture and particles were probably introduced during the packaging process at the distributor.
R&O circulating oils…
All of these ISO R&O circulating oils (which are used in compressors) were packaged at the blend plant. These oils were clean and dry. Supplier D again had the cleanest oils, but all the others also were high-quality and suitable for usage.
EP gear oils…
All of the lubricants in the EP gear oil table are ISO 220, which is the most common viscosity grade for most gear reducers. Supplier B’s product was packaged by the distributor. The others were packaged at blend plants. Gear oils are not as clean as turbine or hydraulic oils, but these lubricants in many cases will be clean enough for unfiltered lower speed gearboxes, especially if this oil is added to existing oil in the reservoir, which is probably dirtier. In splash lubrication, the most common lubrication method for gearboxes, bearings also are lubricated by the same oil. Bearings require cleaner oil than gear teeth. This should be taken into consideration when determining the cleanliness targets for gearboxes and in some cases may require filtration to meet those targets.
Conclusion: encouraging results
The first key link in the cleanliness chain was examined by looking at the contaminant levels of various oil types from their respective blend plants. The results were encouraging. The major lubricant suppliers’ oils were clean and dry for most applications. Some suppliers offer further filtration to meet stringent customer requirements, but at an additional cost. This is particularly true for turbine and hydraulic oils where greater cleanliness is required. It also was encouraging to note that of the 17 oils evaluated for water, only four were higher than 100 ppm—and two of those were packaged by a distributor.
As a group, the gear oils evaluated here were not as clean as the other lubricant types. That was expected. They were, however, found to be clean enough for most applications.
One final word of caution: Be familiar with the lubricants you purchase! Use of that low-quality hydraulic oil previously cited could have caused equipment damage. Overall, though, rest assured that there are many reputable lubricant suppliers—both large and small—that furnish quality products. 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. Telephone: (281) 257-1526; e-mail: email@example.com
Mark Graham is technical services manager for O’Rourke Petroleum in Houston, TX. Telephone: (713) 672-4500; e-mail: firstname.lastname@example.org