Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1275515
ML www . machinerylubrication.com | July - August 2020 | 23 ML mised, which can only be verified through base oil testing. Recla- mation normally will involve the removal of precursors along with the addition of additives, typically antioxidants for turbine oils. e addition of these antioxidants should be validated by compatibility testing. Three case-study examples are detailed below. Case Study #1: Petrochemical Plant Turbine A e reservoir size of this partic- ular turbine was 2,800 gallons. e lube oil system was well maintained and had a nitrogen purge on the headspace. e system filtration used 5-micron absolute filters. Oil was changed based on a timed interval and supported with routine oil analysis. e rotating pressure vessel oxidation test (RPVOT), remaining usef ul life eva luation routine (RULER) and membrane patch colo - rimetry (MPC) are conducted twice a year. e system has been in service for 12 years with no oil changes. Typical results would include an RPVOT value greater than 1,100, more than 55% remaining useful life on the RULER test and an MPC value of less than 10. Case Study #2: Petrochemical Plant Turbine B e reservoir size of this reser- voir was 2,200 gallons. e lube oil system was more than 30 years old. The system's filtration used 25-micron nominal cotton-wound cartridges. e reservoir headspace had a dehumidifier, which had been problematic. Due to a labyrinth seal problem, there was a constant steam leak. e system experienced signif- icant lube oil challenges. Typical results included an RPVOT value of 700, 30 % remaining useful life, an MPC value of 35 and a viscosity change of more than 3% every six months. "Sweetening" of the lube oil was frequent. Varnish was prevalent. e system had a vacuum dehydrator and a balanced charged agglomeration varnish removal unit. The dehy- drator significantly reduces moisture to below 300 parts per million (ppm) and varnish below 20. Without the vacuum dehydrator, moisture will increase significantly and has exceeded 10,000 ppm. Operators have daily noted, a strong ammonia scent from the dehydrator's vacuum pump exhaust. Case Study #3: A Centrifugal Compressor The in-ser vice oil of this compressor did not meet specifi- cations as required by the original equipment manufacturer (OEM). Oil analysis results showed an R PVOT va lue of 900, 50 % remaining useful life and an MPC value of 15. e company did exten- sive testing on the compatibility of the oil with the addition of an antioxidant. e lab results were very favorable. Antioxidant was added under the supervision of the supplier. Oil testing was conducted for a period of one year with favor- able results. Analysis Case study #1 is a clear example of a well-maintained system. e system was well designed with best practice methodologies. Opportuni- ties for ingress have been eliminated. But more importantly, the system is well maintained. Abnormali- ties were addressed with urgency. Reclamation was not required. Decontamination has been main- tained by the system's filtration. e company has invested in training, certification and has partnered with equipment OEMs for maintenance. Case study #2 identifies a situ - ation that is chronic. Other factors unknown are the availability of spare parts or the availability of resources to address issues. e situation is a common "firefighting" situation with no clear objectives. Viscosity changes are forcing "oil sweetening" strategy to be executed periodically. Reclamation cannot be considered as the base oil has been damaged. e equipment is the oldest of these three scenarios. Case study #3 identif ies a system problem that has been allo - cated resources to identify the root cause, with intervention of a long- term solution. e cost associated with this process is considerably higher than scenario two but has lower cost of ownership. Again, it is important to consider all factors including context. e reclamation strategy examined the addition of antioxidant under robust supervi - sion of the management team in partnership with the supplier. is strategy is still uncommon but is gaining momentum as references are increasing worldwide. It is an option that is available for consideration for large turbine oil users; something that would not have been considered many years ago. In summary, reclamation is becoming visible to turbine oil users. As references increase, the risk reduces and users explore their options. It is mandatory that lube oils are tested to ensure they are fit for reclamation as well as to ensure that the reclamation process has been successful. Decontamination Decontamination has been a focus for many in the past with great emphasis on filtration tech- nologies from numerous vendors worldwide. Some have benefitted significantly while others have been "stuck in the middle" with no clear objectives. Some lack under -