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Proper oil flushing of rotating equipment tends to be an afterthought. Whether it is commissioning or maintenance involving end users, construction groups or manufacturers, oil flushing tends to be thought of as a "just do it" item. The only time it becomes a priority is when a system fails, and then it is all about getting back on line quickly and not so much about planning. Fortunately, there is a better way. The following six steps are intended to help you achieve a more successful high-velocity oil flush.
Realizing that most commissioning groups and maintenance personnel are not oil flushing experts is the first step. Understanding that there are subject-matter experts available is step 1A. This step can be tricky. Not all flushing companies are equal. I have had the privilege of working for the same organization for 24 years. We started as a couple of individuals in a two-bay garage and grew to a global corporation, which is to say that size doesn't always matter. We used the same principles in our early years that are still employed today. In fact, many of the larger companies tend to focus more on chemical cleaning and perform oil flushing as a requirement to receive a contract. This leads to step 2.
Any reputable oil flushing company will be able to provide references and case studies, so ask for them and follow up. Review documents, make phone calls and visit the flushing contractor's facility if possible. How a company's facility is maintained can say a lot about how it will execute in the field. How does the contractor handle equipment maintenance? How is product cross-contamination prevented? What does the facility's safety plan look like? Don't just rely on a salesman telling you, "We got this." Finding out later that you were the guinea pig and that the company had never flushed your type of unit before can result in costly delays or damage to your system.
Generally, the only time planning is avoided is during a system failure. Then it becomes all hands on deck to get the unit back up and producing. My philosophy is a little different. If you are an owner or end user, the planning stage should take place while your systems are running and everything is quiet. The process begins with the creation of a customized plan for your unit. This plan should include written procedures, materials to bypass critical equipment, items the site supplies, items the contractor will supply, detailed steps, safety requirements, and most importantly the criteria used to execute the oil flush and deem the system clean. The cleanliness criteria will depend on many factors, such as if the unit is being flushed for commissioning. If so, the manufacturer will supply cleanliness requirements to meet the warranty. When in doubt, refer to API 614 for general-purpose lube oil systems or ASTM D6439-99 (Standard Guide for Cleaning, Flushing, and Purification of Steam, Gas, and Hydroelectric Turbine Lubrication Systems). These standards should be used as the minimum criteria, but it is always best to customize your plan for the individual system using the manufacturer's recommended specifications.
Additional items to consider include deviations to procedures, safety data sheets, a spill prevention plan, emergency contact phone numbers and signature lines for approving the procedure.
Whether you are performing the oil flush yourself or hiring a contractor, several things must be verified first. Develop a checklist and run through it prior to staging for the flush. Check for any foreign material that may contaminate your system, such as different lubricants or rusty fittings. Ask your contractor for foreign-material exclusion plans and confirm that all materials are adequate with pressure testing records for temporary hoses, certificates of calibration for testing equipment, flow charts for temporary pumps and maintenance procedures. Reputable contractors should be able to provide these documents and walk you through their standard operating procedures.
To help your oil flush be a success and avoid undue headaches, it is important to be wary of certain issues, such as the system's coolers. Coolers have the potential to hold dirt, decrease flow and cause delays. If possible, coolers should be pulled and cleaned separately. If time does not allow this, flush as a separate circuit to reduce the possibility of the coolers becoming a dirt trap.
When performing an oil flush, remember that it is about flow and not pressure. Fluid will become turbulent at a Reynolds number of 4000, which takes into account flow, temperature and viscosity. However, while the fluid becomes turbulent at this rate, it is not always adequate to pick up and carry foreign materials out of the system. This can lead to a lot of confusion, as the system will appear clean as you flush it, but then starting and stopping the pump will free debris and send it into your inspection media. Most successful oil flushes utilize targeting flow at two to three times the normal flow rate of the system's pumps. This requires external temporary pumps or running primary and redundant pumps if performing the oil flush yourself.
Regardless of the system's size, it is recommended to have at least a 24-hour "course" flush at a high flow prior to inserting the inspection media. Once the initial 24-hour flush is completed, the inspection media should be inserted at the farthest point from the filter. Run the system for one hour and then review the inspection media. This can tell you if the course flush should continue or if the system is ready for the inspection phase. When performing an oil flush on larger systems, consider extending the initial course flush to 48-72 hours. Shutting down to look at a dirty screen will only delay the process, and the downtime can add up quickly.
Poor decision-making and not having the right people involved can delay an oil flush longer than any of the items listed above. Identifying the decision-maker for all parties on the front end can eliminate many delays. More than 90 percent of oil flushing today runs 24 hours a day and seven days a week, so having decision-makers available at the right time can save days with some oil flushes.
In addition to written procedures, be sure to document all aspects of the oil flush. Keeping logs of the temperature, flow, pressure, filter life and work activity will be vital in determining if the flush is on schedule or if something has changed. At the end of the oil flush, these records, procedures and any photos can be compiled into a complete document, which will be helpful if flushing the unit again in the future. This will also can come in handy when justifying the current or future oil flushing.
In conclusion, it usually is not one item that turns a three- or four-day oil flush into two to three weeks. In most cases, it is a combination of little events. Always start with a good plan and verify that it is being followed. Be adaptable and willing to course correct as needed (but document the changes). Build in contingencies and plan, plan and plan. Good luck in making your next oil flush a successful one.