Don’t Overlook Plant Maintenance

By Raj Mosali | November 21, 2011

Anything that moves in a plant experiences wear and tear and needs upkeep. Plant maintenance is analogous to preventive maintenance. Whether a plant is retrofitted, new, or even running for a long time, the following guidelines are all applicable. The best approach to any maintenance task is to first identify plant equipment that needs maintenance. Whether the required maintenance is minor or major, it needs to be identified and specified so. The equipment manufacturer’s recommendations should be incorporated into the maintenance documentation. Identify the timeline of maintenance and address downtime. This could also help identify critical path items if a plant goes down and personnel need help with troubleshooting.

Once the schedule is put into motion, an often overlooked but critical item is keeping the logs. Logs should not only include the maintenance tasks performed on a piece of equipment, but also any failures and associated fixes. This enables the staff to quickly identify and take corrective action. Logs act as the knowledge base. If they are computerized, you can quickly search for a specific issue and find a solution to it, instead of troubleshooting all over again. The major advantage with preemptive checking and maintenance is substantial reduction of downtime.

The typical biodiesel equipment that need regular checks, calibration or maintenance are pumps, reactors, heat exchangers, condensers, filters, boiler, cooling tower, compressor, vacuum system, automation instrumentation and calibration, scale (if used), pipelines, automated valves and actuators, check and manual valves, chiller (if used), and lab instrumentation and equipment. This is just a starting point; every aspect of the plant should be closely looked at and put on a maintenance schedule as needed.

Pumps: A proper pump needs to be used for function. Mismatched pumps that are not fit for a specific application cause failure. Pumps are built robustly and rarely fail if operated correctly. Two critical items for a smooth pump operation are installation and operating within parameters. Pumps usually fail over a period of time, so closely monitoring the performance will enable identification of the problem before the actual failure.

Heat exchangers: Heat exchangers (HEs) are the hardest working equipment, after pumps, in a biodiesel plant. Any drop in HE performance is apparent right away. HEs need to be monitored for any drop in their efficiency. There is not a lot to maintain, but monitoring performance (drop in heating efficiency or increased time to heat a specific liquid) will enable you to identify any impending issues and address them before the failure point.

Reactors: The most overlooked items in a plant are the reactors. One of the main reasons to check reactors is for sediment. It’s often not thought of, but consider your reactor holds 1,000 gallons; if you get 0.5 percent sediment, that’s 5 gallons worth of sediment that, when heated, drops into the reactor. Now consider getting one bad load of feedstock with 2 percent moisture, insolubles and unsaponifiables that contains 1.5 percent sediment—you can do the math. Every few months reactors need to be checked for deposits, whether your process is continuous or batch. The only time increasing reactor check intervals is advised is if you have a preprocess that removes sediment.

Filters: Whether for finished goods or for incoming feedstock, filters must be examined for any tears in the filter trapping mesh, if being used. Not addressing the issue will result in sediment seepage into end product.

Regular maintenance: Air compressor, boiler/ancillary equipment, cooling tower, and chiller, regardless of size or model, require some form of periodic maintenance.

Automation and Electrical: At a minimum, automation devices and instruments should be looked at periodically. A common failure point for automation instrumentation is not the actual instrument, but the wiring. Regular checks have to be performed to make sure wiring is intact and no process liquids are leaking onto the wiring; and instruments are not experiencing any stresses from mechanical equipment such as piping and reactors. Also, relief valves must be checked regularly to perform to specifications.

Lab equipment: It’s a good practice to clean the entire lab once a year of all the liquids, calibrate all the instrumentation outside of the regular requirements, and swap out the chemicals used for various standards.

The goal of maintenance is to build confidence in the equipment and process—and peace of mind helps too.

Author: Raj Mosali
President, Jatrodiesel Inc.
(937) 847-8050

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