Innovation has always been a key component in the success of the offshore oil and gas industry. New and improved procedures coupled with enhancements in technology have paved the way for economic gains. Lube oil flushing found its way into the industry’s arsenal of weaponry, although not in recent years. This process originated more than 20 years old but has yet to find itself entered into the standard play book of all oil and gas companies.
According to Michael DalDegan, senior operations manager for Gly-Tech Services, Inc., lube oil flushing is defined as the process of removing harmful contaminants from rotating and hydraulic systems. Sometimes referred to as a hot oil flush, oil is circulated through the equipment’s lubrication system at an increased velocity resulting in turbulent flow. Metal shavings, rust and dirt that enter the system during construction and maintenance are then removed. Equipment containing lubrication systems includes gas turbines, compressors, large electric motors and pumps, as well as pump gearboxes.
The process can be compared on an elementary basis to an automobile engine and the oil that circulates through it. Much like changing the oil in an automobile to avoid dirt and possible shavings damaging the working parts of the engine, lube oil flushing refers to the procedure as circulating the hydraulic fluid and cleaning it to remove harmful particles. A screen is inserted in the flow path and captures particles to measure contamination. One might think this process would be seriously valued and utilized by all oil and gas companies; however, that is not always the case.
“Not everyone initially sees the value in lube oil flushing,” says DalDegan. “Gly-Tech’s lube oil flushing business is a mixture of calling on customers who are not necessarily familiar with the process, but a good portion of it is repeat business.”
Normally conducted during the commissioning of new equipment or after major maintenance, the concept of lube oil flushing remains consistent for each project with variations in design, setup and process. Equipment and flow path design are not always the same. Flushing contractors like Gly-Tech must evaluate customer piping and instrument diagrams (P&ID), determine flow path, and specify pumps and hoses to be supplied and used.
The process of lube oil flushing includes interconnecting piping and coolers. Although lube oil coolers and other factory assembled equipment are cleaned by the manufacturer, DalDegan indicates that Gly-Tech has flushed these components in the field to ensure they are not compromised. In DalDegan’s experience, lube oil coolers are usually found to still be contaminated and require extensive flushing to achieve the level of acceptance published in the manufacturer’s cleanliness specifications.
DalDegan identifies lube oil flushing as a staged process using specialized equipment. The system of equipment includes a holding tank that may be potentially heated. In cold weather applications, an external heat source may be used. Pumps must be sized to accomplish turbulent flow. Additionally, the filtration system must be designed to handle the required flow rate. The filter elements figured for the project must be sized appropriately to achieve the required cleanliness. A flow meter is included in the setup to measure flow rate. To reverse flow, a manifold system is designed for the flush. Lastly a basket strainer is equipped with a 100-mesh screen.
According to DalDegan, when listing the steps of a lube oil flush, a strong quality management program is necessary to ensure equipment is clean and functional. Specific to the point, hoses are shipped to project sites with both ends capped to keep their interiors from becoming dirty and compromised. Additionally, flanges to be included in the setup are shipped with their ends capped as well. Filters are packaged in zip up slip covers to protect them from weather.
When planning a flush, environmental concerns are addressed in procedure and setup. Containments are placed at connection points and equipment that could potentially suffer from a leak and lead to an environmental spill. Proactive behavior includes using over-engineered hoses in the flush.
“We use high pressure hose rated at 1000psi,” says DalDegan. “Typically, we’re working with pressure ratings less than 150psi.”
To ensure hose success and avoid leaks while circulating lube oil, specific fittings are used. Connectors are either flanged or JIC fittings. This allows for a locking scenario to occur. Quick disconnect fittings are frowned upon. During the staging of equipment and hoses, grounding and bonding take place.
Although their equipment is managed according to their company’s quality management program, DalDegan states that a proving flush takes place only on Gly-Tech’s equipment arranged in the setup. Customer equipment is bypassed with jumper hoses. Circulation is initiated and a screen test is conducted to measure or check for particles of contamination. These particles are measured in microns. Upon verifying the system is clean, the jumper hoses are removed, and customer equipment designated to be cleaned is then tied into the circulation setup.
“After approval that our equipment is clean, we start our actual flush with a baseline screen,” says DalDegan. “It’s based on the specs of the rotary equipment being flushed.”
The flushing action typically consists of a four to eight-hour time span to monitor the particle count. After the time span is completed, the flush is temporarily shut down and the screen is pulled from the flow path. A particle counter is used to measure the contaminating material collected on the screen. This process continues until the filter count is found to be acceptable, which may take several four to eight-hour flushes. Contamination and cleanliness desired are the deciding factors.
“The number of flushes conducted is dependent upon the specifications and how clean the customer wants the system,” says DalDegan.
When discussing cleanliness specifications, an important factor to understand is the standard or level to which it is measured. NAS Cleanliness codes serve as that standard and were originally developed in 1964 to address aircraft component contamination. Because no other standard was available, NAS codes were broadened to include industrial hydraulic systems. Contamination classes are identified by a number ranging from 00 to 12.
Understanding the value in the process of lube oil flushing, Leonard Dickhaut, commissioning manager with Competentia and contracted to Equinor, says that it takes a level of experience to recognize the need for the process.
“The industry has evolved in seeing the need for lube oil flushing,” says Dickhaut. “The process needs to be taught in school as a good deal of young rotary equipment engineers need to be educated on the process.”
According to Dickhaut, variations can be made when lube oil flushing. At times, an increase in turbulent flow and heat is required to achieve the level of cleanliness desired. Additionally, the size of the pump used to circulate the product is directly related to the actual size of the piping through which this turbulent flow occurs.
“Heat moves dirt and evaporates,” says Dickhaut.
Dickhaut indicates a good practice in lube oil flushing is to include a vacuum dehydrator in the process. A vacuum dehydrator is a piece of equipment that is included in the flow path through which the oil travels. It includes a heating element that removes moisture from the oil.
“During a flush, moisture in oil shows up as a particle,” says Dickhaut, stating that the process of applying heat is specifically useful in warm climates, such as in the South and the Gulf of Mexico. Tanks are atmospherically vented and serve as an intrusion point for humidity. Moisture is the byproduct which contaminates the oil. Heating that lubricating oil during the flush with a vacuum dehydrator removes that moisture product.
History shows that the contamination factor is considered as offshore platform components, such as turbines, are shipped in crates in an attempt to maintain cleanliness. Once they are opened and exposed to the atmosphere, they are contaminated and must be flushed. After the commissioning process of a platform takes place, lube oil flushing is needed.
According to Dickhaut, the expenses associated with the offshore oil and gas industry can easily be described as greater than those experienced with land operations. Logistics serve as an expensive commodity when discussing offshore costs.
“If you’re talking offshore,” says Dickhaut, “you’re talking at least three times longer than on land which adds increased costs.”
When considering the budget matched to rebuilding a turbine, Dickhaut speculates that the rebuild costs are 50 percent of the purchase price of a new unit. The downtime and loss of production must also be added. Respectively, a new turbine price tags in the neighborhood of $10 million. An immediate argument can be formulated for the need in maintaining equipment to avoid costly repairs and the trickle-down effect caused as a direct consequence. Lube oil flushing has proven to be an economically viable option in the maintenance process of rotary equipment.
“There is a clear message to take away when thinking about the process of lube oil flushing,” says Dickhaut. “There is a greater value in doing it now than not doing it in the long run.”
Headline photo: Offshore platform under construction. Flushing services occur at this stage and then on the commissioning side afterwards.
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