November/December 2019

HYDRAULICS 30 HYDRAULICS & PNEUMATICS November/December 2019 www.hpmag.co.uk For any hydraulic system, cleanliness is crucial in order for the equipment to function reliably and to avoid unscheduled costly downtime. Moreover, equipment used within the oil & gas sector can face some of the most challenging environmental conditions found in any industry, making effective cleanliness methodologies even more important. Effective filtration systems are the great enablers of fluid cleanliness, and, as Oliver Barnett, offshore product manager – Offshore Sales Division, Hydac Technology Ltd, explains, filtration applications used within oil & gas are relied on for the wellbeing of a wide range of equipment. “Well Head Control Panels (WHCP), for example, can be found everywhere from oil platforms to deserts, and usually require about three small filters for low flow rates on each wellhead running hydraulic oil,” he explained. “They normally need stainless steel cartridge housings for the filters in order to meet the high corrosion resistant requirements for these types of environments.” Other common applications requiring filtration are hydraulic power units (HPU) used for actuation. Barnett pointed out that these can be found in any kind of offshore/onshore/desert oil and gas application. Lube oil systems commonly found on oil platforms are used for transporting oil from the main tank to the engine. As Barnett explained, stainless steel-housed filters are required for these systems to protect the turbines. Further applications for filtration include installation workover control systems and chemical injection systems. Applications Some of the more unusual applications for filtration highlighted by Barnett include subsea boosting. “When an oil field is closed down there can be approximately 20 to 25% of the oil reserve still left in the well,” he said. “To extract some of this remaining reserve, an HPU is put on the seabed. An HPU normally has three filters mounted to its hydraulic system. If the HPU is means oil purifiers (dehydration) are also needed in order to remove water from systems due to the hygroscopic nature of these fluids. For offshore control applications filters are normally designed for water glycol- based fluids for the likes MacDermid Oceanic series production control fluids. With this in mind, Barnett explained that Hydac has developed and fits special elements to its filters to optimise them for these fluids. Compatibility Wright stated that typical industry standards for filter media materials include glass fibre, polypropylene and nylon and fluid compatibility issues must be considered carefully for each application. “For example, in the case of diesel, polypropylene filter media should not be used,” Wright stressed. “Light hydrocarbons are also not suitable for long-term use with polypropylene. Similarly, for water applications that are running at +60degC, glass fibre is not compatible. Compatibility is important, especially with the wide range of chemicals that are used for injection – you must ensure chemical compatibility for each application.” Further downstream, there are more fluid power-related applications, such as hydraulic motors, pumps, compressors and various other hydraulic systems in an oil refinery or a gas plant, for example. “For this equipment to remain reliable and operational – with little or no unforeseen and costly downtime – correctly sized and compatible filtration systems are crucial,” explained Wright. “Filtration systems used for these types of onshore applications would normally be constructed of standard industrial-grade carbon steel rather than stainless steel or higher alloys, which are commonly used in offshore applications due to the harsh corrosive environment in which they operate.” Integrity As with any hydraulic system, cleanliness affords greater reliability and longevity. submerged to 3000 m deep 300 bar is required, so the deeper the wells the higher the pressure required. We have seen 1400 bar for filters topside and even a few instances – in the case of testing – 2000 bar.” Remote operated vehicles (ROV) in seawater is another important but less common application that requires filtration equipment. “Carbon steel filter housings can be used on ROVs, and I’ve also seen aluminum used,” Barnett pointed out. “However, in many cases they are being swapped out for stainless steel in order to extend their lifespan.” He added that another long-term application is subsea control modules (SCMs) used to control each wellhead. These SCMs normally have two or four filters fitted to them, one medium pressure (345 bar) on high pressure (690 bar). Tim Wright, Northern Europe sales manager (Fuels & Chemicals) and Keith Webb, marketing manager EMEA, both from Pall Corporation, explained that in the case of subsea control systems, there has been a strong trend towards the use of water-based fluids; however, mineral oil-based systems are still used which The importance of cleanliness in the oil & gas sector British Fluid Power Association member companies Pall Corporation, Hydac Technology Ltd. and MP Filtri consider the critical part filtration equipment plays within the particularly challenging environments found within the oil & gas sector. Oliver Barnett, offshore product manager – Offshore Sales Division, Hydac Technology Ltd: “In the case of applications in the desert or subsea, reliability and longevity are particularly important. This is because it can be very expensive to replace parts and equipment due to the relative inaccessibility of where they are situated – you can’t train a dolphin to change an element 3000m below the ocean.”