For any hydraulic system, cleanliness is crucial in order for the equipment to function reliably and to avoid unscheduled costly down time. Moreover, equipment used within the oil and 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, explained, filtration applications used within oil and gas are relied on for the wellbeing of a wide range of equipment.
“Well Head Control Panels (WHCPs), 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 (HPUs) 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.
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 submerged to 3000 m deep 300 bar is required, so the deeper the wells the higher the pressure required. We have seen 1,400 bar for filters topside and even a few instances - in the case of testing - 2,000 bar.”
Remote Operated Vehicles (ROVs) 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 and 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 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 of 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.
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 over 60°C, 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 down-time - 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.”
As with any hydraulic system, cleanliness affords greater reliability and longevity. “Indeed, in the case of applications in the desert or subsea, reliability and longevity are particularly important,” said Barnett. “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 3,000m below the ocean. Therefore, the integrity of the filters is particularly critical in these types of environments.”
Barnett added that when repair or replacement is necessary, having a filter supplier with global presence able to offer speedy supply of spare and replacement parts is very important to keep things operational and productive. The supplier should also be able to provide bespoke filters when required and be able to offer a comprehensive range together with full documentation.
Wright and Webb made the point that equipment monitoring is also important. “Because most of the subsea market is moving to water glycol systems, monitoring their fluid cleanliness becomes more difficult using the laser technology that is common across the industry,” explained Webb.
“In this regard, a key differentiator for Pall Corporation is the use of the company’s PCM500 series fluid cleanliness monitor. The PCM500 series monitor uses a mesh blockage technology that is not affected by the presence of water, so it provides consistently accurate and reliable fluid cleanliness measurements.”
Also, with big data and the growing use of cloud-based solutions, Webb explained that remote and on-site monitoring can be undertaken, bringing additional benefits of convenience and cost savings. “The use of data and data analytics will continue to be a key industry focus with regard to cleanliness monitoring,” Webb said.
“Pall and other filtration companies see the importance of making it easier for equipment users to both maintain the filter element and monitor the service fluids that pass through them as effectively as possible. They’ll do this by offering effective monitoring solutions that are able to harness the benefits of machine learning and the Internet of Things.”
According to Geoff Grant, CMP Product Manager at MP Filtri UK, the main challenges for particle counters and condition monitoring equipment within the onshore and offshore oil and gas sector is education. “It is important to understand the reasons why all fluids and operating systems have to be cleaned to suitable levels. This is to prevent damage to hydraulic components and contamination of tooling and equipment when connecting them to topside and subsea,” he said.
So, what are some of the key functionality must-haves to look for in particle counters to best ensure maximum efficiency and reading accuracy? “Be aware of the fluids you are analysing and use the correct type of particle counter suitable for those fluids, seal material and wetted parts compatibility (i.e., synthetic, water or mineral oil-based),” said Grant. “Also, be vigilant not to cross-contaminate these fluids.”
He added that it is also important to ensure they are flushed and cleaned with the appropriate fluid so as not to affect the readings of the particle counter or monitor they are using. Grant also stressed users should know and use the correct international standards appropriate to today’s technology and equipment.
“Most standards were written many years ago and I feel the levels of cleanliness required today for the majority hydraulic components and systems are not stringent enough,” he remarked, adding that the market has seen an increase in component sensitivity, operating at higher pressures and faster speeds.
Because of the variations among oil wells and what they produce, each well poses different challenges. For instance, Wright explained that if chemicals are put into the water stream they could cause polymerisation and blocks filters. “In the case of condensate filtration and dewatering, waxes may be present. This makes accurate sizing critical in order to ensure you are not sizing the filtration system based purely on hydraulic flow rate.”
Barnett pointed out that there might also be financial constraints at play. When the oil price dropped below US$50 per barrel in 2016 HYDAC was asked to reduce price of its filters by 20%. “To achieve this, we designed a budget filter where features were removed and changes in the grade of stainless steel which is a little cheaper but still highly anticorrosive,” he said. “Thus, we created a larger range, one with all the features such as bowl drain and one known as a budgetary filter housing to give a price saving.”
Safety compliance is also a non-negotiable when it comes to oil and gas applications. As Barnett explained, previously just ATEX was asked for. This then progressed to IECEX and then North American standard UL. “HYDAC therefore supplies an electrical clogging indicator suitable for hazardous areas that has triple approval,” he said.
“There is a lot of work taking place in the background that customers do not see such as the design and updating of technical files to comply to updated Standards and regulations, along with quality assurance. HYDAC pressure-tests every stainless-steel filter that leaves our production facilities. 100% have to be good; we cannot afford a defective filter reaching a customer - especially when it comes to subsea applications.”
And what of ongoing service and support for filtration solutions in the oil and gas sector? Webb pointed out that demand is high for greater ease of service and filter products’ maintenance. “For example, Pall’s hydraulic and lube oil filters now feature a top service cap that can simply be unscrewed to ease service, rather than having to remove the complete element bowl. Users also benefit on space because this design can be put in situ in an environment that is easier to handle and safer for operators to maintain, therefore reducing the risk of workplace injury.”
So, for a wide range of applications within the particularly challenging oil and gas sector, effective filtration systems are a non-negotiable.