www.hpmag.co.uk HYDRAULICS & PNEUMATICS June 2023 33 Electrohydraulic systems for moorings A typical ex-proof electrohydraulic system for a mooring application comprises a central HPU for the Power Generation and various hydraulic manifolds directly mounted on the deck equipment, so that the control valves are as close as possible to the winches and the actuators. Ex-proof solenoid valves are present in every actuation: on/off valves are used for simpler or auxiliary movements, while proportional valves or cartridges are generally applied whenever higher performances are required. A typical example is the Chain Jack System, where high-flow ex-proof proportional valves control the reciprocating movement of a big-bore cylinder used to haul-in and tension the mooring chain. The hazardous area is typically classified according to the IEC 60079 directive as zone 1 for overdeck installation, requiring explosion-proof certification for hydraulic components and electrical equipment. As for corrosion resistance, manifolds, valves and actuators are usually protected with dedicated marine painting cycles with thicknesses up to 300 ?m, while piping and fittings are generally stainless steel made. Although, whenever the installation involves a particularly weathered location or very low temperatures, it is not uncommon to use ex-proof stainless steel valves. Wide range of ex-proof hydraulic components The classification of potentially explosive areas within oil & gas vessels could vary according to ship section. For example, process systems located underdeck are typically classified as Zone 0 requiring Ex-i intrinsically safe valves, while overdeck mooring systems are usually classified as Zone 1 requiring flameproof Ex-d valves combined with certified Ex-h actuators and pumps to prevent eventual risks caused by hot surfaces or mechanical moving parts. One company that offers a complete ex-proof range of multicertified electro hydraulics components for applications in potentially explosive environments, from on-off valves to the complete systems is Atos – see below: Ex-proof proportional valves with on-board digital technology allow smart solutions developed for industrial sector to be extended also to hazardous locations, like the last generations fieldbuses, built-in oscilloscope for advanced diagnostics, high performance axis and pq control. The range includes specific on-off executions aimed to further increase the safety level in hazardous environments, like exproof solenoid valves certified up to SIL2 / SIL3 according to IEC 61508 or ex-proof directional valves with inductive proximity sensors to monitor the spool position. Ex-proof power units and hydraulic blocks designed for marine environments classified as hazardous locations are certified by TÜV, DEKRA, UL, CSA, ABS, BV, DNV GL, RINA: high production quality, strict compliance to customer specifications and specific marine painting cycles are only some of the key factors which Atos Systems Division says makes it the preferred hydraulic partner for the offshore sector. For further information please visit: https://www.atos.com/ Atos ex-proof block for mooring systems BELOW: Atos ex-proof hydraulics certifications Explosion proof proportional valve
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