HVAC SYSTEM – CHILLED WATER VS DIRECT EXPANSION. Where and when it is preferable to use one or other system? Often in the Oil&gas field there is the necessity of a cooling system for switchboard rooms or LER. In this situation it’s not useful to bring water piping over or under electric equipment. It is also true that off-shore complex need packaged equipment’s with the minimum size possible. But if we change the location and the sector of installation it is possible that the chilled water system (water chillers + AHUs) it is the best configuration. A typic chilled water installation is in the Hospital building where different AHU are installed for different departments and a single large chilled water station is necessary to produce the cooling power for all the AHUs.
We have planned, designed and realized solutions to prevent H2S and other hydrocarbon gases from entering the buildings in Oil & Gas complexes. The HVAC fresh air intake is projected in order to give the necessary closure time to Fire & Gas Dampers before the entry of toxic gases in the Electrical Substation. All the outdoor equipments are ATEX Zone 1 IIB T3 rated.
The true challenge of the HVAC engineer is to create systems that can be installed in small spaces especially when talking about SHELTER for electrical switchboards or Local Electrical/Equipment Room (LER) for Oil&Gas complex . Often in addition to the safe fresh air intake, direct expansion systems, 100% redundancy of equipment, sand filtration, chemical filtration and ATEX or IECEx certification of equipments are required.
HVAC SYSTEM FOR A SERVICE MODULE OF A SEA PLATFORM. Typically inside Service Module are located all the electric and control apparatus of an Oil&gas platform. Control room, Instrument room, Radio room, Normal Electric room, Emergency Electric room and Battery room are the main space that shall be ventilated, pressurized and air conditioned. It is very important to give the maximum safety to each ambient in order to assure the correct fire rating to each penetration also in order to prevent the ingress of toxic gasses inside the Module. HVAC SYSTEM FOR OFFSHORE PLATFORM LIVING QUARTER One of the most commonly solutions for the heating/cooling systems of Living Quarter is the installation of AHU Roof-top type with direct expansion system. The advantage is the small size of the Package and the easy installation outside the accommodation module. The focus should be on the Blast Resistance and ATEX Rating requirements that the equipments may need to possess.
6 tips to give an easy pre-commissioning and commissioning session for an HVAC system in a Oil&Gas building. 1)Provide and install temperature and differential pressure transmittal/indicator for each room that is fundamental to control inside the building. If necessary, the instruments will be ATEX rated. 2)Install differential pressure transmittal/indicator for each AHU filter and for each fan. 3)Provide holes with caps in strategical positions of ductworks in order to measure air flow / air velocity. 4)Provide VFD (Variable Frequency Drive) for each motor that will be important for the whole system (typically AHU fan motor, refrigerant compressors). 5)Provide inspection doors near dampers, coils and other important items installed on ductworks. 6)Install manual regulating damper for each section or for each room served by ductworks in order to calibrate the correct air flow everywhere.
HVAC FOR FPSO (FLOATING PRODUCTION STORAGE AND OFFLOADING UNITS) The main design criteria for the engineering of an HVAC system for a FPSO are: - The HVAC system and associated equipment shall be designed according to naval rules for at least 20 year operational life time in a highly corrosive marine environment. - The HVAC equipment shall be designed taking into account the expected accelerations of a floating marine vessel, during all the phases of its operational life. - The system shall keep comfortable indoor climatic conditions (temperature and relative humidity) for people on-board, in summer and in winter condition, for both Living Quarters, operational spaces/rooms, Hull Machinery, Topside and Turret ITR - The system shall provide a proper ventilation and to exhaust polluted air from specific areas like Workshops, Machinery Spaces, Galley, Battery Rooms, Laboratory and all other relevant areas and enclosed spaces - The system shall keep the required overpressure (with respect the outside), in order to prevent penetration of toxic or hazardous gases from outside process areas - The system shall provide a proper integration with the vessel’s F&G system.
HVAC plant for Oil&Gas complex The main characteristics of an HVAC station for a large electrical substation, a L.E.R. or other big Process&Utilities buildings are the followings: - Maximum assurance on continuous operation, 100% of redundancy (1 duty x 100% and 1 stand-by x 100%) for main equipments especially for vital operations systems (for example all the systems installed on Temporary Refuges, Main Electrical Substation, IBEEV, EDG LER etc..) - Perfect indoor conditions also with the presence of predetermined values of toxic elements in the outdoor atmosphere. This performance can be achieved installing Chemical, Polishing and Scrubber filters (controlled and monitored by gas detectors and corrosion monitors) and engineering fresh air intake sized in order to give the necessary gas retention time to the HVAC ductwork in order to prevent the ingress of contaminant inside the buildings. - SIL 1 or 2 for the main equipments/systems also installing double elements (for example two F&G dampers for each penetration or redundant PLC for vital control panels). - Planning system with hight efficiency, performance and reliability giving priority to simple process also in order to give regular maintenance in all the indoor and outdoor conditions.
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