www.delta-mobrey.comIOM-VM-B: NOV 2020Installation, Operation &Maintenance InstructionsVM SeriesModels VM2, VM4 (Pressure Switches)GeneralThe unit is manufactured, checked and supplied inaccordance with our published specification, andwhen installed and used in normal or prescribedapplications, with the lid in place and within theparameters set for mechanical and electricalperformance, will not cause danger or hazard to lifeor limb.THE USERS ATTENTION IS DRAWN TOTHE FACT THAT, WHEN THE UNIT IS‘LIVE’ WITH RESPECT TO ELECTRICALOR PRESSURE SUPPLIES, A HAZARDMAY EXIST IF THE UNIT IS OPENED ORDISMANTLED.UNITS MUST BE SELECTED ANDINSTALLED BY SUITABLY TRAINED ANDQUALIFIED PERSONNEL INACCORDANCE WITH APPROPRIATECODES OF PRACTICE SO THAT THEPOSSIBILITY OF FAILURE RESULTING ININJURY OR DAMAGE CAUSED BYMISUSE OR MISAPPLICATION ISAVOIDED.Operating principlesPressure Switch models VM2 (low pressure) andVM4 (high pressure) are diaphragm operatedswitches.These diaphragms generate a force proportional tothe applied pressure and are balanced by a useradjustable control spring. When the force exceedsthat created by the control spring, the diaphragmmoves causing a push rod to actuate a snap-actingmicros-witch.CERTIFICATIONSFlameproof ModelsFlameproof models carry the following markings:Ex db IIC T6 Gb * ≤ Ta ≤ 65°CII 2 GD Ex db IIC T5 Gb * ≤ Ta ≤ 80°C 0598Ex tb IIIC T75 Db * ≤ Ta ≤ 65°CEx tb IIIC T90 Db * ≤ Ta ≤ 80°C* the minimum ambient temperature (Ta) is dependent onthe O-ring material of the enclosure seals, as below;Nitrile -35°CFluoroelastomer -20°CFluorosilicone -55°CSpecial Conditions of UseThe certificate number has an 'X' suffix whichindicates that special conditions of installation anduse apply. Those installing or inspecting thisequipment must have access to the contents of thecertificate or these instructions. The conditions listedin the certificate are reproduced below:USE HIGH TEMPERATURE CABLESUITABLE FOR AT LEAST 100°C.THE CABLE GLAND, STOPPING PLUGOR BLANKING ELEMENT USED SHALLBE Ex d/tb IIC/IIIC Gb/Db RATED FOR ASERVICE TEMPERATURE OF -55°C TO+100°C MINIMUM.ONLY ONE SUITABLY RATED ANDAPPROVED THREAD ADAPTOR SHALLBE USED WHEN ONE IS REQUIRED.FLAMEPATHS ARE NOT INTENDED TOBE REPAIRED.INSTALLATIONMounting (All models)The instruments are designed to be mountedvertically with the process connection underneath.However, mounting up to 45° from the vertical in anyplane is acceptable, although a small calibration shiftmay occur. They can be mounted either direct toprocess, or to a wall or panel, using the mountingholes provided. Select the mounting point so as toavoid excessive shock, vibration or temperaturefluctuation. Instruments should be mounted to avoidexcessive heat transfer from the process lines oradjacent plant.To avoid undue stresses being imparted to theinstrument when wall/panel mounted, it isrecommended that a short length of flexible line beinstalled between the instrument and process line. Ifsudden changes of pressure (pulsations) are likelythen we recommend that snubbers are fittedbetween the process line and instrument.ATEXATEXATEXATEX