Samson 3510 Mounting And Operating Instructions

Also see for 3510: Mounting and operating instructions

12 EB 8091-1 ENDesign and principle of operation3 Design and principle of oper-ationThe Type 3510 Micro-flow Valve is availableas either a globe or angle valve and is pref-erably combined with a SAMSONType 3271 or Type 3277 Pneumatic Actuatorwith 120 cm² actuator area. It can also becombined with other actuators.The seat (2.2) and plug (2.1) are installed inthe body (1). The plug stem is connected tothe actuator stem (A7) by the stem connectorand is sealed by an adjustable packing withPTFE seal rings (34).The anti-rotation fixture (2.4) prevents aloosening of the screw connection betweenthe valve body and intermediate piece (4).Two anti-rotation fixtures are used for ver-sions with an insulating section or bellowsseal: one anti-rotation fixture between thebody and insulating section/bellows seal aswell as one anti-rotation fixture between theinsulating section/bellows seal and interme-diate piece.The springs in the pneumatic actuator are lo-cated either above or below the diaphragmdepending on the selected fail-safe action(see section 3.1). A change in the signalpressure acting on the diaphragm causes theplug to move. The actuator size is deter-mined by the diaphragm area.The medium flows through the valve in thedirection indicated by the arrow. A rise insignal pressure causes the force acting onthe diaphragm in the actuator to increase.The springs are compressed. Depending onthe selected direction of action, the actuatorstem retracts or extends. As a result, the plugposition in the seat changes and determinesthe flow rate through the valve.3.1 Fail-safe positionsThe fail-safe position depends on the actua-tor used.Depending on how the compression springsare arranged in the pneumatic actuator, thevalve has two different fail-safe positions:Actuator stem extends (FA)When the signal pressure is reduced or theair supply fails, the springs move the actua-tor stem downward and close the valve. Thevalve opens when the signal pressure is in-creased enough to overcome the force exert-ed by the springs.Actuator stem retracts (FE)When the signal pressure is reduced or theair supply fails, the springs move the actua-tor stem upwards and open the valve. Thevalve closes when the signal pressure is in-creased enough to overcome the force exert-ed by the springs.The actuator's direction of action can be re-versed, if required. Refer to the operatingand mounting instructions of the pneumaticactuator, e.g. u EB 8310-1 for Type 3271and Type 3277 with 120 cm² actuator area.Tip