Samson 3277 Mounting And Operating Instructions

Also see for 3271: Mounting and operating instructions Mounting and operating instructions Mounting and operating instructions Mounting and operating instructions Manual

12 EB 8310-5 ENDesign and principle of operation3.2 Type 3277The principle of operation is the same as thatof the Type 3271 Actuator. The Type 3277Actuator is fitted with an additional yoke onthe bottom diaphragm case (A2) (see Fig. 3).The yoke allows the direct attachment of apositioner and/or limit switch. The benefit ofthis design is that the travel pick-off locatedinside the yoke is protected against externalinfluences.Refer to the mounting and operating instruc-tions of the valve accessories to be mountedfor more details on their attachment and theaccessories required.3.3 Direction of actionThe direction of action is determined by howthe springs (A10) and diaphragm plate (A5)are arranged in the actuator.With direction of action "actuator stem ex-tends", the compressed air is applied to thesignal pressure connection on the bottom di-aphragm case.With direction of action "actuator stem re-tracts", the compressed air is applied to thesignal pressure connection on the top dia-phragm case.The actuator's direction of action can be re-versed (see section 6.5).3.4 Signal pressure routing3.4.1 Type 3271In the "actuator stem extends" version, thesignal pressure is routed through the bottomsignal pressure connection (S) to the bottomdiaphragm chamber and moves the actuatorstem (A7) upward opposing the spring force(see Fig. 2, left).In the "actuator stem retracts" version, thesignal pressure is routed through the top sig-nal pressure connection (S) to the top dia-phragm chamber and moves the actuatorstem (A7) downward opposing the springforce.3.4.2 Type 3277In the "actuator stem extends" version, a sig-nal pressure connection (S) is located on theside of the yoke which is connected to thebottom diaphragm chamber over an internalhole (see Fig. 3, left side). The signal pres-sure moves the actuator stem upward oppos-ing the spring force. A positioner can beconnected using a connection block at thispoint. No additional piping to the actuator isrequired. Refer to the associated positionerdocumentation for more details.In the "actuator stem retracts" version, simi-lar to Type 3271, the signal pressure is rout-ed through the top signal pressure connec-tion (S) to the top diaphragm chamber andmoves the actuator stem (A7) downward op-posing the spring force.