A fluid valve actuator comprising: a diaphragm disposed within an actuator housing to define a pressure chamber and a spring chamber; an actuator stem coupled to the diaphragm via a diaphragm plate at a first end of the actuator stem and coupled to a lever at a second end of the actuator stem; and an actuator stem guide apparatus (202, 500) disposed within the actuator housing, the actuator stem guide apparatus (202, 500) comprising: a base (302, 502) having a first opening (310, 508) dimensioned to allow the actuator stem of the fluid valve actuator to tilt or lean within the base (302, 502) to enable the lever of the fluid valve actuator to rotate, and an upper end; a spring seat (308, 506) projecting from the base (302, 502); and a guide (304, 504) having a second opening (314, 518) having a bearing surface (316, 520), wherein a diameter of the bearing surface (316, 520) is greater than a diameter of an outer surface of the actuator stem, the bearing surface slidably receiving the actuator stem, wherein the bearing surface (316, 520) provides a lateral force to the actuator stem to limit a lateral movement of the diaphragm and the diaphragm plate relative to a longitudinal axis of the actuator housing to prevent the diaphragm plate and diaphragm from engaging an inner surface of the actuator housing during operation; and a spring (246a,b,c) disposed within the spring chamber, wherein the spring (246a,b,c) rests on the spring seat (308, 506) such that the spring (246a,b,c) substantially surrounds the actuator stem guide apparatus (202.500), characterised in that: the guide (304, 504) is removably coupled to the base and includes at least one aperture (328, 514) that aligns with at least one aperture (238, 512) at the upper end of the base (302, 502) to receive a fastener (330, 516) to couple the guide to the base (302, 502). a diaphragm disposed within an actuator housing to define a pressure chamber and a spring chamber; an actuator stem coupled to the diaphragm via a diaphragm plate at a first end of the actuator stem and coupled to a lever at a second end of the actuator stem; and an actuator stem guide apparatus (202, 500) disposed within the actuator housing, the actuator stem guide apparatus (202, 500) comprising: a base (302, 502) having a first opening (310, 508) dimensioned to allow the actuator stem of the fluid valve actuator to tilt or lean within the base (302, 502) to enable the lever of the fluid valve actuator to rotate, and an upper end; a spring seat (308, 506) projecting from the base (302, 502); and a base (302, 502) having a first opening (310, 508) dimensioned to allow the actuator stem of the fluid valve actuator to tilt or lean within the base (302, 502) to enable the lever of the fluid valve actuator to rotate, and an upper end; a spring seat (308, 506) projecting from the base (302, 502); and a guide (304, 504) having a second opening (314, 518) having a bearing surface (316, 520), wherein a diameter of the bearing surface (316, 520) is greater than a diameter of an outer surface of the actuator stem, the bearing surface slidably receiving the actuator stem, wherein the bearing surface (316, 520) provides a lateral force to the actuator stem to limit a lateral movement of the diaphragm and the diaphragm plate relative to a longitudinal axis of the actuator housing to prevent the diaphragm plate and diaphragm from engaging an inner surface of the actuator housing during operation; and a spring (246a,b,c) disposed within the spring chamber, wherein the spring (246a,b,c) rests on the spring seat (308, 506) such that the spring (246a,b,c) substantially surrounds the actuator stem guide apparatus (202.500), the guide (304, 504) is removably coupled to the base and includes at least one aperture (328, 514) that aligns with at least one aperture (238, 512) at the upper end of the base (302, 502) to receive a fastener (330, 516) to couple the guide to the base (302, 502).