An axial flow regulator includes a lateral access port through a portion of the valve body that provides access to a valve seat assembly and/or other portions of the valve trim without having to remove or uncouple the outlet flange or the inlet flange from the adjacent pipe sections. The lateral access port may extend through an outlet flange portion of the valve body and is configured to allow a valve seat assembly to be laterally inserted into and removed from the outlet flange. A valve seat assembly which may be configured for installation in the axial flow regulator includes a pad holder and a support ring for the pad holder that is separable from the pad holder. The pad holder may have alignment struts projecting radially outwardly from a pad support body. The support ring may include strut receivers that slidably receive the alignment struts of the pad holder.