The suspension and sealing system consists of two main parts: the casing head and the tubing head.
(1) Casing Head
The casing head connects the various casing strings that are run into the well and seals the annular spaces between them. The connection between the surface casing and its flange can be either threaded or welded (i.e., the surface casing and top flange are welded together). The production casing and the casing spool are typically connected by threads and seated on the surface casing top flange, secured with bolts and sealed with a steel ring. The upper flange of the casing spool connects to either a casing cross or tee.
In recent years, some wells have eliminated the casing spool, replacing it with a single flange. In this design, multiple casing strings are welded to the same flange plate.
(2) Tubing head
The tubing head's function is to suspend the tubing string in the well and seal the annular space between the tubing and casing. As oil production technologies have evolved, particularly to accommodate rigless operations, tubing head designs have been improved accordingly. A common modern design is the adjustable pack-off tubing hanger. This system connects a tubing pup joint to the tubing hanger (also known as a "mandrel") via threads, which then seats on an adjustable flange plate. This adjustable flange plate is positioned between the upper flange of the casing cross and the lower flange of the original tubing hanger. Steel rings seal both the top and bottom of the adjustable flange, which is secured and sealed using multiple bolts.
(3) Integrated Wellhead Suspension and Sealing System
In recent years, manufacturers have developed integrated systems that combine the single-string casing head and tubing head into one unit. In this design, the tubing is connected to the tubing hanger via a pup joint and threads, then seated inside the casing flange. This arrangement compresses a seal ring to isolate the tubing-casing annulus. The system is secured and pressurized using four adjusting screws.
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