Cup tester unit

A cup tester unit comprising:

• a. a BOP test plug insertable into a casing head housing, wherein the BOP test plug is configured to seal a space of a drilling system above the BOP test plug, and wherein the BOP test plug is tapered in vertical downward direction from a bottom side and comprises a ring-shaped sealing surface which in fully inserted condition abuts a corresponding ring-shaped loading shoulder of a casing head housing, and wherein the ring-shaped sealing surface seals on the casing head housing when the BOP test plug reaches to a casing head housing loading shoulder stopper, and-;
• b. a hanger connected to a pin thread arrangement of the BOP test plug by means of a threaded connection with a box thread arrangement at an upper end of the hanger, wherein the hanger has an elongate mandrel shape and comprises an axial bore, wherein the axial bore is selectively closed at its lower end by a one-way backpressure valve;
• and
• c. a test cup arranged within a recess of the hanger, wherein the test cup is configured to seal with the inner surface of a well casing connected to the casing head housing and provides a tight seal against a fluid pressure within an annular space between the hanger and the well casing, wherein the hanger positions the test cup below a connection between the well casing and the casing head housing;
• wherein the BOP test plug comprises at its lower end a pin thread arrangement for a threaded connection with the box thread arrangement at the upper end of the hanger.