Temporary trap door cap

A method of temporarily sealing around a pressure-leaking trap door at an end of a pipeline terminating in a trap, wherein the trap comprises a trap body having a longitudinal axis and a trap door assembly disposed at an open end of the trap body, wherein the trap door assembly comprises a trap door arranged to selectively seal the open end of the trap body and a connection mechanism arranged to secure the trap door to the open end of the trap body, wherein the connection mechanism has a maximum external diameter that exceeds an external diameter of the trap body, comprising:

• fitting a canister over the trap door of the trap terminating the pipeline, wherein the canister comprises a closed end and side walls extending from the closed end, and wherein the side walls and the closed end together define a cup-shaped body having an open end opposite the closed end and wherein an inner diameter of the canister exceeds the maximum external diameter of the connection mechanism;
• compressing an annular rim to form a pressure-tight seal around a complete circumference of an exterior surface of the trap body at a longitudinal location of the trap body inward of the trap door, wherein a diameter of the annular rim at the longitudinal location is less than the inner diameter of the canister and wherein the exterior surface of the trap body at the longitudinal location is exposed when the trap door is closed;
• and
• forming a pressure-tight connection between the annular rim and the open end of the cup-shaped body;
• wherein, when the canister is placed over the trap door assembly, the side walls, the closed end, the annular rim, and the pressure-tight connection together form a pressure-tight inner volume enclosing the trap door assembly within the canister.