Tubing drain

In a well tubing drain assembly to be received in a tubing wall containing a bore intersecting the tubing interior and a counterbore intersecting the tubing exterior, the assembly comprising

• (a) an annular retainer receivable in the counterbore for connection to said wall, the retainer forming a drain passage,
• (b) a retaining member carried by the retainer and projecting into said drain passage, said retaining member comprising a pin extending across said drain passage and received in drilled passages in the retainer,
• (c) a closure in alignment with said drain passage, the entirety of the closure retained by said member with a surface of the closure located at the side of said member closest to the tubing bore interior, the closure adapted to the close off said tubing wall bore, the closure adapted to be blown out said drain passage when fluid pressure in the tubing bore transmits sufficient force via said closure to rupture said member, said closure comprising a disc-shaped piston having a diameter approximately the same as the diameter of said drain passage,
• (d) and a sealing washer to be located in said counterbore, and extending about said closure to have sealing engagement therewith in response to pressure exerted on the washer by the fluid in said tubing, said washer being elastomeric and located in engagement with the end of said retainer closest to the tubing bore interior.