Back seat rising stem gate valve

A back seat rising stem gate valve, comprising:

• a valve body with an open top and a flow passageway therethrough;
• a gate within said body that is vertically positioned to open and close said flow passageway;
• a stem extending upwardly from said valve body, a lower end of the stem being secured to said gate by which said gate is vertically positioned;
• a bonnet secured to said valve body by which said valve body open top is closed, the bonnet having an opening therethrough;
• a packing box slidably and sealably positioned in said bonnet opening and having an opening therethrough receiving said valve stem;
• packing received within an upper portion of said opening in said packing box and surrounding said valve stem;
• a packing gland having an opening therethrough receiving said valve stem and having a tubular portion on a lower end thereof telescopically received in said packing box and in engagement with and for sealably compressing said packing around said valve stem;
• an enlarged external diameter annular stem shoulder on said valve stem below said packing box;
• a back seat ring having an opening therethrough receiving said stem and above said stem shoulder and being slidably and sealably received within said bonnet opening below said packing box, and having at a lower end thereof an annular sealing surface surrounding said valve stem;
• means to selectably downwardly position said packing box and thereby said back seat ring simultaneously within said bonnet to engage said annular sealing surface with said stem shoulder to prevent escape of fluid along said valve stem when said gate is moved to open said flow passageway;
• and
• a test passageway communicating between a lower portion of said bonnet opening to and an exterior surface of said bonnet by which the sealing effectiveness of said back seat ring may be tested to detect any fluid leakage.