bore valve closure elements their location and method of rotation are all as previously described and like numerals refer to like parts but with the suffix u2018 a u2019 added the main difference arises in relation to the actuator rod firstly with reference to fig2 the lowermost portion of a single actuator rod 46 a connects to a yoke 200 which is in turn connected to the two rotation bars 201 one of which is shown this actuator rod 46 a is sealed at its lower end to the valve body via a v type packing 202 above this the rod 46 a provides two piston portions 204 206 the lower of these 204 is the actuation portion comprising the close chamber 208 and open chamber 210 to which control fluid is supplied via lines 48 a 50 a respectively and vented to cause cycling of the valve 22 a the upper piston 206 is an equalising piston with a lower chamber 212 ported to the annulus 27 a and the upper chamber 214 ported to the production bore 26 a these upper and lower piston systems are separated by a seal 216 again of the v packing type the actuator stem 46 a exits the main body 20 a of the production valve assembly via.