Kelly valves are manually operated valves run above and/or below the kelly to shut off back-flow in the drill stem in the case of a well kick.
An upper kelly cock is intended for use between the lower end of the swivel sub and the upper end of the kelly. Upper kelly cocks are furnished in 5,000, 10,000 and 15,000 psi maximum working pressure ratings and have a working temperature rating of 180 degrees F maximum.
On new drill pipe valves, a tong space of 8 inches minimum length and with an outside diameter as shown in Figure D6- 1 and columns 3 and 4 of Tables 1 and 2 is typical. The exact location of the 8 inch long tong space is at the discretion of the manufacturer.
The outside diameters, bores and bevel diameters on each end of upper kelly cocks conform to the dimensions shown in Tables 1 and 2. The O.D. and shape of the kelly cock body will vary with the manufacturer.
API requires that licensed manufacturers of upper kelly cocks subject each valve to a hydrostatic shop test pressure as shown in Table 3. The required manufacturer’s hydrostatic shop pressure test consists of:
A lower kelly cock (shown in Figure 2) is intended for use between the lower end of the kelly and the upper end of the drill pipe or upper end of the kelly saver sub. Routinely lower kelly cocks are furnished with 5,000 psi maximum pressure ratings. Designs for higher working may be acquired from some manufacturers. The working temperature rating for lower kelly cocks is 180 degrees F.
Lower kelly cocks are furnished with box up and pin down (both right hand) rotary shouldered connections in the sizes and styles shown in Tables 3 and 4. For the upper box and lower pin connections on lower kelly cocks used with 4-1/4 and 5-1/4 square kellys and 5-1/4 and 6 hexagonal kellys, two sizes and styles of connections are standard. The purchase order should state the size and style desired.
New lower kelly cocks are furnished in lengths sufficient to provide a minimum tong space of 8 inches after the box and pin connections have been re-cut at least once.
Lower kelly cocks may be furnished with outside diameters as large as operations in the well permit, in order to produce kelly cocks with a minimum strength in torsion and in tension at least as great as the respective strengths of the tool joints used in the string.
API requires that licensed manufacturers of lower kelly cocks subject each value to a 10,000 psi shop hydraulic test pressure. If higher test pressures are required, the manufacturer should be contacted to arrange the testing.
Mud saver valves (shown in Figure 3) are proprietary valves designed to prevent the drilling mud contained in the kelly from running from the kelly when the lower connection is unscrewed. They are intended for use between the lower end of the kelly and the upper end of the drill pipe.
Mud saver valves are available in 4-3/4″ and 6-1/2″ O.D.s.
Mud saver valves are furnished with box up and pin down right hand rotary shouldered connections. Standard sizes and styles of connections are the NC38 (3-1/2″ IF) on the 4-3/4″ O.D. size and the NC50 (4-1/2″ IF) on the 6-1/2″ O.D. size.
Automatic mud saver valves are not designed to hold pressure from kicks in the drill stem. A back flow feature is designed into the valve to permit automatic bleed-off of pressure in the drill stem.