API St 677:2006 pdf download

API St 677:2006 pdf download.General-Purpose Gear Units for Petroleum, Chemical and Gas Industry Services.
2.5.1.11 A removable, gasketed inspection cover or covers shall be provided in the gear casing to permit direct visual inspection of the full-face width of the gear elements. The inspection opening or openings shall preferably he at least one-half the width of the gear face.
2.5.1.12 Permanent coatings or paint shall not be applied to the interior of the casing unless the purchaser approves in advance the material and method of application.
2.5.1.13 On units that have pressurized oil systems with pitch line velocities above 15 m/s (3.000 ftirnin, the gearbox casing shall be designed so that the gears do not dip into the oil during operation or upon shutdown. Gear units at or below 15 rn/s (3,000 ft/mm) pitch line velocity may dip into the oil; however, above 10 rn/sec (2,000 ft/mm) pitch line velocity, an oil pail shall be used to ensure rapid drainage and to minimize foaming.
2.5.2 Joints
Casing splitlines shall use a metal-to-metal joint (with a suitable joint compound) that is tightly maintained by suitable bolting. Gaskets (including string-type) shall not he used on splitlines for parallel shaft gears.
Note: Due to the interaction of the rotating elements of spiral bevel gear units, it is normally required that the elemem’s mounting distances be adjustable to achieve proper tooth mesh contact and backlash. When the adjustment is made by shifting axially, in line with the element’s shaft center line of rotation by use of a combination housing cover-bearing carrier, shim type gaskets are permitted.
2.5.3 Bolting
2.5.3.1 Case bolting may he of the through-bolt, studded, or cap-screw type. Threaded bolt holes shall not penetrate through the wall into the interior of the casing. Disassembly shall not require removal of studs.
2.5.3.2 Studded connections shall be furnished with studs installed. Blind stud holes should be drilled only deep enough to allow a preferred tap depth of 1 I2 times tile major diameter of the stud; the first 1 1/ threads at both ends of each stud shall be removed.
2.5.3.3 Bolting shall he furnished as follows:
a. The details of threading shall conform to ISO 261, ISO 262, ISO 724, ISO 965 (to ASME B1.1).
b. Adequate clearance shall be provided at bolting locations to permit the use of socket or box wrenches.
c. Internal socket-type, slotted-nut, or spanner-type bolting shall not be used unless specifically approved by the purchaser.
2.5.3.4 Manufacturers’ markings shall be located on all fasteners 6 mm (1/4 in.) and larger (excluding washers and set screws). For studs the marking should be on the nut end of the exposed stud end.
Note: A set screw is a headless screw with an internal hex opening on one end.
2.5.4 Assembly and Disassembly
It shall be possible to lift the upper half of horizontally split casings without disturbing the piping of the main oil supply to the gearbox.
2.5.4.1 Lifting lugs or eyebolts shall he provided for lifting the top half of the casing. Lifting lugs or eyebolts not capable of lifting the entire casing shall he clearly and permanently marked on the casing. Methods of lifting the assembled machine shall be specified by the vendor.
2.5.4.2 Mounting surfaces shall meet the following criteria:
a. They shall be machined to a finish of 6 pm (25 pin.) arithmetic average roughness (Ra) or better.
b. To prevent a soft foot, they shall be in the same horizontal plane within 25 pm (1 mil).
c. Each mounting surface shall he machined within a flatness of 42 pm per linear m (0.5 mils per linear ft) of mounting surface.
d. Different mounting planes shall be parallel to each other within 50 pm (2 mils).
c. The upper machined or spot faced surface shall be parallel to the mounting surface.
Hold-down bolts holes shall he drilled perpendicular to the mounting surface or surfaces, machined or spot faced to a diameter three times that of the bolt diameter and to allow for equipment alignment, he 15 mm (/2 in.) larger in diameter than the hold- down bolt.