Internal Alignment Engines and Reciprocating Compressors

The alignment between main bearing saddles, crosshead guides to cylinder bore and the perpendicular relationship between the main bearing centerline and crosshead centerline can be easily verified using optical measurement techniques. These checks would normally be performed during new unit installation prior to grouting, for evaluation after equipment failures, or during re-grouting of older existing equipment.

The optical system used consists of target centering devices holding wire crosshair or glass pattern targets and a precision line scope. A main bearing saddle alignment check is performed with the crankshaft and bearings removed. If the check is being prformed prior to initial grouting or re-grouting of an existing unit, the crankcase is first leveled. This leveling operation may also be quickly and easily performed using optical measurement techniques.

The optical line scope is mounted on a universal adjusting bracket fastened to one end of the crankcase. Targets are centered in each main bearing saddle. Typically, the telescope is adjusted to the axis defined by the first and last bearing saddle target. Intermediate targets are then viewed, and their deviation from the line of sight is recorded.

Boralign Laser on Reciprocating Compressor

The same optical tooling system is used to measure the alignment relationship between crosshead guide centerline and cylinder centerline. For this alignment check, the optical line scope is mounted on the cylinder head, and targets are centered in each end of the crosshead guide and cylinder liner. The relationship of the cylinder centerline is compared with the crosshead guide centerline. Of course, the piston, piston rod, crosshead and connecting rod are removed for this check. In some cases, the connecting rod may remain in place.

Through the use of a special telescope, termed an optical transit square, the perpendicular relationship between the main bearing saddle centerline and crosshead guide centerline may be verified. The transit square is really two telescopes in one, with two focusing scopes built together at precise right angles. Centering targets are located in the first and last main bearing saddle and at each end of the crosshead guide. One line of sight is established through the bearing saddle targets, while the cross scope views the targets located in the crosshead guide. The deviation recorded on the crosshead guide targets is a direct measurement of the perpendicular relationship between the two centerlines.

Optical Transit

Lack of perpendicularity would most likely indicate a machining error or poorly positioned crankcase and bedsections. A twisted or out of level crankcase can drastically affect crosshead and cylinder perpendicularity. Therefore, on cases not yet grouted, this check should be performed after the crankcase and bedsections are established in a level position.