Square Drive And Pin Roller Kelly Bushing , Heavy / Light Type Kelly Drive Bushing

API 7K Square Drive and Pin Drive Roller Kelly Bushing, Heavy, Medium and Light Type

Roller Kelly bushing is a necessary tool for drilling, by matching with rotary square to drive Kelly pipe. Through the rotation of four rolls, the friction between rolls and Kelly pipes is reduced to extend service life. Change different rollers to match with different squares and hexagonal Kelly pipes and connect with different rotary tables. Two transmission styles (square and pin drive) are available. The product is designed and manufactured according to API Spec 7K.

The roller Kelly bushings have two way of drive, the square drive and the pin drive. There are heavy, medium and light-duty according to type. The main technique specification as follows:

The Roller Kelly Bushing is made up of upper body, lower body half, roller pins, and roller assembles, bolts and grease fitting.

There are four-roller assembles inside the Kelly Bushing and the oil nylon bearings are assembled inside the roller assembles. The roller assembles are tightened between the upper body half and the lower body half. There are thrust washers to prevent liquid from permeating in two ends of the roller assembles.

The amount of driving surface on the Kelly is inversely proportional to the amount of slack present between the roller and the face of the Kelly. If there is only 1/16 inch (1.6mm) clearance between the roller and the Kelly, the driving surface of the Kelly will be wide and with the driving forces spread over this wide area, wear will be wide and with the driving forces spread over this wide area, wear will be minimal. However, if the roller to Kelly dimension were 1/4 inch (6.3mm). The driving surface would then be considerably reduced, so that the clearance between the roller and the belly flat surface. The clearance should be not more than 1/8 inch (3.2mm).

During a Kelly bushing inspection, the roller assemblies must be checked. The maximum wear is 1/16 inch (1.6mm) for a hex Kelly and 1/8 inch (3.2mm) on rollers for a square Kelly.