OCTOBER / NOVEMBER 1998

Reducing oil well downtime

Problem: Oil well tubing in pump jack and rotary progressive cavity pump well applications is costly to repair. Excessive wear of the tubing requires the use of a service jig to replace the tubing. The problem is especially bad in deviated wells (those that are horizontal, slanted or crooked), and in sand producing wells. A deviated well can be shut down as many as six times a year due to tubing wear and the resulting costs can be up to $90,000 annually.

Solution: A tubing rotator machine reduces tubing wear by spreading the wear over 360š of the inside diameter of the tubing. Normally wear concentrates on an area of only 19-20š, leading to early tubing failures.

The rotator device was designed in 1993 by Andy Wright of Tubing Rotator Systems in Edmonton (the company is now part of Alberta Basic Industries Ltd.--ABIL). Use of the rotator can increase the life of tubing by as much as six times. It uses a custom gear reducer conceived by Bob Dryden of Edmonton and Ernie Edgerly of Fort Smith, Ark., both Baldor Electric Company representatives. It has a parallel shaft gear reducer with a 320:1 ratio and a worm gear reducer with a 70:1 ratio combined together to achieve a final ratio of 22,400:1. The complete unit is factory mounted and shipped as one package.

For information on the Baldor drive solution, contact Jim Dryden of Dryden Agencies Ltd., Baldor's Alberta district warehouse, at (403) 434-4900. For information on the tubing rotator, contact Andy Wright of ABIL at (403) 496-9218.

Automation brings out backlash concern

Problem: Backlash is common in most machinery, but new automated machinery often requires a significant reduction in gearbox backlash. What's the least costly solution?

Solution: Zero backlash products are technically possible, though seldom really required. They are extremely expensive. Reduced- or low-backlash products are more economical and more often than not will meet the needed criteria. Today, many manufacturers offer low backlash reducers.

Dominion Machinery Repair Ltd. of Malton, Ont., a company that specializes
in upgrading, repair and manufacture of machine tools, was upgrading the CNC on a very large lathe (160-in. swing). The company intended to use PLC servos connected via synchronous belt drives to low-backlash, right-angle reducers with 100 mm hollow outputs.

A special pinion gear fitted to the gearboxes engaged with the lathe's existing gear rack, which would accurately position the cutting tool. In this case, distributor B.G.S. Bearings and Equipment Ltd. of Mississauga, Ont., supplied Wood's QT Power Belt Drives (equivalent to Gates Polychain) and two Lenze GKS 14s (each weighing 1100 lb) with a backlash range of 7-10 arc min..

In another application, a standard 25:1 worm reducer produced an unacceptable backlash of 0.68 degrees or 41 arc min. (which translates into 0.35 in. on a 3-in. radius). A low backlash version of the same gearbox was provided to tighten up the tolerances, reducing backlash to 0.22 degrees or 13 arc min. (0.11 in. on a 3-in. radius). The cost was about 25% higher than the standard unit.

Mr. O thanks Dave Strutt at B.G.S. Bearings and Equipment Ltd., Mississauga, Ont., for this tip.