Pipe gets old and changes over time, needing check-ups just like we do. Pipe hangers can stretch and cause sagging, more load on other supports and flanges, and air pockets. But affecting maintenance more than that is the pipe strain on the pump nozzles. Pipe strain is one of the big issues that cause bearing and seal failure due to misalignment.
Scheduling support adjustments is one maintenance task overlooked by most plants. Too often in our firefighting maintenance modes, we pull, push, jack or come-a-long (hoist) a long pipe to a pump nozzle and bolt it up. Working with scheduled piping maintenance is where many reliability focused plants are improving the mean time between failures.
Spring hangers and other spring supports have a life and adjustment schedule. All thread rods attaching beams to stirrup hangers need to be adjusted as the rods stretch with time and load. Look for loose stirrup hangers, the gap between the hanger and the pipe is a quick giveaway that the load of the pipe isn’t being supported correctly.
Grout can break under supports and should be replaced as needed. And steam shoe supports wear into beams when movement is too great. One plant I recently visited had just drilled and tapped grease injection ports to assist sliding the shoe on the beam support and reduce beam surface wear.
Always look at the piping and supports for vertical and horizontal levelness this can indicate a problem with the support or the piping. U-bolts holding pipe that have slipped or lost their hold will be easy to identify by the drag marks from the original U-bolt position.
So what is the allowable pipe flange face misalignment permissible at your site? A 32nd of an inch is real tight for most plants, but some will accept a 16th of an inch. I like the direction given that, if you can push it over by hand and get the bolts in, it is okay.
Plants are built with piping specifications and engineering standards and should be maintained to those standards.
About the Author: Reliability manager for Houston-based Royal Purple Ltd., Bob Matthews has 35+ years of pump industry experience – from hands-on to supervision, in-plant maintenance management, consulting and training. He has taught advanced pump classes for Fortune 500 companies, universities, the Vibration Institute, ASME and FSA. Contact: www.royalpurple.com
