Alan Garbers with Johnson Controls International contacted me regarding an alignment problem, and asked for my advice. Here is a condensed version of his email.
A client rents portable chillers, and related equipment. They built a 125HP portable pump skid with a Bell & Gossett pump on a VFD. I was there to commission the machines and noticed they used size A shims under the corner of each
The spacer shaft function is used when the alignment is performed on machinery using a membrane coupling. The membrane coupling is a typical high-performance coupling, with no backlash, used for maintenance free operation. It is also suitable for high speeds or high temperature applications.
Before we had the Fixturlaser SMC machine we would basically send an engineer out to site to go and investigate the pump problem, he would then return to office and write a recommendation report to the client. It use to take about two days.
At first thought it may sound like a good idea as the specialized fasteners in the channel make it easy to tighten the motor hold down bolts, however in reality it’s a cause for precision shaft alignment issues. Here’s why.
Laser alignment systems are a tool and as such show the user what is occurring “mechanically” during the alignment process, including if components are moving during said shaft alignment process. “If it moves, the laser will see it”.
It is both possible, and desirable, to minimize the negative effects of soft foot. While it may be difficult to completely get rid of soft foot, it can typically be reduced to a few mils, if the following techniques are used.
Fixturlaser SMC-EX: Automatic diagnostic capabilities, EXtended…
The Fixturlaser SMC-EX is a Smart Machinery Checker designed for use in explosive atmosphere ATEX Zone 2 (EX II 3 G, Ex ic IIC T4 Gc).
It has all the advantages that Fixturlaser SMC has, therefore automatically checks the health of rotating machines in minutes, and benefits of a superior design fitting to
Most industrial maintenance mechanics who are involved with precision shaft alignment are familiar with the phenomenon of soft foot. Alignment standpoint, soft foot causes: Changes in alignment values, between when the hold down bolts are loose, and when they are tight. Non-repeatability in alignment measurements, especially if the bolts are not tightened in the same order and manner each time.
Soft foot is a common issue when aligning rotating equipment. It is a major cause of repeatability problems in shaft alignment measurements. In addition to alignment quality and repeatability problems, it can be a cause of machinery vibration, reduce life in electric motors, and cause internal clearance problems in gearboxes and pumps.
Most laser alignment tools include a soft foot function. However, in truth these tools haven’t measured ACTUAL soft foot, instead they have measured the EFFECT of soft foot at the shaft or coupling as that is where the laser heads or sensors are mounted. While the EFFECT of soft foot is important, correcting the ACTUAL soft foot will also correct the EFFECT of soft foot.
Shaft alignment of rotating equipment is an essential part of machinery maintenance. This machine shaft alignment video presents the concepts of OFFSET and ANGULARITY.
It’s no joke that many machines operate with high levels of vibration due to soft foot. These same machines often have a decreased life span due to this condition.
