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Introducing Bolted Flange Management to the 21st Century

Tuesday, April 12, 2016

Looking at Flanges with a 3 Dimensional perspective.

There have been a substantial amount of improvements over the years with flange leakage prevention. Is it enough? The improvements have been mostly mechanical, bolting two flanges together by forcing them in place. This methodology has its drawbacks; it can introduce unwanted stresses, poor gasket compression, deformed sealing surfaces and many others.

What if we could look at flanges with a 3D perspective and apply proper geometric controls such as parallelism, true position and relationships to mating flanges? What is the long term benefit when two mating flanges have the optimum condition before bolting?

When field machining companies are contracted during turnarounds they bring a range of flange facing machines on-site. They sit in the yard until they are ready to be used. When needed, the flange facers are typically ID mounted to sweep a dial indicator to determine if the flange needs to be machined. Sometimes it can take an entire shift just to get the machine in place. Once in place, the machine runs in one path around the flange with a dial indicator on the end of it. The machinist visually monitors the deviation and writes down the observed highs and lows of the surface in question. When the deviation exceeds the engineering tolerances, the flange is then machined. This has been the process for many years.

There are major problems with this methodology. It never takes into consideration the angularity changes of the flange post-machining. The effect of a flange that changes angle by just a half degree over 20 feet on a pipe run is several inches. Now the bolts holes do not line up, the sealing surfaces are not parallel to one another and a mechanical device needs to pull each flange into position for the bolting procedure. This introduces many unnecessary stresses on the piping and the flanged connection.

The indicating process is not repeatable. If two different technicians set-up a machine on the same flange, their results will likely be different. Also, the technician needs to record everything by hand on a piece of paper, which adds to the possibility of misinterpreted results. This form of documentation is not traceable and is not easily archivable.

Now we step into the 21st century. A trained Metrologist certified in GD&T, sets up a portable coordinate measuring machine (CMM), such as a laser tracker or articulating arm. When the flange(s) to be inspected have been landed in the yard, the metrology specialist can inspect several large flanges in minutes as opposed to hours. When the flange cannot be relocated outside the unit, the laser crew can easily mount the equipment on the flange and inspect it in place just as quickly. No crane, chain falls or hoists are needed.

Once the portable CMM is in position, the technician scans the flange face collecting thousands of data points across the face of the flange. Once the data is collected it is run through a custom macro which displays the results in an easy to understand heat map which details the high spots, low spots and everything in-between. There is no guessing, and the process is completely repeatable no matter if one or five different technicians collect the data. The process is completely electronic, traceable, repeatable, highly precise and the results are easily archived for future reference.

What are the benefits:

1. Reports are digital documents that can be archived for historical  tracking.

2. Repeatability makes it a process based on the most precise measuring  equipment  possible in the field.

3. Set-up and data collection is fast, and speed matters during a turnaround.

4. Process is safer during the data collection.

5. Flanges are less likely to leak due to proper GD&T used during the  machining process to ensure parallelism, position and min/max distance  was applied.

6. Flanges are in the most optimal position possible.

Our focus is on safety, our passion is for precision and our goal is to develop the perfect process.


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