a series of videos produced by SwagelokTM

to get the correct

methodology for making a perfect joint. This may sound trivial but there is a real art in making connections which don’t leak. Remember fi ttings don’t last forever especially in the environments where stack testers work. There are several dos and don’ts with lines and connectors.

1. Try not to make up connections on site where possible. It is rarely the best place, and it is easy to mis-plumb equipment – inputs mixed up with outlets or exhausts connected to another piece of equipment when they should be vented. Remember if something can go wrong it probably will do on site, usually just as it is about to rain or you want to go home!

2. Where possible don’t mix fi ttings made by different manufacturers. They may seem to fi t but will loosen, seize or leak at the most inconvenient of times.

3. Carry a good supply of commonly used fi ttings required by your equipment. Remember that source testing equipment is sourced from different countries. The USA typically uses imperial fi ttings whilst the UK and EU countries use metric. Don’t mix imperial with metric as some bits will fi t, but usually badly. Close enough is not good enough!

4. Don’t drag ends of pipes on the fl oor or on gratings. Gratings snag the end of connectors and can pull them off. Grit in the threads stops fi ttings connecting well, plus acts a source for error in the measurement if the dirt gets into the pipes. The same applies to electrical connectors which gravitate to any puddle around, and water and electricity don’t mix.

5. Rubber tubing sleeved over tubing to make a connector rarely works as a gas tight seal. It may be acceptable in other areas of expertise, but it has no place in stack testing. Likewise, insulation tape or duct tape doesn’t make for a seal.

Below are some examples observed at real sites:

A Probe connected to a SwagelokTM

fi tting to a rubber pipe, to

a PFA Line and secured with insulation tape and then connected at the other end to a heated line. Just remember that these were accredited testing companies!

Finally, heated lines need to be cared for as well, as too often they are moved whilst hot which can crimp or crack the inner PFA/PTFE core.

Heated lines should only be moved when they are cold and then heated up. Most heated lines have a minimum curve radius that they can be bent through to minimise damage to the heating elements, the pipe core carrying the gases or the thermocouples imbedded in the line. This radius is usually based on the heated line being cold. Heated lines are both expensive and diffi cult to clean and hence the need for good front end fi ltration to ensure that heated lines are kept pristine. Ideally, lines should be capped prior to use, the caps removed and then the caps refi tted prior to being moved again. As we move into situations where more diffi cult gases need to be analysed, such as hydrogen chloride, ammonia, water etc., sites for absorption/ adsorption become crucial and need to be kept to a minimum through good housekeeping.

Another common issue is under-estimating the electrical demand of the lines and them either damaging the controller or tripping the site power supply. This under-estimation typically occurs where a series of lines are joined but powered from a single controller. In this case it is better for separate controllers to be used and they may need to be fed from different mains circuits at the site to avoid overloads. Care should be taken where apparently a single controller can feed several heated lines in series, as it is very easy to overload the controller. This appears more frequently with lines sourced from Germany as there it is unusual to connect more than two lines together as sample points are rarely more than 10m from the analysis system.

A Heated Line Connected to a probe via a plastic T-piece to a Horiba PG250 Analyser and an FID. This was not being used to calibrate, but to carry “unheated gases” to a heated line from a turbine.

When running out any form of extension reel or cable it is essential that the cable is fully pulled out from the drum and spread out or else catastrophic overheating and a fi re may occur as the cable overheats in a bundle. We don’t want to burn down the client site, do we?


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