Day of start-up is always an exciting time as all the long hard work of engineers and construction folks can finally show off what they have worked on for typically a long time. Most focus is placed on equipment, infrastructure, controls and plant processes. One item that is often underestimated in air and gas moving equipment is the pipe-work that connects primary air movers and the process. Materials of construction, alignment, thermal growth allowance and most of all cleanliness continue to be one of the most unique challenges start-up engineers continue to encounter.
I will start with cleanliness. Ideally, you should attempt for the construction crew to install the pipes in a clean state. Sometimes that may not be possible and the welding and cutting process is typically a dirty process to begin with. Cigarette butts, rags, welding beads and rods and so much more can be found on the inside of new construction pipe-work. The largest object that has held my progress on site up was a red Sawsall tool box that obstructed the flow to a waste water treatment system. If you have the opportunity at all make sure to open the pipe at a location where it is safe to exhaust all of this debris into the atmosphere and then run the equipment and literally blow the pipe clean. Make sure to do this safely and abide by the local and plant safety codes.
Then there are pipes on the blower or compressor inlet that cannot be cleaned as the air will be moving toward the machine. Here it is imperative to make absolutely sure that the pipes are clean prior to start up. Ideally, such installations should have an inlet start-up strainer installed right upstream of the blower / compressor inlet flange.
Here a installation crew was not so lucky and forgot a 5/8” bolt in the ducted inlet to the GM150S Aerzen blower – the bolt went through the blower upon start up. Amazingly the blower kept working even though the blower lobes sustained severe damage.
Often pipe expansion joints either do not exist, or they exist but they have been abused as pipe installation tools and for correcting misalignment. Neither is a good situation to find during your inspection process. Pipe strain is the leading cause of rotating equipment failure as it exerts stress on the housings that may let the rotors hit the housing. Also, the pipe strain may worsen once the machine is up and running due to additional stress from thermal growth. Expansion joints are meant to compensate for thermal growth and to separate structural borne noise from the equipment to the pipes. They are not pipe assembly and misalignment correcting aids.
One last piece of important safety advice is to always walk the pipe-work from the primary air / gas mover to where the medium enters the designated process. This helped me safe a crew of two pipe installers at a cement factory that had been working on connecting an elbow to the open 6” pipe. Had I not inspected the pipe one last time before start-up, they would have been blasted with hot high pressure air.
Please do yourself a favor and inspect pipework on the inside and as a minimum installed start-up strainers if at all possible. Before switching a machine on make sure to walk the pipe down to the final exhaust point – it may save a life.
Please drop me a note in case you have comments, suggestions or questions.