When changing products, most tubular drag conveyors clean the equipment by using the new material to purge out the former and diverting the first 30 liters or so of contaminated product into a waste receptacle.
As you know, material that is conveyed by a screw is constantly agitated while it is being pushed forward. Depending on the material characteristics, the particle-to-particle friction can cause heating, degradation and compaction, all leading to build up. This can often be exacerbated by ambient humidity, again, depending on the material type and how it reacts. Tubular drag conveyors tend to perform much better with such materials whereas the material remains relatively static within the cavity between flights. Though it is being pushed forward by the flight, it is not being churned so there is no particle-to-particle friction nor the consequences which tend to be caused by it. Though build up may still occur, it will be to a lesser extent.
Regarding clean out, the entire side panel on the drive box is removable and the same goes for idler boxes. These provide easy access to sprockets and easy access for cleaning. Occasionally, customers will have us include a half coupling with a removable plug in one of the lower pipes that can be used to drain the conveyor of wash water. Care must be taken to assure the equipment is completely dry before introducing the new material. Naturally, the more hygroscopic a material happens to be, the more important this is.
You may have noted that we included a chain vibrator on the idler box. This device works very well for dislodging material that adheres to the conveyor chain, enhancing conveyor discharge efficiency and minimizing carryback. We can include scraper flights if those are found to be necessary, as well. I generally recommend trying the conveyors without them whereas they are an easy retrofit and whereas they are wear items that requires additional maintenance.