To progress through a certain section of the Meat Processing Plant, you will need to activate a large conveyor system, often used for transporting carcasses. This typically involves a multi-step puzzle. First, locate the main control panel for the conveyor. It will usually be in an elevated position or a small control room overlooking the conveyor belts. Upon interacting with it, you'll likely find that it's unpowered or requires a specific sequence of actions.
You'll then need to find and activate several power sources or levers that feed into the conveyor system. These might include: 1) A large fuse box that needs a missing fuse (which you'll have to locate nearby, often in a locker or on a workbench). 2) A series of pressure valves that need to be turned in a specific order to build up steam pressure. 3) A broken gear that needs to be replaced (the replacement gear will be found in a nearby storage area). Each of these sub-puzzles will require careful exploration of the surrounding area, often while avoiding Manpigs. Once all components are in place and activated, return to the main control panel and engage the conveyor system. The activated conveyor will either clear a path for you, transport a necessary object, or simply open a new door that was previously inaccessible. Be prepared for the increased noise of the activated machinery, which might attract nearby Manpigs, so plan your escape route accordingly.