Packing plays a crucial role in ensuring the proper functioning of valves by preventing leakage of fluid or gas along the valve stem. It's a sealing material used to create a barrier between the moving parts of a valve, such as the stem and the bonnet, to maintain pressure and prevent leaks.
Cast steel refers to a type of steel casting produced by casting methods. It is mainly used to manufacture parts with complex shapes that are difficult to forge or cut into shape and also require high strength and plasticity.