As industrial application a strainer is essentially a screen installed to allow water to pass through, but not larger items. The larger items fall to the bottom or are held in a basket for later clean out. They normally have an access that allows for them to be cleaned or have the strainer plate or basket replaced.

 Strainer.pdf

Throttling sections are used to reduce the supply pressures to any desired Iower downstream pressure in places where high pressure differentials exist. Throttling sections can also maintain constant supply pressures at constant flow rates. Throttling sections can be used for water and other liquids. A certain amount of erosion can be expected when used with corrosive liquids.

 Throttling-Section.pdf