About Bag Filters by Ross G

You might use a filter, but it's probable you are oblivious they come in many different shapes and sizes, one being in the form of a bag filter. Many applications use filtration bags as a standard.
Liquid bag filters are generally used as a less costly way to take out bulk solids from specific applications. These applications can be coolant filtration, paint strainers; many water pre-filter applications, and ink filtration.
There are a variety of different bag filter options. They generally come in two shapes, welded and sewn, and each has several unique end configurations. Standard bags are the average application of bag filters, but many custom bags are out there for several different filtering needs and applications.
Which type of filter bag you use depends on the application. Temperature, chemistry, and particle size all factor in when choosing one. A large number of filter bags are made from polypropylene felt, so that is a awesome place to start. A lot of people will go with polyester felt for hot temperature applications. For the extremely demanding forms, you should use absolute rated nylon mesh, or NMO. If you find yourself purchasing a bag filter and not getting the endurance of the bag you'd like, it's probably because you've misjudged the workload of the filter. An extreme working filter has its life abbreviated, and is not determined by hours used or gallons used. Bags that filter clean water could last as long as a year, while one filtering mud could last as little as a three minutes. It all requires the application. Also, a fresh bag may appear new to a standard viewer, but in the closer view of a microscope, it may be more extreme than first imagined.
To know when to change bags, identify the inlet pressure. As its surface area is used up, the pressure rises across the bag. When the pressure rises faster, the bag is used up and should be changed. Bags don't have a identifiable rule, but generally, you should get a new bag when you see an 8-12 PSI drop.