Extended life filter apparatus

A pocket filter apparatus including a plurality of longitudinally extending pocket members for removing particulate matter from a fluid stream to be treated comprising:

• at least one pair of pockets formed from at least three layers of graduated expansible-compressible moisture resistant spun fiber glass filter media, the first two upstream layers of filter media being approximately two and one half inches (21/2") thick with each layer having a fiber diameter on the upstream face of approximately forty eight micrometers (48 .mu.m) and a fiber diameter on the downstream face of approximately thirty four micrometers (34 .mu.m) and with each layer having a transversely and uniformly extending tri-aryl phosphate ester gelled to a high viscosity of approximately nine point seven grams per square foot of face area (9.7 gms/sq.ft.) on the upstream face and fifteen point five grams per square foot of face area (15.5 grm/sq.ft.) on the downstream face, with a downstream third layer of filter medium being approximately one half inch (1/2") thickness with a fiber diameter on the upstream face of approximately twenty eight micron (28 .mu.m) side and with a fiber diameter on the downstream face of approximately twenty six micrometers (26 .mu.m) and with the upstream face only having a transversely extending planar, sheet-like application of tri-aryl phosphate ester, gelled to a high viscosity of approximately twenty seven point two grams per square foot of face area (27.2 gm/sq.ft.) face area and with the downstream face having zero adhesive application;
• the three layers of filter media having a four-by-four (4.times.4) polyproprylene scrim net layer on the outer and inner faces thereof and all of the layers being folded as joined sections facing each other to form closed ends of said pockets at one end and terminal supporting mouth portions of said pockets at the opposite end, said facing sections including longitudinally extending filter medium compression seams extending along the edges and in laterally spaced relation intermediate the edges to compress the filter medium therealong to provide said pockets and, a rigid flow-thorough frame member to fastenly receive the mouths of said pockets to provide an open-end mouth for each of said pockets opposite said closed pocket ends.