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Multiple filter bag materials including PP, polyester, nylon and PTFE are optional with filtration precision ranging from 0.5~200μm, suitable for pure water, chemical liquid, circulating water and weak acid & alkali medium filtration.
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Bag Security Filter
1 Product Overview
Bag Security Filter is a pressure-type solid-liquid separation precision filtration equipment, commonly installed at the front of membrane treatment systems including reverse osmosis, ultrafiltration and nanofiltration. It can also serve as terminal purification unit for process fluid. Water treated by multimedia and activated carbon pretreatment still carries fine suspended solids, broken filter media particles and colloidal impurities. Direct feeding into membrane modules will easily scratch membrane surface, cause persistent fouling, shorten membrane service life and greatly increase cleaning and replacement costs.Driven by system pressure, medium enters filter housing and flows through filter bags from outside to inside or inside to outside. Solid impurities larger than bag aperture are trapped inside filter bags, while clean medium flows from outlet to downstream processes. With continuous pollutant accumulation, differential pressure between inlet and outlet rises. When pressure difference reaches preset limit, shutdown is required to open quick-open cover and install new filter bags to restore filtration performance.The equipment adopts sealed pressure vessel structure. Single-bag, double-bag and multi-bag configurations are selected according to treatment flow rate. Flexible selection of filter bag material and precision adapts to neutral, weak acid and weak alkaline liquid media. The whole unit complies with hygienic fluid design standards and becomes mainstream security filtration equipment for water treatment, fine chemical, food and pharmaceutical industries.
2 Main Structural Composition
Pressure-bearing Filter HousingMain materials include 304 and 316L stainless steel; anti-corrosion carbon steel and FRP plastic housing are optional. Cylinder is integrally rolled and welded with hydraulic tightness test before delivery. Mirror polished inner wall reduces dirt adhesion and facilitates cleaning. Inlet and outlet flanges are arranged on cylinder, quick-open sealed cover equipped on top; vent and drain ports reserved at bottom. Lifting lugs can be installed on large-flow multi-bag models for convenient hoisting.
Filter Bag Support BasketEach filter bag is equipped with independent stainless steel punched support basket as rigid carrier. It disperses fluid pressure during operation to prevent tensile deformation and rupture of filter bags, ensures full unfolding of bags and maximizes effective filtration area. High opening ratio of baskets does not obstruct fluid flow and lowers overall pressure loss.
Filter Bag (Core Element)Optional materials: polypropylene needle felt, polyester bag, nylon bag, PTFE acid & alkali resistant bag, precision ranging from 0.5μm to 200μm. Integrally sewn sealing lip on bag mouth matches housing compression ring to thoroughly eliminate bypass leakage. Contaminants are trapped inside bags to avoid secondary pollution of downstream medium during bag replacement. Cleanable reusable bags are available for certain working conditions to reduce long-term consumable investment.
Quick-open Sealing MechanismTwo mainstream types: rocker bolt quick-opening structure and clamp quick-opening design. Rocker type allows cover flipping after loosening fasteners without complete bolt removal; clamp version achieves faster disassembly suitable for frequent maintenance. Matched with high temperature resistant anti-aging rubber gaskets to maintain reliable sealing and medium leakage prevention during long-term operation.
Differential Pressure Monitoring Assembly (Standard Ports)Pressure measuring ports are reserved on inlet and outlet chambers for external pressure gauges and differential pressure transmitters. Operators judge dirt saturation status of bags via pressure difference and establish standardized replacement schedule to avoid blind shutdown or filter bag breakdown caused by over-resistance operation.
Equipment Support StandIntegrated vertical supporting legs welded at cylinder bottom for stable vertical placement. Uniform stand height reserves operation space for drain pipeline connection and bag extraction.
3 Working Principle
Process fluid flows into Bag Security Filter housing through inlet flange and evenly distributes outside each filter bag. Driven by system pressure difference, fluid penetrates fiber pores of filter bags. Particles, flocs and suspended solids larger than nominal bag precision are intercepted on inner wall of bags. Clean liquid continuously passes through filter bags, converges inside housing outlet chamber via support baskets and is delivered from outlet to downstream membrane systems or production processes.
During continuous operation, trapped contaminants accumulate inside bags, gradually blocking material pores, increasing flow resistance and inlet-outlet differential pressure. When pressure difference reaches recommended upper limit of 0.05~0.07MPa, shut down the system, close front and rear shut-off valves and release pressure & air. Open quick-open cover, remove contaminated used bags, install new bags and compress sealing. Close cover, finish venting and restart filtration system.Open bottom blowdown valve regularly to discharge coarse sediment accumulated at cylinder bottom, slow down bag clogging speed and extend service cycle of filter bags.
4 Basic Technical Parameters
Applicable medium: industrial pure water, circulating cooling water, reclaimed water, electroplating liquid, coating, food liquid, weak acid & alkali aqueous solutionHousing material: 304 stainless steel / 316L stainless steel / anti-corrosion carbon steel / FRPDesign pressure: 0.6MPa; non-standard upgrade available for high-pressure conditionsDesign temperature: 0~90℃ (upper limit adjusted according to filter bag material)Optional bag precision: 0.5μm, 1μm, 5μm, 10μm, 25μm, 50μm, 100μm, 200μmStandard bag size: #01, #02; non-standard customized sizes supportedStructure type: single-bag, double-bag, three-bag, multi-bag parallel modelConnection type: flange connection (GB standard, ANSI flange optional)Installation form: vertical floor installation
5 Core Product Advantages
Professional security protection design intercepts escaped impurities from pretreatment, protects expensive membrane elements and reduces membrane cleaning frequency.
Large dirt holding capacity of filter bags brings longer consumable replacement cycle compared with traditional cartridge security filters under equal flow rate.
Quick-open cover enables single-person bag replacement, short maintenance time and minimizes production line shutdown loss.
Diverse material combinations: 304 stainless steel for pure water & food industry; 316L or PTFE bags for chemical corrosive working conditions.
Strict anti-bypass sealing system eliminates short-circuit filtration, ensures stable precision and prevents direct impurity penetration towards downstream.
Hygienic polished housing reduces microbial breeding, suitable for pure water, beverage and pharmaceutical clean fluid processes.
No complicated matched backwashing pipelines required, lowering system construction cost and simplifying pipeline layout.
Complete specification series covers small-flow standalone units and large-flow multi-bag equipment; parallel installation supports capacity expansion.
Moderate operation pressure loss avoids excessive load on front water pumps and saves system energy consumption.
Complete unit delivered from factory. Only inlet, outlet and drain pipeline connection required on site for convenient installation and commissioning.
6 Installation, Commissioning, Operation and Maintenance Specifications
Confirm flow direction mark before installation and connect pipelines strictly according to inlet and outlet orientation. Shut-off valves are recommended upstream and downstream for offline maintenance. The foundation shall remain horizontal with even force on supports to avoid extra stress on cylinder. Install sealing gaskets between flanges and fasten all bolts diagonally and evenly to prevent leakage.Open inlet valve slowly for initial water feeding with gradual pressure rise, avoiding instantaneous high pressure impact leading to bag rupture. Fully open top vent valve before startup to exhaust air inside housing and eliminate air lock reducing filtration flux.Monitor inlet-outlet differential pressure during daily operation; arrange bag replacement in advance when pressure difference approaches upper limit. Long-term over-differential-pressure operation is prohibited to prevent bag rupture and massive impurity penetration damaging downstream membrane components.Pressure relief must be completed before opening cover for maintenance; never unlock quick-open mechanism with internal pressure. Inspect gaskets for hardening and cracking and replace aged sealing parts timely. Flush housing regularly and clean sludge deposited at bottom.Long-term operation exceeding design pressure and temperature is forbidden. Avoid direct impact of massive hard sharp particles on filter bags; install pre-filter on upstream side when necessary.
7 Common Faults and Solutions
Rapid differential pressure rise, re-clogging shortly after installing new bagsCauses: failed upstream pretreatment system with excessive suspended solids in inlet water; over-selected filter bag precision; medium containing massive viscous colloids.Solutions: overhaul upstream multimedia / activated carbon filter; replace filter bags with proper precision; evaluate adding pre-flocculation and sedimentation unit.
Deteriorated downstream water quality with massive particle penetrationCauses: damaged filter bag; fallen or failed bag sealing gasket; improperly installed filter bag; delayed replacement after pressure difference exceeding limit.Solutions: shut down and open cover to inspect bag integrity; re-compress filter bags and replace aged gaskets; strictly follow differential pressure maintenance standards.
Leakage at flanges and quick-open coverCauses: aged and deformed sealing gaskets; uneven bolt tightening; loosening caused by thermal expansion and contraction under temperature fluctuation.Solutions: install brand-new gaskets; lock fasteners evenly in diagonal sequence; retighten bolts regularly under high temperature conditions.
Persistently high system resistance under equal flow rateCauses: heavy sediment accumulated inside housing; inlet & outlet valves not fully opened; pipeline throttling; undersized flow capacity selected.Solutions: fully flush housing via blowdown valve; fully open pipeline valves; recalculate flow parameters and upgrade equipment specification if necessary.
8 Standard Supply List and Optional Accessories
Standard Supply List
Pressure-bearing stainless steel housing, quick-open cover assembly, filter bag support baskets, supporting stand, sealing gaskets, inlet & outlet flanges and connecting fasteners.
Optional Accessories
Complete filter bag sets, pressure gauge /differential pressure transmitter, vent valve, blowdown ball valve, lifting lugs, ANSI flange, thermal insulation cladding and duplex switching pipeline assembly.
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