In applications where plant processes require large volumes of industrial water to be treated prior to use, re-use or discharge, the Boll selfclean strainer offers the optimal solution.
The Boll Selfclean 6.19 Strainer Advantage
Thanks to the unique large filter surface area of specially designed open-ended filter elements, the Boll selfclean strainer sets the standard for process quality and performance in the industry. The advantages are clear:
- maintenance free operation,
- uninterrupted, reliable operation of the entire plant
- reduced plant operating costs by extending the life of systems and machines
The Design
The high precision Boll selfclean strainer features simple, yet rugged construction. Boll housings are manufactured either in cast iron, carbon steel or stainless steel. Boll strainers are available in flange sizes up to 36`` for flow rates up to 40,000 gpm. Filter elements and all internal components are stainless steel. The only moving parts are the flushing and throttling arms. All contact parts are self-adjusting. The carbon-impregnated Teflon bearing and flushing bushings are sealed to guarantee efficient back flushing.
During the straining process, fluid flows through the inlet flange into the bottom of the filter housing. A partial flow of approximately 50% of the unfiltered fluid is fed through a central riser in the filter element assembly to the top of the filter housing and into the open filter elements. The remaining fluid flows through the bottom of the filter elements.The fluid flows through elements from the inside out.
During the cleaning cycle, each element is cleaned in succession, with no interruption of the straining process. Backflow is achieved with filtered process fluid (type 6.18) or an external fluid (type 6.19), for operating pressures less than 29 psi, or when straining sticky contaminants. High-pressure water or steam can be used as the external fluid in the type 6.19. Backflushing is controlled automatically based on either inlet/outlet pressure differential or pre-set time intervals.
The Features
- large filter surface area
- long filter service life
- extended maintenance intervals
- simple, quick cleaning and maintenance
- optimized automatic backflush cycle (complete cleaning in 13 seconds)
- precise degree of filtration
- modular system with multiple options
- efficient removal of filtered solids
- simple handling
- compact design
- low pressure drops
- low operating costs
- minimal backflushing quantity
The Process
The Boll selfclean strainer uses open ended cylindrical filter elements. As fluid flows through both ends of the elements, particles in suspension are trapped along the entire length of the elements. This ensures that contaminants are distributed uniformly over the entire filter surface area. As deposits accumulate, differential pressure across the elements rises and triggers a backflushing cycle automatically. A gear motor starts the cycle by sliding the throttling arm over the upper end of each filter element.
Simultaneously, the flushing arm is rotated, sealing the lower end of each element, and the sludge drain valve is automatically opened. The pressure gradient generated between system pressure and atmospheric pressure allows a small quantity of fluid to flow from the outside through the elements (axial or reverse flow), detaching the particles from the elements. At the upper end of the filter elements, the throttling arm provides a cross flow, flushing down the detached particles. The combination of axial and cross flows provides a highly effective flushing action, uniform across the entire filter surface area.
The Applications
- chemical / petrochemical
- process water
- cooling water for production, air conditioning and power
- fire protection
- sewage treatment
- filtering treated effluent for use as process water
- filtering effluent to be discharged into open waters.
- pulp & paper
- process water
- washing (injection) water for papermaking machines
- oil & gas / offshore
- injection water for oil rigs
- HVAC
- cooling water (e.g. for air-conditioning systems, computer rooms)
- mining
- process water
- cooling water
- automotive
- process water, weld water, cooling water and power
- fire protection
- steel
- caster: spray nozzle cooling water, internal machine (IM)
- hot strip mill: laminar flow, work roll, descale water
- cold mill: makeup water for hydraulic systems, emulsions
- snow making
- water for snow-making machines
- power generation
- cooling water for turbines and oil circuits
The Open-Ended Filter Element Advantage
Because the filter elements are cylindrical and open at both ends, the selfclean strainer offers significant advantages over other strainers that use conical or expanding disc elements:
- The Boll cylindrical strainer elements require less frequent replacement than conical or cylindrical elements as the unique backflush action prevents the elements from getting clogged. The result is savings in labor and replacement part costs;
- The Boll selfclean strainer elements separate solids more reliably than strainers that use expanding discs. With expanding discs, contaminants can become trapped in-between the discs, deteriorating the level of filtration; and
- Unlike conical or expanding disc filter elements, BOLL elements can be fitted with either lateral slot wedge wire or vertical slot wire. This option provides superior cleaning results, particularly suited for fibrous particle filtration.
- Flushing intensity with open-ended elements, throttled at the top
- Lateral slot wedge wire
