- Scraper Strainer Advantage Over Backwash

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Acme scraper strainers resist clogging and fouling when faced with large solids and high solids concentration. Backwash strainers cannot remove oversize solids and will clog, requiring manual removal of the solids and cleaning of the filtration screen.

Acme scraper-type

  • Screen resistance to fouling and clogging: Scraper brushes get into wedgewire slots and dislodge resistant solids, assuring a complete cleaning. Works very well against biofouling.
  • Vessel fabrication and materials of construction: Custom vessel fabrication in CS, SS and alloys to minimize piping modifications in the field. All Acme vessels are fabricated and are cost competitive against most cast vessel pricing.
  • Water use on blowdow: Blowdown occurs only at the end of the intermittent scraping cycle. Valve is opened for a few seconds to remove solids from collector area. Liquid loss is well below 1% of total flow.
  • Speed of screen cleaning: Acme’s 4 scrapers rotate at 8 RPM, resulting in a cleaning rate of 32 times per minute.
  • Ratio of screen net open area to pipe area: Strainers are typically designed with a minimum screen to pipe ratio of 4:1. For finer screens, the vessel height is increased to accommodate a taller screen to increase the effective filtration area.
  • Control packages: Acme can use a wide variety of PLCs and can also control associated equipment such as pumps and valves.

Backwash-type

  • Screen resistance to fouling and clogging: Backwash often ineffective against stubborn solids which remain in screen openings and reduce performance.
  • Vessel fabrication and materials of construction: Usually cast vessels with pre-determined connection locations and orientations. Fabricated vessels on custom orders only, resulting in substantially higher prices.
  • Water use on blowdow: Backwash must be flowing in order to clean the screen. As screen becomes clogged with resistant solids, backwash intervals increase. Water loss is typically 5% of total flow.
  • Speed of screen cleaning: Backwash arms usually rotate at 3-4 RPM, resulting in longer backwash times to clean screen.
  • Ratio of screen net open area to pipe area: Strainers are typically designed with a screen to pipe ratio of 3:1 using a 1/16” screen slot. If the standard cast vessel is used and a smaller slot size is specified, the net open area decreases resulting in a lower flow rate or a higher pressure drop.
  • Control packages: Limited standard packages are offered, custom panels result in much higher pricing.

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