Duplex strainers

The feed should feature constant viscosity and be free of foam and grit which can dog nozzles. Duplex strainers just before the feed pump are often used to accomplish the latter. 

Windsor. Berks SL4 IRD Tel +44(0)1628 440906 Fax +44 (0) 1628 475667 Email info oxfordfiltration.com Web wAW.oxfordfiltration.com Manufacturer and Supplier of Simplex. Duplex Strainers and Self Clean filters for virtually any fluid duty... 

Multi-element candle Multi-element leaf Plate frame press Precoat Nutsche and multielement leaf Precoat plate frame press Recessed plate filter press Sheet filter Single leaf Nutsche Bag Cartridge Dead-end membrane Fibre bed Low shear crossflow Sand bed Simplex strainer Belt press Duplex strainer High shear crossflow Rotary disc Rotary drum Sand bed Tower press Diaphragm filter press Expression (screw) press Horizontal element tube press Vertical diaphragm filter press Vertical element tube press... 

Figure 1.54 Schematic side and top views of a duplex strainer with two baskets (top) and photograph courtesy of Plenty Filtration (bottom).

An obvious disadvantage of a permanent strainer of the types just described is the need to shut down the plant flow so that they may be cleaned. Where continuous operation is required in a pipeline service, duplex strainers can be used in an integral unit with the provision to isolate one element at a time for cleaning, or even having multiple strainers in one unit (as shown in Figure 3.6). Individual strainer elements or baskets are then made accessible via cover plates with static seals (usually 0-rings). 

Duplex bosket strainer T-type strainer (pirmonent) T-type strainer (temporory) Vent... 

Duplex basket strainer —H )— T type strainer permanent) —— T type strainer temporary) X" —- Vent... 

Strainer body Cast iron Cast cupronickel Gimmetal 6% Mo austenitic high duplex... 

The duplex or multi-basket strainer must stiU be watched to check for the need to swap baskets. Self-cleaning strainers may be used as an alternative to dual or multiple strainers where continuous operation is critical in the process system. Two methods of self-cleaning are illustrated in Figure 3.7 - one uses a brush and the other a scraper. Brush cleaning is suitable for most applications, with scraper types more specifically suited for handling high-viscosity products. 

A eonsiderable proportion of hydrauhc filters are of the in-line strainer type (Figure 5.27), with an easily replaceable cartridge element, very often supplied in duplex form so that the element in one can be changed, while the other keeps filtering. The most common medium is a pleated paper or nonwoven sheet, fitted with protective layers front and back to provide the necessary strength (Figure 5.28). 

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