Filters · Continuous Process Duty

Duplex filters

Two filtration chambers served by a single changeover valve, permitting the element to be exchanged without stopping the process. Flow is directed through one chamber while the other is isolated, vented, drained and opened, after which the duty is transferred.

Duplex filters differ from duplex strainers in the element they accept. Where a duplex strainer carries twin baskets on coarse and medium retention duty, a duplex filter is configured for basket, cartridge or bag elements according to the required cut point, which extends the arrangement to fine filtration on continuous process lines.

Request a quotation View specification

Flair twin chamber duplex filter with transflow changeover valve

Photograph of completed unit
Duplex Filters

Configuration

Basket, cartridge or bag, on the same changeover

Basket configuration 5 micron and above

Mesh lined or wedge wire baskets retaining from five micron upward. Cleaned and reinstated rather than replaced.

Cartridge configuration Fine filtration

Replaceable cartridge elements for fine filtration, ordinarily downstream of a coarser stage. Cartridge count and length selected against the flow rate and the required change out interval.

Bag configuration Higher solids

Replaceable filter bags supported in perforated restrainer baskets, applied where solids loading is higher and operating cost is the governing consideration.

Changeover Transflow standard

Three way transflow valve of our own manufacture as standard, with a twin valve arrangement where line size, pressure rating or material selection requires it. Lever, gear operated or actuated.

Specification

Standard range

Where a stated range does not cover a particular requirement, equipment is engineered to the customer specification.

Size range	25 mm to 400 mm
Construction	Twin chamber, fabricated or cast
Design code	ASME Sec VIII Div 1, IBR on request
Filtration range	5 micron and above with basket elements, finer with cartridge or bag elements
Element type	Basket, cartridge or bag according to configuration
End connections	Flanged, screwed, socket weld or butt weld
Changeover	Three way transflow valve or twin valve arrangement
Operation	Lever, gear operator, pneumatic actuator or electric actuator
Options	Differential pressure gauge across both chambers, individual drain and vent connections, pressure equalising line, jacketing, internal polishing, skid mounting

Materials of Construction

Grades routinely handled

Carbon Steel SS 304 SS 304L SS 316 SS 316L

Alloy and duplex grades are quoted against the process fluid. Where the duty requires a cleanable finish, internals are polished and the geometry is arranged to drain completely.

Applications

Where these units are installed

Continuous process lines in refineries and petrochemical facilities Lubricating oil and seal oil systems serving rotating equipment Fuel oil supply to boilers, engines and turbines Pharmaceutical and fine chemical process streams Any filtration duty where isolation of the line would require a plant shutdown

FAQ

Common questions

Which element type should be selected?

Baskets where the retention is five micron and above and the element is to be cleaned and reinstated rather than replaced. Cartridges where the cut point is finer and a replaceable medium is acceptable, ordinarily downstream of a coarser stage. Bags where solids loading is higher and operating cost is the governing consideration. Send us the flow rate, the solids loading and the required cut point and we will recommend against the duty.

Is flow interrupted during changeover?

No. The transflow port maintains flow throughout the transition rather than closing at mid travel, so the standby chamber takes up the duty before the duty chamber is isolated. The isolated chamber is then vented, drained and opened with the process still running.

What is the difference between a duplex filter and a duplex strainer?

The element it accepts. A duplex strainer carries twin baskets on coarse and medium retention duty; a duplex filter is configured for basket, cartridge or bag elements according to the required cut point. See our duplex strainers where the duty is strainer duty.

Can the changeover be actuated for remote operation?

Yes. Pneumatic and electric actuation are both available, with limit switches fitted for position indication back to the control room. Actuation is ordinarily specified where the filter is installed at height, in a hazardous area, or on a line that is monitored rather than attended.

Enquiry

Request a quotation for Duplex Filters

Give us the line size, flow rate, fluid and operating conditions and we will engineer directly against them. Most enquiries are answered the same working day.