Strainers · Pump Suction Duty

Pot strainers

A pot strainer is installed immediately ahead of a pump to retain scale, weld spatter, sand and construction debris carried in the suction line. The body is cast in the smaller sizes and fabricated from rolled plate in the larger, and the strainer is also referred to as a bucket strainer where the element lifts vertically out of the housing.

Suction duty places a particular requirement on the design. The strainer must retain debris without absorbing suction head the pump cannot spare, which makes open area the governing figure rather than the finest mesh that will physically fit. We size the element against the available NPSH margin and state the clean pressure drop in the offer.

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Flair cast pot strainer on a pump suction line

Photograph of completed unit
Pot Strainers

Construction & Types

Cast in the smaller sizes, fabricated in the larger

Cast General service

Cast body in the smaller sizes, economical for standard duty on water, oil and general service. Cover is bolted or eye bolt, and the element lifts clear without disturbing the pipework.

Fabricated Larger sizes

Rolled and welded from plate, constructed to ASME Sec VIII Div 1 where the duty requires. Applied in larger sizes, at higher pressures, and wherever a specific material or a non standard dimension is called for.

Cover arrangement On cleaning frequency

Bolted, swing bolt, eye bolt or quick opening, selected against the anticipated cleaning frequency. Where the element is heavy, a hinged davit is fitted so the cover is handled by one operator.

Specification

Standard range

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

Size range	15 mm to 600 mm
Construction	Cast or fabricated, simplex
Design code	ASME Sec VIII Div 1 on fabricated units, IBR on request
Filtration range	Coarse to medium
Open area ratio	Ordinarily 3:1 or 4:1 against pipe bore, selected against available NPSH margin
Element type	Perforated sheet, mesh lined perforated sheet, wedge wire
End connections	Flanged to ASME B16.5 or equivalent, screwed, socket weld or butt weld
Cover type	Bolted, swing bolt, eye bolt or quick opening
Options	Differential pressure gauge, drain and vent connections, magnetic insert, lifting davit, legs or support lugs, jacketing

Materials of Construction

Grades routinely handled

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

Alloy steel, duplex stainless and other grades are quoted against the process fluid. Element material is selected independently of the body, and a carbon steel housing fitted with a stainless element is a routine specification.

Applications

Where these units are installed

Pump suction protection on transfer, circulation and booster duty Fuel oil and lubricating oil supply lines Cooling water circuits in power and process plants Raw and utility water services Chemical and solvent transfer where a compatible grade is specified Protection ahead of positive displacement pumps sensitive to particulate

FAQ

Common questions

What is the difference between a pot strainer and a basket filter?

Pot strainers are applied to coarse and medium retention at pump suction, where pressure drop governs the selection. Basket filters are applied to inline filtration where the cut point governs. If the object is to keep debris out of a pump, specify a pot strainer and size it on open area. If the object is to achieve a stated micron rating, see our basket filters.

How much pressure drop should be allowed at pump suction?

Pressure drop across a clean strainer is a function of open area, not of mesh alone. As the open area of the element rises relative to the pipe bore, the clean pressure drop falls and the margin before cleaning is required widens. Suction duty rarely tolerates much: send us the available NPSH margin with the flow rate and fluid, and we will calculate the required open area and state the clean pressure drop in the offer.

Can a replacement element be supplied for a housing of another manufacture?

Yes. Send us the original element, or the housing dimensions together with the required mesh or perforation, and we will manufacture a matching replacement. Element material is selected independently of the housing, so a stainless element for a carbon steel body is a routine supply.

Should a differential pressure gauge be fitted?

We recommend it on any continuous duty. Differential pressure across the housing, not elapsed time, is the reliable indicator of when the element requires cleaning. Fitting the gauge at the time of order means the interval is read directly rather than estimated, and the element is cleaned when it is actually dirty.

Enquiry

Request a quotation for Pot Strainers

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.