High-flow, large-bore lines where fabricated construction, screen area, weight and access govern the design.
Above a certain diameter a strainer stops being a piping component that can be lifted by hand and becomes a fabricated vessel that has to be supported, accessed and maintained like one. Cast bodies are not available at these sizes, so construction is fabricated and the design is driven by flow area, weight and access rather than by a catalogue size.
Hydrotherms supplies fabricated basket and tee strainers to 78″+ (1980 mm+) and fabricated duplex strainers to 48″+ (1200 mm+). At these diameters the practical questions are how the basket is removed, how the unit is supported, and how the assembly is lifted and handled — and those answers have to be settled during design.
A large basket loaded with debris can exceed safe manual handling well before the strainer reaches its maximum size. Davit arms, hinged covers or lifting provision have to be designed in, not improvised.
The filled weight of a large strainer imposes real loads on the piping. Support arrangement, and often a skid or support legs, has to be considered alongside the piping stress analysis.
The space needed to withdraw a large basket is substantial and vertical. If it is not reserved in the plant layout, the strainer can be installed and still be effectively unmaintainable.
Large-bore strainers are fabricated to suit the required diameter, pressure class and flow area, with screen surface area sized to hold the pressure drop within the allowable figure at full flow. Where the required open area exceeds what a single basket can present, multiple basket arrangements or wedge-wire and pleated elements are used to increase surface area without increasing body size proportionally.
Access is engineered alongside the hydraulics. Quick-opening closures, hinged covers and davit arms make the basket recoverable at sizes where manual handling is not realistic, and support legs or skid mounting carry the filled weight. Welding is carried out to ASME IX with NDE to code requirements, and offset or rotated nozzles can be provided where the piping layout demands it.
Six governing inputs, one evaluation, four engineered outputs. At large bore the maintenance access and support arrangement carry as much weight as the hydraulic sizing.
Clearance for basket withdrawal is treated as a design input, because a strainer that cannot be opened in situ cannot be maintained.
| Requirement | Possible Solution |
|---|---|
| Large bore, high dirt-holding capacity | Fabricated Basket Strainer — to 78″+ |
| Large bore, continuous duty | Fabricated Duplex Strainer — to 48″+ |
| Large bore, compact space envelope | Fabricated Tee Strainer |
| Large bore, high or variable solids load | Automatic Strainer — to 48″+ |
At large diameters the deciding factors are usually the available clearance for basket removal and the acceptable downtime for cleaning, rather than the strainer body itself.
For large-bore duties we also need the space envelope and any site handling limits, because they constrain the design as much as the flow does.
Fabricated construction in carbon steel, low-temperature carbon steel, alloy steel, stainless steel, duplex and super duplex, and nickel alloys. For seawater and similar service, special external and internal coatings and zinc anodes are available. Material selection should be confirmed against the fluid, temperature and corrosion requirements of the project.
Reserve the vertical clearance required to withdraw the basket, and confirm it against the installed elevation early in the layout. Specify support legs or skid mounting for the filled weight, and davit arms or hinged covers where basket handling exceeds what is reasonable manually. Confirm lifting points and total assembly weight before the unit arrives on site.
Fabricated basket and tee strainers are available to 78″+ (1980 mm+), fabricated duplex strainers to 48″+ (1200 mm+), and automatic self-cleaning strainers from 4″ to 48″+ (1200 mm+). Consult Hydrotherms for sizes beyond these ranges.
Cast bodies are not practically available at large diameters. Fabricated construction also allows the body geometry, nozzle orientation and screen area to be configured to the specific duty and piping layout rather than to a standard casting pattern.
Through a quick-opening closure or hinged cover, usually with a davit arm to swing the cover and support the basket. The vertical clearance for withdrawal has to be reserved in the layout — it is frequently the constraint that determines where the strainer can be installed.
Usually. The filled weight of a large strainer imposes significant load, so support legs or skid mounting are commonly provided and the arrangement should be considered together with the piping stress analysis.
By screen surface area. Where a single basket cannot present enough open area, multiple basket arrangements, pleated baskets or wedge-wire screens increase the effective area without a proportional increase in body size.
Send flow rate, line size, fluid, pressure and temperature, allowable pressure drop, filtration rating and the clearance available for basket removal — plus any site handling limits.
Submit RequirementConstrained on space or lifting? Send the layout constraint and we will engineer the access arrangement around it.
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