LKIF Inline Strainer

The LKIF is the simplest variant. Its perforated element sits between two pipe sections secured by clamp rings or union connections (DS, SMS). Liquid passes through the element; particles accumulate inside and are cleared by pulling the element out. Flow can run in either direction, which is useful for installations where the strainer must handle occasional reverse flow without repiping. Connection options include DS unions, SMS unions, and ISO clamp ends. Pressure drop and capacity data follow VDI 2173, measured with water at 20 °C.

LKSF Slot Strainer

The LKSF targets finer filtration duties. Its strainer element is welded at every intersection of vertical rod and surface wire, producing precise, repeatable slot openings. Standard slot sizes include 74, 105, 177, 500, 707, 1 000, and 2 000 µm; dozens of optional sizes extend from 53 µm up to 4 mm. Two housing variants exist. The LKSF-BL uses a two-part housing where product enters from the bottom, and particles collect inside the element for manual removal or backflushing. The LKSF-CL uses a three-part housing designed for vertical installation; product enters from the side, and most impurities settle at the bottom for manual or automatic discharge via paired valves.

LKVF Coarse Strainer

The LKVF is purpose-built for coarse particle removal. Its perforated tube element is available with 1, 2, or 3 mm holes. The recommended flow direction enters through inlet A (top) with a working pressure of up to 10 bar; reversing flow through inlet B reduces the maximum to 7 bar. Alternative seal materials — NBR or PTFE — are available alongside the standard EPDM. Connection options cover DS, SMS, ISO male, BS, DIN, and ISO clamp. If you need to protect a pump or membrane filtration unit from debris in a raw-product line, the LKVF is the typical first choice.

Upstream and downstream positioning

Strainers sit at points in a process line where unfiltered or partially filtered liquid could damage sensitive equipment or contaminate downstream product. A common upstream position is immediately after a receiving tank or tanker unloading point, where coarse debris — gasket fragments, scale, packaging residue — enters with the raw product. The LKVF serves this role with its 1–3 mm hole sizes and housing rated to 10 bar.

Downstream of mixing or blending vessels, finer filtration becomes the priority. Agglomerated ingredients, undissolved solids, or crystallised particles need to be caught before the liquid reaches homogenisers, heat exchangers, or filling equipment. The LKSF, with slot sizes down to 53 µm, handles these duties without excessive pressure drop at flow rates up to 120 m³/h.

CIP return lines present a different case. Here, the strainer protects the CIP return pump from debris flushed out of process equipment during cleaning. The LKIF is often sufficient — its perforated element and bi-directional flow capability mean it can stay in the line during the cleaning cycle without removal. Particles accumulate inside the element and are cleared during the next scheduled maintenance stop.

How filtration demands vary by sector

Dairy and brewery plants tend to process liquids with relatively large suspended solids — curd particles, hop fragments, grain husks — and prioritise throughput. Coarse or medium strainers (LKVF, LKIF) handle most of the work, with occasional fine straining (LKSF) before sensitive membrane filtration stages.

Food and beverage operations often deal with syrups, brines, or juices that carry finer particles. Adjustable slot sizes on the LKSF let operators match the strainer to the product without replacing the entire housing — just swap the element. The LKSF-CL variant, with its bottom-drain automatic discharge, suits continuous production runs where stopping to clean the element would disrupt output.

Chemical and pharmaceutical applications impose tighter requirements on materials and traceability. The AISI 316 wetted surfaces and EPDM seals meet standard hygienic material expectations, and the semi-bright surface finish simplifies cleaning validation. For pharmaceutical lines, the LKSF's 53 µm minimum slot size provides particle control ahead of sterile filtration stages.

Operating principle: mechanical screening

Every Alfa Laval strainer in this range operates on the same basic principle. Liquid enters the housing and is forced through a strainer element — a perforated or slotted barrier that allows the liquid to pass while trapping particles larger than the element's openings. The element is held in position inside a stainless steel housing secured with hygienic clamp connections. No moving parts, no consumable media, no external power. Filtration happens passively as liquid flows through.

The LKIF and LKVF use perforated elements — cylindrical tubes with drilled or punched holes. The LKIF element has a perforation rate of 40.2 % with hole dimensions of 1.5 mm and 2.25 mm. Strainer area on the LKIF ranges from approximately 4 400 mm² at 25 mm up to 50 600 mm² at 101.6 mm, and the element itself weighs between 0.027 kg (25 mm) and 0.299 kg (101.6 mm). The LKVF offers three hole sizes (1, 2, or 3 mm) with perforation rates of 23 %, 30 %, and 33 % respectively. Strainer area on the LKVF is 430 cm² for sizes 25–51 mm and 840 cm² for the 63.5 and 76.1 mm sizes. The higher open area of the LKIF means lower pressure drop for a given flow rate; the LKVF trades open area for structural strength, since its perforated tube must withstand pressure in both flow directions.

The LKSF uses a fundamentally different element. Its strainer is built from vertical rods wrapped with surface wire, welded at every intersection. This construction produces precise slot openings, measured in micrometres, that remain dimensionally stable under pressure and temperature cycling. The weld-at-every-point design also means there are no loose joints to harbour bacteria — a direct benefit for hygienic process lines. The LKSF's strainer area is 1 100 cm², and capacity reaches 10–120 m³/h with water at a differential pressure of 1 bar.

Flow paths and discharge options

Flow direction matters. The LKIF allows bi-directional flow — liquid can enter from either end, and particles accumulate inside the element regardless of direction. The LKVF has a recommended flow direction (inlet A, top) at up to 10 bar; reversing the flow through inlet B reduces the maximum working pressure to 7 bar. The element can handle both directions, but the housing geometry favours the standard path for particle collection and cleaning.

The LKSF offers the most flexibility. The LKSF-BL (two-part housing) works with bottom-entry flow and supports manual cleaning or backflushing — reversing the flow to flush accumulated particles out of the element. The LKSF-CL (three-part housing) adds a side inlet and a bottom collection zone. Two valves at the bottom enable automatic discharge during operation: the upper valve stays open during production, impurities settle between the two valves, and periodically the upper valve closes and the lower opens to purge debris with minimal product loss.

Selection factors

Choosing between the LKIF, LKSF, and LKVF comes down to several key variables.

Particle size target. If you need to catch debris above 1 mm, the LKVF is the straightforward option — select 1, 2, or 3 mm hole sizes. For general-purpose straining with moderate particle loads, the LKIF's perforated element at 1.5 / 2.25 mm works well. For anything below 1 mm, the LKSF is the primary choice, with standard slot sizes from 74 µm to 2 000 µm and optional sizes as fine as 53 µm.

Working pressure and vacuum rating. All three models are rated to 10 bar (1 000 kPa) in their standard flow direction. The LKIF and LKVF are both rated down to full vacuum. The LKVF drops to 7 bar if flow enters through the side connection (inlet B). The LKSF's maximum differential pressure in the flow direction is 10 bar.

Temperature. All three models share the same range: –10 °C to 140 °C with EPDM seals. This covers pasteurisation temperatures and hot CIP cycles without seal changes.

Connection standard. The LKIF supports DS unions, SMS unions, and ISO clamp ends. The LKVF supports DS male, SMS male, ISO male, BS male, DIN male, and ISO clamp. The LKSF covers DS, SMS, IDF, BS, Clamp, and DIN across all sizes. Match the connection to your existing pipework to avoid unnecessary adapters.

Strainers compared to other filtration methods

Inline strainers are not the only option for particle removal. Cartridge filters, bag filters, and membrane filtration systems also serve hygienic process lines. The comparison depends on your process conditions.

Strainers use a permanent, cleanable element. There are no consumable cartridges or bags to replace, which reduces ongoing material costs and waste. The trade-off is that strainers cannot achieve the sub-micron filtration that membrane or cartridge systems provide. A strainer's practical lower limit — 53 µm with the LKSF — is well above the ratings typical of sterile-grade cartridge filters.

Where strainers excel is in coarse-to-medium pre-filtration. Placing an LKVF or LKIF upstream of a cartridge filter housing extends the life of the consumable cartridges by removing the bulk particle load first. This is standard practice in beverage and pharmaceutical plants to control replacement costs. Strainers also tolerate full vacuum on the suction side and offer low pressure drop (documented per VDI 2173 for the LKIF) as a permanent line component.