Control and check valves maintain the integrity of hygienic process lines by ensuring single-directional flow and precise pressure management. A check valve is a self-acting one-way device engineered to prevent reverse flow, while a control valve typically involves an external signal to modulate flow rates. Engineers and procurement teams frequently evaluate these components together as they provide the integrated flow security required in high-purity skids and transfer lines.

This category profiles the Alfa Laval LKC family of hygienic non-return valves, designed for industries ranging from dairy and brewing to biotechnology and pharmaceuticals. The range includes the LKC-2 for vertical flow and the LKC-H for horizontal configurations. These valves feature product-wetted steel parts made from 1.4301 (304) or 1.4404 (316L). Standard models are rated for a maximum inlet pressure of 1000 kPa (10 bar) and operating temperatures up to 140°C with EPDM seals. For high-purity sectors, the LKC UltraPure variant offers enhanced surface finishes and full supply chain transparency through the Q-doc documentation package.

You can find each variant of the sanitary check valve listed in the control and check valves collection, with the LKC and LKC UltraPure. The following sections provide the technical depth required for valve selection, including connection standards and working principles for hygienic installations.

Selecting the correct valve depends on the required function: flow modulation or backflow prevention. While control valves actively manage process variables, check valves react to line pressure to protect upstream equipment and maintain product quality. Within the non-return category, the Alfa Laval range is segmented by installation orientation and industry-specific hygiene requirements.

Non-return valves in this category share a common internal architecture consisting of a two-part valve body, valve plug, spring, and guide disc with four legs. However, the surface finish and elastomer selection vary by model. The LKC UltraPure provides internal finishes as low as Ra < 0.5 µm (SF1 designation), whereas standard LKC models typically feature Ra < 0.8 µm. For chemical compatibility, FPM (Fluorinated rubber) options are available alongside standard EPDM seals.

Mechanical connection options include weld and clamp ends to accommodate ISO and DIN tubing standards. Sizes range from ISO 25 to ISO 101.6, ensuring compatibility with pipeline diameters common in large-scale beverage and dairy plants. Selecting the specific model (LKC-2 vs LKC-H) is critical for system drainability and proper valve alignment during operation.

Hygienic non-return valves are utilized throughout process lines where reverse flow could lead to contamination or equipment damage. Because these valves are self-acting, they provide a secondary level of safety that does not rely on electrical or pneumatic infrastructure. The LKC range is widely employed in dairy, beverage, food, and personal care industries, covering both standard hygienic duties and high-purity requirements.

In dairy processing, the LKC-2 is typically installed on vertical risers following a pump to prevent milk from flowing back through the inlet when the pump stops. These units must withstand Cleaning-in-Place (CIP) cycles using caustic soda or nitric acid at temperatures up to 70°C. For brewing, the 316L stainless steel construction protects against the corrosive effects often found in fermentation and yeast handling environments.

For the pharmaceutical and biotechnology sectors, the LKC UltraPure variant meets the stringent demands of high-purity water (WFI) and product transfer. The availability of ASME BPE SF1 and SF3 surface designations ensures that these valves do not harbor microbial growth. Furthermore, the EPDM seals are compliant with both FDA and USP Class VI standards, providing the regulatory validation necessary for validated manufacturing processes. For more on monitoring, see our sensing and control collection or the CIP guide for cleaning recommendations.

Operating Principle

The operating principle of the LKC non-return valve is based on a spring-loaded pressure balance. The valve consists of a valve body in two parts, a valve plug (cone), and a spring, all secured by a clamp ring. A guide disc with four legs ensures the accurate alignment of the spring-loaded valve plug with its O-ring seal. When the inlet pressure exceeds the combined force of the spring and any backpressure from the outlet, the valve plug lifts off its seat, allowing for single-directional product flow.

If a reverse flow condition occurs, the spring force, aided by the downstream pressure, returns the plug to the seat, sealing the line. When installed in a vertical pipe, the differential pressure required to open the valve is approximately 6 kPa (0.06 bar). This low cracking pressure minimizes energy loss and cavitation risks while maintaining effective backflow prevention.

Selection Factors: Sizing and Materials

Effective valve specification requires balancing process pressure, fluid type, and installation geometry. The LKC range is rated for a maximum product pressure of 1000 kPa (10 bar). For vacuum applications, the valves are rated to full vacuum, providing flexibility in tank evacuation and suction-side duties.

The choice of elastomer is the primary driver for temperature and chemical resistance. EPDM seals are suitable for temperatures between -10°C and 140°C and are standard for most hygienic applications. If the process involves higher temperatures (up to 180°C) or aggressive fluids, FPM (Fluorinated rubber) seal rings should be selected. All seals are housed within the valve body and are accessible for maintenance by dismantling the clamp ring.

Installation and Maintenance Guidelines

Installation of these valves must account for flow direction, which is marked on the valve body. For welding ends, the valve should be disassembled prior to welding to avoid heat damage to the internal seals and O-rings. A minimum axial clearance of 5 mm must be maintained between the valve halves during welding to allow for future separation and maintenance of internal components. Proper vertical or horizontal mounting is necessary to ensure the valve remains fully drainable and functions according to its design specification.

Maintenance requirements for the LKC are straightforward. Alfa Laval recommends replacing seal rings every 12 months as part of a preventive maintenance schedule. If leakage is detected, the seal ring should be replaced by the end of the day to prevent escalation. Cleaning is typically achieved through Cleaning-in-Place (CIP) using caustic soda (NaOH) or nitric acid (HNO3). It is vital to use chloride-free water and to rinse the valve thoroughly after each cleaning cycle to prevent corrosion. During reassembly, all O-rings should be lubricated with USDA-H1 approved lubricants, such as Unisilcon L641 or Paraliq GTE 703, and the clamp screws should be tightened to a maximum torque of 10 Nm.