OK-18

OK-18 High-flow check valve

OK-18 is a high-flow check valve that provides one-way passage and automatic reverse-flow protection in a compatible pressure line. It is a functional part of the applicable hydraulic or pneumatic system and should be selected by exact designation and installation documentation rather than by appearance alone.

Operating function of OK-18

Forward differential pressure opens the internal element, while reverse pressure closes it against the seat. The action is automatic and does not require a separate cockpit command or electrical supply. Reliable operation depends on clean working media, serviceable seals, correctly connected lines and a calibrated configuration that matches the technical documentation.

Role in the aircraft system

The existing technical record gives 25.5 MPa nominal pressure and 200 L/min nominal flow, making this a higher-capacity member of the related OK check-valve group. Hydraulic resistance at nominal flow is recorded as not more than 0.1 MPa. Connected units form one operating circuit, but each performs a separate task and must not be presented as interchangeable merely because it is installed in the same system.

Installation and maintenance checks

Public information does not reliably confirm the exact aircraft system or working medium for this execution. Selection must therefore be based on the product passport, 18 mm passage, M30×2 connection and the hydraulic or pneumatic schematic of the installation. Maintenance checks normally cover connection tightness, body condition, contamination and compliance with the specified test limits. Any calibration or adjustment must follow the product passport or approved repair documentation.

Identifying OK-18 for ordering

Confirm the OK-18 marking and compare pressure, medium, port thread and flow direction. Similar OK-series bodies can have materially different capacities, so related catalogue positions are not automatic substitutes. Other related items are listed in the valves category. An enquiry should identify the required execution, condition, delivery set and supporting documentation.

Product Type: High-flow check valve

Designation: OK-18

Russian Designation: ОК-18

Function: One-way flow with automatic reverse-flow protection

Nominal Pressure: 25.5 MPa / 255 kgf/cm²

Nominal Flow Capacity: 200 L/min

Hydraulic Resistance: Not more than 0.1 MPa / 1.0 kgf/cm² at nominal flow

Opening Pressure: Approximately 0.5 kgf/cm²; exact tolerance must be checked in the passport

Operating Temperature: −60 °C to +150 °C

Length: 135 mm

Passage Diameter: 18 mm

Connection Thread: M30×2

Mass: Not more than 0.65 kg

Working Medium: Must be confirmed from the product passport for the exact installation

Installation: In the marked flow direction according to the applicable system diagram

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Returns & Changes (Restocking Fee)
For selected items, a RESTOCKING FEE of 10% may apply in case of return, order cancellation, or changes to the order specifications. This condition applies only to certain products and is confirmed at the order approval stage.

Warranty
All products are covered by a standard 6-month warranty.
Extended warranty is available upon request and is agreed individually; it may affect the final product price.