OK 10A

Purpose of OK 10A in an onboard system

OK 10A is a Hydraulic check valve that allows the working medium to pass only in the direction marked on the body and automatically blocks reverse flow. Its published working medium is AMG-10 hydraulic fluid. The unit is a functional element of a defined line, not an independent pressure source. Correct selection depends on more than the body marking: connection geometry, working medium, flow direction, pressure class and the exact execution must all agree with the installation. This page was rebuilt from the specialist Uralprom catalogue and cross-checked against available aviation documentation; specifications were not borrowed from visually similar products. This check is particularly important for legacy designations that may appear with a space, a hyphen or no separator in paper passports, stock databases and export lists. Search forms help identify the item, but they do not change its physical execution.

How the OK 10A unit operates

Differential pressure from the permitted direction overcomes the closing element and opens the passage. Reverse differential pressure drives the element onto its seat and isolates the line. The action is automatic, with no electrical command or separate actuator. The valve does not create pressure and does not regulate normal flow; its defined task is to prevent unwanted movement of the medium in the opposite direction. Reliable operation depends on a clean working medium, serviceable seating surfaces and seals, undamaged threads and correct body orientation. If a connected actuator does not hold position or line pressure falls, maintenance personnel normally inspect not only OK 10A, but also the pump, filter, pipelines, fittings, power cylinder and adjacent valves in the same circuit.

Published operating data and connections

Published catalogue data gives a nominal pressure of 25.5 MPa / 255 kgf/cm², a nominal flow capacity of 30 L/min, hydraulic resistance of not more than 0.1 MPa / 1.0 kgf/cm² at nominal flow, an operating temperature range of −60 °C to +150 °C, and the following opening parameter: approximately 0.05 MPa / 0.5 kgf/cm²; exact tolerance must be checked in the passport. Mass: not more than 0.22 kg. Length 99 mm; flow-passage diameter 10 mm; connection thread M18×1.5. These values help distinguish the unit from similar catalogue positions and verify the mounting location. The published family table contains a typographical defect in the opening-pressure row, so the catalogue value is not presented as a precise tolerance without a passport check. Before installation, the figures should be checked against the product passport, current technical specification and documentation for the particular aircraft. If the supplied unit or its passport records a different execution, the documentation accompanying that unit takes precedence.

Installing OK 10A and confirming aircraft applicability

Installation area: Aircraft hydraulic pressure line. The OK 10A designation is documented in the main and backup hydraulic systems of Mi-8 / Mi-17 family helicopters and in Tu-154 hydraulic-system documentation. This confirms use of the designation, but it does not make different family executions interchangeable. Routine maintenance normally includes checking the marking, flow direction, connection tightness, body condition and contamination. Selection by diameter or photograph alone is unsafe because a similar body may be produced for another medium, thread, flow capacity or setting. Pumps, cylinders and distributors connected in the same circuit are associated components, but they perform different tasks and must not be presented as interchangeable with this unit. Before installation, the unit should be examined for corrosion, damaged threads and evidence of unsuitable storage; after connection, the approved leakage and functional checks should be completed. Test pressure, preservation method and depreservation procedure cannot be assigned from a general family description and must come from the passport or approved repair documentation. If the nameplate and accompanying documents disagree, installation should stop until the execution is clarified.

Designations, documents and related products

The primary English catalogue designation is OK 10A. Procurement lists, export records and Cyrillic documentation may also use: OK-10A; OK10A; ОК 10А; ОК-10А; ОК10А. These forms are included to identify one product, not to create separate items. An enquiry should state the complete marking, system type, working medium, mounting position, required condition, delivery set and whether a passport or test record is needed. The control valves and hydraulic units category also contains related positions: OK 8A, OK 10B, OK 12A, GA 111. They belong to the same commercial and functional group, but an internal link does not establish compatibility or interchangeability. The final selection must follow the illustrated parts catalogue and approved aircraft documentation. Serial number, production date and actual delivery set are confirmed separately for the specific supplied unit.

Product Type: Hydraulic check valve

Designation: OK 10A

Russian Designation: ОК 10А

Alternative Designations: OK-10A; OK10A; ОК 10А; ОК-10А; ОК10А

Function: Passing the working medium in the permitted direction and blocking reverse flow

Working Medium: AMG-10 hydraulic fluid

Nominal Pressure: 25.5 MPa / 255 kgf/cm²

Nominal Flow Capacity: 30 L/min

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

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

Opening Parameter / Thermal Relief: approximately 0.05 MPa / 0.5 kgf/cm²; exact tolerance must be checked in the passport

Connection Data: Length 99 mm; passage 10 mm; thread M18×1.5

Mass: not more than 0.22 kg

Aircraft Type: Mi-8 / Mi-17 family; Tu-154

System / Installation Area: Aircraft hydraulic pressure line

Nearest Associated Components: Pump, filter, pipeline, distributor and power cylinder in the applicable circuit; exact Part Numbers must be checked in aircraft documentation

Interchangeability: Not established; related positions are not automatic substitutes

Condition: New

Warranty: 6 months

Technical Documentation: Product passport, technical specification, system diagram and illustrated parts catalogue when available

Technical Data Source: Specialist Uralprom catalogue; ambiguous rows are identified and require passport verification

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