© ISO 2016 Aerospace series — Constant displacement hydraulic motors — General specifications Série aérospatiale — Moteurs hydrauliques à cylindrée fixe — Spécifications générales INTERNATIONAL STANDA[.]
Order of precedence
The detail specification shall take precedence in the case of a conflict between the requirements of this International Standard and the detail specification.
Hydraulic system characteristics
The hydraulic motor shall be designed to be operated by the hydraulic system as defined in the detail specification.
The detailed specifications must encompass the characteristics of the hydraulic system where the motor will be installed This includes providing flow versus pressure curves for the supply, return, and case drain lines across various hydraulic fluid temperatures Ensuring comprehensive details about these parameters is essential for optimal motor performance and system reliability.
— normal operating temperature (for example, +20 °C);
Airworthiness regulations
The hydraulic motor shall comply with the applicable airworthiness regulations.
Qualification
Hydraulic motors furnished under this International Standard shall be products that have passed the qualification tests that are specified in the detail specification.
Hydraulic fluid
The detail specification shall state the applicable hydraulic fluid.
Pressures
Rated supply pressure
The rated supply pressure value must be specified in the detailed specifications, selecting from the standard rated supply pressures listed in Table 1, which are derived from ISO 6771.
Pressure Class Metric system kPa basic Imperial system psi basic
Rated differential pressure
The rated differential pressure shall be specified in the detail specification.
No-load break-out pressure
The no-load break-out pressure shall be specified in the detail specification.
Motor return port pressure
The nominal return pressure shall be specified in the detail specification.
The rated motor return pressure (where applicable) shall also be specified in the detail specification Unless otherwise specified in the detail specification, the rated motor return pressure shall be
Case port pressure
The rated case port pressure shall be specified in the detail specification.
Caution should be taken defining the rated case pressure Too high a pressure may cause abnormal shaft seal and shaft bearing loading, affecting their operation and reducing the motor life.
The maximum case drain port pressure shall be specified in the detail specification.
Flows
Rated consumption
The detail specification shall state the value of the rated consumption, which shall be in l/min (or gpm).
Case drain flow
The detail specification shall state that the motor shall be capable of producing at least a minimum case drain flow.
The motor case flow rate [which shall be in l/min (or gpm)] shall be specified under the following conditions:
1) the motor turning at rated torque and speed;
2) the motor turning at zero torque;
3) the motor stalled, shaft locked at any position.
The minimum and maximum case drain flow shall be stated at conditions specified in the detail specification.
Shaft seal leakage flow
The detail specification shall state the value of the maximum dynamic shaft seal leakage (which shall be in drops/min) at the following conditions: a) New build:
— the motor filled with fluid, but un-pressurized;
— when subject to proof pressure at ambient temperature;
— when the motor is operating at rated consumption flow. b) Qualification testing:
— over the expanded test envelope;
— at the completion of the endurance test;
— when subject to proof pressure at rated temperature;
— when subject to ultimate pressure at rated temperature.
External leakage
No leakage sufficient to form a drop from the motor case or any static seal case is permitted, ensuring the integrity of the sealing system It is important to note that dynamic shaft seal leakage is not regarded as external leakage, emphasizing the importance of maintaining proper seal performance without unnecessary concern for acceptable shaft seal emissions These standards uphold operational safety, prevent environmental contamination, and ensure the reliable performance of motor equipment.
Speed and direction of rotation
Speed
The rated speed of the motor shall be specified in the detail specification.
NOTE As an indication, the maximum recommended values are given in the Nomograph in Figures 1 and
2 If speeds are kept well below those indicated by the curves, the operating life may be improved However, several system factors such as fluid, temperature, duty cycle, contamination, expected life, etc will also influence the values.
The motor must be capable of operating without failures at 125% of its rated discharge flow for a duration of 30 minutes, as specified in the detailed specifications This performance standard applies under the conditions outlined in Table 6 and/or Table 7 Ensuring reliable operation at 125% of rated flow is essential for pump system safety and efficiency, complying with relevant technical requirements. -**Sponsor**Looking to enhance your article's SEO and coherence? [Slim SEO](https://pollinations.ai/redirect-nexad/6OujH8g4) can help you optimize your content effortlessly, ensuring it ranks higher and is easily understood Slim SEO helps you to automatically optimize your content and meta tags for improved search engine performance For your article, focus on clearly stating that the motor should operate without failures at 125% of rated motor discharge flow for 30 minutes, as specified in relevant tables This ensures clarity and aligns with SEO best practices by highlighting key information succinctly.
The maximum no-load speed shall be specified in the detail specification.
The hydraulic motor is designed to operate efficiently in both directions of rotation without requiring modifications It should function satisfactorily unless specified otherwise in the detailed specifications To change the rotation direction, there is no need to alter the motor itself; simply reversing the flow direction will suffice This ensures easy and reliable operation in various applications.
NOTE For single direction of rotation applications, an improvement of weight and efficiency may be obtained by optimizing the timing design parameters for the intended direction of rotation.
Torque
Rated torque
The rated torque shall be specified in the detail specification.
Break-out torque
The break-out torque shall be specified in the detail specification.
Stalling torque
The stalling torque shall be specified in the detail specification.
Hydraulic motors operate with remarkable efficiency at low speeds, typically achieving up to 99% mechanical efficiency between 500 and 800 rpm This high efficiency highlights the importance of considering the hydraulic motor's performance when designing and stressing the mechanisms it powers.
Torque pulsations
The motor must be designed to provide continuous torque without excessive amplitude ripple, defined as over ±10% of the rated torque, when operated within the rated speed range This performance should be maintained under all conditions specified in Clause 15, ensuring reliable and efficient operation Proper design to minimize torque ripple enhances motor stability and longevity, aligning with best practices for motor performance compliance.
Y rated motor displacement in millilitres per revolution
X motor speed in rpm × 1 000 a Recommended maximum rated speeds.
Figure 1 — Nomograph of maximum recommended values for rated speeds against motor displacement (Metric units)
Y rated motor displacement in cubic inches per revolution
X motor speed in rpm × 1 000 a Recommended maximum rated speeds.
Figure 2 — Nomograph of maximum recommended values for rated speeds against motor displacement (American units)
Motor overall efficiency
The following efficiency values shall be stated in the detail specification:
— the overall efficiency of the motor when new;
— the overall efficiency of the motor after the endurance test, this value being considered as an
When calculating output power, only the net pressure difference between the inlet and outlet ports of the motor should be used The flow rate can be measured on the low-pressure side of the discharge line, provided that proper compensation for compressibility is applied during efficiency calculations Accurate assessment of pressure difference and flow rate is essential for precise power determination in hydraulic systems.
Dynamic characteristics
General
If requested by the purchaser, the motor polar moment of inertia and motor impedance shall be supplied to assist in developing system dynamic performance.
Dynamic braking
The motor shall be designed to withstand, at rated conditions, a braking torque which stops it in 0,02 s with no operating damage and with no reduction in performance.
The detailed specifications must specify situations where the motor experiences reversed pressures, known as pumping mode, caused by an overrunning load The motor should be designed to withstand the pressures and flows produced under these conditions, ensuring reliable operation in all scenarios.
Rapid reversals
If required by the application, the motor shall withstand, at conditions specified in the detail specification, rapid reversals of direction of rotation without damage.
Passive operation
Passive operation of the motor (for example in redundant systems), without fluid supply, shall be specified in the detail specification.
Rated temperature
ISO 8625-3 provides the requirements for temperature classification (Type I, Type II, or Type III) if the motor is to be used in a military aircraft or helicopter.
If the application is for a commercial aircraft, the detail specification shall state the rated temperature.
Acoustic noise level
If required, the motor shall have a maximum acoustic noise level at rated operating conditions The detail specification shall state its value together with the measuring procedure, when applicable.
During acoustic noise testing, the hydraulic test rig must have a circuit impedance as specified in section 15.3.5.2 It is essential to account separately for acoustic noise generated by nearby hydraulic or structural components attached to or surrounding the motor This ensures accurate measurement of noise levels attributable solely to the test rig Proper isolation and evaluation of external noise sources are critical for reliable acoustic testing results.
Rated endurance
The detailed specifications must include the duration and conditions of the endurance test If these details are not provided, the endurance test shall be conducted in accordance with Table 2 and clause 15.3.6, ensuring consistent testing standards.
The endurance test shall be conducted with the fluid cleanliness of the hydraulic fluid at the maximum
Table 2 — Duration and conditions of the endurance test
Category of motor (see Clause 4)
Operation with alternating load cycles A
Types I and II military applications 750 2 × 10 6
Types I and II military applications 250 1 × 10 6
Environmental requirements
The detailed specifications must specify the environmental and operating conditions that the motor will be exposed to, based on various ISO standards These include temperature and altitude, humidity, fluid susceptibility, vibrations, and acoustic vibrations, all in accordance with ISO 7137 and ISO 2671 Additionally, the specifications should address steady-state acceleration (ISO 2669), resistance to fungus and mould, salt spray, water, sand and dust, shock, and ice formation, primarily following ISO 7137 For motors used in fire zones, fire resistance as per ISO 2685 must also be detailed, ensuring comprehensive understanding of the motor’s durability under specific environmental and operational challenges.
Dimensionally critical components
Parts shall include mechanical means to prevent them from being installed incorrectly if a) they are likely to cause incorrect operation, b) they can cause damage if the installation direction is reversed, and c) they can be incorrectly located on assembly.
Maintainability features
All wear surfaces shall be replaceable or repairable.
Connections, mounting, and wiring provisions shall be designed to prevent incorrect coupling.
The design shall permit the line replacement of the unit or a module of the unit using standard tools only.
The design shall be such that special or unique equipment is kept to a strict minimum for shop repair, overhaul, and maintenance checks.
Seals
Static and dynamic seals must conform to ISO 3601-1:2012 series A standards The use of non-standard seals is permitted to meet this standard's requirements, provided that approval is obtained from the purchaser.
For motors used in commercial aircraft and military type III systems, back-up rings used shall be subject to the approval of the purchaser.
Lubrication
The motor shall be self-lubricated with no provision for lubrication apart from the circulating hydraulic fluid.
Balance
The motor's rotating parts must be inherently balanced around their primary operating axis to ensure smooth operation Proper balancing prevents vibrations caused by self-generated accelerations, maintaining motor integrity across the entire speed range The design must ensure that no part experiences structural compromise or yield, even at the maximum specified overspeed condition, to guarantee reliable and safe motor performance.
Self-contained failure
The motor must be engineered to securely contain all internal components in the event of a failure caused by an overspeed condition Specifying the maximum overspeed limits in the detailed specifications ensures safety and reliable operation under all conditions.
No loss of fluid from the motor shall occur as a result of the failure, other than the external and shaft seal leakages specified in the detail specification.
Safety wire sealing
A manufacturer’s non-metallic seal of guarantee may be used to indicate if the motor has been tampered with internally.
Lead-type safety wire sealing shall not be used.
Electro-conductive bonding
Ports
For optimal operation and maintenance, each hydraulic motor should have clearly and permanently marked inlet ports for each direction of rotation, alongside the case drain port and shaft seal port Proper identification of these ports ensures correct installation, troubleshooting, and ease of maintenance, promoting system reliability and efficiency Accurate markings help prevent operational errors and facilitate quick repairs, making clear port identification essential in hydraulic system design.
Proof pressure
Motor case
The motor case must withstand a minimum static pressure of 5,000 kPa (750 psi) unless specified otherwise It should endure the greater of its maximum case pressure or 1.5 times its rated pressure without sustaining permanent damage or compromising performance These specifications ensure the durability and reliability of the motor under defined pressure conditions.
Motor inlet port
The motor inlet port must be capable of withstanding a static pressure of 1.5 times the rated supply pressure without sustaining permanent damage or compromising performance, unless specified otherwise in the detailed specifications.
Motor return port
The motor return port is designed to withstand a static pressure of 1.5 times the rated pressure, provided the detail specifications do not specify a different value This ensures the port maintains its integrity without suffering permanent damage or impaired performance under such pressure conditions.
Ultimate pressure
Motor case
The motor case must be designed to withstand either the full system pressure or 2.5 times the rated pressure for the case, whichever is greater, ensuring no structural failure Unless specified otherwise in the detailed specifications, this standard guarantees the motor's durability and safety under operating conditions Properly engineered motor casings are essential for reliable performance and compliance with safety standards.
Motor inlet port
The motor inlet port must withstand a static pressure of 2.5 times the rated supply pressure, unless specified otherwise in the detailed specifications This ensures the inlet port's structural integrity under maximum pressure conditions Designing for this pressure threshold helps maintain motor performance and safety standards Adhering to these specifications is essential for reliable operation and compliance with industry safety requirements.
Motor return port
Unless the detail specification states a different value, the motor return port shall statically withstand a pressure equal to 2,5 times rated pressure for the motor return with no structural failure.
Pressure impulse (fatigue)
The motor shall withstand the fatigue effects of all cyclic pressures, including transients and external loads.
The detailed specifications must include the overall predicted duty cycle for various motor components throughout its operational lifetime, ensuring accurate performance assessment Additionally, they should specify the scatter factor used for analysis or fatigue testing, particularly for pressure impulse evaluations, to account for variability External loads impacting the motor must also be clearly defined to ensure comprehensive understanding of operating conditions and durability.
Port strength
The port structure and relevant areas of the motor case must be designed to withstand 2.5 times the maximum torque specified for attaching or removing unions and lines during installation and maintenance This ensures the motor remains undamaged and maintains correct operation without permanent distortion or alterations Properly engineered ports enhance the motor's durability and reliability in demanding operational conditions.
Materials
General
All materials shall be compatible with the hydraulic fluid that is specified in the detail specification. Materials and processes used in the manufacture of the motor shall
— be suitable for the purpose, and
— comply with the applicable official standards.
Metals
All metals used in hydraulic systems must be compatible with the fluids they contact, ensuring performance under designated service and storage temperatures Metals that are not in direct contact with hydraulic fluids should possess adequate corrosion-resistant properties or be properly protected, as outlined in section 9.2, to prevent corrosion and ensure system reliability.
If the use of specified materials and processes risks compromising the motor's properties or safety, alternative materials and procedures may be approved by the purchaser These alternatives should be selected to ensure maximum corrosion resistance while meeting the motor's operational requirements.
Ferrous alloys in hydraulic systems must contain a minimum of 12% chromium in their internal surfaces that are in constant contact with hydraulic fluid or be adequately protected against corrosion as specified in section 9.2 This ensures they maintain durability and performance in hydraulic applications, highlighting the importance of corrosion resistance in critical internal components Proper corrosion protection of these ferrous alloys is essential for the longevity and safety of hydraulic equipment, complying with industry standards.
Use of tin, cadmium, and zinc platings is prohibited for internal parts or surfaces that contact hydraulic fluid or are exposed to its vapors, ensuring compatibility and safety It is important to note that grooves designed for external O-ring seals are not classified as internal surfaces in constant contact with hydraulic fluid, avoiding misinterpretation of material requirements Follow these guidelines to ensure proper material selection, enhance device reliability, and comply with safety standards in hydraulic systems.
Magnesium alloys shall not be used.
9.1.2.3 Motors for type II and III systems and for commercial aircraft applications
Ferrous alloys used shall be suitably protected against corrosion as specified in 9.2.
Tin, cadmium, and zinc platings shall not be used for internal parts that are in contact with the hydraulic fluid or exposed to its vapour.
Magnesium alloys shall not be used.
Corrosion protection
General
Metals lacking inherent corrosion-resistant properties must be appropriately protected to prevent deterioration Suitable protective measures are implemented based on guidelines outlined in subsequent subclauses, ensuring resistance against conditions that may cause corrosion This includes safeguarding metals from environmental factors such as moisture, chemical exposure, and other corrosive elements that could compromise their integrity and longevity Proper corrosion protection enhances the durability and reliability of metal structures and components in various applications.
Ferrous and copper alloys
Ferrous alloys requiring corrosion-preventive treatment and all copper alloys, except for parts with bearing surfaces, shall receive surface plating selected from the following:
— electrolytic tin plating, in accordance with ISO 2093;
Electrolytic tin should not be used for internal parts, surfaces in contact with hydraulic fluid, or exposed to vapors, as well as surfaces subjected to abrasion, to ensure safety and durability Unless otherwise specified, the class and type of plating are determined at the supplier’s discretion, emphasizing the importance of proper material selection for optimal performance.
Electrolytic tin plating at 85% is a reliable metal coating that requires protection, typically achieved through anodizing In environments where abrasive conditions are absent, these plated metals can alternatively be protected with a chemical film for enhanced durability Proper surface treatment ensures the longevity and performance of metal coatings in various applications.
Exceptions shall be submitted to the purchaser for approval.
Aluminium alloys
All aluminum alloys must be anodized according to ISO 8078 and ISO 8079 standards In the absence of abrasive conditions, they may instead be coated with a chemical film following ISO 8081 These procedures are mandatory unless explicitly authorized otherwise.
Exceptions shall be submitted to the purchaser for approval.
Castings
Castings shall be of high quality, clean, sound, and free from cracks, blow holes, excessive porosity, and other defects.
Defects that do not significantly impact the suitability of castings can be repaired either at the foundry or during machining through methods such as peening, impregnation, welding, or other approved techniques All inspection and repair processes must adhere to quality control standards acceptable to the purchaser, ensuring the castings meet specified quality requirements.
Dimensions
Dimensions pertinent to the installation of the motor in aircraft shall be specified on the supplier’s installation drawing and in the detail specification.
Mass
The installation drawing of a fully assembled motor must specify its dry mass Additionally, the supplier and purchaser should mutually agree on the fluid volume contained within the motor to ensure accurate specifications and proper functioning.
Mounting
Unless otherwise specified in the detail specification, all motors shall incorporate a standard mounting flange, which shall be in accordance with ISO 8399-1 and ISO 8399-2.
When the mounting flange complies with ISO 8399-1 and ISO 8399-2 standards, the maximum motor displacement must correspond to the specific flange type as outlined in Table 4 This ensures proper mounting and optimal motor performance according to international standards Adhering to these guidelines guarantees compatibility and reliable operation of the motor assembly.
Table 4 — Relation between displacement and flange type
Maximum displacement cm 3 /r Maximum displacement in 3 /r Flange type —
Orientation
The mounting conditions of the motor shall be defined by agreement between the manufacturer and the purchaser.
Drive shaft
An easily removable shaft should be installed at the interface between the motor's rotating group and the actuation means it drives, such as a gearbox, unless otherwise specified in the detailed specifications This design ensures straightforward maintenance and assembly, enhancing operational efficiency Proper installation of a detachable shaft also facilitates easier replacement and servicing of the motor components Following the specified guidelines improves system reliability and flexibility for various applications.
The drive shaft shall be held in place by means of a positive locking system.
If required by the Procurement Specification, the drive shaft shall include a shear section.
The end of the drive shaft shall comply with ISO 8399-1 and ISO 8399-2 unless otherwise specified in the detail specification.
The following shall be specified in the detail specification:
— the loads other than those self-induced by the motor torque;
Ports
Unless otherwise specified in the detail specification, the port configuration shall be in accordance with ISO 7320.
Maintenance concept
The detail specification shall state the specified maintenance concept, for example, “On Condition”.
Service life limitations and storage specifications
The detail specification shall state the specifications and appropriate definitions and shall include the following: b) the storage life; c) the service life limit.
Equipment compliance
All of the reliability specifications shall be met throughout the service life of the equipment, assuming that all approved maintenance cycles have been carried out.
Requirements
The detailed specifications must clearly define key performance metrics such as the defect rate, failure rate, and safety rate (if applicable) Additionally, the specifications should include a comprehensive Failure Mode and Effect Analysis (FMEA) to ensure a thorough understanding of potential failure modes and their impacts, aligning with quality assurance and safety standards.
Responsibility for inspection
Unless otherwise specified in the contract or order, the supplier
— is responsible for carrying out all the inspection operations specified in this International Standard, and
— may use his own inspection and testing facilities or the services of any industrial laboratory approved by the national authorities.
National authorities have the authority to conduct necessary inspection operations as outlined in this International Standard to ensure that supplies and services meet specified quality and safety standards.
Classification of tests
The following test program shall be performed for the purposes of checking whether the motors comply with this International Standard: a) acceptance tests (see Clause 14); b) qualification tests (see Clause 15).
Test stand requirements
The tolerance limits for test stand operating conditions are established for acceptance and qualification tests, unless otherwise agreed upon by the supplier and purchaser Specifically, the discharge pressure tolerance is ±2% of the rated discharge pressure, with a maximum of ±200 kPa (±30 psi) The differential pressure tolerance is also ±2% of the maximum differential pressure, not exceeding ±200 kPa (±30 psid) Tolerance limits for inlet temperature are set accordingly to ensure consistent and reliable testing standards.
— +43 to + 107 °C, within ±6 °C. f) flow: within ±2 % of rated flow; g) shaft speed: ±100 r/m; h) torque: ±2 % of maximum motor input torque.
The accuracy of the instrumentation shall be consistent with the measurement tolerances required.
The test stands shall use sufficient filtration so as to maintain the cleanliness of the fluid to ISO 11218:— 2) Class 5, or better, except for the qualification endurance testing (see 15.3.6).
The hydraulic fluid in the test circuit shall be the same as that specified for the application (see 6.1).
General
Each motor delivered under a procurement contract must undergo specific examinations and acceptance tests to ensure quality and compliance It is important to note that approval of materials during manufacturing does not guarantee the acceptance of the final product Acceptance testing, as outlined in this International Standard, includes visual examinations and a comprehensive test program designed to evaluate the motor's quality, design, and adherence to performance requirements.
The initial production motor must undergo a First Article Inspection (FAI) with the purchaser’s representatives present Any identified deviations during the FAI must be corrected or mutually agreed upon before the first motor is delivered This process ensures quality control and compliance with specifications prior to full production.
Examination of the product
The motor must be thoroughly inspected to ensure compliance with all relevant international standards and the specific requirements outlined in the detailed specifications This examination is essential, especially for aspects not covered by specific testing procedures, to confirm the motor's adherence to quality and safety regulations Proper evaluation guarantees that the motor meets all necessary standards and performs reliably under specified conditions.
Test programme
General
Filters shall be installed in all the lines to and from the motor, as applicable.
The supplier must repeat relevant parts of the conformance test procedure if any working parts need replacement during testing However, the break-in run can be skipped if the rotating group assembly remains unaffected.
Throughout the test programme, the hydraulic fluid used shall be that specified in the detail specification.
External leakage requirements
Other than at the shaft seal, no external leakage of sufficient magnitude to form a drop shall be permitted.
During acceptance and calibration tests, the shaft seal leakage shall not exceed the values specified for new build conditions (refer to 6.3.3 a).
Break-in run
The break-in run should be conducted using specified pressure levels in the inlet and return lines, ensuring a test duration of at least 30 minutes at 30% to 75% of rated speed Additionally, the run must include a minimum of 30 minutes at 80% to 100% of rated speed, with a differential pressure maintained between 80% and 100% of the rated differential pressure.
Proof pressure and overspeed tests
Operate the hydraulic motor for 2 min at a speed equal to 125 % of the rated speed with a differential pressure as specified in the detail specification.
The motor must pass the test without any changes to its proper functioning, demonstrating its reliability and durability During testing, there should be no external leaks, except for shaft leakage, which must not exceed 5 cm³ per hour Ensuring these conditions confirms the motor's compliance with quality and safety standards.
Operate the hydraulic motor at its rated speed for 1 minute, maintaining an inlet pressure equal to 125% of the rated pressure Unless specified otherwise in the detailed specifications, use an inlet pressure of 3,500 kPa during testing.
(500 psi) at the outlet and case drain ports.
The motor must successfully pass testing without any changes to its proper functioning It should exhibit no external leaks, except for shaft leakage, which must not exceed 5 cm³ per hour Ensuring these standards guarantees the motor’s reliability and compliance with safety regulations.
14.3.4.3 Inlet port proof pressure test
With the motor shaft locked, pressurize the motor for 5 min to 1,5 times the rated supply pressure.
In the case of a bi-directional motor, both inlet/return ports shall be subjected to an independent proof pressure test.
14.3.4.4 Case port proof pressure test
With the motor shaft locked, pressurize the motor for 5 min to 1,5 times the pressure determined from 8.2.1.
Operational tests at rated conditions
The operation was conducted for 60 minutes at the rated inlet pressure, during which the opposing torque on the output shaft was varied from 50% to 100% of the rated value This testing was performed at a frequency of 6 cycles per minute to evaluate the system's performance and durability under different torque conditions.
There shall be no external leakage sufficient to form a drop Case drain flow shall be monitored There shall be no evidence of malfunction.
Break-out torque test
Operate the motor smoothly within a speed range of 0.5 rpm to 3 rpm, ensuring precise control Adjust inlet and return pressures to establish the specified pressure differential according to the detailed specifications Record the motor output torque continuously for at least 2 minutes to monitor performance The break-out torque is defined as the lowest torque value observed during the test, indicating the motor’s minimum operational threshold.
The test shall be conducted in both directions of rotation.
Teardown inspection examination
A teardown inspection shall be conducted on a minimum of ten motors of a given model of an initial production run or as specified in the detail specification.
The teardown inspection must be redone whenever there is an interruption in manufacturing continuity, with permissible downtime clearly specified in the detail specifications Additionally, a new teardown inspection is required when alternative tooling or production facilities are selected, ensuring compliance and quality assurance throughout the production process.
Following the break-in run and proof testing, thoroughly dismantle and inspect the motor for any signs of wear or damage If all components are found to be in acceptable condition, proceed with reassembly and run-in the motor according to the guidelines outlined in section 14.3.8 to ensure optimal performance.
If, at any phase in the testing, working parts require replacement, the entire conformance test procedure shall be repeated.
When the teardown inspection is no longer required, the run-in in accordance with 14.3.8 may be deleted.
Run-in
The run-in after teardown inspection shall be performed at 50 % to 100 % of rated speed for a period of
15 min with a differential pressure of 80 % to 100 % of the rated differential pressure.
Once the acceptance tests have been completed, measure and record the following parameters at rated conditions: a) supply pressure; b) inlet port flow; c) case drain port flow; d) rated torque.
This test is essential to prevent the shipment of motors that are functionally acceptable but exhibit material deterioration, indicating incipient failure It involves inspecting the motor case drain and/or discharge fluid for contamination, as specified in the agreement between the supplier and the purchaser, ensuring reliable motor performance and quality.
Inline particle counters are essential tools for early detection of motor failures by continuously monitoring particle sizes in the system An increase in particle count in the case drain line indicates potential motor wear or damage, signaling the need for maintenance If a noticeable rise in particles is observed after the initial break-in run, the motor should be shut down and removed for thorough teardown inspection to prevent further damage and ensure optimal performance Regular particle monitoring enhances maintenance strategies and extends motor lifespan.
When inline particle counters are unavailable, using filter patches is an acceptable alternative to detect early motor failures The standards for filter patches are either set by the manufacturer and specified in the detailed specifications or established during the functional testing of the first 25 motors.
Unless otherwise specified in the detail specification, all the filters used during the test shall be able to filter to a value less than or equal to 5 àm absolute.
Install filters in the outlet and case drain or cooling port lines of the test setup to prevent contamination Regularly check the fluid in the filter bowls following the procedure outlined in 14.3.10.3 to identify any contamination Conduct these checks after functional testing as specified in section 14.3.5 to ensure system cleanliness and optimal performance.
Collect the fluid from each filter bowl in clean containers and rinse both the bowl and element with an appropriate volume of suitable fluid solvent, then combine the rinsed fluid Pass the combined fluid through a 47 mm (1.85-inch) diameter membrane to trap contaminants, with the membrane material specified in the detail specifications Wash the membrane with fluid solvent to remove residual fluid, dry it thoroughly, and then coat the resulting filter patch with clear lacquer before permanently attaching it to the test log sheet.
All fluid solvent shall be filtered through a 0,45 àm pore size membrane prior to use in all stages of the patch preparation procedure.
Each filter patch specified in the acceptance test procedure shall be compared with the standard patch then in effect and any discrepancy noted in the test log.
If the contamination level exceeds the standard during testing, the filter patch test can be repeated The second patch must demonstrate contamination levels equal to or lower than the standard patch to be considered acceptable If it does not meet this criterion, the filter fails the test, ensuring strict quality control and safety standards are maintained.
To accurately diagnose contamination issues, up to two additional patch tests can be conducted to identify any ongoing trends If the patches continue to be deemed unacceptable, the motor should be disassembled to pinpoint the source of contamination Taking corrective action based on these findings is essential to restore motor performance and prevent future problems.
To ensure proper electrical insulation, measure the resistance between any point on the mounting flange face and designated points on the motor, such as the pipe connections The resistance value must not exceed the limit specified in the detailed specifications, ensuring safety and compliance.
The detail specification shall state the procedures for preservation and packing.
Effective packaging for motor shipments must protect against typical handling damages during transit, ensuring the motor's integrity Special attention should be given to safeguarding electrical connectors, thin metal components, and delicate parts to prevent any damage Proper packaging practices help maintain product quality and reduce return rates due to shipping-related damages.
The packaging must be suitable for storage in accordance with the shelf life requirements detailed in the specifications, ensuring proper care by the storage facility If the motor depends on internal hydraulic fluid for corrosion protection, hydraulic plugs should create a leak-free seal to maintain system integrity.
General
Qualification tests, with the purpose of checking whether the motor design is in conformity with the requirements of this International Standard, shall comprise the tests specified in 15.2.3.
Qualification procedure
Qualification by analogy
Qualification tests for motors may be waived if the motor shares the same or similar components as a previously qualified motor and operates under conditions that are not more restrictive than those of the qualified motor.
A report, substantiated by drawings showing the similarity with the already qualified motor, shall be submitted instead of carrying out the tests.
Motor qualification test report
A comprehensive test report must be compiled, detailing the performance and compliance of the motors with the specified requirements The report should include a thorough assessment of test results, describing the testing procedures, instruments used, and providing schematic diagrams and photographs as appropriate Complete test data should be presented in table format, with specific descriptions of the hydraulic test systems for each test Additionally, assembly and installation drawings should be appended to provide a full understanding of the testing process and equipment used.
Samples and program of qualification tests
The qualification tests shall be conducted on two sample motors (A and B) It is essential that these sample motors are representative of the motors to be manufactured.
The qualification tests, together with the suggested order that they are conducted, are given in Table 5.
Table 5 — List and sequence of qualification tests
Tests Sample Clause, subclause, etc to be referred to
— Stalling torque and internal leakage X X 15.3.5.7
Proof pressure at rated fluid temperature X 15.3.8.4
Supplementary tests X or X 15.3.9 ensure that shaft seal leakage is permitted to degrade only up to the limits specified in the detailed specification (see 6.3.3) If a fire resistance test is required, an additional test specimen must be used to accurately assess performance under fire conditions.
Qualification testing
Dimensional check
Before beginning the qualification test, perform a complete acceptance test on both test sample motors to ensure optimal performance If required, conduct the run-in process outlined in 14.3.8 after resetting the motors, prior to resuming the test sequence This ensures the motors meet quality standards and are prepared for the qualification testing phase.
Check the critical wear dimensions and record the dimensions of each test sample motor Check these dimensions again for comparison purposes once the qualification tests have been completed.
Expanded envelope acceptance tests
Acceptance tests must be repeated, during which the motor is operated across a range of fluid temperatures from minimum continuous to rated, and pressures from zero up to the rated differential pressure, ensuring comprehensive performance verification.
Overspeed test
The hydraulic motor must demonstrate no signs of deterioration after operating at 125% of its rated speed for 2 minutes During testing, it should maintain optimal performance under a differential pressure specified in the detailed specifications This ensures the motor's reliability and durability under high-speed conditions.
Operational test at overpressure
Hydraulic motor performance must remain unaffected after running for 1 minute at its rated speed under an inlet pressure of 125% of the rated pressure, with 3,500 kPa (500 psi) at the outlet and case drain ports, unless specified otherwise in the detailed specifications For bi-directional motors, this testing procedure should be conducted on both inlet ports to ensure consistent performance.
Calibration
The calibration test is carried out before and after the endurance test, and comprises the tests described in 15.3.5.3 to 15.3.5.7.
The hydraulic system impedance, along with the inertia and stiffness of the opposing load applied to the motor shaft, must match the specified operating conditions outlined in the detailed specifications Ensuring these parameters align is crucial for optimal system performance and reliability Proper calibration of the load's inertia and stiffness helps maintain system stability and efficiency during operation Adhering to the specified impedance values ensures the hydraulic system functions effectively within its designed parameters.
Measure the motor torque and case inlet and drain flow rates at the specified fluid inlet temperature outlined in the detailed specification Conduct these measurements after operating the system for at least 5 minutes at motor rotation speeds of 25%, 50%, 75%, and 100% of the rated speed under the designated testing conditions.
— motor outlet and case drain pressures of 200 kPa to 1 400 kPa (30 psi to 200 psi, relative);
The motor must deliver an output torque at all specified rotation speeds that is not below the rated torque, ensuring reliable performance under various operating conditions Additionally, the drain flow rate must stay within the limits detailed in the specifications to maintain system efficiency Efficiency should be calculated based on the obtained test results, providing an accurate measure of the system's performance.
Install a relief valve set at 125 % of the rated pressure, adapted to the test conditions, in the supply line.
With the motor at rated supply and speed conditions, apply a braking torque to the shaft in order to decelerate continuously from the rated speed to zero within 0,02 s.
The motor shall not be damaged in any way which would jeopardize its subsequent operation.
This test shall be specified in the detail specification.
This test shall be specified in the detail specification.
15.3.5.7 Stalling torque and internal leakage
To measure the stalling torque, set the outlet port and case drain port pressures according to the specified values in the detailed specifications Gradually reduce the speed while increasing opposing torque until the rotation halts Ensure the measurement is taken at the rated supply pressure to obtain accurate results.
The measurement shall be taken at four equispaced stopped positions Only the minimum value shall be recorded and it shall be specified in the detail specification.
For each of the measurements, the leakage flow rate shall be less than the specified values.
Endurance testing
The requirements for the endurance test programme for motors in continuous operation are given in Table 6 and for motors subjected to alternating loads in Table 7.
The endurance time or the number of cycles in operation for the motor category and the type of system is specified in Table 2.
The motor under test shall satisfactorily complete the specified endurance test programme with no failure of parts and no excessive wear.
Table 6 — Endurance testing — Continuous operation
Percentage of rated differential pressure
Case and outlet fluid pressure Inlet fluid temperature
6 a 110 ± 2 60 to 100 Minimum a See 15.3.6.5. b The low-pressure operating period (50 % of the rated differential pressure) lasts for
The testing process involves a 12-minute (±0.5 minutes) high-pressure operating period at 100% of the rated differential pressure This is immediately followed by a 3-minute (±0.25 minutes) high-pressure phase, maintaining the same rated differential pressure The transition between these two periods must occur in less than 1 second to ensure precise and reliable testing conditions.
Table 7 — Endurance testing — Alternating load
Percentage of total number of cycles
Percentage of corresponding load at rated torque a
Case and outlet fluid pressure b
1 25 See Fig- ure 3 0,25 100 ± 2 50 400 kPa to
The load is driven on a half-sine wave, ensuring smooth and efficient operation For servo-controlled motors, it is essential to display inlet, outlet, and case pressure values to monitor performance accurately The sine wave should be positive in the clockwise direction and negative in the counter-clockwise direction, passing through zero RPM to ensure proper directional control and stability.
Key a Clockwise. b Counter-clockwise. c 80 % of speed change shall be within this time interval. t time in s
Figure 3 — Square wave speed cycle test
Carry out 500 starts and stops at the beginning and end of the endurance test, under the conditions of the first and last phases, respectively.
The test system loading and supply conditions shall be controlled so that motor differential pressure surges of 120 % to 150 % of the rated differential pressure occur during each start and stop.
15.3.6.3 Endurance in operating reversibility (bi-directional motors only)
Avoid applying any static or dynamic loads to the output shaft during operation To test the shaft's performance, reverse the rated speed following a sine wave cycle at a frequency of one cycle per second, utilizing suitable supply methods.
The test shall last 1 h without interruption.
The hydraulic fluid used in the endurance test must meet the specifications outlined in the detailed documentation, with the test system filled at the start and no additional fluid added until the test concludes Exceptions to this rule include replacing fluid lost during filter checks, fully replacing the fluid if the system suffers damage leading to loss or contamination unrelated to the motor's endurance, and adding fluid as necessary to maintain its physical and chemical properties within specified limits set by the purchaser.
A record shall be made of when and how much fluid is added.
15.3.6.5 External leakage permissible during endurance testing
Throughout the endurance test (including the recalibration time), there shall be no external leakage sufficient to form a drop, except for the shaft seal (refer to 6.3.3 b).
Pass the hydraulic fluid used for the endurance tests through a 5 μm absolute filter before entering the test system.
For endurance tests, install 15 μm absolute filters on the fluid inlet, outlet, and drain lines unless the detailed specifications specify a contamination class or filter capability If the specifications specify a contamination class, ensure the appropriate filters are used to meet the required fluid cleanliness level, maintaining optimal system performance.
During endurance tests conducted at intervals of 100 hours ± 20 hours, ensure all three filters are fitted with clean filter elements After resuming the test for 2 hours, replace the used filter elements with new, clean ones and inspect the removed filters in accordance with section 14.3.10.3 to evaluate their condition.
If a part failure causes an interruption in the endurance test programme, the motor must be replaced or repaired with a part of a modified design In cases of material defects or manufacturing errors, it may be possible to use a replacement part of the same design as the original, provided it is free of defects.
The program is deemed complete once all motor parts meet the detailed specifications without failure If tests continue after some parts fail and are repaired or replaced, subsequent failures of parts that previously met endurance requirements will not be grounds for rejection.
After completing the endurance test, operate the motor at 20% rated speed and 100% rated pressure for 15 minutes to assess performance under sustained load conditions Recalibrate the motor at 25%, 50%, and 100% of rated speed, ensuring measurements are taken at zero or the lowest possible outlet pressure and at 100% rated inlet pressure This process optimizes motor calibration, ensuring accurate operation and reliability across varying operational parameters.
The rate of leakage of the shaft seal shall not exceed 5 cm 3 /h.
The motor consumption shall not have increased by more than 25 % from the consumption rate prior
Environmental tests
Tests must be conducted on the motor or its relevant parts if compliance with environmental requirements cannot be demonstrated through analogy or analysis, ensuring adherence to regulatory standards.
All temperature requirements must be consistently maintained for the motor body, hydraulic fluid, and ambient environment, which may vary by ±10 °C To ensure optimal performance, start the motor and uniformly accelerate to 50% of the rated flow rate within 10 seconds, unless specified otherwise in the detailed specifications, following a minimum wait time of 72 hours.
— at the minimum inlet temperature specified in the detail specification, or
— between –50 °C to –55 °C, unless otherwise specified in the detail specification.
After at least 18 h at the minimum inlet temperature, start the motor with no load and accelerate consistently up to the rated speed.
To ensure reliability, repeat the test 25 times at 120% of the rated differential pressure with a load matching at least the motor's rated torque During these tests, the refrigerating equipment's capacity and start interval should maintain the motor body temperature and oil reservoir at −55 °C ± 5 °C across all 75 starts, unless specified otherwise in the detailed specifications.
A trace of break-out torque shall be made during the 25 loaded starts.
There shall be no evidence of any deterioration in the motor structure or subsequent operational performance.
To ensure proper motor testing, maintain the motor at a temperature of −55 °C ± 5 °C for at least 6 hours in the absence of specific detailed conditions Subsequently, supply the motor with fluid heated to at least +90 °C and accelerate it to its rated speed in under 2 seconds while applying the rated torque on the output shaft Once at the rated speed, sustain this operation for 5 minutes to verify performance and reliability.
There shall be no evidence of any deterioration in the motor structure or subsequent operational performance.
The detail specification shall state the motor running speed and the flow rate to be used for this test.
Structural tests
15.3.8.1.2 Position of a motor under test
To ensure comprehensive testing, mount the motor sequentially in three different positions on a vibration-generating mechanism Conduct all specified tests outlined in the detailed specifications for each position, emphasizing that in one position, the vibratory movement must occur parallel to the motor's centerline This approach guarantees accurate assessment of the motor's performance and durability under various vibration conditions.
15.3.8.1.3 Motor operation during vibration tests
During the vibration tests, the motor shall operate at the rated load and speed, unless otherwise specified in the detail specification.
Identify the resonance frequencies by analyzing the double amplitude and frequency charts according to ISO 7137 Ensure that the applicable procedures and test values are clearly specified in the detailed specifications to maintain accuracy and consistency in testing. -**Sponsor**Struggling to make your technical writing SEO-friendly? It's tough! With [Article Generation](https://pollinations.ai/redirect-nexad/NgD4lDN0), you can transform complex text into engaging, SEO-optimized content instantly Imagine turning dry ISO standards into compelling paragraphs that rank high and save you thousands compared to hiring a writer Get 2,000-word articles without the content creation hassle!
Submit the motor to vibration testing at the resonance frequency, followed by cyclic vibrations in accordance with ISO 7137 The specific procedures and test parameters must be detailed in the technical specifications to ensure compliance with industry standards.
Other vibration tests shall be specified in the detail specification when a special installation imposes particularly severe environmental conditions.
The motor shall be subjected to a pressure impulse test to demonstrate that the motor complies with the requirements of 8.3 The detail specification shall state the following:
— the frequency of the application of the pressure impulse;
— the shape of the pressure impulse wave form;
— if the fluid temperature is at room temperature only or at various temperatures including the minimum continuous, ambient and the rated temperature.
A permanent record detailing the pressure impulse test's dynamic pressure and time history must be maintained Unless mutually agreed upon by the purchaser and supplier, this testing process should be repeated systematically at each specified interval to ensure consistent performance and compliance.
15 000 cycles to ensure that the pressure/time history of the impulse is maintained.
No evidence of cracks in any part of the component shall occur.
No permanent distortions or alterations in the ports and the relevant areas of the motor case shall occur.
15.3.8.4 Proof pressure test at rated fluid temperature
Prior to the test, take measurements of key dimensions Then conduct the proof pressure tests as specified in 14.3.4.3 and 14.3.4.4, but with the hydraulic fluid at its rated temperature.
Then measure the same dimensions and check that no permanent damage has been caused to the motor.
The ultimate pressure test to verify compliance with section 8.2 must be conducted once for a duration of 5 minutes For bi-directional motors, both inlet and return ports are required to undergo independent ultimate pressure tests to ensure proper performance and safety standards.
Conduct the test with the hydraulic fluid at its rated temperature.
This test should be conducted last on one specimen since no further operations on that motor are specified.
Remove the drive coupling from the motor and prepare it for the torsion test Apply torsional load to the coupling until failure occurs, ensuring accurate recording of the load at failure The coupling should fail at the shear section, indicating the maximum torsional strength This procedure verifies the coupling's durability under torsional stress, essential for assessing its performance and safety.
Supplementary tests
Supplementary tests such as a bench handling drop test and a package drop test (together with the test procedures to be used) may be specified in the detail specification.
[1] ISO 6771, Aerospace — Fluid systems and components — Pressure and temperature classifications