This SAE Aerospace Information Report (AIR) establishes the specifications and descriptions of the critical components and operational guidelines for the standard hydraulic impulse machine for testing hydraulic hose assemblies, tubing, coils, fittings and similar fluid system components.
This revision to the AIR1228 provides a description of a system that meets the requirements for specifications including: AS603, AS4265, and ARP1383. This impulse system utilizes closed loop servo control with specifically generated command signal waveforms.
Data accuracy and integrity are emphasized in this revision. Knowing the uncertainty of the pressure measurement is important whether using a resonator tube system, as described in the original release of this document, or a closed-loop systems as described in this release. The accuracy of the data measurement system and consistency of the pressure waveform are fundamental to test validity, regardless of the system type. This is discussed in more detail in Section 5.
The standard impulse test system is established for the following purposes:
As referee in the event of conflicting data from two or more nonstandard impulse machines. Such a referee system might be built by an impartial testing activity.
A design guide for future test systems being built by manufacturers and users, or the upgrading of present systems.
A design guide for higher pressure test systems or special purpose machines being designed.
It is not the intention of this document to obsolete present resonator type machines. The specification for the resonator type machine is available in the original release of this document.
A simple block diagram of the revised system is shown in Figure 1.
The simplified block diagram shown in Figure 1 does not use a resonator tube as in the original release of the specification. To eliminate undesired resonances the hydraulic system is as closely coupled as possible. In this design, the pressure waveform is created in closed loop proportional control via the command signal generated by the test controller system.
If the test controller is a computer with an impulse specific software application, it is possible to control all parameters of the specified waveform, within the capabilities of the hydraulic system. These parameters include things such as rise rate, damping, secondary oscillation amplitude, etc. In a resonator tube system, it is difficult to make adjustments to these parameters.