Law of superposition
The law of superposition states: If an input variable (xe1) brings about an output variable (xa1) and also another input variable (xe2) brings about an output variable (xa2), therefore: if the law of [...] superposition applies, the sum of the input variables (xe1 + xe2) is therefore equal to the sum of the output variables (DIN 19 226):
Volumetric efficiency
absorbed or issued) flow rate to the theoretical flow rate based on the displacement kinematics and the rotation speed. For pumps: Effectively delivered flow rate Q 1eff to the theoretically delivered flow [...] flow rate ( displacement volume V 1, drive rotation speed n 2 ): For motors: Theoretically absorbed flow rate Q 2th ( displacement volume V 2, rotation speed n 2 ) to effectively absorbed flow rate.
Class of accuracy
identifier that mostly corresponds to a the value in % of the actual value or of the end value. Example for electrical measuring instruments: 0.1 — 0.2 — 0.5 — 1 — 1.5 — 2 (VDI 2600).
Surface roughness
elastomers, which are liable to become scratched, very strict regulations are laid down with regard to surface roughness: For the purpose of sealing non-moving surfaces, an R a of 0.5 to 1.5 μm is often used. However [...] refers to the unevenness of actual surfaces based on the material involved and how is has been processed. Surface roughness is largely responsible for the wear experienced by seals. In order to provide [...] However, in order to minimise the debris from seals on moving surfaces, the R a for these must not exceed 0.25 μm. However, since the R a value — just like R t or R max — does not say anything about whether
Time constant
Also called the delay time. It is the time, which the output signal of a 1st order delay element requires to reach 63% of the end value. After 3 · T 95 % and at 5 · T almost 100 % of the end value (Figure [...] The term time constant is –– not completely correctly –– used if systems (e.g. ) can be assumed to be 1st order systems (e.g. if the natural frequency is somewhat dampened and the valve behaviour in the [...] the subsystem does not play a role) or in the case of comparable elements with an increase according to an exponential function. The time constant results as the inverse of the loop gain :
Pressure
pascal: 1 Pa = 1 N/m2. In fluid technology p is mostly stated in bar (1 bar = 105 N/m2). However, MPa (106 N/m2) is also used. Pressure figures, if not otherwise stated, in fluid technology are to be understood
HFD fluids
and HFD S. Other compositions (HFD U). Common to All HFD fluids is the lack of compatibility with most materials for seals and a high density of 1.15 to 1.4 g/cm3 (intake characteristic!), which complicates
Power limiting
combustion engines, i.e. with variable rotation speed, the torque M 1 will be kept constant the same way by V 1 adjusting itself to the changing pressure. If more than one pump is being used at a combustion [...] easier to adjust the installed power to the maximum pressure or flow rate requirements associated with a load cycle ( Figure L 15 ). In practice, power limiting is still predominantly referred to as "power [...] product of the flow rate Q and pressure p to a maximum value, so the power drawn cannot exceed the drive power installed. Power limiting may be subordinate to some form of pressure reduction ( pressure
Servo motor
characteristics: Uniform movements over a large range of speeds, velocities and loads (often more than 1:1,000). This means that the displacement, oil leakage flows and friction moments should be independent [...] from stick slip . The inertia should be small to achieve a good dynamic performance. When moving from a standstill, slight pressure differences must enable it to break away. The movement should be equal in
Damping D
an undamped continuous oscillation and D = 1 an aperiodic oscillation (Figure D 5). For reasons related to control technology, D should be between 0.5 and 1.