How to Select APS, ABS or GBS Air Isolators from Operating Conditions

Air isolator selection should not begin with product appearance or total mass. It should begin with the customer's actual operating conditions.

For engine, powertrain, NVH, durability, four-poster road simulation and heavy floating-foundation systems, the same total mass can lead to a different series and model when the center of gravity, support coordinates, dynamic loads and allowable motion change. The correct sequence is to define the operating condition, select the series, and then use point support reactions and the required working point to screen the model.

Step 1: Collect eight operating-condition inputs

1. Test object and equipment purpose: engine, powertrain, component, NVH, durability, road simulation or precision platform.
2. Total load and center of gravity: include the bench, fixtures, test specimen and accessories, with center-of-gravity coordinates.
3. Support layout: support count, coordinates, available envelope and local structural stiffness.
4. Excitation range: lower and upper frequency limits, speed range, dominant orders and transient shock.
5. Allowable motion: vertical travel, lateral displacement, torsion and start-stop motion boundaries.
6. Foundation conditions: building floor, ground foundation, floating mass or existing steel platform stiffness and settlement conditions.
7. Installation space: target working height, equipment envelope, maintenance access and air-line routing.
8. Air supply and controls: available pressure, air quality, leveling method, condition monitoring and fault protection.

Step 2: Decide whether APS, ABS or GBS is the right series

The AISTECH V1.0 Performance and Selection Data Manual defines three current engineered-isolation series with 23 controlled models. The following boundaries are for initial series screening and do not replace working-point calculations.

APS membrane air isolators

Best suited to: engine, powertrain, NVH and precision test benches where stable support, leveling and environmental resistance are important.

• Eight controlled models: APS165, APS200, APS280, APS320, APS380, APS530, APS640 and APS800.
• Rated working height: 158 mm; working pressure: 3-6 bar.
• Primary checks: point load, center-of-gravity offset, torque reaction, working height and leveling.

ABS convolution air isolators

Best suited to: fatigue, durability and dynamic test benches or floating foundations that require more dynamic travel, a broader height range and a wide support-load range.

• Ten controlled models: ABS165, ABS215, ABS250, ABS325, ABS385, ABS440, ABS530, ABS580, ABS715 and ABS950.
• Rated working height: 115-200 mm; working pressure: 3-7 bar.
• Primary checks: point load, load distribution, travel, lateral stability and air-system response.

GBS belted air isolators

Best suited to: four-poster road simulation, large inertia platforms, heavy floating foundations and systems with vertical, lateral and multi-axis dynamic loads.

• Five controlled models: GBS510-300, GBS610-300, GBS720-300, GBS845-300 and GBS845-1200.
• Rated working height: 300 mm or 1200 mm; working pressure: 4-8 bar.
• Primary checks: dynamic and lateral loads, foundation stiffness, restraints and motion boundaries.

Step 3: Confirm the model from point reactions and performance curves

A model code or quick-selection table is only a screening tool. The final model must be checked on its controlled model curve at the same working height and pressure used to evaluate support force and dynamic performance.

1. Calculate the reaction at each support from total mass, center-of-gravity coordinates, support coordinates and structural constraints.
2. Select a candidate model and available pressure curve within the chosen series.
3. Confirm the intersection of target working height and point reaction, with adequate air-pressure adjustment margin.
4. At the same working point, read stiffness, vertical and lateral natural frequency, travel and motion limits.

Important: support force, dynamic stiffness and natural frequency vary with pressure and height. Do not use linear or proportional extrapolation outside the controlled curves.

Four common selection errors

• Dividing total mass evenly and ignoring center-of-gravity offset or torque reaction.
• Checking only static support force without start-stop loads, shock, lateral force or maximum travel.
• Comparing isolator bodies without defining leveling, air lines, auxiliary volume, restriction and restraints.
• Ignoring the stiffness of the foundation or steel platform, which changes the actual system response.

What should be submitted for an engineering review?

Prepare the equipment purpose, total mass, center-of-gravity coordinates, support coordinates, speed or excitation range, maximum allowable motion, target height, foundation drawings, air-supply conditions and required control method. AISTECH engineering will first confirm the series direction and then review the support layout, working point and system configuration.

Review the 23 controlled models | Download V1.0 performance and selection data | Submit operating conditions