AIR AMPLIFIERS

Typical Applications:

What is a Haskel Air Amplifier?

An Air Pressure Amplifier is an air pump that is driven by part of the incoming compressed air supply enabling it to cycle and pump the balance of the supply to a higher output pressure. Pressure is generated by the use of a differential area piston assembly (Fig 1). Low pressure air applied to a large area creates high pressure air on the small area. Cycling is achieved through the use of two pilot valves that alternately pilot and vent the large area end of an unbalanced cycling spool. The small area end of the cycling spool uses a permanent air spring. This unbalanced cycling spool ensures that the air amplifier cycles on demand.

Unique seal technology enables the drive section of its pressure generating products to operate without air line lubrication. No lubrication of any kind is used in the high pressure sections where non-metallic bearings and wear compensating seals are employed.

The ratio of the areas between the connected pistons is called the area ratio and is the dash number used in all model codes. This ratio and the available air drive source pressure determines the maximum outlet pressure of the air amplifier.

The completely sealed air amplifier will “stall” at its maximum capable outlet pressure and consume no energy or generate any heat while doing so. When pressure drop is seen at the air amplifier outlet, the unbalanced spool ensures cycling to make up the pressure loss and will again “stall” after having done so.

Double acting and two stage models are available which provide increased output and efficiency as well as using input air directly on the high pressure piston(s) in both stroke directions to increase drive force and output pressure capability.

A proven range of horsepower sizes is available to meet most high pressure air requirements; from our 1/3 HP for low flow/static applications to our 8 HP used for high flow dynamic applications.

Sizing Air Amplifiers

Several factors are involved in the proper sizing of Haskel air amplifiers. Some involve the specific parameters of the application while some involve the application itself.

Specific parameters include:

• Outlet pressure required (Po)?
• Minimum available air drive pressure (Pa)?
• Available air drive flow (Qa)?
• Supply pressure (Ps)? (In most cases, Pa = Ps)
• Required flow (Q) at the outlet pressure?

Application data includes:

• Duty cycle?
• What is the high pressure required for?

Testing — what is the volume of the vessel and time required?

Part Ejection — what is the cycle of volume requirements?

Actuation — what is the bore & stroke of the actuator(s)?

• single or double acting?
• is high pressure air required on each stroke (double acting)?
• Which stroke?
• is high pressure air required for the entire stroke length(s)?
• what are the cycle requirements?

Selecting Required Ratio

Dividing the outlet pressure (Po) by the drive pressure (Pa) will provide us with the minimum area ratio of the amplifier(s). The dash number in the model code represents the area ratio. More than one amplifier may be required: in certain high flow or heavy duty applications two or more amplifiers can be used in parallel; in certain higher flow/high pressure applications, a two-stage amplifier or multiple amplifiers can be used in series. Haskel offers a range of standard multipump units. Multipump units are most effective when the models selected produce the same flow for their respective pressure amplification.

Determining Flow

We should verify the of flow required (Q) by evaluating the application data. Finding that high pressure air is required only at the end of stroke or only on one stroke of the cycle may reduce the initial assessment of flow (Q).

Another consideration will be whether an air receiver used downstream can reduce the size of the amplifier required when the system cycle is taken into account (use high pressure air from the receiver during the on cycle and recharge the receiver during the off cycle) or enable momentary high flow requirements that initially are thought to exceed the capacity of our units. Haskel offers system options that include air receivers and controls.

Operation Guidelines

While Haskel manufactures air amplifiers for a wide range of pressures, care must be taken when sizing units for high outlet pressure applications. All air contains moisture and as you compress air, the moisture level does not reduce along with the volume of the air. The result is the same volume of moisture in a reduced volume of air. This saturation can lead to excessive maintenance for the air amplifier and the system. Dry, inexpensive gases such as nitrogen can be effectively used in the high pressure sections for these higher outlet pressure requirements (600PSIG and higher for example). For critical gas quality, refer to the use of our gas booster compressors which feature separation between drive and high pressure sections.

Other considerations include cycling rate and operation in unloaded conditions (i.e., before supply pressure has equalized or with small differential between supply and outlet pressures).

Cycling rate will be a factor of outlet pressure but can also be controlled by “throttling” the air drive volume. Various manual and automatic controls are available to prevent “no load runaway”.

Cycle Rates

The maximum outlet flow and cycling speed are represented on the performance curves at the point where the outlet pressure and supply/drive curves intersect. These maximum cycling rates are not recommended for continuous duty (where the pressure and flow requirements for a system are constant) and the air amplifier performance should be derated for these applications to approximately 50% of maximum. Cycling speed at a given outlet flow can be calculated by dividing the outlet flow by the ‘free air volume’ displacement per cycle. The ‘free air volume’ for each air amplifier model can be calculated from the Piston Displacement per cycle (Db).

Piston Displacement per cycle data is shown in the Model Selection chart.

When the maximum outlet flow from a performance curve has been determined, it can be converted to cycling speed by dividing the outlet flow by the ‘free air volume’ displacement per cycle. This cycling speed can be then de-rated for a for a continuous duty application and converted to rated continuous outlet flow (multiply ‘free air volume’ displacement per cycle x de-rated cycle speed) for improved seal life.

Multiple units can be used in parallel if necessary to meet required outlet flows and maintain acceptable cycle rates for continuous duty applications.