How does an air driven liquid pump work?

Key Characteristics

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Air Inlet Port

Air Drive Tube

Drive Piston

Upper Tappet Valve

Pilot Air Tube

Spool Valve

Lower Tappet Valve

Pilot Vent

Outlet Muffler

Inlet Check Valve

Outlet Check Valve

Drive Air Flow

Exhaust Flow

Air Drive Mechanism

This part features a lightweight piston with a seal inside a robust aluminum barrel. In any given series, the air piston size remains uniform. The drive air propels the piston downward in the compression stroke and upward in the suction stroke. Thanks to the low friction forces and pre-assembled lubrication, air drive line lubricators are not required.

Hydraulic Mechanism

Attached to the air piston, the hydraulic piston/plunger resides within the hydraulic pump head's lower section. The size of this piston determines the pressure ratio, output flow, and maximum pressure capability. Its role is to draw liquid into the hydraulic body via the inlet check valve and expel it through the outlet check valve at a high pressure.

The spring-loaded check valves direct the liquid's path through the pump. During the hydraulic piston’s suction stroke, the inlet check valve fully opens, and liquid is drawn into the pump while the outlet check valve remains closed. In the pressure stroke, the inlet check valve shuts as the hydraulic piston forces the liquid out through the outlet check valve.

A seal around the hydraulic piston prevents external leaks and cross-contamination with the air drive. The seal's material and design depend on the liquid being pumped, its temperature, and pressure rating.

NOTE: A separation piece can often be used between the air drive and hydraulic sections for contaminant-free operation.

Spool Valve Operations

This part includes an unbalanced, pilot-operated spool that directs compressed air to the air piston based on its position. The air piston activates pilot valves at each stroke's end, alternating air pressure and vent control to the spool valve, enabling automatic cycling. The main drive air vents out through an exhaust muffler. Advanced pumps may use a pilot air port for enhanced friction and pressure control. This area is also suitable for deploying pump control devices.

Air driven liquid pumps employ a reciprocating differential area principle that transforms compressed air power into hydraulic power via a large air drive piston connected to a smaller hydraulic piston. The relationship between the hydraulic plunger's area and the air drive piston is depicted in the model number, indicating the maximum pressure the pump can generate. Real-world ratios may vary, so consulting technical charts is recommended.

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Example:

P.R = Pressure Ratio = 1:49

PA = Air Drive Pressure = 80 psi

PO = Max Outlet Pressure = 39 x 80 = 3,120 psi

Raising the air drive pressure to 100 psi would result in an outlet pressure around 3,900 psi at stall. All pumps have a maximum air drive pressure rating of 160 psi.

Initially, the pump cycles rapidly, acting as a transfer pump filling the test piece or actuator. As outlet pressure increases, the pump's cycling rate slows and eventually stalls when air drive and hydraulic pressures balance.

Due to minimal friction from the large diameter air drive piston and hydraulic seals, the hydraulic pressure drop needed to restart the pump is low, sometimes as low as twice the pump's ratio.

The minimum air drive pressure required is 15 psi, maxing out at 145 psi depending on the pump.

Double Air Head Pumps

To boost pressure capabilities without changing hydraulic plunger size, stacking two air pistons is effective, doubling the pressure ratio. Double air head pumps are identified by a -2 suffix in the model number and use less air than single air head pumps of similar area.

Example: A pump with a nominal 1:100 ratio (L100) will have a model number L100-2, indicating a 1:200 ratio.

NOTE: Maximator pumps can be installed in any position, but vertical is preferred for optimal seal life. Connections for both liquid and air drive lines must match or exceed the pump connection sizes.

Filtered drive air between 5μ and 40μ and a maximum dew point of 50°F is recommended. Very dry air may require lubrication.

The maximum recommended pump height above fluid level is 10 ft. for LO and L pumps, 7 ft. for S pumps, and 3 ft. for PPO and PP pumps.

Special seals for various applications are available. Contact your local distributor or High Pressure Technologies for more information.

Currently, air driven pumps and boosters are becoming favorable alternatives to electric and gasoline-driven options due to their cost efficiency and energy savings. Additionally, air driven pumps are safer for handling hazardous or combustible liquids since they use compressed air instead of electricity. This has heightened their popularity in the Oil & Gas, Chemical, Industrial, and Research sectors. But you might wonder, how exactly do air-driven hydraulic pumps work? Let's unravel this topic and explore their common applications.

Here is a step-by-step explanation of how air driven hydraulic pumps function:

• The spool valve initiates drive air flow from the air port to the bottom of the air piston.
• As the air piston in the drive unit shifts to the right, a suction stroke occurs.
• The intake valve opens, and high-pressure piston sucks fluid through the suction port.
• The pilot valve is activated by the air piston, now at the upper stop position.
• Control air moving from the air port to the spool valve changes the valve's switching position.
• The spool valve connects the silencer and the chamber below the air piston, allowing drive air to escape through port R. Simultaneously, the air piston’s top receives drive air.
• A pressure stroke follows, moving the air piston leftward, causing the inlet valve to close.
• This sequence opens the pressure valve, allowing the high-pressure piston to drive the pumped fluid out through the pressure outlet.

Applications of Air Driven Hydraulic Pumps

Air driven liquid pumps are used in various applications due to their notable advantages. Here are some areas where these high-pressure pumps are commonly employed:

Pressure Testing Applications in Various Industries:

• Diving industry for certifying divers’ air bottles and equipment.
• LPG/CNG industry for certifying storage bottles, tanks, and relevant equipment.
• Firefighting industry for certifying extinguishers and associated equipment.
• Industrial gas manufacturers and suppliers for certifying gas storage bottles, tanks, and related equipment.
• Manufacturers of pressure vessels requiring certification and testing.
• Oil and gas pipeline installers requiring pre-use testing and certification.
• Tube, pipe, and fitting manufacturers.
• Hydraulic (and other types) hose manufacturers and suppliers.
• Defense industries.

Fluid Transfer Applications in Various Industries:

• Firefighting industry for filling extinguishers with CO2.
• Refrigeration and air-conditioning industry for evacuating and refilling refrigerant systems.
• Defense industries.

Other Applications:

• Fluid power applications requiring a non-electric high-pressure hydraulic source.
• High-pressure applications for hydraulic and isostatic presses.
• Offshore oil and gas platforms needing a non-electric high-pressure hydraulic source.
• Pumping fluids in hazardous areas.
• Pumping hazardous fluids.
• Providing hydraulic pressure for various on-site jacking applications.
• Supplying dust suppressant fluids in mining operations.
• Functioning as chemical injection pumps in upstream oil and gas systems.
• Serving as chemical injection pumps in downstream oil and gas plants.

That's how these hydraulic pumps work. If your industry requires a high-pressure pump, it's crucial to consult an expert. High Pressure Technologies LLC is renowned for supplying top-tier air driven liquid pumps and systems in the US.

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