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Pick-A-Pack

The Stone Pick-A-Pack product range is based on a system of modular construction which was pioneered by Stone Hydraulics when the company was founded in 1968. This concept and the components utilized have been continuously refined and improved through the years. Today, Stone applies the most advanced manufacturing technologies and the highest quality materials and components available to provide this unique and extremely flexible product range.



International Distributor Pick-A-Pack Product Range

This section is designed to aid the user in selecting a combination of pump, motor, reservoir, and valves which will precisely suit their needs.

All of the components in the Pick-A-Pack product range are designed to be interchangeable with mating components. All components are modular in design and the “international” endhead is the key component of this interchangeable system. Any desired combination of drive motor, pump, reservoir, and control valving can be either assembled into or manifolded onto this endhead. This is available in three configurations, with either NPTF, SAE or G3/8 porting.



How to Select Pump and DC Motor Combinations:

The following section contains pump/motor curves for various combinations of pumps and motors used on Stone hydraulic power units. It is important to select the correct motor and pump for a given application so proper pressure, flow and electrical amp draws can be accounted for appropriately in the design circuit. Proper selection also ensures the motor does not overheat and become inoperable.

There are motor curves for both S2 and S3 duty cycle categories.

  • S2- Absolute Continuous On-time. Indicates how long a motor can be run continuously before it must be allowed to cool back to ambient temperature.
  • S3- Percentage On-time. Based on a 5 minute duty cycle, it indicates the duty cycle (percent on vs percent off) the motor can be run continuously without overheating the motor.


The following is an example of how to select a motor and pump based on specific application criteria:

Assume the given application parameters require a flow rate of 1.5 GPM at 2000 psi, intermittent operation and 12 VDC supplied power. (If continuous operation is needed, a Hi-Power 12V motor needs to be selected). Referring to the 12 VDC pump/motor graphs show that a KP-2.5 pump (2.5 cc/rev) is required and will draw 260 amps with this combination.

  • Since the application dictates that the motor needs to be run intermittently, the S3 graph indicates how long the motor can operate as a percentage of 5 minute (300 second) intervals without needing to cool back to ambient temperature. Referring to the S3 graph shows that the standard duty motor (KMD1 and KMD2) can operate with a 8% on-time, or for 24 seconds on, 276 seconds off continuously. If an extended duty motor is selected (KMD3), it can operate with a 13% on-time, or for 39 seconds on, 261 seconds off continuously.

Relief valves are extremely important in that they limit the amount of pressure the power unit can generate. Stone AFC pumps can potentially generate in excess of 5000 psi. If the pressure is not limited by the use of relief valves, the excess pressure could damage the mechanical components used in the hydraulic circuit, resulting in potential injury or death. Always ensure that the mechanical components selected in the application design can handle the working pressure needed. Once the working pressure is determined, select the relief valve that will allow full flow at the working pressure. Relief valves “crack” at about 80% of their pressure rating, opening to full “dump” to tank once the rated pressure is obtained (typically referred to as “full bypass pressure and flow”).

The working pressure in the application should be 80% or less than the rated relief valve pressure. For example, if the working pressure needed is 2300 psi, a relief valve rated at 2875 psi should be selected. (2300 divided by 0.8).



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