Mini Excavator Auxiliary Hydraulics: Match the Circuit
Qisheng Machinery · Buyer Guide · Prepared October 21, 2026
Quick Answer
Specify mini excavator auxiliary hydraulics by the services required at the attachment: usable flow, pressure, return conditions, control mode and any separate case drain. Total pump flow is not automatically the flow available through the auxiliary couplers.
Start with the exact attachment model and its installation requirements. Then match the carrier circuit in writing. Two hoses and a similar-looking connector do not establish hydraulic compatibility.
Read Pump Flow and Auxiliary Flow as Different Figures
A manufacturer may publish several hydraulic numbers for one machine. They describe different parts of the system and should retain their labels in a comparison.
For example, Caterpillar's 301.5 specification lists the following figures. These are Cat data, not QS specifications.
| Cat 301.5 published field | Metric value |
|---|---|
| Pump flow at 2,400 rpm | 66 L/min |
| Primary auxiliary flow | 33 L/min |
| Secondary auxiliary flow | 14 L/min |
| Primary auxiliary pressure | 213 bar |
The table does not mean an attachment receives 66 L/min, or that every listed maximum is available simultaneously. Obtain the operating conditions for the required circuit and tool. Where the job involves moving the boom while a powered tool runs, the assessment needs to reflect that combination.
As a hypothetical screening example, a tool requiring 25–35 L/min is not cleared by a “66 L/min pump” entry. First establish whether the auxiliary service can be set and maintained within the tool's range. Pressure, return limits, cooling and controls remain separate checks even when flow ranges overlap.
Match the Circuit Layout to the Tool
| Tool requirement | Carrier information needed |
|---|---|
| Flow in one working direction | Approved supply and return arrangement |
| Reversible movement | Suitable two-way circuit and controls |
| Continuous running | Approved continuous-flow control and duty |
| Motor case drain | Separate connection meeting the motor's drain limits |
| Several hydraulic functions | Available services and control of each function |
| Restricted return pressure | Verified return route under the stated conditions |
“Single-acting” and “double-acting” help describe circuits, but the attachment's diagram governs the connection. A drain line is not interchangeable with a working return. Counting hoses does not identify every service.
Kubota's KX040-5 announcement distinguishes standard AUX1 from optional AUX2 and describes proportional and continuous-flow controls. The number of services and their controls therefore belong in the purchase specification.
This is a selection guide, not a hose-connection or pressure-adjustment procedure. Isolation, depressurisation and connection must follow the supplied machine and attachment instructions.
Write a Circuit Schedule Before Ordering
For each tool, record its model, flow range, pressure limits, return and drain conditions, control requirements and complete installed mass. Beside those fields, record the offered machine service and supporting document. An empty field identifies a question to resolve before shipment.
Keep auxiliary hydraulic flow separate from oil grade and reservoir capacity. A correctly filled tank does not establish that a carrier can run a motor. Larger connectors do not create another circuit or make an unsupported attachment compatible.
For a QS quotation, catalogue pictures identify attachment categories; they do not publish a complete circuit rating for every carrier-and-tool combination. Request the configured machine's hydraulic schedule and a demonstration appropriate to the proposed tool. Retain the settings and attachment identity with the order rather than relying on a general “hydraulic attachments included” line.
The hydraulic schedule complements the mechanical interface record. A tool can have a matching mount but an unsuitable circuit, or suitable hydraulic requirements but the wrong pickup dimensions. Both sides need a documented match.
Frequently Asked Questions
Can I select an attachment by engine horsepower?
Not alone. Engine power does not state usable flow, pressure or return conditions at the tool connections.
Is more flow always better?
No. The tool must operate within its permitted range. Excess flow is not a substitute for the specified circuit.
Does a thumb use the same service as a rotating tool?
Requirements depend on the designs. Identify every function and any need to use them together before allocating circuits.
Related Guides and Model Information
Use the attachment compatibility checklist alongside the auger guide and hydraulic breaker guide. Compare QS-18 and QS-25 after defining the required service. Send Qisheng Machinery the tool data sheet for a factory-direct compatibility enquiry.