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Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 5559
Experience:  17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
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I have a 1999 komatsu wb140 backhoe. The overall hydraulic

Customer Question

I have a 1999 komatsu wb140 backhoe. The overall hydraulic system's working pressure is 3,000 psi and max delivery is 43.6 gpm.
I need to know the hydraulic flow rate in gallons per minute in the lines going to and from the telescoping arm cylinder and that are operated from the foot pedal control valve.
I will periodically disconnect the two lines and use them for operating an auger. I need the flow rate to pick the right auger model which have these gpm flow rate ranges: 6-15, 10-20, 15-30, 20-35. The lines look to be about 1/2" id and use #12 fittings.
Submitted: 1 year ago.
Category: Construction and Road Equipment
Expert:  Dan replied 1 year ago.

Hi Roger. My name is***** will be glad to try to help. I worked for a Komatsu dealer in the past as well as Cat, Volvo, and Deere and have plumbed and installed many attachments. I will check for a flow spec but I do not think there is going to be one for that function or any of the cylinder functions as the manuals are not specd out like that. I believe you probably already heard there are pressure specs but not flow for those circuits. I realize you are trying to save some money on plumbing an additional function and what you will likely need to do is run a flow meter to get the actual flow for that cylinder since that circuit is not currently spec'd out for continuous flow use there is a possibility there may be some other operational problems since it is a two way valve better suited for a thumb, etc. Let me know

Customer: replied 1 year ago.
You have basically said that you can't tell me what the flow rate might be and I need to hire someone to come out and do a pressure test. Oh well.
Expert:  Dan replied 1 year ago.

I wish I had better news for you. We would flow check even add on circuits when adding a third valve and function for whatever attachments are installed to insure proper flow and pressures to prevent damages to the machine and attachment and potential safety hazards. I understand this is not the news you wanted to hear but it is how this is done properly without cutting corners which could result in costly mistakes and repairs down the road. This system is Load sensing as well so flow varies depending on the way each circuit is plumbed so it is not a good idea to just tie into a circuit without reviewing the schematic first that the circuit is plumbed for that application.

Hydraulic System

The Hydraumind hydraulic system affords the operator very precise backhoe movements. This system is energy efficient and incorporates two different working modes: economy and constant power. The advanced hydraulic system includes the “speed up” function to increase the working speed of the front loader.

Closed center Load Sensing System (CLSS) with economy /power selector switch (power mode is the default setting)

Pump type Variable displacement axial piston

Pump control system Load Sensing set to adjust the hydraulic power

Main Valve “Load Independent Flow Divider” LIFD modular type

Max delivery 43.6 gal/min 165 ltr/min

Work pressure 3,000 psi 207 bar