Stanley Hydraulic Tools
Frequently Asked Questions


  1. What are the torque capacities of the various Stanley Impact Wrenches?

    Many applications require a specific bolt torque. Although an "exact" torque setting is not possible with Impact Wrenches, the following information should be useful in determining the Torque Range for the various Stanley Impact Wrenches.

    Since an impact wrench is a rotary hammer (not a steady torque), bolt torque is affected by several factors such as thread and thrust face friction, mass of adapters and sockets, loose connects, and time under impact. Long shank screws may spring twist and bounce back after impact, reducing maximum attained torque. Low flow rate can be used to reduce torque.

    For reliable torques, testing GPM flow rate plus controlling impacting time, followed by a torque wrench check, can be used to establish repeatable torques for specific applications.



    GPM Flow


    Lb./Ft. Torque





















  2. Hydraulic tools have had a reputation of oil leaks. Comment.

    Hydraulic tools got that reputation before the advent of dripless couplers (a spin off from the space program). This is not a problem any longer - in fact, air tools spew out more lubrication oil in mist form than hydraulic tools leak.

  3. What about dirt in the hydraulic fluid?

    Dirt in any system (air, electric, or hydraulic) will cause wear. Air tools suffer most from dirt because the compressor is sucking in dirt all the time and tool exhaust ports allow dirt to get into the tool. Since the hydraulic system is a sealed system, dirt gets in only by carelessness. And, to protect against this, the hydraulic system has a full-flow filter.

  4. Does hydraulic fluid have to be changed often?

    No. Hydraulic fluid will maintain its operating characteristics if it's kept cool and clean.

  5. How does the maintenance cost of hydraulic tools compare with similar air tools?

    Frequency of repair is much lower than with air tools. Our experience indicates that repair costs for hydraulic tools are only about half of air tools (analysis of sales of parts by Stanley Air Tools Division, Cleveland, Ohio, substantiates this).

  6. Why is this?

    In hydraulic tools the parts are bathed in oil and, generally, have fewer moving parts. Air lines feed dirt and moisture into air tools which corrode and wear the tools.

  7. What about safety if a hose breaks?

    If a hydraulic hose should break, someone might get an oil bath - but that's all (dry cleaning takes it out of clothes). However, a broken air hose with metal fittings on the end violently whipping around is very dangerous. In fact, see the OSHA requirement for attaching air hoses to tools.

  8. Do hydraulic tools get too hot to handle?

    Not if the hydraulic power system is correctly designed with an adequate oil cooler. Air tools have a problem in that they freeze up in cold weather. It's easier to cool hydraulic tools than heat up air tools (including dryers).

  9. Double hydraulic hoses are hard to handle.

    There have been improvements in hydraulic hoses over the years. Hydraulic hoses are available which are lighter in weight than air hoses. Plumbed hydraulic hose reels are more convenient and compact than for air hoses.

  10. Hydraulic oil leakage causes a loss of insulative properties in line trucks.

    Dripless couplers have reduced leakage. The hydraulic fluid is nonconductive; but surface dirt on the tools and truck equipment does reduce the insulation effectiveness. Water in air lines is dangerously conductive and requires expensive filtering/drying devices.

  11. What size hydraulic hoses do you recommend for an 8-gpm tool circuit?

    3/8" I.D. - up to 25 feet each way
    1/2" I.D. - up; to 50 feet each way
    5/8" I.D. - up to 150 feet each way
    3/4" I.D. - up to 300 feet each way

  12. Which is less expensive to run, air tools or hydraulic tools?

    Hydraulic tools have an efficiency of 40 - 90% vs. only 10 - 35% for air tools. Air compressors are less efficient than hydraulic pumps. The lower the efficiency, the higher the power and fuel cost to operate. An equivalent hydraulic system can be operated with 1/3 the power input of an air system.

  13. When filled with oil, hydraulic tools weigh as much as air tools.

    Very little oil fills the hydraulic tools. Talk in terms of power to weight. When you compare the amount of work done by each, hydraulics show a much better power to weight ratio.

  14. How quiet are hydraulic tools?

    The only noise you hear with a hydraulic tool is that of the work being done. There is no exhaust noise with hydraulic tools.

  15. In general, hydraulic tools cost more than air tools; why?

    Higher quality and more durable tools just cost more. However, a hydraulic system actually costs less because you either eliminate the air compressor cost completely by using the truck's hydraulic system or use a hydraulic power unit that costs 1/2 of an air compressor.

  16. What are the causes of heat in a hydraulic system that should he minimized in the tool circuit?

    In brief, heat occurs any time power is "wasted". The greatest heat producers are power supply flow controls, priority valves and relief valves set too low.

  17. Will an air-to-oil cooler completely covering the engine radiator cause overheating of the engine?

    No. The recommended coolers are designed for minimum air resistance and will not restrict air flow to the radiator. Also, the oil temperature will be lower than the engine coolant temperature.

  18. At what pressure should the hydraulic tool be operated?

    A tool is designed to operate on a specific flow. The tool will develop only that pressure required to do the work. The hydraulic circuit should have the capability to provide required flow to tools at pressures up to minimum of 2000 psi relief setting.

  19. What back pressure can Stanley Hydraulic Tools handle?

    Maximum allowable is 250 psi.

  20. Can you run hydraulic tools from a back-hoe?

    Yes. Also from tractors, line trucks, or other vehicles with hydraulic systems. Consult the factory for your particular application.

  21. What effect does OSHA have on the use of hydraulic tools?

    In general, the OSHA regulations favor hydraulic tools over air tools. See section on OSHA and EPA regulations.

  22. In some areas, air compressors are also used to spray paint, sand blast, etc. Why not use the air for running all tools?

    Look at it the other way, run the air compressor with a hydraulic motor (Stanley's AC24) so you don't lose the advantages of hydraulic tools.

  23. What happens to Stanley hydraulic tools if a customer inadvertently runs them in reverse?

    Our reciprocating tools (breakers, tampers, etc.) will not operate in reverse and will not be damaged. Impact wrench operation is not affected since they offer forward-reverse anyway. Other rotary tools will run in reverse and will wear the motor seals quickly since the wrong side of the dynamic seals will be pressurized. Try to avoid systems that allow reverse oil flow.

  24. What's the difference between open center and closed center tools?

    1) Closed Center: Closed center tools stop system oil flow entirely when the trigger is released. Oil flow is totally stopped. The system then senses the pressure increase and automatically shuts down the pump. When the tool trigger is pulled the system pressure fails and the system then activates the pump again. John Deere and Hi-Ranger utilize closed center systems.

    2) Open Center: Open center tools do not stop oil flow. They either divert oil to the tool mechanism when the trigger is pulled or they allow the oil to flow back to the tank when the trigger is released. Oil flow is not stopped. The great majority of existing hydraulic systems are open center (including all our power units).

  25. What if I use an open center tool on a closed center system or vice-versa?

    Closed center tools on open center systems will stop oil flow entirely when not in use. Full system flow will then be forced through the system relief valve. No damage; but some noise and the oil will heat rapidly.

    Open center tools on closed center systems will not stop oil flow and the system will continue to pump oil. No damage; but the advantages of the c.c. system will be negated.

  26. What are the advantages of either an o.c. or a c.c. system?

    Open center systems are less complicated than c.c. systems and are thus less expensive to install. Also, when a cooler is used an o.c. system continues to pump oil through the cooler even when the tool is not in use and thus offers improved cooling.

    Closed center systems require an accumulator and a pressure sensing device in addition to pump, filters, etc. However,since the system shuts down when the tool isn't being used there is a potential savings in fuel. Remember: Probably 90% of existing hydraulic systems are open center.

  27. What happens if a customer overspeeds our tools by putting too much oil through them?

    In general all the tools operate noticeably faster and possible damage can occur.

    Our reciprocating tools will not be damaged since they'll only accept a limited flow until pressure rises above 2000 psi. The excess flow will then be diverted over system relief back to tank.

    The rotary tools will spin faster and impact wrenches will suffer extremely rapid failure of the impact mechanism. Wrenches should not be oversped.

    Many people think that a tool designed for operation at 8 gpm will work better at 10 or 12 gpm. Not true. Operate our tools at the suggested gpm's, they'll work right.

  28. One of my customers has an eight year old bucket truck that has a circuit capable of 8 gpm at 2000 psi. Our tools don't work well though. What's wrong with the tools.

    Probably nothing is wrong with the tools. They are all tested before shipment. Most likely, the eight year old hydraulic system has worn out and isn't providing 8 gpm any more.

    Run the tools from your demo truck to check operation and test the customer's circuit with our flow and pressure tester. Remember although the customer always blames the tools, in many instances it's the circuit thats causing the problem with high backpressure, low relief settings, or inadequate gpm's. Check the circuit first!!

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