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  • Users: HPost
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  1. HPost

    NPSH of hydraulic gear pump

    Irrespective of the age of the pumps, it is the vapour pressure of the oil that dictates the NPSHr. The vapour pressure of mineral oil is as close to zero as makes no difference. The seals in the pump will be drawn into the pump before the oil boils. Most pumps have a maximum inlet pressure...
  2. HPost

    Flow makes it go,,,,, NOT!!! Newton did not include flow in his 3 laws of motion.

    Those of us that don’t add our company name and web link are giving advice for altruistic reasons. You seem to want to fight and argue with everyone and advertise Delta Motion and Control at the same time...good luck.
  3. HPost

    Flow makes it go,,,,, NOT!!! Newton did not include flow in his 3 laws of motion.

    Peter There is no doubt that you are correct in your statements on cylinder velocity calculations. There are no arguments. As I see it, this forum is about giving free advice and “tips”. The folks that ask questions about fluid power don’t really have much of a clue about what they are doing...
  4. HPost

    Electro-hydraulic pressure control system

    Peter likes to unload ALL of the information in one go. He is not wrong, I just prefer to overlook the fact that a vacuum will exist in the head of the cylinder and where I say cylinder velocity is Q/A - that is not wrong either. It is the steady state velocity once the cylinder has been...
  5. HPost

    Electro-hydraulic pressure control system

    You also need a check valve to go around the motion control valve - to lift the press
  6. HPost

    Electro-hydraulic pressure control system

    You would be better off having a pressure switch on the rod end of the cylinder. Use it to sense the pressure in the rod and when the pressure in the rod end drops off, unload the big pump. If there is a risk of breaking the workpiece, I would suggest changing PPR3 to a proportional pressure...
  7. HPost

    Electro-hydraulic pressure control system

    What I mean is that spool valves leak. The flow control valve will stop it falling under gravity, but it will creep down as oil leaks over the spool. This may not be a problem for you, but don’t expect the press to stay up, it won’t. Your plan to measure the rod side pressure to control the...
  8. HPost

    Electro-hydraulic pressure control system

    You need to consider what gravity will do to your press if the rod side is open to tank. It will drop like a stone. You also cannot rely on the directional control valve to hold the press up. You would therefore need a motion control valve of some sort to hold the press up. During the down...
  9. HPost

    Electro-hydraulic pressure control system

    You don’t need a servo valve for this application. You would only use a servo valve if you want fast response and a high degree of accuracy. Even the pressure setting is not highly accurate if you can live with +/-5% Using a pressure reducer or a relief valve is dependent on what other...
  10. HPost

    adapting BSP to Metric

    Google Parker 4300 catalogue. You will find what you need in the adapters section. You don’t need to buy them from Parker, but this catalogue will give you a visual reference and part numbers for what you need.
  11. HPost

    Code 62 1" to 1/2" Hose Fitting

    If you start with Parker Hannifin, you'll be there all day. Such is the scale of the product base. There are just too many. There are many types of SAE flanges, what sort do you want? NPT, JIC, BSP, ORFS, Butt weld, Socket weld... Identify the size of the flange by the hole centre dimensions...
  12. HPost

    Cleaning Hydraulic lines

    The ultimate standard, that is the one that cleanliness levels of components are set to achieve, is ISO 4406. The level of cleanliness of the system, under 4406 is measured as the number of 4,6 and 14 micron particles per ml of fluid. Part cleanliness, including tube and hose, is measured in...
  13. HPost

    Controlling 5 Hydraulic Motors with the same speed and different torque

    Flow does NOT make it go... I hate it when people say that. None of us want to write a story. This is on the basis that most OP’s don’t read or respond to our free help. I agree with all your points, except where you misunderstand my point and say that I am so wrong. Whack a mole is a very...
  14. HPost

    Controlling 5 Hydraulic Motors with the same speed and different torque

    So wrong? Is it not the case that for a motor of given displacement in CC/rev, it will rotate at a particular speed, dependent on the flow of oil into the said motor at a rate of cubic metres/sec? Less any losses for volumetric efficiency... Speed determines flow? Are you sure Peter? Is...
  15. HPost

    Controlling 5 Hydraulic Motors with the same speed and different torque

    The flow determines the speed. The displacement x pressure (plus some math) determines the torque. Selecting 5 flow divider elements that have the same displacements as the motors will keep them all at the same speed. For a given torque requirement, select the appropriate motor for the...
  16. HPost

    Controlling 5 Hydraulic Motors with the same speed and different torque

    Are you controlling the torque with pressure or motor displacement? If you are using displacement, then you just need a 5 way flow divider.
  17. HPost

    Freight Elevator Classes C3 European standard equivalent ?

    Look here...then follow your intuition https://en.wikipedia.org/wiki/Lifting_Operations_and_Lifting_Equipment_Regulations_1998 LOLER is an EU directive. It is the directive that governs lifting equipment, not EN standards.
  18. HPost

    Selecting Hydraulic Pump for Hydraulic Winch 180 bar, 104 l/min

    Check your power requirements... 180 BAR @ 104 litres/min is 31.2 kW Your motor torque is 572Nm At 580 RPM, that is about 15kW at 85% efficiency Your pump power is 235kW Clear mismatch there... If you give the motor too much, you will over speed it and it won’t last long. The brake is...
  19. HPost

    Marks Handbook - 12th vs. 11th Edition

    10th edition - in PDF For quick reference and occasional knowledge top up. No pages missing...
  20. HPost

    Hydraulic Motors & Negative Braking - Small Tracked Vehicle

    Back driving hydraulic motors needs about 80% of their full torque to get them started. If you have a brake on the motor, the forces will have to overcome the brake friction for each motor and the each of the motors on the machine. If the motors do start to turn, that is the point at which oil...

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