Questions tagged [hydraulics]

Questions about the flow and use of fluids.

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27
votes
4answers
25k views

Why do hydraulic systems use special fluid - what's wrong with water?

As a hydraulics layman thinking about hydraulic systems, it seems that the important factor is to have a liquid that doesn't compress much or at all. Doesn't water meet this requirement, and what ...
14
votes
3answers
244k views

How to calculate flow rate of water through a pipe?

If a water pipe is 15 mm diameter and the water pressure is 3 bar, assuming the pipe is open ended, is it possible to calculate the flow rate or water velocity in the pipe? Most of the calculations I ...
10
votes
2answers
602 views

Hydraulic siphon spillway entry and exit velocity magnitude and profiles

I am working on the hydraulic seawater flow though a siphon spillway. My task is to determine at a location in front of the spillway the flow velocity and profile when The flow enters the spillway ...
9
votes
1answer
1k views

Calculate force to lift piston from a given closing pressure

I am trying to calculate the force required to close the valve on an annular blow-out preventer. A rubber ring (called a packing unit) closes around the pipe when a force is applied from underneath, ...
8
votes
2answers
4k views

Why do hydroelectric plants use turbines instead of an efficient 'water wheel' configuration?

I have been thinking about hydroelectric plants and I have been wondering why they are built the way they are. As in understand it, a stream of water is sprayed at a turbine, located at the bottom of ...
8
votes
3answers
2k views

Motor for a hydraulic pump in a hydraulic system

I am a complete beginner to hydraulic systems, and I've wanted to learn more about this area. I'm designing a hydraulic system that involves using hydraulics to push/pull objects using pistons. I have ...
8
votes
2answers
14k views

Force required to crop/cut a mild steel bar

I have cropping/cutting wedges with a thickness of 4 mm cutting either side of a round mild steel bar (17.5 mm). Imagine two wedges being driven together with a round mild steel bar in the middle (...
7
votes
1answer
133 views

Which is more durable in sandy desert conditions: electric motors or hydraulic pistons?

If we have a tracking system placed in a tough desert environment with occasional sandstorms and temperatures that go as high as 50C, which actuator would be better: a hydraulic piston or an electric ...
7
votes
2answers
371 views

On a Diesel/hydraulic DMU train what exactly does the “go faster” lever control?

Let's say that you are driving a Diesel Multiple Unit† with either mechanical* (i.e. an actual gearbox with multiple ratios) or hydraulic (i.e. two or more torque converters) transmission. When you ...
5
votes
6answers
3k views

Does a motor suffer damage when resistance to the intended motion is met?

I'd like to create something similar to a hydraulic press. I know I need some sort of motor, but I was curious about a fundamental question about motors when used in a system where the force required ...
5
votes
4answers
711 views

How do I add a resistance to mechanical movement in both directions, apart from friction?

What options do I have for creating a resistance to a mechanical movement apart from simple friction? Assume I have a lever, which will result in either circular or linear motion. I want to be able ...
5
votes
1answer
2k views

Hydraulic power source

I'm looking for a power source that is able to deliver 12V at 15-30A (yes, amps). I was looking at high capacity batteries, but looking at the specs, they either say they have a lower discharge ...
5
votes
2answers
135 views

Recoil of hydraulic lift/elevator

I noticed that when a group of people enter in an hydraulic lift/elevator often when the last person steps in the lift/elevator has a small but noticeable recoil: the lift goes down a few mm then it ...
5
votes
1answer
212 views

Minimising permeation rate of hydraulic fluid through hydraulic hose

I am designing an experiment where the hydraulic hose is going to be subjected to relatively high internal pressure for prolonged period of time and it is absolutely imperative that the rate of ...
5
votes
0answers
39 views

Bedload discharge for canals of triangular cross-section

All the methods I know of for calculating bedload discharge are for canals of rectangular cross-section (constant depth of flow). The bedload is first computed for a unit of width (using the constant ...
4
votes
2answers
1k views

How do I calculate the weight needed on a press board to deliver a certain amount of pressure?

I'm building a press for cider. I'm going to be using a 24" x 24" press board. I'm looking to deliver 40 psi to the cider. How can I determine the amount of weight required, in tons? What sort of ...
4
votes
3answers
86 views

How to make sure a pipe does not take all of the water from a stream?

I am trying to design a pipe which takes water from a river and transports it to a reservoir. However, I do not want my pipe to take all of the water from stream, because that will create all sorts ...
4
votes
1answer
3k views

Where exactly will a hydraulic jump occur?

I know that an hydraulic jump can occur only when the Froude number is higher than 1 (supercritical flow), and I am familiar with the Bélanger equation. However, I feel like I have a fundamental ...
4
votes
3answers
104 views

What would a track in a culvert be used for?

A colleague works in a closed (no public access) watershed and came across this culvert today. These smooth "tracks" down the center of the culvert are something we have never seen before. Any idea ...
4
votes
1answer
481 views

Fluid mechanics - how to calculate flow distribution in piping network?

I am trying to build flexible, visual tool to calculate flow distribution through the piping network (mobile hydraulics). I have root node of the network which has defined flow and pressure inputs. ...
3
votes
2answers
57 views

What kind of pressure switch can I use for pressures up to 5-10 tons/cm^2?

I need a pressure switch for an electric circuit that has to be closed once a piston is compressing at a pressure of (approximately as we haven't specified how much force we have to use, and maybe it ...
3
votes
1answer
663 views

Hydraulic Symbols

Hi all!, I am currently working on a hydraulic project. One of the procedure requires me to setup a line as shown in the picture. I am fairly new to this field, I am not sure what does the symbol ...
3
votes
3answers
109 views

I cannot properly understand the "pressure" referred to in Bernoulli's Principle despite my efforts

I get that with Bernoulli's Principle an increase in area = a decrease in velocity = an increase in pressure. I also understand the concept of pressure being force per unit area. My difficulty is with ...
3
votes
2answers
85 views

How is high static water pressure avoided in municipal water systems?

Most cities get their water supply from local sources (springs, rivers, lakes) so the pressure in the system is never more than what is produced by the pumps. But some cities get their water from ...
3
votes
0answers
62 views

Hydrostatic transmission to directly translate movement

I have been thinking about small hydrostatic transmission to directly translate movement of stepper motor (NEMA 17-23 size, geared with 3:1 or 5:1 ratio). My design currently involves 2 identical ...
3
votes
0answers
37 views

Volumetric oil pump efficiency goes up when viscosity goes down?? Strange behaviour

Riddle me this : we are driving an external gear pump (this kind) at a fixed RPM. At start, when the oil temperature is low (and viscosity high), the volumetric flow is much less than when the oil ...
3
votes
0answers
35 views

What domestic water valve is least likely to jam over time?

I'm doing some work on a domestic water system, mostly 15 or 22mm copper pipe with compression fittings. The work includes replacing various stop-cocks and drain valves some of which are probably 30 ...
3
votes
0answers
53 views

Difference between direction of ramming in hydraulic press?

In Printed circuit board/Plywood lamination Hydraulic Press machines (seen here). The ramming action comes from bottom in all the machines I saw so far. For such action from bottom, excavation has to ...
3
votes
0answers
34 views

The use of Theis equation based on time

The storage coefficient (s) for artesian basin can be determined by the following equation (Theis equation): $$s=\frac{Q}{4\pi T}\int_{\frac{r^2S}{4Tt}}^\infty\frac{e^{-u}}{u}du$$ Does this ...
2
votes
2answers
687 views

Why no hydraulic piston gas compressors?

I've been looking at solutions to compress gases and getting stunned by the cost and maintenance requirements of existing systems to fill cylinders (whether for SCBA or chemical storage) to 2000-...
2
votes
2answers
185 views

What is the best way to dry something that is quite thick?

I wonder what is the best way to dry something that is quite thick. The gravity will attract the water down, but the sun will "elevate" the water. So I can choose to flip the object every 30 min so ...
2
votes
2answers
782 views

What is the difference between hydraulic and ABS brakes?

Recently I read an article about ABS brakes. In that, they repeated several times the term that traditional hydraulic brake replaced with ABS brakes. Why it so? The reason for choosing ABS is ...
2
votes
2answers
36 views

HPU minimum oil temperature

Two different HPU systems in different locations with slightly different oils Chevron Ranco HD 68 and HDZ 68 have the same minimum oil temperature 55. Their flash points are are 455 and 414 F ...
2
votes
1answer
48 views

How does hydraulic pressure booster works?

This photo shows hydraulic booster used in HPHT Hydraulic Press. I could not understand its function. How does this pump boost the hydraulic pressure ? Thanks.
2
votes
1answer
377 views

hydraulic Motor/pump minimum speed

I have seen in many data sheets of Hydraulic Gear motor a spec called : "Minimum Speed = 450 RPM" ( 450 is an example) here is a capture from the linked datasheet below : In your experience ...
2
votes
1answer
254 views

Linear force multiplication (or division) without hydraulics

Gears are used to transfer power between two rotating shafts, either by increasing or decreasing the angular speed, with a corresponding inverse change in the torque. If I want to do the same for ...
2
votes
1answer
83 views

How do I recognize a good Hydraulic Servovalve? [closed]

How do I recognize a good Hydraulic Servovalve? It is probably the frequency response but what do I have to look for in these diagrams? Is it correct to assume that the higher the frequency at a ...
2
votes
1answer
47 views

How to compensate for losses in a hydraulic system?

I have an engine ( 72240 kW... ) , probably the biggest internal combustion engine in the world and this engine has no camshaft. Instead it has an hydraulic system which controls the combustion, the ...
2
votes
1answer
59 views

Running a hydraulic pump below minimum RPM

If I had a pressure compensated, hydraulic piston pump, how might the performance look in terms of pressure if I were only looking in the regime of 0 RPM and the minimum ratedRPM? I.E If a pump was ...
2
votes
2answers
67 views

Stop Spa-to-Pool Siphoning Thru Spa Pump

I have a partially above ground Spa and an in-ground pool. When the spa is filled to spillover with pumps off, water siphons through the spa pump and into the pool until the spa water level drops ...
2
votes
1answer
72 views

Help with simple hydraulic circuit to use for a four legged Robot

Firstly i am new to hydraulics, i want to build a hydraulic circuit that powers 4 cylinders at each leg of a Quad-Wheeled-Robot. The idea is to move the Chassis of the Robot up and down in all ...
2
votes
3answers
86 views

how are these radial piston rotors machined

A typical radial piston rotor can have simple holes machined from the outside through the inner diameter to create flow channels for hydraulic fluid to actuate the pistons. I came across this model ...
2
votes
1answer
238 views

Low flow hydraulic motor to run high flow pump?

I would like to get some opinions on using a low flow hydraulic MOTOR to drive a high flow pump ? Would the high flow pump be able to create a useable pressure to drive a piece of equipment that ...
2
votes
2answers
333 views

Calculate hydraulic torque from motor HP, hydraulic pump and gearbox

I am curious about the design considerations for a hydraulic system. Let's say you have a 3HP 1200RPM motor you also have a hydraulic pump that's rated 4LPM and pressure of 40MPA rated for 40RPM MAX ...
2
votes
1answer
65 views

What (if any) are the engineering limitations for producing "simulation" exoskeletons

To clarify the title since it cannot be said within the word limit: A "simulation" exoskeleton, is an exoskeleton that doesn't exist to support a disabled user's movement or to help someone carry ...
2
votes
1answer
94 views

Need help identifying component on hydraulic schematic

I'm relatively new to hydraulics, and I'm trying to understand this schematic. I've got the majority of the system figured out, but I cant for the life of me understand what the symbols at positions ...
2
votes
1answer
90 views

Difference in flow measurements in an open channel

I'm undertaking a civil hydraulics question. It involves the flow of water in an open channel down a river at $5m^3/s$ until the flow is split in two by a weir acting as a sluice gate allowing flow ...
2
votes
4answers
490 views

Why to avoid low and high fluid velocities in hydraulic systems

I know that different geometries of piping, orifices etc... have different critical Reynolds values. If the value is exceeded laminar stream will turn to a turbulent form which causes a variety of ...
2
votes
1answer
335 views

Hydraulic System design help/ directional valves

Default Hydraulic solenoid valve issue Hello all, I'm having a weird issue with some solenoid valves in a simple hydraulic circuit, let me try and describe the situation as best as I could.. So ...
2
votes
1answer
149 views

Does this exist - Water flow control with energy recovery

Classically, if you have free flow (high level to low, no pump) between two vessels you want to control you use some restricting orifice, or flow over a variable height weir. Both dissipate energy. ...