# Questions tagged [hydraulics]

Questions about the flow and use of fluids.

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### 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 ...
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### 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 ...
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657 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 ...
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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 ...
• 317
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, ...
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5k 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 ...
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15k 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 (...
498 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 ...
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142 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 ...
1k 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 ...
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### 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 ...
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171 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 ...
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251 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
4k 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 ...
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581 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. ...
73 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 ...
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175 views

### Why excavators use Hydraulic motors for rolling or moving forward instead of diesel engine?

I am currently studying How excavators work? and came to know that "In excavators diesel engine is used to drive the hydraulic pump. The high pressure fluid from hydraulic pump is used to run the ...
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62 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 ...
931 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 ...
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### 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 ...
178 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 ...
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99 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 ...
107 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 ...
36 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 ...
37 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 ...
812 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-...
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### 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 ...
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### What are the tradeoffs between using hydraulic motors and electric motors?

My limited understanding of hydraulic systems is that they aren't nearly as efficient as electrical systems, and that wire is cheaper than high pressure lines. Example: In a zero turn mower, each of ...
119 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 ...
483 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.
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### 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 ...
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### 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 ...
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### 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 ...
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400 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 ...
167 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. ...
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### 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 ...
52 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 ...
56 views

### Component selection type for fluid-mechanical system

I am creating an enclosure and need to get a water supply through a plastic wall inside to the core device. I imagine this water line will be a flexible tube and will screw on or snap to an adapter on ...
516 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 ...
176 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 ...
98 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 ...
81 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 ...
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### 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 ...
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### 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 ...
881 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 ...
380 views

### Hydraulic System design help/ directional valves

Default Hydraulic solenoid valve issue 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. Coming out of a 2 ...
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