Fluid system components - the hardware for pumping systems, and some for pneumatics and hydraulics.

Image Video Lesson Description and Link Duration Date Download
  Fluid Components 21:04 min 20140721  

Video: Fluid Components


  • Pipes, channels, tubes and ducts, Pipe fittings
  • Valves - gate, globe, non-return/foot, needle, ball, plug cock, diaphragm, pressure regulating/reducing, safety
  • Measurement: Gauges and instruments: Venturi and orifice meters, pitot tube, rotameter, anemometer
  • Tanks/vessels
  • Filters/strainers
  • Nozzles/spray heads
  • Pumps/compressors, motors/turbines
  • Actuators - linear/rotary
  • Selection of equipment/instruments



(Compiled by Darryn Reid, Wikipedia)



Ball valve:
A ball valve is a valve with a spherical disc, the part of the valve which controls the flow through it. The sphere has a hole, or port, through the middle so that when the port is in line with both ends of the valve, flow will occur. When the valve is closed, the hole is perpendicular to the ends of the valve, and flow is blocked. The handle or lever will be inline with the port position letting you "see" the valve's position. The ball valve, along with the butterfly valve and plug valve, are part of the family of quarter turn valves.


Plug valve:
Plug valves are similar to ball valve but with cylindrical or conically-tapered "plugs" which can be rotated inside the valve body to control flow through the valve. The plugs in plug valves have one or more hollow passageways going sideways through the plug, so that fluid can flow through the plug when the valve is open. Plug valves are simple and often economical, and easier to maintain (rebuild) than the ball valve - especially in larger sizes. However, it does not give perfect flow (zero head loss) when open since the hole is not circular.


Butterfly valve:
 A butterfly valve is a valve which can be used for isolating or regulating flow. The closing mechanism takes the form of a disk. Operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves are generally favored because they are lower in cost to other valve designs as well as being lighter in weight, meaning less support is required. The disc is positioned in the center of the pipe, passing through the disc is a rod connected to an actuator on the outside of the valve. Rotating the actuator turns the disc either parallel or perpendicular to the flow. Unlike a ball valve, the disc is always present within the flow, therefore a pressure drop is always induced in the flow, regardless of valve position


Diaphragm valve:
Diaphragm valves (or membrane valves) consists of a valve body with two or more ports, a diaphragm, and a "saddle" or seat upon which the diaphragm closes the valve. The valve is constructed from either plastic or steel.


Gate valve:
A gate valve, also known as a sluice valve, is a valve that opens by lifting a round or rectangular gate/wedge out of the path of the fluid. The distinct feature of a gate valve is the sealing surfaces between the gate and seats are planar, so gate valves are often used when a straight-line flow of fluid and minimum restric­tion is desired.



Needle valve:
A needle valve is a type of valve having a small port and a threaded, needle-shaped plunger. It allows precise regulation of flow, although it is generally only capable of relatively low flow rates


Globe valve: (straight)
A globe valve is a type of valve used for regulating flow in a pipeline, consisting of a movable disk-type element and a stationary ring seat in a generally spherical body.


“Y” Globe valve:
Globe valves are typically two-port valves, although three port valves are also produced mostly in straight-flow configuration. Ports are openings in the body for fluid flowing in or out. The two ports may be oriented straight across from each other on the body,[5] or oriented at an angle such as a 90° angle.[6] Globe valves with ports at such an angle are called angle globe valves. A globe valve can also have a body in the shape of a "Y".


Globe valve (angle):
Globe valves are typically two-port valves, although three port valves are also produced mostly in straight-flow configuration. Ports are openings in the body for fluid flowing in or out. The two ports may be oriented straight across from each other on the body,[5] or oriented at an angle such as a 90° angle.[6] Globe valves with ports at such an angle are called angle globe valves. A globe valve can also have a body in the shape of a "Y".


Check Valves
A check valve, clack valve, non-return valve or one-way valve is a mechanical device, a valve, which normally allows fluid (liquid or gas) to flow through it in only one direction

Swing check valve

Lift check valve

Ball check valve and other examples.



Relief valve:
The relief valve (RV) is a type of valve used to control or limit the pressure in a system (or vessel) which can build up by some sort of fault. (Incorrect setup or operation, or an instrument or equipment failure).



Regulator valve:
A pressure regulator is a valve that automatically cuts off the flow of a liquid or gas at a certain pressure. Regulators are used to allow high-pressure fluid supply lines or tanks to be reduced to safe and/or usable pressures for various applications


If outlet pressure increases, the diaphram begins to rise which closes the poppet valve.

If output pressure falls below the set value, the diaphram pushes down on the poppet which releases more air through the valve.

Outlet pressure can be increased by tightening against the diaphram spring.


Rotodynamic Pumps (Relatively high flow, low pressure like a fire fighting pump) vs Positive Displacement pump (High pressure, low flow, like a hydraulic pump)

Rotodynamic pumps

A rotodynamic pump is a kinetic machine in which energy is continuously imparted to the pumped fluid by means of a rotating impeller, propeller, or rotor, in contrast to a positive displacement pump in which a fluid is moved by trapping a fixed amount of fluid and forcing the trapped volume into the pump's discharge.[1] Examples of rotodynamic pumps include adding kinetic energy to a fluid such as by using a centrifugal pump to increase fluid velocity or pressure.[2][
Some types of rotodynamic pump include:

Centrifugal pump: This is the classic pump for pumping water. (Fire pumps, irrigation etc). The design can be modified for "pumping" air - which we usually call "blowing". (e.g. vacuum cleaner, furnace blower, leaf blower)

Water pump

To increase the pressure of a centrifugal pump, you could;

  • Increase the RPM (to the square of the RPM, because Fc = mrw^2)
  • Increase the diameter
  • Increase the fluid density.

If a centrifugal pump running at rated load is blocked, the pressure up a little but power will go DOWN. They do not have a fixed pressure or flowrate, but the pump curve gives the ratio of flow to pressure. Every pump has it's own pump curve (for a certain RPM and fluid - e.g. water)

The example below shows pump curves for centrifugal pumps running at 1470 RPM, with impellor diameters from 274 to 342mm.

From these curves, an example duty point (operating flowrate & head or pressure) could be:

308 mm impeller at 100 L/s giving 25 m head.

Check: Power = P*V = (1000*9.81*25) * (0.100) = 24.525 kW. Using the efficiency curves, we expect around 79.5%, so input power (shaft power) = 30.8 kW. This matches the dotted lines representing power - where 30kW was just below this duty point.

More about this later!

(Note NPSHR = Net Positive Suction Head Required in order to avoid cavitation)

See also: Pump_curves.pdf

Video Lectures on Centrifugal Pumps:

Basics of pumps and pump curves

Geoff Brown, Applications Consultant, Drives & Motors, ABB

Part 1: Basic Terminology

Part 2: Pump Curves

Part 3: The Affinity Laws

Part 4: Parallel Pumps



Design of a cavitation-free submarine propellor. Cavitation is the boiling (vapourisation) of the water due to low pressure areas behind the fast moving propellor blade. By slowing the propellor down, adding extra blades and modifying the shape the cavitation is almost eliminated - which makes it quiet.

Positive displacement pumps

(Relatively high pressure, lower flowrate)
Positive displacement pumps, unlike centrifugal or roto-dynamic pumps, will produce the same flow at a given speed (RPM) no matter what the discharge pressure. Thus, positive displacement pumps are "constant flow machines".

If the flow of a positive displacement pump is blocked, the pressure will spike dangerously high. So these types of pumps usually have a pressure relief valve to avoid damage by over-pressurizing. This is typical for hydraulic circuits. An air compressor also has a relief valve, although with air the pressure does not spike so suddenly as hydraulics does).
The main types of positive displacement pump use the method of piston, gear, vane or screw. There are variations on these - such as swash plate to drive pistons, internal gear, balanced vane etc, lobe pumps with same principle as gear pump, and various screw-type pumps (e.g. mono pump).

Example Piston Pump arrangments. (Common in air compressors)



A piezometer is either a device used to measure static liquid pressure in a system by measuring the height to which a column of the liquid rises against gravity
                                                                                              Similar to a manometer   seen below.     



Pressure/Vacuum gauges:
A vacuum gauge is used to measure the pressure in a vacuum—which is further divided into two subcategories, high and low vacuum (and sometimes ultra-high vacuum). The applicable pressure range of many of the techniques used to measure vacuums have an overlap. Hence, by combining several different types of gauge, it is possible to measure system pressure continuously from 10 mbar down to 10.


Pressure: There are many ways to measure pressure. The classic pressure gauge is a Bourdon gauge, where a flattened tube tends to unravel under pressure - driving the needle to give the pressure reading.

This can be done electronically with a Piezoelectric sensor (nothing to do with piezometer, except they both measure pressure) turns a pressure change into an electric signal. They are made from a ceramic material (there are some polymers that do this too). Common uses include a Piezo buzzer, piezo lighter, and piezo guitar pickup, and.... pressure sensors.

Pressure is a very useful measurement. For example, in hydraulics it can be used to check the condition of the pump, or detect a dirty filter (pressure is too high = filter in getting blocked), or determine the load on a cylinder (F=PA).

Temperature is also measured using various methods. A thermocouple is a very simple device where a pair of wires of different metals are welded together. When the temperature changes a voltage is created at the metal junction, this is processed by a circuit to read in degrees. Various combinations of metal compositions give various temperature ranges. Electrical resistance devices simply measure the resistance of a metal (which increases with temperature for most metals). Semiconductor devices that measure temperature can be based on simple silicon chips or a combination of mechanical deformation and semiconductor transducers and circuitry. Circuits are required on most semiconductor circuits because sensitivity to all parameters (pressure, temperature, capacitance, inductance, magnetism etc) is common to most chips - so special circuity is needed to REMOVE the unwanted effects.

Flowrate can be measured using hot wire anamometer (electricity heats up a wire, airflow cools down the wire, hence we know the speed of the air). Another method is a simple propellor (fan) that spins and measures RPM to git fluid speed. A third method, often used in permanent flow situations is the rotometer (below), where the "float" (that doesn't actually float - it sinks) rises as the flowrate increases - and the flowrate is read off the scale. Typically made of glass or plastic, so the float is visible. The "roto" part is only refering to the design where the float is made to spin a little to keep it more stable.

Rotometer for measuring flowrate





Homework Assignment: Kinksy new edition
Do all questions; Chapter 9: Basic Properties of Fluids
8.1 to 8.16 (page 186-188)

Do all questions.
Relevant pages in MDME
Web Links
  • Google search: Fluid Mechanics is a little tricky to search on the web. You will probably find most sites are highly technical, usually requiring advanced Engineering Mathematics. We are studying Fluid Mechanics at a level somewhere in between the mechanical trades (Hydraulics/Pneumatics/Fluid Power) and Engineering (Fluid Mechanics). 
  • Information on Pumps
  • Information on Valves