3D
Lifeboats and liferafts
Lifeboat safety and the rules
Why lifeboats hurt people, which rules keep crews safe, and what to check, log and leave to specialists.
8 lessons1 h 30 minIntroductory
Course content
Level 1 · Foundations
1 Pascal's law: how a small push lifts a heavy load Open
Pressure in a trapped liquid pushes equally on every surface it touches, so a small piston and a big piston share the same pressure, and the big one gets the bigger force.
2 Hydraulic pressure and flow: what each one really does With an account
Flow decides how fast things move. Pressure is how hard the oil has to push to make that happen, and it comes from the load and from every restriction the oil passes through.
3 The basic hydraulic circuit: pump, relief valve, control valve and cylinder With an account
The pump makes flow, the load makes pressure, the relief valve sets the limit and the control valve decides where the oil goes. Every hydraulic machine is built on these four parts.
4 Hydraulic symbols explained: how to read an ISO 1219 diagram With an account
A hydraulic diagram is drawn with a small set of standard shapes: circles for pumps and motors, squares for valves, rectangles for cylinders. Learn twelve and you can read most machine schematics.
5 Hydraulic oil viscosity: why temperature changes everything With an account
Viscosity is how thick the oil is. Hot oil thins and leaks through every clearance; cold oil thickens and starves the pump. Choosing the grade means keeping the oil in its ideal band at your real working temperature.
Level 2 · Components
6 How a hydraulic gear pump works, and why it wears With an account
Two meshing gears carry oil round the outside of the housing in the spaces between their teeth, and the mesh in the middle squeezes it out. Every turn moves the same volume, so flow follows speed.
7 How an axial piston pump works: the swashplate, the valve plate and the case drain With an account
Pistons in a rotating barrel slide on a tilted swashplate, so each one draws oil in for half a turn and pushes it out for the other half. Change the tilt and you change the flow without changing the speed.
8 How a hydraulic relief valve works: direct-acting and pilot-operated With an account
A relief valve is a spring holding a poppet shut. When pressure times seat area beats the spring, it opens and sends oil back to tank, which caps the system pressure and turns that flow into heat.
9 How a directional control valve works: spools, ports and centre types With an account
A directional valve is a precision spool sliding in a bore. Its lands open and close passages between the pump, the tank and the two sides of a cylinder; the shape of the lands in the middle position decides what the machine does when you let go.
10 Check valves and pilot-operated check valves: how a load is held With an account
A check valve lets oil through one way and blocks it the other. A pilot-operated check adds a small piston that can push it open on command, so a cylinder holds its load until you deliberately lower it.
11 How a counterbalance valve stops a crane load running away With an account
A counterbalance valve sits on the cylinder and holds the load until pilot pressure from the other side opens it just enough to let the oil out as fast as the pump fills the cylinder. The load comes down under control instead of falling.
12 Hydraulic cylinders: push, pull, speed and regeneration With an account
A cylinder turns pressure into force and flow into speed. The full piston area pushes, the ring around the rod pulls, and regeneration trades force for speed.
13 Hydraulic motors and winches: how flow makes speed and pressure makes torque With an account
A hydraulic motor is a pump run backwards: oil flow turns it, and the pressure needed rises with the torque the load demands. On a winch a spring-applied brake holds the load whenever the oil is off.
14 Hydraulic accumulators: how nitrogen stores oil under pressure With an account
An accumulator stores oil under pressure by squeezing nitrogen in a bladder. How much oil it gives back depends on the precharge and the working pressure range, not just its size.
15 Hydraulic contamination: particles, clearances and filters With an account
Most hydraulic failures start with dirt. Particles the size of a valve's clearance jam and score it, so the filter has to catch them, and the oil cleanliness code tells you whether it does.
Level 3 · Systems and faults
16 Load sensing explained: one job, three pumps, and where the power goes With an account
A load-sensing pump reads the pressure the load needs and makes only a small margin more, delivering only the flow the valve asks for. The same job that wastes most of a fixed pump's power wastes almost nothing.
17 Where hydraulic heat comes from, and why the oil overheats With an account
Every kilowatt the motor puts in that doesn't do useful work ends up as heat in the oil. The oil settles at the temperature where the cooler and tank get rid of heat as fast as the system makes it.
18 Pump cavitation and aeration: why a hydraulic pump gets noisy With an account
Cavitation is a pump starved of oil, so bubbles form at the inlet and implode on the pressure side. Aeration is air getting into the oil. Both make noise and both destroy pumps, but the fixes are different.
19 How ship steering gear works: rams, the Rapson slide and two pump units With an account
Pumps push oil into rams, the rams push a crosshead along the tiller, and the tiller turns the rudder stock. Follow-up control stops the rudder at the helm order, and locking valves hold it there against the water.
20 How a hydraulic crane circuit works: slew, luff and hoist from one pump With an account
One pump feeds a valve bank with a section for each movement. Run two at once and the oil goes to whichever needs the least pressure, so the crane's behaviour depends as much on the circuit as on the load.
Final quiz
After the lessons
After the lessons
Course completed card
At the end
At the end
