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Glossary of terms you will come across during your Phase 2 training.

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A U-tube operates by the following principle:

Diagram illustrating the u-tube principleIf you have liquid in a u-tube, and both sides of the tube are exposed to the same pressure, the level of liquid in one side of the tube will always be exactly the same as the level of liquid in the far side.

If I want to alter the levels of liquid in either side, I can raise or lower the pressure on one side only to achieve the desired effect.

For example, in the Small Plant Module, Petrol and LPG Learning Unit, we look at float chamber carburettors.

In this device, the float chamber, main jet and main jet orifice form a u-tube.

In this arrangement, we allow atmospheric pressure to act on the surface of the fuel in the float chamber.

When the engine is not running, atmospheric pressure also acts on the main jet orifice.

Because there is equal pressure on both sides of this arrangement, no fuel will flow from the float chamber and out of the main jet orifice.

Float chamber carburettorHowever, once we run the engine, air being induced into the engine on the induction stroke is forced to speed up in order to get through the venturii of the carburettor.

This increase in air speed produces a corresponding drop in air pressure around the main jet orifice.

Now we have a situation where we have atmospheric pressure acting on the fuel in the float chamber (one side of the u-tube), and less than atmospheric pressure acting on the main jet orifice (the other side of the u-tube).

This imbalance of pressures causes fuel to flow from the float chamber, through the main jet and out the main jet orifice, where the air stream will carry it into the combustion chamber for burning. 


Harness repair kit, supplied by Perkins:

Harness repair kit supplied by Perkins


This is the Perkins part number of a fuel line blanking kit. The kit consists of four different size blanks, designed for use with the 1104 and 1106 common rail engines.

Fuel line blanking kit


Company contact for Unilokomotive Ltd.

Telephone: 093 52150



The only authorised absence from Phase 2 training is certified sick leave. Certified sick leave is where you furnish a sick note from a medical doctor.

Your instructor also has limited discretion to authorise short absences on compassionate grounds, such as the death of a family member.

All other absence is unauthorised and will attract a formal verbal warning (DR1) for the first absence, and a written warning and suspension from the course (DR2) for a second absence.

Further absence will attract a DR3 can result in the termination of your Phase 2 training and your apprenticeship.


From their website:

Unilokomotive Limited manufactures the Unilok road / rail wagon mover or shunting locomotive used for moving railway wagons, carriages or locomotives. Uniloks are not truck conversions, but purpose built rail yard workhorses that travel as easily on road as on rail. Uniloks carry out shunting tasks that locomotives 4 to 5 times there weight would do, but with greater mobility and at a fraction of the cost. Read More...



Unit injectorThis refers to a fuel injector in a diesel engine that is constantly connected to a high pressure fuel rail (common rail). When the ECM (the engine computer) wants the injector to fire, it sends a signal to an electrical solenoid in the injector, which lifts the needle. Because the fuel inside is under massive pressure, injection occurs at this instant.

CAUTION: This unit is connected to a very high pressure supply, in the region of 1,600 bar (approx. 23,000 psi). Always wait until the engine has been switched off for one minute before attempting to disconnect the fuel supply pipe.

Never re-use an injector pipe, always fit a new one.

In the context of fuel, specifically petrol, lead (or more precisely, tetraethyl lead) used to be added to fuel, where it acted as an anti-knock inhibitor. It was very good in this role, but the problem was that 75% of it was passed out the exhaust and into the environment.

Uniform resource locator. This is the unique address of a web site on the Internet.

For example, the URL, or Uniform Resource Locator, or web address of the CP Fitters' Homepage is:


Universal Serial Bus:

USB symbolThis is an external interface that allows us to connect various devices to a computer. It gives these devices access to the computer's internal bus.

This is a serial bus, and data to and from these devices follow each other down the signal line of the USB cable. (With a parallel port, eight signals (one byte) travel together down eight parallel lines and all arrive at the computer at the same time)

The USB connection is a fast connection (especially USB 2.0)

As well as providing a data connection, USB connections can also supply power to smaller devices such as USB memory sticks or mice. Larger devices such as printers have their own power supply.

USB devices are "hot-plugable" - equipment or devices can be plugged in, or unplugged, when the computer is switched on. Before equipment is unplugged from a USB port, you must inform the computer that you are about to do so. There is an icon in the system tray for disconnecting USB devices

A computer can handle up to 127 USB devices, and a computer usually has between 1 and 6 USB Ports built in. If you need more you can add a powered or non-powered USB hub.