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Brass fittings
Metals are some of the main materials used in plumbing: pipes, fittings, boilers, radiators.
Metals are some of the main materials used in plumbing: pipes, fittings, boilers, radiators.
Steel, Iron, Ferrous metals, Non-ferrous metals, Plastic and Alloys
Steel, Iron, Ferrous metals, Non-ferrous metals, Plastic and Alloys
Ferrous
These are metals that contain iron. They are magnetic and will corrode easily if not treated (ferrous oxide or rust).
Non-ferrous metals
Any metal that does not contain iron (copper, lead, zinc, aluminium etc).
Alloys
A mixture of two or more metals, these are commonly used in the plumbing industry.
Brass – copper and zinc
Bronze – copper and tin
Gunmetal – copper, tin and zinc
Steel – iron and carbon.
Bronze
Gunmetal
Plastics
Plastics
Common uses for plumbers when using plastics are for cold water, hot water, central heating, guttering, above ground drainage and below ground drainage. There are two main types known as;
Thermoplastic
Made from polymer resin; can be heated and re-shaped but become brittle when frozen, (guttering). These plastics are recyclable.There are many types of thermoplastics, which are suitable for different situations.
Thermosetting
These are rigid plastics that can cope with high temperatures, but are not recyclable.
Thermoplastic
Thermosetting
How do we measure weight?
How do we measure weight?
We firstly need to clarify that our common use of the Kg as a weight unit is not exactly true, Weight is the force of gravity pulling on a mass:
1 kg = 10N (9.81N)- Watch this video for an explanation on how your mass affects your force (weight).
What is density?
What is density?
We need to know that water has a density of 1 g/ml (1 gram per millilitre). As shown in the video anything with a density of less than 1 will float in water. Relative density is when we compare the mass of material.
Heat transfer through differing materials can vary according to their density, like a heat exchanger.
Dry to wet Boiler
Dry to dry Warm air unit
Wet to dry Radiator
Wet to wet DHWC
Heated molecules pass on heat to the adjoining material, which in turn heats up. Some materials are better at conducting heat than others. Eg metal (copper) is a good conductor of heat but wood is not.
Strength of materials
Strength of materials
The following terms are related to how a material will react in certain situations dependant on its molecule make-up;
Strength
Hardness
Malleability
Ductility
Elasticity
Durability
Thermal expansion
Conductivity (thermal and electrical).
As plumbers we use a lot of materials and some examples such as copper is very ductile ideal for our pipe bending without fracture and lead is very malleable which makes it ideal for bossing into shape without breaking.
Specific heat capacity
Specific heat capacity
It is the amount of heat required to raise 1kg of a substance through 10C.
Specific heat values change as the temperature increases. For plumbers, it may be important to work out how much heat is needed to heat a volume of water from one temperature to another.
Formula
Specific heat value x kg x temperature rise
1kg of water to rise 50C
4.186 x 1 x 5 = 20.93 KJ/kg/0C
Kilojoules/kilogram/degrees centigrade
Water 4.186KJ/kg
Aluminium 0.887KJ/kg
Cast iron 0.554KJ/kg
Zinc 0.397KJ/kg
Copper 0.385KJ/kg
Lead 0.125KJ/kg
Mercury 0.125KJ/kg
Linear expansion
Linear expansion
How much does a piece of material expand by when heated?
Plastic uPVC 0.00018
Lead 0.000029
Copper 0.000016
Steel 0.000011
Length of material x the temperature rise x the coefficient of expansion for that material.
How much will a 6 metre length of plastic guttering expand by, if the temperature rises by 100C?
6000mm x 10 x 0.00018 = 10.8mm
Corrosion
Corrosion
Electrolytic corrosion: the further away metals are in the electromotive series, the quicker the electrolytic corrosion takes place.
In a hot water cylinder, we install a sacrificial anode made of magnesium.
For a central heating system, they can go in
the boiler.
Pitting: after a solder joint is made, if flux is not cleaned off the outside of the tube and flushed out of the inside of the copper tube at the commissioning stage, the copper could be affected by: Type 1 pitting corrosion on the inside of the tube.
Plastics:
Can be effected by:
Heat: Thermal movement and distortion
UV: Sunlight degrading
Oxygen: Degrading
Light: Yellowing of plastic
Chemicals: Degrading
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