Resource Library

How much do copper alloy cages cost?

The exact cost of using copper alloys in aquaculture enclosures depends on multiple factors such as the cage size and the transportation of materials to the building site, and then of the cage to the farming site.  Overall, the total cost is offset by the long-term cost savings associated with longer service life, decreased fish losses, lowered maintenance, etc.

Is it possible to heat treat aluminium bronze CW307G (CA104) to improve its corrosion resistance?

Yes, this is covered in Def Stan 02-833. For extruded rods and sections of size 40mm and below, an anneal at 740°C plus or minus 20° followed by air cooling is carried out. This mandatory heat treatment is to eliminate phases which are likely to give rise to selective corrosion in sea water.

How do I prevent staining of leaded brass components which is produced after machining?

After machining clean the components with hot detergent, rinse thoroughly in cold water then immerse in a tarnish inhibitor (a mixture of monoethylene glycol and benzotriazole) then dry in air.

High conductivity is needed in electrical equipment running at high temperatures. What grade of copper should be used?

At room temperature, Cu-ETP should be used. However, it begins to soften at 150oC, so at higher temperatures the following may be used with only a slight loss of conductivity:

  • CuAg0.10 up to 250oC to 300oC
  • CuZr,CuCr1zr,CuNi2Si  to 350—400oC
How can bronze works of art be protected from corrosion if they are situated outdoors?

Either by the use of lacquers, wax polishing, or both.

How can corrosion or staining of machined aluminium bronze components be avoided during shipping?

The key is to clean them thoroughly, remove water, protect them and keep them dry, so:

  1. After cleaning dry thoroughly using a dewatering fluid such as WD40.
  2. Remove displaced water with forced warm air.
  3. Coat with a protective coating such as benzotriazole inhibitor, or a block co-polymer.
  4. Pack into benzotriazole treated paper lined wooden boxes. Moisture absorbent granules may also be used to keep the air inside the boxes dry.

When unpacked, remove the coatings with a phosphoric-based solution and dry them thoroughly.

Standard transformers are very efficient. Is there really an advantage in purchasing a high efficiency version?

It depends on the type of load on the transformer.

Transformer losses are of two types; those that are independent of the load (known as ‘no-load’ losses) and those that vary with load (known as ‘load losses’ or, sometimes, as ‘copper losses’).  ‘No-load losses’ are present all the time that the transformer is energised, whether loaded or not.  Most of the no-load losses occur in the magnetic steel of the core.  ‘Load losses’ are proportional to the square of the load current and so are greatest when the transformer is highly loaded.  Transformers are manufactured to meet standard types defined by standards or to meet specific customer requirements.

As a rule of thumb, if the loading is high, such as in an industrial plant, purchase of a transformer with reduced load losses will be beneficial.  If the transformer is lightly loaded, such as a hot standby transformer, a transformer with reduced no-load losses will be beneficial.  In other cases, it is necessary to calculate the benefit.  The SEEDT report gives more information on transformer losses.   (2008, 32pp).

How is copper fixed to a roof?

Copper sheets are fixed with clips, some fixed and some sliding, which allow the copper to expand and contract with changes in the temperature. If the copper is fixed rigidly then splits in the sheet may occur.

Should I take energy losses in installation cable into account?

For long circuits, or high power or high duty cycle circuits, energy losses in cable should be considered. Wiring standards normally recommend that the voltage drop in installation wiring is kept to below 2.5%.  That represents a power loss of 2.5%, so the cable, as installed, is only 97.5% efficient. Increasing the conductor cross-section reduces voltage drop and energy loss, but increases the cost of the cable. The process of finding the optimum conductor size – for which the lifetime cost is lowest – is described in Pub 116 – Electrical Energy Efficiency. Our cable sizing software allows the optimum size to be calculated easily.

Some sources suggest painting busbars black to increase the current rating. Is this a good idea?

No. Black matt surfaces are better at radiating heat than bright shiny surfaces, and that is why painting is sometimes suggested. The efficacy of radiation is the emissivity of the surface; for a perfect radiator (matt black), the emissivity is 1 and for a perfect reflector, emissivity is zero. In practice, bright shiny copper has an emissivity of about 0.3, dull copper is about 0.7 and darkened copper – such as a busbar after a few weeks of service – can reach 0.9. Since only around 10-20% of heat is lost by radiation, the difference between dull copper and a matt black surface is only 3-6% of the total.  To achieve this apparent improvement, the 90% of the heat that escapes by convection has to pass through the thermal insulation provided by the paint layer, so the temperature of the bar increases rather than decreases.

There are a number of types of sprinkler heads, including concealed. If you saw a concealed sprinkler head in-situ what would you see?

Only the cover plate, a disc on the ceiling.

There are two types of compression joints - Type A and Type B. Which is ‘manipulative’?

Type B is manipulative, it requires the end of the tube to be flared.