Resource Library

Are small diameter tubes necessary for increasing the energy efficiency of air conditioners?

No. The system energy efficiency can also be achieved with conventional tubes (such as 3/8 inch diameter tubes) simply by using more tubes and thereby increasing the surface area available for heat transfer. Nevertheless, a penalty is paid in terms of the increased weight of tube material and fin material as well as increased refrigerant volume. In general, if larger diameter tubes are used then a larger coil size is necessary to achieve the same performance and energy efficiency that could be achieved in a more compact system with smaller diameter tubes.

Are the 1, 2 and 5 Cent Euro coins pure copper?

No, they are made from steel coated with a thin layer of copper.

Are hygienic copper surfaces coated?

No, the hygienic property of copper is intrinsic to the metal.  In order to maintain this benefit, oils, waxes, glosses, paints and other coatings must NOT be applied.

An engineering report suggests that Stress Corrosion Cracking (SCC) is a problem in brass tubes. What steps may be taken to avoid SCC?

SCC occurs due to the combined effect of stress and corrosion. The stress may be removed by a stress relief anneal at 250 to 300° C for ½ to 1 hour.

Are 90-10 and 70-30 copper-nickels susceptible to stress corrosion cracking?

They do not experience chloride or sulphide stress corrosion. They have a high resistance to ammonia stress corrosion compared to other copper alloys and do not require a stress relief anneal for seawater service.

Are 90-10 welding consumables available for welding 90-10 copper-nickel?

They are available but 70-30 copper-nickel consumables are preferred for welding both the 90-10 and 70-30 alloys due to superior deposition characteristics.

Are copper-nickel alloys susceptible to the attachment of marine organisms in seawater?

Copper-nickel alloys can harbour slimes, but the attachment of macro-organisms—such as marine grasses and shellfish—is impaired. If these do become attached under quiet conditions, adherence is poor and they can be easily removed mechanically.

Are lead-containing solders being phased out for all engineering applications?

Lead is NOT being categorically phased out but the use of lead (and cadmium) is being increasingly recognised as being undesirable both in terms of the long term environmental impact and recyclability of products. The End of Life Vehicles (ELV) Directive (2000/53/EC), the RoHS Regulations (2002/95/EC) and WEE Directive (2002/96/EC) prevent the use of certain hazardous substances including lead (and cadmium) containing materials. The use of leaded solder in potable water systems has also been prohibited in Europe and in many countries worldwide.

Are the 1, 2 and 5 Cent Euro coins pure copper?

No, they are made from steel coated with a thin layer of copper.

Adhesion of marine organisms is a major issue in fish farming. Do copper alloys suffer from attachment of micro and macro-organisms?

Copper alloys can harbour slimes, but the attachment of macro-organisms—such as marine grasses and shellfish—is impaired. If these do become attached under quiet conditions, adherence is poor and they can be easily removed mechanically. Copper alloy mesh prolongs the intervals between periodic cleaning, thus promoting a cleaner and healthier environment for aquaculture.

Brass is said to be non-magnetic, but a sample reacts to a magnet. Why?

Probably due to the high iron content from recycled scrap. If a non-magnetic copper alloy is required use a nickel aluminium bronze to Def Stan Specifications (were NES).

Can brass be used for architecture?

Yes, brass and bronze alloys are available.