Chemicals and petrochemicals can be challenging to handle mostly because of their corrosive properties. Many metals melt upon contact with them or react to form compounds that make them unusable for the intended purpose. This is why industries and refineries only use suitable metals or alloys to create pipes, valves, seals, pumps, reaction chambers, and other essential containers to handle these substances. One of these alloys is called Monel 400.
Monel 400 is an alloy made up mostly of Nickel and Copper. It also contains small amounts of Iron, Sulphur, Silicon, Carbon, and Manganese. It is corrosion-resistant and can withstand high temperatures. This alloy is also exceptionally strong (even stronger than steel) and retains its ductility in cold temperatures, making it ideal for subsea fluid transport.
Petroleum companies use Monel 400 pipes to extract crude oil and gas from subsea reservoirs because of their resistance to pressure and seawater corrosion. They also use pipes and valves made from the alloy to collect fractions of petroleum after refining.
Chemical and petrochemical companies find Monel 400 invaluable because they produce substances that are harsh on most metals but the alloy handles them comfortably. It is also reliable, durable, and resistant to oxidation. However, these properties come at a high cost. Monel 400 is expensive; approximately five times as costly as pure copper or nickel. Companies only use them when there are no suitable alternatives.
One of its greatest assets is that it retains its strength at extremely low temperatures, where most other metals become brittle.
Composition of Monel 400
All the elements that make up Monel 400 have been listed above but here are the standard compositions of each expressed in percentages. Note that each percentage listed is the maximum allowable amount to form the alloy.
- Nickel - 63% to 70%
- Copper - 28% to 34%
- Iron - 2.5%
- Manganese - 2%
- Silicon - 0.5%
- Carbon - 0.03%
- Sulfur - 0.024%
Properties of Monel 400
These are the properties of the Nickel-Copper alloy that make it ideal for handling chemicals and petrochemicals:
- Specific Heat Capacity - 0.102 BTU/(lb*ºF)
- Density - 549 lb/ft3
- Electric Resistivity - 54.7*10-6 Ohm*cm
- Modulus of Elasticity - 26,000 ksi
- Elongation - 48%
- Thermal Expansion (at 68ºF) - 7.7*10-6 in/(in*ºF)
- Thermal Conductivity - 151 BTU*in/(hr*ft2*ºF)
- Solidus Temperature - 2,370º F
- Liquidus (News - Alert) Temperature - 2,460º F
- Yield Strength (when annealed) - 34,800 psi
- Tensile Strength (when annealed) - 79,800 psi
Limitations of Monel 400
There are not many limitations of Monel 400, but the few ones are noteworthy:
- It is more difficult to shape than most other metals.
- The only way to strengthen it is through cold working.
- While it can withstand corrosion from chemicals like hydrofluoric acid and sulfuric acid, it can be attacked by hypochlorites, sulfur dioxide, nitric oxide, and nitrous acid.
- Monel 400 resists corrosion, but not galvanic corrosion. Metals like zinc, aluminum, and iron can corrode if they are used with the alloy.
Endnote
Monel 400 is a strong and corrosion-resistant alloy of Nickel and Copper that is used in chemical and petrochemical industries because of its ability to handle harsh chemicals. Its strength and durability make it reliable even in subsea and cold environments. Although it is expensive, its ability to remain strong in below-zero and high temperatures makes the cost worthwhile.
