Maintaining spares and redundant machinery in a prime state, ready for operation, can be a daunting proposition, particularly given that most of the planet is covered with a substance that tends to attack these stored and stand-by machines.
We call the substance water. It is vital to life, health, happiness, and keeping the wheels turning in the wide world of petroleum products and in particular subsea field development. Water also has the distinct potential to wreck idle equipment (both surface and subsea equipment).
Machinery/Equipment can be idle from intermittent use, stand-by (redundancy), storage for spare parts, or for temporary decommissioning.
Preservation before and during layup reduces corrosion and enables faster startups. Active preservation will help prevent seizing of moving parts and maintain the life of seals & gaskets. To preserve and maintain equipment and systems is more cost beneficial than repairing or buying new ones after a lay-up period.