Vacuum deyhdration is an old principle. It helps to understand how it works: Simply put, when water is placed under a vacuum it can boil off at a much lower temperature then when it is at ambient pressures. You may remember school science experiments where water is boiled in a flask and then sealed. Once it is cool you can boil the remaining water by holding the flask in your hand. It is an extremely efficient way of moisture removal and doesn't require high maintenance cost once the system is in place. But moisture, as with all forms of ingress, shouldn't be regarded as an accepted problem. In the long term, it is usually much cheaper to find the source of the problem and stop the moisture at the point of entry. Then equipment can be hired rather then purchased to remove any remaining contamination. There is a saying in Australia which is suprisingly accepted: "The oil is in good condition considering the environment in which it operates". It's important to distinguish between what is easily achievable and what is actually appropriate for a sustainable operation.