Like SRT says, it is possible. I have held 2 SA passports for about 10 years now
with no issues from the authorities in SA. I was given a letter by my employer that I handed in with my application for the second one and it was accepted without query.
At renewal time, I get another letter for each passport and continue from there. It does make life easier, especially with some visas taking longer to acquire than the tour of duty they are intended for.