The detachable hat and veil should only be hand washed.  A soaking in mild bleach such as Napisan helps clean and sterilise. 

If it is put through a washing machine the rim is liable to be damaged or will cut through the cloth. 

Allow the damp hat to dry naturally.  Do not tumble dry.  If it is a warm day you could wear it while it dries.

Cleaning your suit or jacket