For FDA approved valves, we usually ship them in air-tight seal for the whole valve. The general practice is to sanitize the area and packaging prior to opening the seal. So, it applies to the whole valve and not the seat/trim/wetted parts only.
Wonder if it's too late but you can refer back to your supplier to check on the spring range of the axial flow check valve. Since capacity is too low (which does cause chattering or premature closing and slamming) and you do not have an option to change the size, the next best thing is to look...
