IP68 can be regarded as 'Superior' to IP56?

[LiamKim]

Hi,
my project requirement for IP grade is IP56 but electric actuator supplier's standard is IP68. I thought IP68 is simply acceptable but one of my colleague experience is that it should be deviation. The reason is that IP56 is jet water resistant but IP68 is submergable. It could have good protection for submerged situation but if jet watered, packing may be forced and protection would not be assured.
I've been trying to find a proof that IP68 is superior to IP56 but if anybody can educate me, if will be grateful.
Thanks.

 

[SEP87]

IP56 offers protection against a jet of pressure up to 1 bar. If your actuator is deforming under 1 bar pressure then I suggest you consider an alternative actuator. If your actuator can handle 1 bar pressure without deformation then it will be further protected by a higher IP rating.

Its a bit like asking if an IP54 box is protected against the ingress of a screw; certainly the box won't allow the ingress of the screw, but whether the level of protection is maintained if the screw impacts the box at high velocity is a different question. That is more a level of physical integrity rather than ingress.

I would have thought that the IP rating must assume that the item integrity is maintained. After all IP ratings are simply ingress protection rather than protection against deformation.