SKF hydraulic seals: profiles, sizes and part numbers

The leading letters name the seal profile and, through it, its role in the cylinder. CUT 50X39X4.2 and GH 25X17.5X3.2-AD1 are two different profiles, each with three dimensions separated by X, while ZW 25X32 has two. The order of the diameters depends on the profile, so don't compare dimensions across families.

DTW-25X33X5-J2G shows its dimensions, and the ending identifies the material. DSW-625-J2G instead carries a number that is not a direct millimeter dimension. Either way, the ending belongs to the part number: one profile is made in compounds for different fluids and temperatures.

When a cylinder leaks, the common approach is to replace the full set instead of one seal. They have all run the same hours, and taking the cylinder apart twice costs more than the parts. As you disassemble, note which groove each seal came from and which way its lip faced; a single-acting seal installed backward will not seal.

Check the rod and the bore as well. A lengthwise scratch, a dent or corrosion will cut a new seal within the first few cycles. Inspect the guide rings too: when they are worn, the rod runs at an angle and loads the seal on one side. Fluid and temperature determine the material, so it is worth keeping the same one.

Send the part number of each seal and the quantity. If you lack part numbers, give us the rod diameter, the bore diameter and each groove's bottom diameter, width and depth. Tell us the working pressure, fluid, temperature and whether the cylinder is single or double acting. A photo of the removed seals laid out in their installed order helps us recognize the profiles.