Product code

HTMS - High Tech Metal Seals

Seal diameter

The seal diameter is described in millimeters with 2 digits behind the decimal point. For seal types indicated with “I”, such as CI, CSI, OI, etc., the diameter in the product code is the outer diameter of the seal. For seal types indicated with “E” the diameter in the product code, such as CE, CSE, OE, etc., the diameter in the product code is the inside diameter of the seal.

To choose the right diameter it is important to take both the diametrical clearance and the plating into account. The diameter is always the diameter without plating.

To select the right diameter for “E” seals the following formula must be applied:
DSI = Groove Diameter (DG) + Diametrical Clearance (DC) + Plating Thickness x 2

To select the right diameter for “I” seals the following formula applies:
DSO = DG – DC – Plating Thickness x 2     (See the figure below)

Using the product code above as an example:
DSO = 99.82 – 0.41 – 2x 0.05 = 99.31 mm


The first digit designates the base material, the second digit designates the spring material. The second digit is “0” in case no spring is present.

Heat Treatment

The applied treatment with “1” being work hardened.


Information about the plating code and the thickness code can be found on the tab on the last page of the catalogue.

The example above shows the product code for a CI type seal with an OD of 99.31 mm, an axial section of 3.96 mm and medium wall thickness.

The code for the base material is “2” which is Inconel 718 and the seal does not contain a spring.

The seal is work hardened and has a tin plating ranging from 30 µ to 50 µ.


This example starts out to chose the right seal for a known flange.
For the sake of the example an O-ring made out of Stainless Steel 321 without a heat treatment, with 50 µm silver plating is required.

The groove diameter (DG) of the flange below is 100,00 mm. The groove depth is 2,60 mm.

Assuming an excess pressure on the inside the choice will be made for an OVI-seal.

For an internal pressure seal the diameter of the seal is the outside diameter. To determine the right diameter for the seal the following formula is followed:

OD = DG – DC – 2 x maximum plating thickness

The diametrical clearance depends on the chosen axial section of the seal. In this case the groove depth of 2,60 mm corresponds to the groove depth of a seal with an axial section of 3,18 mm, for the sake of the example the M version of the section is chosen. The diametrical clearance for a seal with this axial section is 0,25 mm.

As said earlier in this example the maximum plating thickness will be 50 µm.

This gives us:

100,00 mm – 0,25 mm – 2x (50 µm) = 99,65 mm

All that is needed to complete the product code is the information that was already stated in the beginning of this example.

  • The code that corresponds with the Stainless Steel 321 is “3”.
  • The O-seal does not contain a spring, hence the spring code is “0”.
  • The absence of a heat treatment gives the code “1” for the heat treatment.
  • And the plating code for a seal with 50 µm of silver is “S50”.

This give the following product code for this particular setup:


  • For C(S)A seals the seal diameter is always the outside diameter of the seal. This is calculated based on the bore diameter.
  • Plating thickness on radial seals should be limited to 50 µm. Seal diameters remain unchanged for plated seals
  • For COI seals the diameter is always the shaft diameter without plating.
    DSI = SD
  • For COE seals the diameter is always the bore diameter without plating.
    DSO = BD