The Dowty seal or a Bonded seal is a metal washer with a vulcanized rubber insert for use in high pressure applications where other means of sealing are unsuitable. Bonded seals are now available in self centralising form, which eliminates seal offset and makes for easier installation.

Dowty seals are used for making pipe joints in hydraulic systems leak free. They are designated according to the size of the pipe thread where it is used.

When the bolted connection is tightened, the sealing lip is pressed against the flat surfaces. The metal washer ensures that the components to be connected are reliably and securely held. The thickness of the washer limits the compression of the elastomer seal, eliminates any over torque of the joint, thereby ensuring a reliable sealing system. The internal pressure increases the sealing force by energising the sealing lip.