HAND WHEEL
A wheel located at the top of a manually operated valve that is used to actuate the valve stem.
HAT (FLANGE) PACKING
An old form of sealing rods, which seals on the ID only.
HEAD
The pressure at any point in a fluid can be thought of as being caused by a vertical column of the liquid that, due to its weight, exerts pressure at the point in question. The height of this column is called the "static head" (or sometimes simply "head") and is expressed in terms of feet or meters of liquid.
HEAT EXCHANGER
A piece of equipment designed to transfer thermal energy from one media to another. The unit is typically a long cylindrical body with multiple tubes passing within the body. Media of one temperature flows within the body but external to the tubes, while media of another temperature flows within the tubes, thus allowing thermal energy to exchange without cross-contamination of the products.
HEEL
Synonym: Heel Section.
HEEL SECTION
The portion of a lip seal which is attached to the seal case and bounded by the flex section and the outside face.
HELICAL MOTION
The circular, screw-like, up and/or down motion of a rod or valve stem.
HELICOFLEX® SEAL
Metal seal composed of a helical, wound spring with a single or double jacket wrapped around the spring. Cross-section of the seal is circular and various shapes and sizes can be created using different jacket wrappings.
HELIUM SEAL
A sealing level that does not exceed 1.0 x 10-9 atm cc/sec of Helium.
HELIX CONTACT WIDTH
The axial width of that portion of the contact surface of a helix seal which is formed by the helical ribs. It is equal to the total axial width of the contact surface minus the width of the static lip.
HELIX SEAL RIB SEAL
The angle formed by the leading edge of the rib and a line perpendicular to a plane tangent to the outside lip surface at the centerline of rib base.
HELIX SEAL RIB WIDTH
The maximum width of a helical rib measured perpendicular to the ribOs longitudinal axis.
HOMOGENEOUS
Of uniform composition throughout.
HOUSING BORE
A cylindrical surface which mates with the outside diameter of the outer seal case.
HYDRODYNAMIC SEAL
A dynamic sealing device which utilizes the viscous shear and inertia forces of the fluid; imparted by a helically grooved or ribbed seal lip, to generate a pressure differential that opposes fluid flow.