External Cover
A device used to protect the bellows from foreign objects or mechanical damage. The Cover may also act as a pressure containing device for externally pressurized expansion joints.
Internal Liner
Specified for all Expansion Joints, regardless of the metal of the bellows in the following cases: 1) Where it is necessary to hold friction losses to a minimum and smooth flow is desired; and 2) Where flow velocities are high and could produce resonant vibration of the bellows.
Sleeves are recommended when flow velocities exceed the following values:
Air, Steam and other Gases
- up to 6” dia. – 4 ft/sec. per inch of dia.
- over 6” dia. – 25 ft/sec.
Water and other Liquids
- up to 6” dia. – 1-2/3 ft/sec. per in. of dia.
- over 6” dia. – 10 ft. sec.
Reinforcing Ring
Used on some bellows which fits closely in the root of the convolution. The primary purpose of these devices is to reinforce the bellows against applied pressure – internal pressure in the case of rings fitted in the roots of the convolutions.
Tie Rods
Devices, usually in the form of rods or bars, attached to the Expansion Joint assembly whose primary function is to continuously restrain the full bellows pressure thrust during normal operation while permitting only lateral deflection. Angular rotation can be accommodated only if two tie rods are used and located 90° opposed to the direction of rotation.
Limit Rods
Devices, usually in the form of rods or bars, attached to the expansion joint assembly whose primary function is to restrict the bellows movement range (axial, lateral and angular) during normal operation. In the event of a main anchor failure, they are designed to prevent bellows over-extension or over-compression while restraining the full pressure loading and dynamic
forces generated by the anchor failure.
Weld Ends
The ends of a bellows unit equipped with pipe suitably beveled for welding to adjacent piping or equipment.
Flanged Ends
The ends of a bellows unit equipped with flanges for the purpose of bolting the unit to the mating flanges of adjacent piping or equipment.
Center Pipe
A common connection which joins two bellows.
Van Stoned Ends
In this type of construction, the flanges are slipped over the ends of the bellows and the bellows material is flared out or “Van Stoned” over the faces of the flanges. The bellows material prevents contact between the flanges and the medium flowing through the pipe. During installation, the Expansion Joint flanges can be rotated to match the bolt holes in the mating pipe line flanges. Although flat faced flanges are generally used for this type of construction, the Van Stoned portion of the bellows material overlapping the face of the flanges creates a condition which is, in effect, equivalent to a raised face.