Accessories

Expansion Joints

THERMAL EXPANSION

1. Elbows, tees, and joints are not designed to resist bending moment forces as a result of thermal expansion. The forces due to thermal expansion therefore need to be compensated by expansion joints.
2. Whether in the vertical or the horizontal run, the thermal expansion of the inner pipe is directly dependent on the internal wall temperature and the length of pipe between fixed points.
3. Proper installation practice requires that expansion greater than 1/4” will be compensated by using a bellows Expansion Joint (EJ) or Variable Length (VL), depending on the maximum pressure encountered.
4. Models IPPL, IPPL2 and IPPL2F chimneys have an expansion coefficient of 8,9 in the formula below. (See Fig. F-1.)
5. Though thermal expansion may be calculated from the formula, a rule of thumb for exhaust pipe expansion estimation is that the axial growth will be approximately 1” per 100’ of pipe length for each 100ºF the flue gas temperature difference between flue gas and surrounding air ambient temperature. (See Table-F-1.)
6. Because the amount of outer casing axial movement is the same as inner casing movement, the outer piping jacket must slide to avoid excessive forces on tees, elbows or fixed points. To accommodate outer casing movements, external guides along walls at floors, or in lateral breechings, must allow for movement of pipe.
7. When resupporting a system with considerable height and expansion, Variable Lengths (VL) or bellows Expansion Joint (EJ) must be used just below every support above the first to compensate for thermal expansion.
8. For engine or turbine exhaust systems requiring pressures up to 60 inches of water column, or where the construction must be absolutely gas tight, all welded bellows Expansion Joints (EJ), either with a liner or without a liner are recommended for expansion and vibration movements of the exhaust piping.
9. Low pressure systems, such as boilers (up to 6 inches water column), can effectively use the Variable Length (VL) expansion joint.
10. Spacing of guides and supports, when a thermal expansion part is used, should not be greater than what is specified in Section A. Table A-5.
11. Proper guiding and support of expansion parts often requires closer spacing.

BELLOWS EXPANSION JOINT (EJ)

1. For exhaust pressure up to 60 inches water column, bellows Expansion Joints (EJ) are recommended to compensate for piping expansion and vibration. See fig. F-3 for an illustration of a bellows Expansion Joint (EJ).
2. Fig.F-2 illustrates the use of bellows Expansion Joints (EJ) in a typical installation. The use of the lined bellows Expansion Joint (EJ) is shown to compensate for the axial expansion of the long horizontal run.
3. System is used for axial movements and vibration only and must be accurately supported and guided. This part has limited lateral movement. Lateral offsets and parallel misalignments should be avoided.
4. The lined bellows requires careful positioning of piping guides to avoid interference on thermal expansion.

5. Any IPPL, IPPL2 and IPPL2F piping system requiring low axial expansion forces, the bellows Expansion Joints (EJ) will deflect with minimum friction at a known “spring rate”. The values for spring rates given in the tables assume there are no other frictional constraints and also proper alignment of the liner in case of the bellows Expansion Joint (EJ).
6. At an operating gas temperature of 1000ºF (70ºF ambient), the IPPL2F inner pipe in a typical engine exhaust system will be subject to a temperature of approximately 650ºF.
7. Allowable expansion movements for bellows Expansion Joints (EJ) are given in figure F-3 and in Table-F-1.