During the installation and overhaul of flue system, how to deal with the connecting rod (also called tie rod) on the expansion joint is a problem that often trouble field technicians. One may ask: Is the flue expansion joint connecting rod to be removed? The answer to this question is not a simple "yes" or "no", but depends on the specific type of expansion joint and the functional positioning of the connecting rod. Wrong handling of connecting rods-not removing what should be removed or removing what should not be removed-may cause the expansion joint to fail to work properly or even lead to pipeline safety accidents. This paper will systematically analyze the functions, dismantling conditions and correct operation methods of different types of flue expansion joint connecting rods, and provide clear guidance for engineers and technicians.

1. Two types of expansion joint connecting rods and their functional distinction

To answer "Do you want the flue expansion joint connecting rod to be removed", you first need to understand the two basic types of connecting rods: transport tie rods and load-bearing tie rods. The functional positioning of the two is completely different.

1. Transportation tie rod (temporary)

The transport tie rod is a temporary component set by the expansion joint when it leaves the factory. Its main functions include:

• Prevent transport damage: Protect bellows from impacts and shocks during transportation
• Prevent deformation before installation: Keep the geometry of the expansion joint before installation
• Easy hoisting in place: Provides rigid attachment points for hoisting

This type of tie rod is usually simple in structure and made of general materials. It needs to be removed or loosened after the installation of the pipeline system, otherwise the expansion joint will not work properly.

2. Load-bearing tie rod (permanent)

The load-bearing tie rod is part of the expansion joint structure and has clear engineering functions:

• Bear pressure thrust: Absorb the blind plate force generated by the bellows
• Limit compensation direction: guide the expansion joint to perform displacement compensation according to the design direction
• Protect bellows: Prevent bellows from exceeding the allowable deformation range

This kind of tie rod must not be removed, otherwise the expansion joint will be damaged due to excessive displacement, and even lead to the instability of the pipeline system. The tie rod device of the double tie rod type expansion joint is arranged precisely to withstand the pressure thrust and its additional external force。

2. Principles of connecting rod treatment of different types of expansion joints

1. Universal (axial) expansion joint

For general-purpose expansion joints, the connecting rod is typically a transport tie rod。 The connecting rod of this type of expansion joint mainly plays a protective role in the transportation process. Once the pipeline system is installed, it must be removed so that the expansion joint can play its compensation function normally。

However, there is an important exception: If the manufacturer paints the screw with yellow paint, it means that the tie rod can be kept for use。 In this case, it is recommended to communicate directly with the manufacturer for confirmation to avoid affecting the product performance due to misoperation.

2. Large tie rod/small tie rod type expansion joint

For the transverse expansion joint of large tie rod, the tie rod is an unremovable load-bearing member. This type of tie rod mainly plays the following functions:

• Prevent axial compensation: Guide expansion joint for radial compensation
• Withstand pressure thrust: Prevent blind plate force from damaging pipelines and equipment
• Ensuring safe pipeline operation

If this tie rod is removed in error, the expansion joint will not be compensated in the design direction, and the pressure thrust will act directly on the pipe support and equipment interface, which may cause serious consequences.

3. Compound tie rod type expansion joint

Compound tie rod type expansion joint is mainly used for compensation and absorption of transverse displacement when the temperature is high, the diameter is large or the fixed bracket cannot be placed。 The connecting rod of this type of expansion joint is a permanent load-bearing member and cannot be removed.

Its working principle is that the pull rod device is subjected to pressure thrust and its additional external force, so that the two ends can use intermediate fixed brackets, and the axial force acting on the pipeline is only the deformation reaction force generated by the expansion joint, only need to cooperate with the guide bracket。

4. Hinged/universal expansion joint

The hinge and universal expansion joints are used by hinge plates or universal hinges to withstand pressure thrust and guide the direction of displacement。 The connecting members of such expansion joints are permanent structural members and must not be removed.

III. Summary table of connecting rod treatment methods

4. Correct operating procedures

1. Confirmation before installation

After the expansion joint arrives, check the product manual and manufacturer's identification first:

• Confirm Expansion Joint Model and Type
• Check for "removable" marking (e.g. yellow paint) on the tie rod
• Record the initial position and state of the tie rod

2. Removal of transport tie rods

If it is confirmed to be a transport tie rod, attention should be paid to the following when removing it:

• Must be removed after the installation of the pipeline system and before the system is put into operation
• If pre-stretching or pre-compression is required, the relevant operation should be performed only after the pre-deformation is completed
• Keep safe after removal, but it is not recommended to discard (reuse if you need to remove the expansion joint)

3. Adjustment of load-bearing tie rod

For non-removable load-bearing tie rods, attention should be paid when installing:

• It should not be forcibly removed, otherwise it will leave potential safety hazards for the pipeline operation
• The position of the limit nut can be adjusted appropriately according to the design displacement
• Ensure that sufficient compensation space is reserved for nuts at both ends of the tie rod

4. Final inspection after installation

• Confirm that all transport rods that should be removed have been removed
• Verify that the tightening condition of the load-bearing tie rod is good
• Record the factory number and installation date of the expansion joint for future maintenance identification

FAQs and Risk Warnings

Problem 1: Mistakenly remove the load-bearing tie rod

Consequence: The expansion joint cannot withstand the pressure thrust, and the blind plate force acts completely on the pipe support and equipment interface, which may result in:

• Deformed or damaged pipe support
• Equipment interface stress exceeds standard
• Damaged by excessive elongation of the expansion joint

Prevention: Be sure to check the product information or consult the manufacturer before removal to confirm the type of tie rod.

Question 2: Transport tie rod not removed

Consequence: The expansion joint cannot carry out normal axial compensation, the function is completely lost, and the thermal stress cannot be released.

Prevention: Include "Remove Transport Tie Rod" in the installation checklist.

Question 3: Unclear about the pull rod function

Handling method: Communicate and confirm with the manufacturer directly to avoid the expansion joint not working properly due to not removing or not removing。

VI. Summary h2>

Is the flue expansion joint connecting rod to be removed-the answer to this question depends on the specific type of expansion joint and the functional positioning of the connecting rod. The core conclusions can be summarized as follows:

1. First classify, then decide: the transport tie rod of the general expansion joint needs to be removed, while the load-bearing tie rod of large tie rod, small tie rod, double tie rod and other types must not be removed
2. Transport tie rod must be removed: This type of tie rod is only used to prevent transport damage. If not removed after installation, the expansion joint will not be able to normally compensate for thermal displacement
3. Permanent retention of load-bearing tie rod: This type of tie rod bears pressure and thrust, guides the compensation direction, and is part of the expansion joint structure. Dismantling will cause serious safety hazards
4. Note the yellow paint mark: If the tie rod is painted with yellow paint, it means that it may have load-bearing function, and you should consult the manufacturer before handling it
5. Pre-tensioning should be completed in advance: If pre-tensioning or pre-compression is required, it must be completed before tie rod adjustment or removal

For field technicians, one principle should be remembered when handling the expansion joint connecting rod: consult the manufacturer first when you are unsure, and never remove it at will based on your feeling. Only by correctly identifying the type of tie rod and handling it according to requirements can the flue expansion joint play its due compensation function in actual operation and ensure the safe and stable operation of pipeline system.