In industrial flue systems, non-metallic expansion joints (also known as non-metallic compensators) are key components to absorb thermal displacement, isolate vibration and reduce noise。 When the expansion joint reaches its service life or is damaged, the skin (i.e. hemming) needs to be replaced in time. So, how to remove the edging of the flue expansion joint? This paper will systematically explain the removal methods, pre-preparation, operation points and safety precautions of non-metallic expansion joint edging in combination with the general construction specifications of the industry, and provide professional technical guidance for on-site construction personnel.

1. What is flue expansion joint edging?

Before understanding how to remove the edging of flue expansion joint, we need to clarify the definition of edging first. The "edging" of the flue expansion joint usually refers to the skin part of the non-metallic expansion joint, which is the flexible sealing structure of the outermost layer of the expansion joint。

The skin of non-metallic expansion joints is generally made of multi-layer composite materials. Common structures include：

• Outer layer (weather resistant layer): silicone rubber or fluororubber coated fiberglass cloth for sealing and corrosion resistance
• Reinforcement layer: polyester fiber cloth or alkali-free glass fiber cloth to provide tensile strength
• Insulation: Insulation cotton wrapped in fiberglass cloth or stainless steel wire mesh
• Inner layer: Anti-corrosion layer directly in contact with smoke

The skin is secured to the metal frame of the expansion joint by a platen and bolts. When the skin is aged and damaged, it cannot be effectively sealed, and there will be problems such as smoke leakage and water leakage. At this time, the old skin must be removed and replaced with a new skin。

Preparation before demolition

The prerequisite for proper demolition is adequate preparation. Before the flue expansion joint edging removal operation, the following preparatory work must be completed:

2.1 Confirmation of Construction Conditions

• Shutdown isolation: Confirm that the flue system has been shut down to cool down, close the front and rear valves of the expansion joint, and empty the internal media
• Scaffolding erection: For high altitude or inconvenient parts, standard scaffolding should be erected in advance
• Power supply and gas supply: Ensure that the power supply and gas supply required for electric wrench and gas cutting equipment are available on site

2.2 Material and Tool Inspection

The following materials and tools should be counted before construction:

• New skin: confirm that the size, width and technical parameters match the original expansion joint
• Pressing plate and bolts: check the quality of the pressing plate (if the original pressing plate can be reused, it is necessary to confirm that there is no deformation); Prepare matching bolt assemblies
• Insulation cotton and insulation nails: If the internal insulation cotton needs to be replaced, prepare stainless steel wire mesh and insulation nails in advance
• Main tools: electric wrenches, wrenches, gas cutting equipment, fire extinguishers, etc.

2.3 Safety measures

• Fire prevention preparation: clean up the surrounding flammable items and equip fire extinguishing equipment (fire extinguishers, fire sand, etc.)
• Personal protection: construction workers should wear protective gloves, goggles and safety helmets; Working at height must wear seat belts and be supervised by safety officers
• Warning isolation: Warning signs are set up in the construction area to prohibit unrelated personnel from entering

3. Detailed explanation of the removal steps of edging of flue expansion joint

The following is the core operation process of how to remove the edging of the flue expansion joint. It should be noted that the removal method introduced in this paper is mainly suitable for the replacement scenario of non-metallic expansion joint skin.

3.1 Removal of fastening bolt assembly

This is the first step in the demolition work. Use a wrench and gas cutting equipment to cut or unscrew all the bolt assemblies of the original expansion joint fixing skin。

Operation Points:

• Try to remove lightly corroded bolts with a wrench first
• For bolts that are seriously corroded or cannot be twisted, gas cutting can be used to treat them
• Pay attention to controlling the flame direction when cutting to avoid damaging the metal frame

3.2 Removal of platen and old skin

After the bolts are removed, remove the pressure plate and the old skin and store them in the designated position respectively。

Key Notes:

• For platens that can be reused, be sure to mark the installation sequence (such as number or orientation mark)
• Proper marking ensures accurate alignment of the pressing plate openings with the flange openings when installing the new skin again, so as to avoid hole offset
• Centralized storage of old skin and uniform treatment after construction

3.3 Check the internal insulation cotton and metal frame

After removing the old skin, the internal structure of the expansion joint is exposed, and a full inspection is required at this time：

1. Insulation cotton inspection: If the original flue is filled with insulation cotton, judge whether it can be reused. If it can be reused, store it separately and protect it
2. Frame inspection: Inspect deflectors, counter flanges, and metal frames for deformation, corrosion, or damage
3. Repair treatment: For slightly deformed or damaged parts, make corrections; Seriously damaged needs to be replaced

This step is a key prerequisite to ensure that the new skin can be fitted properly and sealed tightly.

3.4 Cleaning the mounting surface

After removing old parts, clean the flange surface of the metal frame with a wire brush or sanding tool to remove residual sealant, rust and debris, and ensure that the surface is smooth and clean。 If the surface is uneven, the new skin cannot fit tightly, which will directly lead to leakage.

IV. Precautions during demolition

4.1 Protecting Reusable Parts

• Reusable components such as pressure plates and bolts should be handled carefully when dismantled to avoid deformation
• The marked pressing plates should be stored in order, and reset according to the marks during installation

4.2 Damage prevention framework

• Pay attention to protecting the metal frame during gas cutting operation, and it is strictly prohibited to cut to the flange surface
• After removing the old bolts, check that the threaded holes are intact

4.3 Safety First

• Pay attention to fire prevention in the whole process, hot fire operation needs to handle hot fire ticket and have special person supervision
• Fasten safety belts when working at height, and fix tools with safety ropes to prevent falling

V. Brief Guide for Installation of New Skin

After removing the old hemming, a new skin needs to be installed as soon as possible to restore system operation. The installation process is briefly described as follows:

1. Install heat insulation cotton: first install the inner skin cotton, distribute and set heat insulation nails, inner layer of heat insulation cotton wrapped with stainless steel wire mesh, then install other layers of heat insulation cotton in turn, and fix it smoothly with heat insulation nails
2. Lay a new skin: The skin must be placed flat on the metal frame flange (to prevent wrinkles). Installation starts at the lower part and unfolds outward in sequence
3. Fasten the platen: After the skin is tightened, press it with the platen and bolts. All compression bolts are tightened with electric wrenches. No missed screwing is strictly prohibited
4. Special requirements: For horizontal flue expansion joint, the upper interface should be pressed down at the outermost skin interface to prevent water seepage

VI. SUMMARY

How to remove the edge of flue expansion joint-this problem is related to the quality and safety of expansion joint replacement project. The core points are summarized as follows:

1. Safety first: shutdown isolation, fire and electricity prevention and high-altitude protection are the prerequisites for demolition operation
2. Orderly removal: first remove the bolts → take the pressure plate → remove the old skin → check the insulation cotton and frame → clean the surface
3. Protection of reuse parts: Mark the reusable plates in order to ensure that the holes are aligned during installation
4. Inspection in place: After removal, deflectors, flanges and frames must be inspected for deformation or damage, and corrected or replaced if necessary

Mastering the correct dismantling method can not only improve the construction efficiency, but also lay a good foundation for the subsequent installation of new skin, ensure the expansion joint to restore good sealing performance, and ensure the long-term stable operation of flue system.