How to Replace the Seal in a Bellow Sealed Globe Valve: A Step-by-Step Guide

Introduction

Bellows sealed globe valve is the core control component of industrial pipelines, which is indispensable in fields such as petroleum, chemical, and power. Its core advantage is the efficient sealing brought by the corrugated pipe structure, which can prevent medium leakage and ensure system stability. However, as vulnerable parts, seals work in high-pressure, high-temperature, and corrosive environments for a long time, and aging, wear, and deformation are inevitable, which can lead to seal failure and medium leakage - not only disrupting system operating conditions, but also potentially laying safety hazards and causing economic losses. Replacing seals is the most direct and economical solution, as it can restore sealing performance and extend equipment life without the need for a complete valve replacement. This article focuses on knowledge related to seals, tool replacement processes, safety points, and common issues, providing practical guidance for practitioners and maintenance personnel. At the same time, it interprets the advantages of Lixin bellows sealed ball valves to assist in efficient maintenance work.

What is a Bellow Sealed Globe Valve Seal?

Definition

The sealing of a bellows sealed globe valve is essentially the combination of bellows components and seals, forming a tight barrier when the valve is opened and closed, which not only blocks the communication between the medium and the outside, but also prevents the medium from leaking in the gaps between internal components. Unlike ordinary globe valves, its sealing system consists of a bellows, sealing gasket, and packing in coordination: the bellows is the core sealing element, balancing sealing and guiding; Seals fill the gaps between components and strengthen the seal, forming a dual protection. Simply put, the sealing system is the "anti-seepage heart" of the valve, directly determining the sealing level and service life.

Core Function

The core function of seals is primarily to prevent seepage and leakage - this is the bottom line. Prevent the leakage of gas and liquid media from the gaps between the valve stem and valve cover, valve body and valve cover in the pipeline, avoid media waste and environmental pollution, and prevent corrosive media from damaging equipment and personnel. Next is pressure sealing. Bellows sealed globe valves are commonly used in high-pressure conditions, and the seals must withstand high-pressure impacts without deformation or damage, ensuring that the valve operates normally within its rated pressure. Furthermore, there is cushioning protection. Seals are mostly made of elastic materials, which can compensate for small gaps in component processing and assembly, cushion mechanical wear during opening and closing, and protect core components such as bellows and valve seats. In addition, seals under special working conditions also need to have temperature and corrosion resistance characteristics, adapt to different media environments, and ensure stable sealing.

Tools and Materials Required

The replacement of seals requires the preparation of suitable tools and materials in advance to avoid obstruction during operation. Choose practical and safe tools, and the materials should match the valve model and operating conditions. Core tools: torque wrench, multi specification wrench, screwdriver, sealing surface cleaning tool (copper brush, fine sandpaper, etc.), special disassembly tool for seals, pressure gauge; Prepare gloves, goggles, and rust inhibitors as needed for auxiliary tools. Core materials: Select new seals (fluororubber corrosion-resistant, nitrile compatible with oil, PTFE compatible with high pressure) according to the original valve specifications, and match them with new sealing gaskets, bolt anti seize agents, and cleaning solvents to ensure that all materials are free from damage and aging.

Step-by-Step Seal Replacement Process

Pre-Operation Safety Precautions

Implement Lockout and relieve system pressure

The replacement of seals involves high pressure and medium contact, and safety is the top priority. It cannot be taken lightly and directly affects personal and equipment safety. It must be strictly implemented.

Drain residual medium and prepare work area

First, confirm the shutdown of the pipeline, close the upstream and downstream shut-off valves of the valve, and cut off the source of the medium. Continuing with the implementation of the lock and hang system, hang the "under maintenance, no opening" sign, and assign a dedicated person to guard against misoperation. Then slowly open the pressure relief valve to release residual pressure. The pressure relief should be slow to prevent sudden drops in pressure from impacting the valve pipe. Observe the pressure gauge until it reaches normal pressure, confirm that the pressure is completely released, and then proceed with the operation. Remember: Disassembling valves and replacing seals under pressure is absolutely prohibited, this is the bottom line principle.

Disassemble valve actuator and bonnet

After the pressure is released, the residual medium in the valve tube should be drained. Liquid media should be discharged into designated containers from sewage outlets or temporary pipelines to prevent leakage and pollution; Slowly discharge the gas medium to a safe area, and direct discharge of toxic and flammable gases is strictly prohibited. After cleaning, wipe the surface and connection parts of the valve, clean up the surrounding debris and oil stains, and tidy up the work area. The work area should be clean and spacious, with protective equipment readily available. Operators should wear complete clothing and confirm that there are no hidden dangers before starting work.

Remove old seal and clean sealing surfaces

Before disassembling, observe the valve structure, remember the connection method between the actuator, valve cover, and valve body, as well as the quantity and specifications of bolts, to avoid confusion during subsequent assembly. First, disassemble the actuator: Use an appropriate wrench to slowly unscrew the connecting nut, loosen it, gently lift the actuator, and separate it from the valve stem. Be careful not to bend the valve stem or damage the actuator with excessive force. After separation, place it in a clean and stable place for protection. Disassemble the valve cover again: The valve cover is connected to the valve body by bolts. Use a torque wrench or open-end wrench to evenly loosen the bolts diagonally, not only on one side, to prevent deformation of the valve cover. After loosening all bolts, gently lift the valve cover to separate the valve body; If there is adhesion, a small amount of rust inhibitor can be applied in the gap, and the edge can be lightly tapped with a rubber hammer to assist separation. It is strictly prohibited to damage the sealing surface with hard objects. After removing the valve cover, place it on a soft cloth to prevent scratching the sealing surface.

Install new seal and replace gaskets

After removing the valve cover, the internal seals, bellows, and valve seat can be seen. Gently pry the edge of the old seal with a special tool and remove it from the sealing groove. The operation should be gentle and avoid scratching the sealing groove and sealing surface. At the same time, observe the wear of the old seals, determine the cause of failure, and provide reference for subsequent maintenance. After removing the old seal, focus on cleaning the sealing surface - cleanliness directly affects the effectiveness of the new seal. If there are oil stains, impurities, or scratches, they must be leaked. Clean up any debris residue with a copper brush or brush, and then repeatedly wipe with a non-woven fabric dipped in cleaning solvent until it is clean and free of oil stains. Polish the slight scratches evenly with fine sandpaper and then wipe them clean; If the damage is severe, parts need to be replaced and cannot be used reluctantly.

Reassemble valve components and torque bolts to specs

After cleaning, start installing new seals. First, double check the model, specifications, and material of the new seal to confirm that it is compatible and free from any damage or impurities. During installation, a thin layer of lubricating grease compatible with the medium can be applied to the surface of the seal and the sealing groove to facilitate installation, enhance sealing, and reduce wear. Slowly insert the new seal into the sealing groove according to the position of the old seal, gently press it to ensure a tight fit without looseness or deviation, align the edge with the sealing groove, and avoid twisting or wrinkling. After installing the sealing component, replace the gasket with a new one - place it on the connection surface between the valve body and the valve cover, align it without deviation, match the specifications, and have a uniform thickness. The gasket is strictly prohibited from being reused, even if there is no obvious damage, it should be replaced with a new one.

Post-replacement leakage and operation testing

After installing the new seals and gaskets, assemble them in the reverse order of disassembly to ensure that the components are in place and tightly connected. First, install the valve cover: gently place it on the valve body, align it with the connecting hole, ensure that the sealing surface is tightly fitted without gaps, insert the bolt and manually tighten it in place. Then use a torque wrench to evenly tighten the bolts diagonally, and control the torque according to the rated specifications of the valve and the manufacturer's requirements, avoiding over tightening or over loosening. After tightening, check that the valve cover is not offset or loose, and then install the actuator: align the valve stem sleeve, adjust the position to ensure a tight connection, and use a wrench to tighten the nut moderately without damaging the valve stem and actuator. Finally, conduct an overall inspection to confirm that all components are in place and not loose.

LIXIN Bellow Sealed Globe Valve Parts

In industrial pipelines, selecting the right valves is essential for a stable, safe, and cost-effective system. The bellows sealed ball valve itself is more efficient and reliable than ordinary valves, and LIXIN, with its excellent quality and adaptability, has become the preferred choice in many industries. Firstly, seal the top to prevent leakage. Adopting a dual sealing structure, suitable for harsh working conditions such as high pressure, high temperature, and corrosiveness; The sealing components are made of imported high-quality materials that have undergone special treatment, resulting in slow aging, wear resistance, longer lifespan, and a significant reduction in maintenance frequency and cost. Secondly, the structure is reasonable, easy to operate and maintain. Compact design with small volume, easy installation to adapt to various pipelines. Maintenance is also simple, with easy disassembly and assembly of vulnerable parts such as seals and corrugated pipes, which can be completed by ordinary maintenance personnel, reducing downtime and maintenance costs. Thirdly, the material has wide adaptability and strong universality, covering the needs of multiple industries such as petroleum, chemical, and power. Fourthly, reliable quality and high cost-effectiveness.LIXIN has a comprehensive production and testing system, with each valve undergoing strict pressure, sealing, and operation testing, resulting in low failure rates and stable operation; The price is affordable and more cost-effective than similar imported products, which can help enterprises reduce investment. There is also a professional after-sales team that provides one-stop service for selection, installation, and maintenance, ensuring worry free service throughout the entire process.

Conclusion

Seals are the core vulnerable parts of bellows sealed globe valves, and their aging and wear can directly lead to medium leakage, affecting system operation and even causing safety hazards. Replacing the seal does not require a complete valve replacement, which is an economical and efficient solution that can quickly restore valve performance and extend equipment life. LIXIN bellows sealed ball valve, with excellent sealing, reasonable structure, wide adaptability, and high cost-effectiveness, can meet the system needs of multiple industries and ensure the stable operation of the system. I hope this article can help practitioners and maintenance personnel standardize seal replacement operations, reduce leakage hazards, improve maintenance efficiency, and assist in the safe, stable, and efficient operation of industrial pipelines.

FAQs

Q1: How often is the sealing component of the bellows sealed globe valve replaced?

A1: No fixed cycle, depending on the operating conditions. Strong corrosion, high pressure and high temperature working conditions, check once every 6-12 months, replace if damaged; Mild working conditions, checked once every 1-2 years, replaced as needed, and the core is regular inspection.

Q2: There are slight scratches on the sealing surface, can it continue to be used?

A2: Slight scratches, can be used after being polished flat and wiped clean with fine sandpaper; Scratches are deep and damaged, requiring repair or replacement of parts. If used reluctantly, leaks are inevitable.

Q3: What are the differences in the compatibility of seals made of different materials?

A3: Fluororubber is temperature resistant (-20 ℃ -200 ℃) and corrosion-resistant; Nitrile rubber is suitable for ordinary oils and water, and is not resistant to high temperature corrosion; Polytetrafluoroethylene is suitable for high pressure, high temperature, and strong corrosion, with good sealing and long service life, making it the most widely used.

Q4: The leakage test pressure cannot be increased, why?

A4: There are three common reasons: bolts are not tightened, seals are offset and twisted, and there are impurities and oil stains on the sealing surface. After troubleshooting and rectifying them one by one, they can be tested again.

Q5: What should I do if the valve stem bends when disassembling the actuator?

A5: Slight bending. After professional tool correction, check the straightness and strength. If there are no problems, continue to use; Severe bending cannot be corrected and the valve stem must be replaced, otherwise it will affect opening, closing, and sealing.

Q6: Do seals need to be lubricated during installation?

A6: Not necessary, but it is recommended to apply. Apply lubricating grease compatible with the medium for easy installation, scratch resistance, enhanced sealing, and reduced wear; Strong corrosive media are not necessary.

Q7: Can the sealing components of the bellows sealed globe valve be used interchangeably with ordinary globe valves?

A7: Cannot. The structure, size, and sealing requirements of the two are different. The corrugated pipe type seal needs to be compatible with the corrugated pipe and sealing groove, while the ordinary type does not match the size and shape, and will leak when installed.

Q8: How to handle residual media?

A8: Material treatment: Non toxic liquids can be discharged into the sewage pipe; Toxic and corrosive media should be collected in specialized containers and handed over to professional institutions for disposal; Flammable and explosive media should be collected in a sealed manner, kept away from sources of ignition, and handled by professional personnel.

Q9: Why is the valve opening and closing stuck after replacement?

A9: Either the actuator installation is offset, or the seal is installed too tightly or there are debris in the sealing groove. Adjusting the actuator position, reinstalling the seal, and cleaning the debris can solve the problem.

Q10: What are the advantages of Lixin bellows sealed ball valves compared to other brands?

A10: Core three points: superior sealing, dual sealing to prevent leakage; More worry free maintenance, easy disassembly and assembly of vulnerable parts, no need for a professional team; Higher cost-effectiveness, reliable quality, affordable price, and comprehensive after-sales service.