The Complete Manual for Installing and Repairing Globe Valves

Globe valves are often used piping parts in a wide variety of industrial environments. They are ideal for frequent on/off flow control and throttling because to their tried-and-true design. However, all valves eventually need to be maintained or repaired. Let's go over how to install new globe valves according to best procedures, disassemble them, diagnose typical problems, and then rebuild them to like-new condition.

What You'll Discover

• The structure and operation of globe valves
• Correct installation and alignment of globe valves
• Identifying leaks and other issues
• Detailed disassembly and examination
• Reassembling valves and putting them back into use

After we go over the entire servicing procedure, you will know how to maintain your globe valves for many years of dependable flow control.


 

How Does a Globe Valve Work?

Let's take a quick look at the construction and flow control of globe valves before diving into issues and searching for a repair kit. The subsequent troubleshooting and component replacement procedures will be considerably simpler to understand as a result.

There are three main parts to globe valves:

• Body – all internal parts and the flow channel are located in the center shell. a two-piece body that is bolted together.
• Bonnet –the upper part that fastens to the body and contains the packaging box and disk/plug assembly.
• Disk/plug – the stem-connected moveable regulating element. modulates flow by raising or lowering.

The globe valve flow direction is then lined with numerous interchangeable trim parts, such as seats, guides, and disks/plugs designed for particular uses.

The handwheel raises and lowers the disk/plug away from the seat by turning the stem. As a result, flow through the valve body is either allowed or restricted. Until the disk hard seats against the body seat ring, globe valves are not completely closed off.
 

Correct Configuration for Globe Valve Installation

Important globe valve installation considerations follow the selection of the best globe valve and trim for a given application. Setting up the valve to permit appropriate disk movement and guard against fluid damage is crucial.
 

1. Globe valve direction – Globe valves are unidirectional in their operation. Proper flow is shown by an arrow on the body. Installing with flow entering beneath the seat is always recommended.
2. Orientation – When the handwheel is erect and the valve is positioned horizontally, it works well. The disk can now completely close on the seat as a result. Full closure may be hampered by vertical mounting.
3. Piping stresses – To prevent the valve's body from bending due to weight or side loads, use pipe hangers and supports.
4. Thermal relief – Give extended-bonnet valves room to expand and compress without coming into contact with adjacent equipment. Think about valves with bellows seals.
5. Insulation – Never put insulation over the handwheel or bonnet. This causes warming, which harms the stems and packings.
    

Solving Common Issues with Globe Valves

Globe valves ultimately experience problems due to corrosion, wear, or contamination, even with the greatest installation techniques. The most common issues are as follows:

External Leakage

When operating, leaks from the packing box or bonnet gaskets are a sign of worn seals. Moderately tighten the packing gland nuts; nevertheless, frequent loosening and tightening causes packing wear to increase. It could be necessary to change the packing completely.

Additionally, look for leaks between the two casing parts by inspecting the body-bonnet gaskets. Over time, leaks may also be caused by loose flange bolts.
 

Internal Leakage

When the valve is completely closed, fluid seeping out the outlet indicates internal damage. It's likely that the disk on the seat isn't completely sealed, which lets fluid go past the sealing surfaces. This is a serious problem that necessitates disassembly in order to reach interior components.

Other Faults

Other issues include emissions from the hood, a noisy flow, and stiff handwheel turning due to scale and dirt accumulation. When friction-reducing lubricants are removed from the packing, binding stems and hard shutdown also eventually happen.

Inspection and rebuilding are necessary if any of these operational changes occur. Overall wear is reduced when issues are identified early.
 

Procedure for Disassembling a Globe Valve

It's time to unscrew the globe valve for inside access after you've identified a problem. The disassembled components must be carefully arranged for this. Observe these detailed instructions:

1. The valve should be isolated and depressurized. Remove any fluid that has become stuck. If there is insulation, remove it.
2. Keep a record of the initial handwheel position and orientation. Capture images for future use.
3. Remove the bonnet from the body by unscrewing it. Check for damage to the gaskets.
4. Remove the stem assembly and plug/disk. Take note of any unique trim or shims.
5. If the body has seats, guides, or other internal parts, remove them.
6. If necessary, clean and degrease every component without causing any surface damage.

Planning Repaires and Examining Internals

Examine every component taken out during disassembly in detail for:

• Cracks – particularly in regions of the body or bonnet that have threads. Welding repairs might be necessary.
• Erosion –from chemical damage, cavitation, or flashing. Change the impacted sections.
• Scale/deposits – accumulation preventing a function that could require cleaning.
• Corrosion – damage that could jeopardize sealing or integrity.
• Wear – Check for loose stem fittings, flattened seats, scoring, and galling.
• Leak points – Make a note of any particular locations that permit leaks.
• Other defects – dents, missing pieces, misalignments, etc.

Reassembling Globe Valves After Service

After replacing all worn parts, the globe valve should be carefully put back together in reverse order:

1. Remove any remaining gasket debris from the seating surfaces and body channel.
2. Replace the plug tip, seat ring, guides, and any internal trim.
3. After inserting the plug or disk onto the valve stem, fasten it to the body.
4. Place the stem into the stuffing box after sliding fresh packing and spacers onto it.
5. Carefully mate the bonnet to the body after installing a new gasket. Fasten flange bolts firmly.
6. For a stem seal that doesn't leak, slightly compress the box by adjusting the gland nuts and packing.
7. Verify the handwheel's action during the entire stroke. If necessary, lightly lubricate the stem and packing.
8. Put the valve back where it was originally put. During operation, pressurize and inspect for leaks.
9. For upcoming maintenance, think about storing extra packing, gaskets, and other components on hand.

Commonly Asked Questions – FAQs

How to service a globe valve?

In order to service globe valves, you must first isolate, depressurize, disassemble, clean, check, and replace old components like seats and packings before carefully reassembling them.

Should globe valve installation be vertical or horizontal?

For the best disk movement and sealing, install globe valves horizontally while keeping the handwheel upright. Full closure may be hampered by vertical mounting.
 

How to fix a stuck globe valve?

To release stuck globe valves, apply penetrating oil around the packing and stem, use a mallet to tap the bonnet and handwheel, and slowly turn the handwheel back and forth. Disassembly may be necessary for severely jammed stems.
 

Conclusion

Globe valves are used in everything from HVAC systems to chemical facilities because of their demonstrated ability to control flow direction. However, in order to preserve tight shutdown and hassle-free operation, their moving parts eventually need to be serviced. Gaining knowledge on how to install, diagnose, disassemble, fix, and rebuild globe valves will pay off in the form of dependable service for many years to come. You can ask any questions you may have about industrial-grade globe valves by getting in touch with JONLOO Valves.