How to Troubleshoot a Gate Valve?

Gate valves are essential for controlling fluid flows in various industrial systems. Effective troubleshooting will help these valves operate efficiently and reliably. This guide will give you useful information on how to identify common problems as well as the solutions for each.

Common Problems with Gate Valves and Their Solutions

Below are the typical faults that you may experience when operating gate valves. We’ve provided possible solutions for each:

Gate Valve Leaking when Closed

Possible causes: 

• Worn seals, since over time seals deteriorate leading to leaks
• Corrosion may cause the gate or seat to become misaligned

Solutions:

• Replace worn seals using a gate valve repair kit.
• Ensure the gate seats are correctly against the valve seat.
• Address corrosion issues promptly to prevent further damage.

Difficulty in Operating the Valve

Possible causes:

• Rust and corrosion have accumulated on the valve stem, making operation difficult.
• Foreign objects block the valve’s movement

Solutions:

• Regularly apply lubricant to the valve stem to reduce friction.
• Remove debris that blocks the valve’s movement.

Inflexible Handwheel Rotation

Possible causes:

• This may be due to overuse or improper handling.
• Insufficient lubrication may lead to stiffness

Solutions:

• Avoid hard twisting of the handwheel.
• Lubricate the stem regularly and clean it to prevent rust buildup.
• Copper materials for the stem nut may help avoid corrosion.

Bonnet Spillage

Possible causes:

• There are defects in casting such as blisters, cracks, or poor-quality iron casting.
• Heavy objects or frost may damage the valve.

Solutions:

• Check for defects in the bonnet and replace seals if necessary.
• Address any rough surfaces or casting defects to prevent leaks.

Valve Seat and Gate-Shaped Wedge Spillage

Possible causes:

• Expansion and contraction due to thermal stress may cause leaks
• Continual stress between the valve stem and guide.

Solutions:

• Ensure the seat and wedge surfaces are smooth and accurate.
• Replace or grind surfaces as needed. Clean up any debris before installation.

Unable to Close the Valve

Possible causes:

• There is an accumulation of debris (dirt, iron deposits, etc.) that makes closing the valve difficult.

Solutions:

• Thoroughly clean the valve or replace it if necessary to restore proper function.

How to Test a Gate Valve

One gate valve sign that needs testing involves how it handles pressure. Test standards become necessary to ensure you know what issue your valve has. This section outlines key pressure testing methods and their applications to help maintain and verify the health of gate valves.

Middle-Pressure Test

Also called the intermediate pressure test, this is designed to assess the valve’s ability to handle pressure without leakage.

To test gate valves of DN32mm or larger, open the gate, increase the pressure to the specified value, then close the gate and, if possible, remove it from the system. Check for leaks by inspecting both ends of the gate or by inserting the test medium into the plug on the cover.

Blind Plate Test

This test is done to check for leaks by isolating one end of the valve during testing.

To test larger valves or those needing detailed leak testing, open the gate, increase the temperature, then close the gate and open the blind plate on one side. Check for leaks by inspecting through the open blind plate and adjust or rotate the valve head as needed until no leakage is detected.

Back Seat Test Method

For this method, you will test the gate valves with backseat elements. This test helps verify the integrity of the valve’s sealing mechanism.

Prepare the valve by loosening or uninstalling the packing gland, then open the valve to access the backseat. Follow the approved testing procedure to assess the valve’s sealing performance. This method is specific to gate valves with backseat features for thorough testing of the sealing elements.

What Maintenance is Required on Gate Valves?

Here’s a guide to essential maintenance procedures for gate valves:

1. Regular operation. This involves rotating the valve monthly. Even if the valve is not in regular use, rotate it at least once a month. This helps prevent the gate from becoming stuck or seizing in place due to lack of movement.
2. Pressure relief. Before performing any maintenance, ensure that the system is fully relieved of pressure. To do this, slowly open the drain valves.
3. Gate replacement. 
4. Stem and handwheel inspection.

Ensure the valve’s stem is straight and free from bends or damage. Confirm that the hand wheel is correctly aligned at the top of the valve.

PANS: A Leading Manufacturer of Reliable Gate Valves

PANS is a prominent name among rising stem gate valve manufacturers. The company has catered to several industries worldwide thanks to its quality valves that meet rigorous industry standards.

PANS specializes in manufacturing valves with precise rising stem gate valve dimensions. The team’s commitment to quality results in valves characterized by durability, reliability, and ease of use.

FAQ

• Can gate valves fail to close?

  Yes, gate valves can fail to close due to issues like seal wear, debris, or mechanical malfunctions. Regular maintenance helps prevent this problem.

• What is the failure mode of a gate valve?

  The failures of gate valves typically include corrosion (20%), leakage at bonnet and flange connections (20%), and hard to actuate (22%). These highlight how essential regular maintenance is.

• Can you do a pressure test against a gate valve?

  Yes, gate valves can be pressure tested to ensure they can handle the required system pressures. Follow appropriate test standards for accurate results.