Gate valves are control valves that stop fluid flow entirely or let it run freely through a pipeline. A gate valve has a valve body, a gate, a seat, a stem, a gasket, and a wheel for turning the valve on and off. When the gate and seat work together, they stop fluid flow. A leaky gate valve can disrupt any system’s efficiency, performance, and environmental compliance. The impact of a leaky gate valve relies on the kind of leakage. The first is fugitive emissions, which occur when process fluid leaks. The other occurs when the leakage remains within the pipe system. Both types are dangerous, but fugitive emissions do additional environmental damage. This article will explain the reasons for leaks, the different types of leaks, solutions, and how to replace them.
What are the Causes of Leaking Gate Valves?
Several factors can contribute to the leaking of a gate valve, including the following:
One of the leading causes of valve discharge is corrosion. Due to corrosion, the valve components in contact with the process fluid lose material with time. The rate at which this occurs must be predicted during the design phase. Yet, the necessary material corrosion allow must be noted when selecting the valves.
In facilities such as oil production plants, however, the composition of petroleum may alter as the oil well depletes. Consequently, corrosion rates may increase, resulting in premature valve failure. Regular monitoring of the process fluid helps minimize leakage issues in this condition.
- Valve Component Wear:
In addition to corrosion, other factors can contribute to valve component deterioration. In oil and gas facilities, sand or solid debris is present along the flow path. This may result in the removal of valve material. This becomes worse at high flow rates, particularly during gas production.
- Blockage of the Valve Stem:
Debris accumulates on the valve seat or other locations within the body. It obstructs the movement of the stem. Thus, the valve outlet is completely closed.
- Change in Operating Conditions:
Changes in temperature and pressure along the process while the valve works may cause a reduction in bolting torques. It particularly happens in the stem packing area, where a torque loss will lead to leakage through it. If this is the case, live loading must be required in the packing area.
- Wrong Valve Size:
It is possible to use the incorrect valve size on a given project. The effect would be identical if the correct-sized valve were used, but its design is subpar. Both of these would result in leaks because the valve would not correctly close.
Gate Valve Issues and Their Possible Solution
Multiple factors can affect gate valves. Effectively fixing each issue prevents additional problems. Corrosion and typical wear and strain over time are the leading causes of gate valve failure. The following sections provide an overview of some of the most significant challenges gate valves face and how to solve and repair them.
When sediment accumulates within the body of a gate valve, it does not close properly. Primarily, sediment accumulation occurs when the gate valve remains entirely open for longer than usual. It allows dirt to accumulate on its sides and prevents its closure.
When the gate is lowered, sediments become trapped between the interiors of the gate and the valve, causing complications.
How Do We Resolve the Issue?
- Begin by closing the gate valve as completely as feasible. During this phase, excessive force should not be applied.
- Open the sink’s faucet to remove debris from the system.
- Open the gate valve.
- Repeat the opening and closing cycle until all seats are filled or the gate ceases making closing. This action typically dislodges and cleanses the valve of any accumulated debris. If the valve does not indicate downward movement without stopping the water flow, it must be removed for evaluation.
- Proceed to Step 5 if this occurs.
- Remove the gate valve and turn off the water supply.
- Remove the valve housing from the top using a wrench. Ensure not to loosen the packing nut, which secures the packaging and prevents water from escaping around the handle.
- Before reassembling the valve, check the outer margins of the gate and scrape off any deposit.
- Slide the gate back into its direction and use a wrench to secure the top of the valve enclosure.
- Turn on the water supply and check the valve.
- Replace the valve if it is significantly corroded or full of debris.
Gate Valve Stuck
Another typical issue with gate valves is that they can become obstructed. The gate valve can become stuck open or closed, preventing it from performing its intended function.
- Before inspecting a blocked gate valve, perform the following steps:
- Stop the water flow to better understand the problem.
- Isolate your work area to prevent further breaches from having negative effects.
- Examine the area to determine whether external factors, such as excessive cold or a broken water line, are causing the problem. Wear and corrosion can also prevent the opening of gate valves.
- Before removing or repairing the damaged valve, place a container underneath it to discharge excess water (in case the gate valve is stuck open).
Resolving A Stuck Gate Valve
- Remove any impressive deposits from the threads of the gate valve
- Apply penetrating or 3-in-1 lubricant to the gate valve. Using a cloth, remove excess oil and ensure that the oil reaches the passages of the valve.
- Check the valve’s position by tapping the handle with a mallet to see if it changes from open to closed.
- Attach a channel lock or an adjustable spanner to the valve handle. It is advised to wear gloves while working to prevent slipping and ensure a stable operating area.
- Turn the valve handle to see whether the valve position changes.
Leaks from Seat or Seal
The seat or seal is in constant contact with the fluid and gas medium in the gate valve. It exposes the valve to attack from any corrosion agents in the medium. When a gate valve reaches the end of its useful life, its inability to seal or seat properly becomes an issue.
Dislocation of the gate valve can occur due to the accumulation of dirt around the seat or seal. The gland, nut, and connecting section of the main valve body develop leaks.
Inadequate flushing fluid or too much heat within the seal chamber can potentially cause the sealing or seating surface to burn. Inadequate sealing flushing can have several reasons, including the medium cut-off in the pump cavity, ring damage, and an abrupt reduction in chamber pressure.
How to Solve it?
If a gate valve starts leaking because dust and silt have settled on the seat, the user is responsible for taking corrective action. Tightening the nut close to the gland is the most rapid and straightforward solution. If this doesn’t work, try unscrewing and replacing a thread or installing a new washer close to the seat.
Gate Valve Leaking from Stem
Both old and new valves are susceptible to leaking in the stem packaging and handle. Old and new valves are susceptible to leaking in the stem packaging and handle region, particularly when opening and closing. This is due to sediment accumulation preventing the valve from closing completely or causing the stem to stay open. Additionally, the stem may deteriorate over time due to corrosion or erosion.
Leakage from the valve stem packaging may indicate an inadequately designed valve, an insufficient stem material, or the application of the incorrect valve size.
Tightening: Turn the gate valve handle to determine if the spill is due to the valve failing to close. When sediment accumulates within the body of a gate valve, it cannot close completely.
Damaged valve stem: Check for damage to the valve stem. Wear and corrosion are the most prevalent causes of this type of injury.
Check the design and dimensions of the valves: Assure that the valve stem is compatible and designed for the valve in question. Replace the valve stem if not.
How to Resolve the Issue?
Tighten the packing nut: Where the valve stem meets the water line, the packing nut forms a strong watertight seal. Therefore, a leak at the valve stem indicates that the valve does not entirely halt the flow. Consequently, the first step in stopping the discharge is to tighten the packing fastener.
Replace the packing material or gasket on the valve‘s stem: When the packing fastener of the gate valve is tightened, the packing material is pressed against the washer to prevent water from passing through. Over time, this packing material hardens and forms a solid seal, causing the valve to discharge. In this instance, replacing the stem packing material readily available at most hardware stores is preferable.
How to Take Apart a Gate Valve for Repair
Perform the procedures below to disassemble a gate valve for repair:
1. Turn the main water supply off.
2. Detach the valve from the pipelines by removing the bolts from the flanged extremities.
3. Loosen the valve cover with forceps. Do not loosen the packing fastener, as this component ensures the stem has no leakage.
4. Remove the top of the valve to detach the seat and handle from the body.
You can now scrutinize each component for potential defects. Use a toothbrush or other cleansing instrument to scrub each valve component. Replace any defective components;
otherwise, commence the reconstruction process. Place the gate in the correct position in the valve’s body, then tighten the bonnet until it is secure. Now, turn the handle to test the valve’s functionality. The shutter should open and close completely. If everything is in order, reattach the valve to the pipeline.
To reinstall the valve in the conduit, it is advisable to use valve adhesive tape.
Substituting a ball valve for a gate valve: Whenever feasible, always choose ball valves over gate valves. Ball valves are typically more efficient, albeit more expensive. When closed, ball valves create a firmer seal and are more effective and durable than gate valves. Follow the instructions below to replace a gate valve with a ball valve. Before replacing the gate valve, heat the parts (valve joints and handle stem) with a torch to facilitate removal.
Stop the water flow: Turning the water off will drain the pipelines. Then, heat the valve joints while the gate valve is open.
Utilize channel locks; whack the valve with a mallet to determine if it is movable. If it does, it is sufficiently heated. If it does not move, apply heat to the elbows adjacent to it and lateral pressure. Install the ball valve in its final position.
Tips for Maintenance
Proper maintenance is required to continue using a valve for an extended period of time. One can accomplish this by operating each valve under the appropriate temperature conditions. Adjust a valve’s temperature to the optimal level, based on the type of material, for it to function correctly.
Brass: Valves made of brass must not be used in temperatures exceeding 450 degrees Fahrenheit, as they may be damaged.
- Iron: Valves made of iron should not be used at temperatures above 450 degrees Fahrenheit.
- Stainless steel or White Iron: A high-pressure ball valve is suitable for low-temperature environments. On the other hand, a corrosive flow valve cannot be utilized at elevated temperatures.
Other essential gate valve maintenance tips include the following:
If the gate valve is not utilized frequently, it should be cycled at least once per month.
Relieve the system’s pressure before executing any maintenance.
Reverse the installation of the testing procedure for gate valves to remove debris from the pipelines.
Remove the valve’s upper body (bonnet) and stem before replacement. To replace the previous gate with the new one, unscrew the old one. Install the entire body into the line.
Conditions of Using for A Gate Valve
A gate valve operates similarly to any other form of valve. To open it, one must resolve the handwheel, which raises or lowers the gate on the stem via threads. This valve requires more than 360 degrees of rotation to fully open or close.
When the gate is raised, the inlet to the outflow is unblocked, allowing the media to circulate freely. When the gate of a water spigot butterfly valve descends, it closes and blocks media flow.
There is a non-linear connection between the vertical movement of the gate valve and the flow rate, with the greatest variations occurring near the valve’s complete closure. Its relatively high velocity at partial opening causes gate and seat wear when used to regulate flow. Along with possible gate vibrations, it reduces the valve’s service life. Therefore, it should only be used for on/off switches.
As this valve opens and closes multiple times, its sluggish operation prevents water pressure. This testing standard for gate valves applies to a wide variety of fluids under the following operating conditions:
- Potable water, effluent, and neutral liquids: Temperature must be between -20 and +70 degrees Celsius, with a maximum flow velocity of five meters per second and a maximum differential pressure of 16 bars.
- Gas: Temperature must be between -20 and +60 °C, with a maximum flow velocity of 20 m/s and a differential pressure of up to 16 bar.
Gate valve leakage can be mitigated through proper selection, installation, and maintenance. Regular inspections and adherence to safety guidelines are essential for minimizing leakage risk and ensuring gate valves’ reliable operation in various industrial settings.
What Issue We Resolve in this Article?
Gate valve leakage can be a significant concern in various industries, including plumbing, oil and gas, and manufacturing. While gate valves are known for their ability to provide tight shut-off, they can still experience leakage with time due to wear and tear, improper installation, or other factors. So, in this article, we resolve the issue for our customers as they experience different leakage issues while using the gate valves; so, by reading this article, they will be capable of resolving any issue they experience with the gate valves.