In domestic applications, a gate valve is used to turn off the gravity-fed water supply temporarily during repairs. But sometimes, it may be dysfunctional and start leaking for various reasons, such as the valve not being fully closed due to debris, dirt, or other substances. But the other times, it may be because the valve seat or seal is damaged.
A leaking industrial gate valve can expose the industrial or domestic pipelines to risks. So it is essential to find a reliable solution to make it operate before it is too late.
In this blog, we will learn everything about inspecting leakage in a gate valve and different ways to avoid and fix it. It is vital to immediately fix a malfunctioning gate valve caused by the mineral build-up by fully opening and closing it every few months. It helps clear any potential problems in the device while allowing the users to make the most out of it without hindrances.
Since it is not so difficult to repair a gate valve leakage, one must consider doing it on their own.
Please Check Beforehand:
Here are a few things to check in a gate valve before performing any kind of repairing work on it.
Proper Gate Valve Type:
A gate valve controls gas and liquid flow in almost every process and system. But choosing the right one is equally crucial. One can begin the selection process by gathering some basic information on system performance requirements as it makes finding a valve easier.
Here are four tips for learning how to match the features of a gate valve with the requirements:
- Tip 1: Valve Size and Type
An ideal wholesale actuated gate valve for an industrial or domestic pipeline application should be able to perform a few critical functions, such as shut-off flow, diver flow, mix flow, backflow prevention, adjusting the flow, and pressure relief. Besides, its size must match the expected flow through the system.
- Tip 2: Material Construction
It is essential to learn about the chemical compatibility requirements of a valve. Its material must be compatible with the gases or liquids flowing through it. If it is built of plastic, it will resist harsh or corrosive chemicals much better than the ones made of metal.
- Tip 3: Performance Needs
When purchasing a gate valve for a particular application, one must determine its pressure range and temperature requirements. Valves made of metal can withstand higher pressures and temperatures better than plastic ones. They are also suitable for pressurized gases because they have a sturdier build.
- Tip 4: Maintenance Needs
Any valve choice must include attention to maintenance needs for both application stability and device reliability. The connection type of a particular China electric knife gate valve significantly affects its repair or replacement speed or ease. Whether its connection is threaded, barbed, or push-in, each has its pros and cons.
Leakage Tolerance:
Gate valve leakage is a common occurrence in industrial settings. Even the valves labeled as 0 leakages or bubble-tight are not necessarily completely leakage-free. Let’s explore the types and common causes of gate valve leakages!
The two main types of valve leakages include fugitive emissions and the ones that remain in a piping system. Fugitive emissions are leaked into the atmosphere, causing environmental and safety hazards. On the other hand, leakages in the piping system also pose potential safety risks.
Common causes of a pneumatic gate valve leakage include:
- It is not being fully closed due to dirt, debris, or other obstruction
- Its seat or seal is damaged
- is of the wrong size for a certain project, and
- It is not designed to close 100%, which means it does not have excellent on/off capabilities.
The API (American Petroleum Institute) has set acceptable liquid and gas testing leakage rates. According to API standard 598, all gate valves should meet the leakage criteria before shipment from the manufacturer to the industry. In the case of liquid fluid, there shall be no evidence of drops on the external surface. If it is gas, no leakage shall be revealed by a detection method.
According to section 5 of the pressure testing of steel gate valve test, a leakage rate of 10 cc/hr per inch of nominal pipe diameter is permissible in a gate valve.
Operating Pressure Limit:
In industrial pipelines, a gate valve is used for a range of applications, either above-ground or underground. Since it can fully open or close, it functions as an isolating valve. When operating this valve, either clockwise or anti-clockwise, its gate moves upwards or downwards on the threaded part of the stem.
A gate valve is often used where minimum pressure loss and a free bore are required. When fully open, it has no obstruction in the flow path, resulting in a low-pressure loss. Since it is multi-turn, its operation is done by a threaded stem. Its slow operation helps prevent water hammer effects as it turns multiple times to an open or close position.
One can use a gate valve for a vast number of fluids. In potable water, wastewater, and neutral water, the temperature should be between -20 and +70 degrees C, maximum of five m/s flow velocity and up to 16 bar differential pressure. In gaseous working conditions, the temperature should lie between -20 and +60 degrees C, with a maximum 20 m/s flow velocity and up to 16 bar differential pressure.
If the pressure rating is 150 at 100 degrees Celsius, the valve can withstand 150 PSI at 100 degrees Celsius.
Common Gate Valve Leakage and Solutions:
Gate valves are the main components of the industrial pipeline. But it faces several faults, giving the users a tough time. Here are some common gate valve leakages and their easy solutions:
Leakage Between Actuator and Valve
Description: In an industrial pipeline, a regulator is the primary type of actuator. It receives the control signal of the unit output with the help of a dynamic operation to change the fluid flow. A gate valve includes an actuator and a valve further divided into electric, hydraulic, and pneumatic, depending on the actuator’s power.
In the modern factory automation control system, a hydraulic actuated gate valve receives a control signal to realize the regulation of the chemical process as a terminal actuator of the automation regulation system. Its motion sensitivity directly depends on the quality of the regulating system. But, about 70% of the fault is caused by the leakage between the actuator and the valve.
Possible cause: Some of the most common reasons causing leaks between the actuator and a gate valve include stem length discomfort. When the length of the stem is too long or short, it results in a gap between the seat and the spool. Thus, they cannot contact fully, resulting in lax closure and internal leakage.
Similarly, when the valve stem of the air closing valve is too short, it results in a gap between the gate valve backseat test and its core. It too fails to contact entirely, causing loose closing and, thus, internal leaks.
How to Fix: To fix the leakage issue between an actuator and the gate valve, one should strictly control the force but not through a hard twist. It is equally vital to improving the processing quality to meet the specification requirements. Some common steps include using the devices carefully, maintaining the normal lubrication state, straightening or fixing the stem nut, and revising or updating it to meet the standard specifications.
One must also regularly clean the dust on the stem nut, lest rust and cover the valve stem of the outdoor gate as it also needs protection.
Shut-off Failure
Description: It is essential to shut off a gate valve completely if maintenance or plumbing repairs are to be done. But sometimes, if the main control valve is a gate type, it may fail to close rightly.
In such situations, a little water will continue to flow even after a gate valve is closed completely. Since it is a significant problem, some people may try exerting an additional force on the handle, causing permanent damage to the device and a loss of water supply.
Possible cause: After a certain period of continued usage, users may find that the dirt or scale build-up on a gate valve becomes common and frequent. It is not a good sign because it causes problems with the closing mechanism.
Sometimes, the issue is also caused by seizing the gate valves. When dirt or deposits get between the operation of a stainless 3 way ball valve, it may seize up. It happens when the water flowing around the piping system includes scales and iron deposits that stick to rough patches of the valve, thus causing the mechanism to jam.
How to Fix: Because of prolonged usage, a gate valve may keep the closing mechanism from shutting off properly. Fortunately, fixing the issue by replacing the valve or cleaning it is possible. People who replace their valves because the issue persists should remember that they do not always have to drain down, as long as they have the experience and tools to do so.
If sediment or mineral deposits are preventing the gate from shutting off properly, one must flush out the inside of it. The right way to do so is to open a faucet on a sink to mimic the flow of water and then gently and repeatedly open and close the valve. If the handle fails to turn freely, loosen the packing nut above the valve body and around the stem.
Repeat lowering its gate routinely to break free the sediment and flush it away with a water flow.
Leaks When Closing
Description: Gate valves are usually used as the main supply valves in houses. They are often installed in spots where a washer might harden, decay, or become dislodged over a long period of use. But it does not mean gate valves cannot develop problems if kept neglected.
Sometimes, a gate valve may break even in the closed position, requiring a lot of repair work. It is a tricky and dangerous task as changing the valve under water pressure is tough, especially if electric services are nearby.
Possible cause: Some users might experience leakages while closing a valve gate to shut off the water flow. In most cases, it happens due to small bits of debris in the liquid medium. As most supply valves are left open, debris may build up, causing damage to the valve and leakages even when closed.
How to Fix: If a gate valve starts leaking in the closed position, it can be raised back up to restore water service. Drill a small hole near the bottom of the valve body in line with the gate using a sharp object.
After pushing the gate of a top entry floating ball valve, insert a like-sized sheet metal screw into the hole to stop the water flow.
Leaks From Seat or Seal
Description: The seat or seal of an industrial gate valve is always in direct contact with the fluid and gas medium flowing in the pipeline. It makes the valve vulnerable to any corrosive elements that may be present in the medium. It causes the sealing or seating of the gate valve to fail after it has reached its service life threshold.
Possible cause: The building up of deposits and dirt around the gate valve seat or seal causes displacement in the device. It further leads to leakages in the gland, nut, and olive area and the connecting part of the main valve body.
Sometimes, burnout of the sealing or seating surface also occurs when the flushing fluid is insufficient, or there is excess heat inside the seal cavity. A few root causes of inadequate sealing flushing include the pump cavity medium cut-off, damage to the ring, and sudden pressure drop in the chamber.
How to Fix: If the build-up of sediments and dust in a gate valve causes leaks from the seat and seal, the user must take steps to fix the problem. The simplest way to fix it is by tightening the nut near the gland. But if this trick fails to work, one may also try unscrewing and placing a thread or using a new washer near the seating area.
Leaks From Stem
Description: Sometimes, a new gate valve may leak near the handle or stem area when turned on. It is a common phenomenon during the installation or maintenance of the valves, which requires an immediate fix as it may damage the device over time.
Possible cause: The most common causes of a leak from the stem of a gate valve are wear and corrosion of the wedge and seat. The inner parts of a valve tend to wear over time, causing the wedge to stick in the open or closed position. When pressure is placed upon the handwheel, the steam leading from it to the wedge may break off, rendering the valve useless.
How to Fix: To repair a gate valve leaking from stem, tighten the packing nut one-eighth to one-quarter turn using a wrench. One may do so by shutting off the water to the leaking valve. The next step is removing the handle from the stem and loosening and removing a packing nut. Replace the old washer with the new one. Reinstall the packing nut by tightening it lightly with a wrench and re-attaching the handle.
But remember not to over-tighten it. Switch on the water, open the repaired valve, and check for leaks. If it is still leaking, tighten the packing nut one-eighth of a turn at a time until it stops.
Working Conditions For a Gate Valve:
The working of a gate valve is similar to any other valve type. To open it, one needs to turn the handwheel which moves the gate up or down on the stem through the threads. This valve needs more than 360 degrees to turn to open or close entirely.
When the gate lifts, it opens the inlet to the outlet, allowing the unobstructed passageway for the media to flow. When the gate of a water lug butterfly valve lowers, it closes and blocks the media flow.
There is a non-linear relationship between the gate valve’s vertical travel and the flow rate, with the most significant changes occurring near the complete closure. Its relatively high velocity at partial opening causes gate and seat wear when it is used to regulate the flow. It, along with possible gate vibrations, shortens the valve’s service life. That is why it should only be used for on or off controls.
As this multi-turn valve turns open or closes multiple times, its slow operation helps prevent water hammer effects. This gate valve testing standard is used for a vast number of fluids under the following working conditions:
- Potable water, wastewater, and neutral liquids: Temperature must be between -20 and +70 °C, with a maximum of five m/s flow velocity and up to 16 bar differential pressure.
- Gas: Temperature should lie between -20 and +60 °C, with a maximum 20 m/s flow velocity and up to 16 bar differential pressure.
Storage Conditions For a Gate Valve:
A gate valve is made using a variety of materials and seat types. These devices are easy to use and long-lasting if installed and maintained correctly. However, their installation techniques vary slightly for different end connections, but the other instructions remain the same.
Like any other industrial equipment, it is essential to store a valve under ideal storage conditions to keep it from wearing before time and spending money on gate valve repair. People wishing to make the most out of this device should keep it in a cool and well-ventilated space if stored for an extended period. But doing this much is not enough.
To protect the seat and seals of a hydraulic lift valve, it is suggested not to unpack it until they are ready for installation. By doing this, people preserve the valve from catching dust and debris, which may eventually cause seat leakage and thus cause the device to malfunction.
Maintenance Tips:
To continue using a valve for a long time, it is necessary to look after its maintenance. One may achieve it by operating each valve in suitable temperature conditions. To let a valve function properly, adjust it to the ideal temperature, depending on the material type.
- Brass: Valves made of brass must not be used under temperatures above 450 degrees F as they may damage under such conditions.
- Iron: Valves made of iron should also not be used under temperatures greater than 450 degrees F.
- Stainless steel or White Iron: A high pressure stainless steel ball valve is suitable for conditions with low temperatures. In contrast, a corrosive flow valve must not be used in high temperatures.
- Stell Steel: Valves made using this material are suitable for high temperature and high-pressure working conditions.
Some other essential maintenance tips for a gate valve include the following:
- If the gate valve is not used regularly, cycle it at least once a month.
- Before performing any maintenance work, relieve the system pressure.
- Reverse the installation of a gate valve testing procedure to remove debris from the pipelines.
- When replacing the valve, remove its top body (bonnet) and stem. Screw out the gate to replace it with the new one. Install the entire body and refit into the line.
The Bottom Line:
We hope this blog helps everyone learn everything about gate valve leakage, from its inspection to avoidance and fixing. Since this device is available in multiple designs and materials to offer effective sealing for different applications, it should be taken care of. If the users do not provide it with proper maintenance, it may malfunction after a certain period.
If a gate valve starts leaking, the best thing to do is to replace it with a new one. Please contact us to purchase the most trustable and long-lasting gate valves in the market.
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