Gate valves, often called sluice valves, are common linear valve types often used in pipelines to start and stop liquid flow through ducting, allowing users to separate a section of pipe when required.
The fluid flow through the valve can be in either direction. These valves are often used in refineries and petrochemical plants applications where pressure is low.
However, many users do not have the necessary maintenance knowledge of the usage of gate valves and lack related guidance during assembling and installation of the valve. Minor problems spring up as a result.
Therefore in this article, we will be dishing out a complete guide to problems faced by users, how to fix them easily, handle and seat replacement guides, and other gate valve troubleshooting methods.
How To Test Your Gate Valve
Before we go into how to test your valve, it is imperative to understand that valves are a crucial application in many industries, and they must function accurately by diverting the right pressure without leakages.
Often, these high-pressure systems have exploded due to leakages or inaccurate pressure transfer. Therefore, it is important to ensure proper maintenance for safety and productivity.
Testing, therefore, is performed as a gate valve maintenance procedure to assess the condition or health of an operational valve. These conditions include mechanical friction, flashing, cavitation, choked flow, erosion, and noise in valves, to name a few.
Having understood the importance of testing your valves, here are two easy methods explaining how to test your gate valve.
Alternate Gate Valve Testing Methods
The alternate testing has two easy methods, namely, Middle-Pressure Test and Blind Plate Test.
- Middle-Pressure Test: In this test, the gate is opened to boost the pressure in the valve to the specified value. Then shut the gate, immediately remove the valve and look for leakage at the seals on both ends of the gate. Alternatively, directly insert the test medium into the plug on the cover, and check for the seals on both sides of the gate.
The method above is called the medium or intermediate pressure test and is not applicable in gate valves with a nominal diameter below DN32mm.
- Blind Plate Test: This method also requires opening the ram to increase the test pressure of the valve to the specified value. After that, shut the gate and open the blind plate on one side to check for leakage. Turn the head and repeat the test above until it is qualified.
Back Seat Tests Method
These tests are commonly conducted on valves with backseat elements, such as gate valves. The back seat tests follow the approved test procedure, but they often involve opening the valve with the packing gland loose or uninstalled.
Commons Gate Valve Failures And How To Fix Them
The most common causes of gate valve failure are wear and the seat’s and wedge’s corrosion. The inner areas of a valve wear off over time, and corrosion can make the wedge stick in the open or closed position.
When the handwheel is overused, the stem leading to the wedge breaks off and renders the valve useless.
Therefore, gate valve manufacturers are careful about the safety aspects of the valves from the early design stage of the system. The failure of valves in the process control industry may lead to disastrous events that can jeopardize the safety of lives, investments, environment, and reputation.
Safety and risk management have to be important aspects of the system. Safe systems require industrial control valves communicating well with process liquid and equipment. Hence, let us explore some common problems faced with sluice and their solutions:
- Leakage Between Sluice and Sluice Valve Connection
The leakage from the gate (sluice) valve is from the gate valve gland. This spillage results from a buildup of deposits against the seal, displacing the seal. To stop the leak, all that needs to be done are:
- First, check whether the bolts joining the valve and the sluice are tight. If they are not sufficiently connected, the seal gasket ring and the surface of the flange sealing groove often result in leakage.
- Ensure the bolts and nuts are in place, tightening them until the gasket ring is pressed. The next step would be to check the size and accuracy of the seal and flange sealing groove surface, and in the case where the contact surface size is not accurate or too rough, then the gasket ring needs to be repaired or renewed.
- Also, check the contact surface of the seal ring and the flange sealing groove for sand holes, sand eyes, pitting, or impurities. These defects will be revealed at any time during the valve operation and pose serious threats to a safe operation. Hence, it is necessary that corresponding welding, repair, or clean-up is carried out.
- Inflexible Handwheel Rotation
- Bent or twisted valve stem.
- The surface precision is insufficient.
- Damaged thread due to hard operation.
- Lack of lubrication or lubricant failure.
- Tilting of the stem nut
- Incorrect tolerance of fit.
- A lack of protection for the open air gate valve results in the stem thread being covered with dust and sand or rusted by rain, frost, and snow.
- The threads are corroded by the medium (non-rising stem gate valve or the gate valve with the stem nut in the lower part).
- Incorrect selection of materials like the stem and its nut.
Preventive Measures and Solutions.
- Ensure strict control of the force of the proportion and avoid hard twists on the hand wheel and stem, which is directly linked to the gate valve.
- Ensure careful operation, do not go hard when closing, do not open to the upper dead point, to the stop point should be reversed one or two turns of the handwheel so that the upper side of the threads close so that the medium to push the valve stem upward impacts. Make sure to operate carefully. Do not open and close it unduly.
- Check the lubrication condition frequently to maintain the normal lubrication condition.
- Straightening or fixing the stem nut.
- Correct or update the stem nut to make it meet the standard specification.
- Frequently clean the stem nut dust and sand to prevent rusting.
- Ensure protection of the valve stem of the outdoor gate.
- It is better to use copper material for the stem nut. Do not use the same material as that of the valve stem.
- Bonnet Spillage
- Presence of defects like blisters, loose tissues, and squeezes on the valve and bonnet body. Also, when the quality of iron casting is below standard.
- Frosty and cracked valve body due to low temperature
- Defects include stress cracks, poor or non-welding, slag inclusion, etc.
- Damage to the cast iron valve after being hit by a heavy object.
- This common problem often occurs in packing seal leakage. The first step to fixing this is to check if the fitting is correct and if it matches the sealing groove. If there is such an issue, repair the seal groove or replace the ring.
- Secondly, ensure the seals are without burrs, cracks, and fractures and replace the seals if any. Then, check the surface for roughness or other defects, replacing or updating the damaged parts, if any.
- Again, remove and carry out proper installation if you check and find that the upper and lower packing is installed upside down. Finally, check if the accuracy of the contact surface of the seal meets the requirements.
- Valve Seat and Gate-Shaped Wedge Spillage
- The cylinder head expands and contracts throughout its operating cycle leading to thermal stress.
- Fictional stress between the valve stem and the guide when the valve opens and closes.
In the installation or maintenance of the sluice, leaking of the valve plate is the most common phenomenon and can be divided into two categories; leaking seal root and leaking sealing surface.
- To solve this problem, first of all, check the accuracy of the seat and plate contact sealing surface. This sealing surface needs grinding, and if the surface precision is rough, it should be removed and re-grind.
- Secondly, inspect the sealing surface for sand eye, indentation, pitting, crack, and other defects, and if any of these occurs, the valve seat should be replaced.
- For the one with a pressure spring, check the elasticity of the pressure spring to ensure it meets the requirements, and if the elasticity does not meet requirements, the pressure spring should be renewed.
- For valve seats that have pressure springs, the elasticity of the spring must be in conformity with the requirements. If the elasticity is weakened, the pressure spring should be renewed. Additionally, remove the valve plate and adjust it to a suitable size if its T-shaped joint is too loose and results in a slope.
- In the installation process, it is easy to drop the welding check, scrap iron, and impurities. Therefore, the clutter should be cleaned before installation. If you forget to clean up or clean up thoroughly, it will cause the valve plate to close less than the expected depth, resulting in leakage. To solve this, remove and clean the valve body.
- Finally, the valve seat should be installed with special tools. Also, check whether the seat is installed correctly. If the thread is fastened less than the expected depth, there would be a leak. Hence, make sure special tools are used for re-installation.
- Unable To Close The Sluice Valve
- As the valve ages, it seizes as water circulates via the pump around the central heating system and accumulates iron and dirt deposits. All the deposits stick to rough areas, getting in the mechanisms and causing the moving parts to jam up.
- The best solution is to clean the valve thoroughly or, even better, replace the valve.
- Gate Valve Breakages
- The reason for the rupture of the gate valve is that the valve is weak, and when too much pressure is applied to the valve, it breaks away.
- The spindle thread is not deep enough, leaving little room to stop resistance.
- In most cases of breakage, repair work has to be done using a curb box key. Once the water is closed, you can remove the broken valve with little trouble.
- Leakage at the Filler
- Clog caused by accumulated debris
- Stuck parts
- Excessive water pressure
- Misalignment of parts
- The packing gland should be evenly compressed and increase the packing if the packing is not enough.
- Replace the packing gland if it has been used for a long time or if it becomes invalid due to inappropriate storage
Gate Valve Assembly and Installation Guide
Gate valve overhauling procedures are simple and last longer when installed and maintained correctly. The overhauling procedures and installation techniques vary slightly for different end connections (e.g., flanged, victuals, rolled groove), but the other instructions remain the same.
Valve Installation and Maintenance Procedure
- Industrial gate valves can be installed using any method; however, it is best if they can be installed upright, especially in larger sizes, for easy hand wheel access.
- Extension spindle is used to operate the gate valves below the ground. In utility holes or above-ground installations, hand wheels or electric actuators may be used.
- Ensure that no vertical force from the extension spindle clamps down directly on the top of the valve stem, especially when the valve is installed in a chamber with an extension spindle above ground level.
The extension spindle must be supported by wall mounts or similar to prevent vertical forces and thereby support the weight of the extension spindle.
- Examine the material, seat, and disc before installation. Also, make sure that there are no defects caused by storage or transportation.
- All welding works should be completed before installation, and ensure that the flange has cooled to ambient temperature by installing the sluice valve using the suitable gasket.
- Ensure there are no welding deposits, rust, pickle paste, waste, or other debris in the pipe before installation. Ensure to wash with water or a mild detergent if needed.
- Ensure there is no misalignment of the valve relating to the flange. Lack of correct pipe alignment is the most common cause of valve problems. Ensure the valve is supported where necessary to reduce the load on the piping assembly.
- Install the spacing bolts and ensure no damage to the valve seat. Also, adjust the face to face of the two flanges, so there is sufficient space to slip the valve in or out for servicing.
- Center the pipes, then insert the bolts so that the bottom of the valve can rest upon them to prevent the valve from falling through.
- Handwheels and transmission mechanisms are not for lifting, and any collision is strictly warned against.
- Tighten each of the bolts differently (one at a time). This is so that the pressure is evenly applied and a seal is formed between the valve, gasket, and flanges.
- When installing gate valves mounted with electric actuators, please observe closing torques and the number of turns from the datasheet.
- They are only used for full opening and closing. Partial opening and closing are not deemed safe to ensure the sealing surface is not damaged when the medium flow rate is high.
- The rotating and trapezoidal parts should be lubricated to ensure easy rotation and corrosion protection.
- When installing, the inner cavity and sealing surface should be cleaned to avoid dirt.
- On the completion of the installation, operate the valve several times to ensure it has not moved during installation.
Gate valve maintenance procedures may seem too much to do, but a few minutes of your attention goes a long way to keep a system running smoothly. Valve maintenance can save you time and money in the long run, and ignoring it can leave you stuck with malfunctioning machinery, tubing, or pipes that may require taking apart or even replacing.
The only items that require maintenance on the gate valve are packing and the lubrication of the stem. The packing gland may require adjustment after installation, especially if the valve has been stored for a long time.
When adjusting the packing gland, it is best to first tighten the bolts on the side opposite the seat side.
Below are a few maintenance procedures to follow:
- Rotate the valve at least once a month if not used regularly.
- Make sure the system is relieved of pressure before performing any maintenance.
- Replace the valve gate by removing the top body (bonnet) and stem. Unscrew the gate and replace it with a new part. Install top of the body and refit it into line.
- Ensure the valve’s stem is straight and the hand wheel is on the top.
Gate Valve Seat Replacement Guide
To replace a seat, use one that is as good as the original one, if not better. Hard seats are necessary for high load and temperature and dry fuel (propane or natural gas applications). Hard seats, however, are not required for light-duty passenger applications.
The seat and valve materials must be compatible. They must also be suited for the application.
The following are easy step-by-step guides to replacing a gate valve seat.
- Cut through the old seat and remove it from the valve body using a chisel with a narrow blade or a screwdriver.
- Ensure all the burrs and sharp edges from the seat groove are removed.
- Use a clean rag or brush to clean the seat and ensure it is free of any oil and dirt.
- Ensure the replacement seat is not damaged before placing it into the groove. Also, check if the seat is evenly tangled.
- Gate valve seat replacement is now complete.
Gate Valve Handle Replacement Guide
When the gate valve handle isn’t working properly, your pipes may leak. A straightforward repair will be needed if the handle or extension rod connecting the handle to the valve is broken.
However, If the valve won’t close all the way or if it is leaking, you need to replace the entire handle.
The following, therefore, are easy guides to replacing a gate valve handle.
- Order a Replacement Handle: If the plastic or metal T-handle at the end of the extension rod broke off, make an order for another one online. Also, order a replacement handle from your valve’s manufacturer. Check for the manufacturer’s name printed directly on the handle or a sticker near the valve.
Due to the repeated pulling and pushing of the handle in and out of the extension rod, the threading wears down and eventually breaks after a few years of use.
- Slide the Extension Rod Out 1–2 in (2.5–5.1 cm): Pull the extension rod by hand or grab the broken piece with channel locks and slide it out a little. Grip the metal rod behind the handle with pliers to hold it still and restrain it from spinning while you replace the handle.
- Unscrew Handle by Turning Anticlockwise: With the pliers holding down the extension rod, use your free hand to spin the handle. Keep turning the handle over in an anti-clockwise manner until it pops off the end of the extension rod.
Now, this is a perfect time to clean the threading down with a neat rag if the end of the rod looks a little dirty.
- Attach Your New Handle:The final step to this guide is to attach the new handle and install it by turning clockwise. Ensure your grip with the pliers is not released. This is to keep the extension rod from sliding inside the valve.
Glide your new handle over the end of the rod, and turn it until the threading hooks together. And when it does, keep turning it by hand until you can no longer. Then, release the handle and the pliers to finish replacing the valve’s handle.
Being the most common valve for water supply, the gate valve represents a linear motion isolation valve with the function of stopping or allowing the flow.
Like other types of valves, the gate valve has problems that users have to deal with. However, most of these failures can be prevented by proper maintenance.
This post discusses how to test, assemble and install your gate valve, their common failures, and how to fix them, including its seat and handle replacement guide.
Dombor valve is an industrial valve manufacturer that provides high-quality valve solutions to fit market requirements and pipe specifications. We pride ourselves on creating suitable valve types in various conditions. So contact us today!