A gate valve is a widely used general-purpose valve that is rather common. It is mostly utilized in the metallurgical, water conservation, and other sectors. The market has acknowledged its broad range of performance. Along with studying the gate valve, it also conducted a more thorough investigation into how to utilize and troubleshoot gate valves.

The following is a broad explanation of gate valves’ design, application, troubleshooting, quality control, and other features.

structure

The gate valve’s structure consists of a gate plate and a valve seat, which are used to regulate the valve’s opening and closing. The basic components of a gate valve include its body, seat, gate plate, stem, bonnet, stuffing box, packing gland, stem nut, handwheel, and so forth. The channel size can alter and the channel can be closed off depending on how the relative position of the gate and valve seat changes. The mating surface of the gate plate and the valve seat is ground in order to make the gate valve close tightly.

Gate valves can be split into two categories: wedge type and parallel type, based on the various structural shapes of gate valves.

The wedge-shaped gate of the wedge gate valve seals (closes), using the wedge-shaped gap between the gate and the valve seat, which forms an oblique angle with the channel’s center line. It is possible for the wedge plate to have one or two rams.

There are two types of parallel gate valves: ones with an expansion mechanism and ones without, and their sealing surfaces are perpendicular to the channel’s center line and parallel to each other. Double rams with a spreading mechanism are present. The wedges of the two parallel rams stretch out on the valve seat against the gradient to obstruct the flow channel as the rams descend. The wedges and the gates will open when the rams rise. The wedge is supported by the boss on the gate plate, which rises to a given height and separates the matching surface of the plate. The double gate without expansion mechanism uses the pressure of the fluid to force the gate against the valve body on the outlet side of the valve in order to seal the fluid when it slides into the valve seat along the two parallel seat surfaces.

The gate valves are split into two categories: rising stem gate valves and concealing stem gate valves based on how the valve stem moves when the gate is opened and closed. When the rising stem gate valve is opened or closed, the gate plate and valve stem both rise and fall simultaneously. In contrast, when the concealed stem gate valve is opened or closed, the gate plate simply rises and falls and the valve stem only rotates. The benefit of the rising stem gate valve is that the occupied height can be reduced while the opening height of the channel can be determined by the rising height of the valve stem.Close the valve by rotating the handwheel or handle counterclockwise while facing it.

Principles of gate valve selection and circumstances

V-shaped gate valve

Applications for slab gate valves include:

(1) The flat gate valve with diverter holes makes it simple to clean pipelines carrying natural gas and oil.

(2) Refined oil storage facilities and pipelines.

(3) Equipment for oil and gas extraction ports.

(4) Particle-filled suspended pipe systems.

(5) A transmission pipeline for city gas.

(6) Plumbing.

The slab gate valve selection method:

(1) Use single or double slab gate valves for pipelines carrying natural gas and oil. Use a single gate valve with an open stem flat gate valve if cleaning the pipeline is required.

(2) Flat gate valves with a single ram or double ram without diverter holes are chosen for refined oil transportation pipelines and storage equipment.

(3) Single gate or double gate slab gate valves with hidden rod floating seats and diversion holes are chosen for oil and natural gas extraction port installations.

(4) Knife-shaped slab gate valves are chosen for pipelines that contain suspended particle media.

Use single gate or double gate soft-sealed rising rod flat gate valves for urban gas transmission pipelines.

(6) Single gate or double gate gate valves with open rods and no diversion holes are chosen for tap water installations.

wedge gate valve

Application scenarios for wedge gate valves: The gate valve is the most frequently utilized valve type. Generally speaking, it cannot be utilized for regulating or throttling and is only suitable for full opening or full closing.

Wedge gate valves are typically employed in locations with somewhat tough operating conditions and no strict restrictions for the outward dimensions of the valve. For instance, the closing components are necessary to maintain long-term sealing when the working medium is both high temperature and high pressure.

In general, it is advised to use a wedge gate valve when the service conditions call for reliable sealing performance, high pressure, high pressure cut-off (large pressure difference), low pressure cut-off (small pressure difference), low noise, cavitation and vaporization, high temperature, medium temperature, or low temperature (cryogenic). Many industries employ water supply and sewage treatment engineering, including the power industry, petroleum smelting, petrochemical industry, offshore oil, urban development, chemical industry, and others.
Selection criterion:

(1) Requirements for the properties of valve fluid. Gate valves are chosen for applications where there is little flow resistance, substantial flow capacity, excellent flow characteristics, and stringent sealing requirements.

(2) A medium with high pressure and temperature. such as high temperature, high pressure oil, and high pressure steam.

(3) A cryogenic (low-temperature) medium. such example liquid hydrogen, liquid oxygen, liquid ammonia, and other substances.

(4) High diameter and low pressure. such as sewage treatment and waterworks.

(5) Installation site: Select the concealed stem wedge gate valve if the installation height is constrained; select the exposed stem wedge gate valve if it is not.

(6) Wedge gate valves are only effective when they can be fully opened or fully closed; they cannot be adjusted or throttled.

Common Errors and Fixes

common gate valve issues and their causes

The following issues frequently arise after the gate valve is utilized as a result of the impacts of medium temperature, pressure, corrosion, and relative movement of different contact parts.

(1) Leakage: External leakage and internal leakage are the two categories. External leakage is the term for leakage to the outside of the valve, and external leakage is frequently observed in stuffing boxes and flange connections.

The packing gland is loose; the surface of the valve stem is scraped; the type or quality of the stuffing does not satisfy the standards; the stuffing is aging or the valve stem is damaged.

The following factors can cause leaks at flange connections: inadequate gasket material or size; poor flange sealing surface processing quality; improperly tightened connection bolts; unreasonably configured pipeline; and excessive additional load generated at the connection.

Causes of the valve’s internal leakage include: Internal leakage brought on by the valve’s slack closure is brought on by damage to the sealing surface of the valve or a lax root of the sealing ring.

(1) The valve body, bonnet, valve stem, and flange sealing surface are frequently corrosion targets. The action of the medium and the ion releases from fillers and gaskets are the main causes of corrosion.

(2) Scratches: Localized roughening or peeling of the surface that happens when the valve seat and gate move in relation to one another while being in contact with one another.

Gate valve maintenance

(1) Fixing an exterior valve leak

To prevent the gland from tilting and leave a gap for compaction, the gland bolts should be balanced before compressing the packing. To prevent affecting the rotation of the valve stem, causing the packing to wear out faster, and shortening the packing’s service life, the valve stem should be rotated while compressing the packing to make the packing around it uniform and prevent the pressure from being too tight. The valve stem’s surface is scraped, which makes it simple for the medium to flow out. Before usage, the valve stem should be processed to remove the scratches from its surface.

If the gasket is damaged, it should be replaced. If the material of the gasket was improperly chosen, a material that can meet the requirements of use should be chosen. If the flange sealing surface’s processing quality is subpar, the surface needs to be removed and repaired. Up till it is qualified, the flange sealing surface is reprocessed.

Additionally, adequate flange bolt tightening, pipeline construction that is appropriate, and avoiding excessive additional stress at flange connections are also helpful in preventing flange connection leaks.

(2) Fixing interior valve leaking

When the sealing ring is fastened to the valve plate or seat by pressing or threading, the repair of internal leakage entails removing the damaged sealing surface and the loose root of the sealing ring. There is no issue with a loose root or leakage if the sealing surface is immediately treated on the valve body and valve plate.

If the sealing surface is directly processed on the valve body and the sealing surface is significantly damaged, the damaged sealing surface should be removed first. If the sealing surface is formed by a sealing ring, the old ring should be removed and a new sealing ring should be given. The new sealing ring should be taken off, and then the processed surface should be ground into a new sealing surface. Grinding can get rid of faults on the sealing surface that are less than 0.05mm in size, including scratches, lumps, crushes, dents, and other flaws.

The sealing ring’s root is where the leak starts. Tetrafluoroethylene tape or white thick paint should be used on the valve seat or the bottom of the ring groove of the sealing ring when it is fixed by pressing. When the sealing ring is threaded, PTFE tape or white thick paint should be used between the threads to stop fluid from leaking between the threads.

(3) Repairing corroded valves

The valve stem is frequently pitted, but the valve body and bonnet are typically uniformly corroded. The corrosion products should be eliminated before fixing. If a valve stem has pitting pits, it should be machined on a lathe to remove the depression and then filled with a material that will slowly release over time. Alternatively, the filler should be cleaned with distilled water to get rid of any filler that could harm the valve stem. damaging ions.

(4) Touching up dings on the sealing surface

Try to avoid scratching the sealing surface while using the valve, and be careful not to close it with too much torque. Grinding can get rid of scratches on the sealing surface.

Examining four gate valves

Iron gate valves make up a significant component of the market and user requirements nowadays. You must be knowledgeable with product quality inspection as well as the product itself in order to be a successful product quality inspector.

items for iron gate valve inspection

Signs, a minimum wall thickness, pressure tests, shell tests, etc. are the key components. Wall thickness, pressure, and shell test are among them and are essential inspection items. Unqualified products can be assessed outright if there are any unqualified things.

In short, it goes without saying that the product quality inspection is the most crucial stage of the complete product inspection. Only by having a thorough understanding of the inspected items can we perform a better job of inspection. As front-line inspection employees, it is imperative that we continually improve our own quality.