Stop Valve

Gate Valve

 There are Two Type of Gate Valve

  • The Rising Stem Gate Valve

Cast Iron Gate Valve is designed with straight through bore type with rising stem, outside screw & yoke, bolted bonnet and stainless steel trim. The open and closed position of the valve is easily distinguished by the stem position. The Wedge is replaceable without needing to remove the valve from the pipelines. 

Cast Iron Gate Valve allows for two-way flow direction and used for closing or opening the medium flow. This valve can be installed in horizontal and vertical positions in the piping systems. It is widely used in process industries such as Palm Oil and Refinery Plant, Food Industries, Petrochemical, Fire Protection System, Power Plant and Cooling System. 

  • Non-rising Stem Gate Valve 

Used in fire protection systems for on/off operation, Tyco Resilient Seated Gate Valves incorporate high strength stainless steel stems, dezincification resistant copper alloy components, high-grade elastomers and quality coating systems. The lightweight ductile iron body weighs less than conventional cast iron valves, which allows for easier handling on site and reduces shipping costs. A fully encapsulated EPDM ductile iron wedge is intended to achieve bubble-tight sealing. Components that are not designed to be inherently corrosion resistant are coated with a thermally applied fusion-bonded epoxy.

The gate sealing design combines wedge and compression mechanisms to achieve low torque, drop tight sealing. The stem seal arrangement incorporates five separate O-rings designed to provide a lifetime seal. Available end connections include flange-by-flange, flange-bygroove and groove-by-groove configurations. 

There are Two Type of Gate Valve Body

 

Body acts as an enclosure to stem and disc assembly and flow passage for the fluid to flow.  in most of the gate valve body construction ,the upper portion is extended to enclose the disc when the valve is at fully open condition. This provision can also give in bonnet by changing the bonnet design ,if a short body is prefered.

  • Casted Body

Casted valve bodies are mainly used for large sized valve where other fabrication process not feasible. 

  • Forged Body

Forged body can use  for smaller sized high pressure application of gate valves.

There are Two Type of Gate/Disc

 

Parallel Gate

For a parallel gate both the faces of the gate is parallel

  • Knife Gate

Knife gate is a parallel gate having sharp bottom edge used in slurry handling pipelines to separate the slurry by slicing the flow.  

  • Through Conduit Gate

A through hole is drilled in the gate.to achieve full port see more details about full port double expanding through conduit gate valve.  

Wedge Gate

The gate design is in the form of a wedge having two flat inclined surfaces.Two are inclined but might have a slight angular mismatch. Sealing will be in tight contact with the wedge by wedge action. Due to the inclined contact between the wedge and the seat, an immediate disengagement without any sliding action between the wedge  and the sealing ,when the gate starts to travel upward during valve opening. This reduces the wear due rubbing action and increases the life of sealing and gate compared to parallel gates.

  • Single Solid Wedge Gate

This is the most common and stronger wedge design. Due to the simple construction of the wedge, the fabrication cost is much less compared to other wedge designs.Solid wedge design can be assembled and operated in any orientation and can used in any fluid application even for a turbulent flow.

Solid wedge working in high temperature applications like steam pipelines may undergo slight expansion due to the temperature gradient and will induce more compression forces during  tight shut off condition and undergoes deflection as shown in figure. This may cause seating mismatch and leads to leakage.This can be solved using split or double plate wedge design by inducing wedge flexing. 

  • Split Flexible Wedge gate

The solid wedge is stilted all round the perimeter.This makes the single piece wedge into two piece which can flex  to correct any angular miss match between the wedge and seating and more tight seating as shown in figure without loosing much  strength of the wedge.

  • Double plate Wedge Design

 Double plate design having two plates assembled using ball and socket to adjust any mismatch/alignment problems or any solid entrapment like dirt between the wedge and seating.  This types of wedges mainly used for non condensing gas and liquid applications.

 

001-what-is-gate-valve
  • The Gate valve is a linear actuating  valve used as flow isolater in a fluid pipeline.  As the name says the gate valve, a flat  circular or rectangular plate acts as a 'gate' in a pipeline. We call this plate as disc ,gate or wedge. When the valve actuates down the gate slice the fluid  to total shut off .The disc can moved up fully into the upper portion of the body and results no hindrance to the fluid flow cross section area.  This  makes the valve  full open with very less pressure drop.

Gate valves (also known as knife valves or slide valves) are linear motion valves in which a flat closure element slides into the flow stream to provide shut-off. They are one of the most common valves used.

003-gate-valves-are-used-in-the-petroleum-industry

Gate valves and knife valves are advantageous in applications involving slurries, as their “gates” can cut right through the slurry. They are also used in applications that involve viscous liquids such as heavy oils, light grease, varnish, molasses, honey, cream and other non-flammable viscous liquids. They are available in large sizes to better handle thick flow. However, gate valves do have low-pressure limitations, and are not optimal in applications that require cleanliness or sanitary conditions.  They are excellent for use anywhere a shutoff valve is needed. When needed, they can also be used where throttling capabilities are desired, although this is not generally recommended as erosion of the seat and disc occurs due to the vibrations of the disk in throttling applications. 

Gate valves and knife valves are designed to minimize pressure drop across the valve in the fully opened position and stop the flow of fluid completely. The direction of fluid flow does not change, and the diameter through which the process fluid passes is essentially equal to that of the pipe. Hence, they tend to have minimal pressure drop when opened fully.

Gate valves are used in many industrial applications including the oil and gas industry, pharmaceuticals, manufacturing, automotive, and marine.

Non-rising stem gate valves are very popular on ships, in underground applications, or where vertical space is limited because they don't take up extra space. Gate valves can be used in demanding environments such as high temperature and high pressure environments. They are often seen in power plants, water treatments, mining, and offshore applications.

Valve Applications

Valves serve a variety of purposes in the industrial, engineering, manufacturing and scientific communities. Selecting the right valve can determine the success or failure of the system or process.

The main purpose of a valve is to control media flow through a system. The valve may be used to start, stop, or throttle the flow to ensure safe and efficient operation of the process. To learn more about the mechanisms that valves use to control flow, please read Valve Types.

Industries

Valves play a large role in most industries. They are used in many parts of daily mechanical devices, including in HVAC and water systems in an office and the gasoline mechanism for an automobile. Below are a few examples of the many industries in which valves play a major role in proper operation.

  • Pipelines

This use is an essential aspect of many industries, but there are hundreds of thousands of miles of crucial pipelines that transport media from its source to the place where it will be transformed into its final product. This media could include piping for crude oil and gas, both onshore and offshore. Valves are used to optimize the pipeline operating conditions, and can be found in the upstream, midstream and downstream section of the piping. Upstream starts at the bottom of the hole in the ground and covers everything on the wellhead up to the choke. In this case, the choke is a specialized globe valve that is mounted on the wellhead to regulate the output of the well. Midstream starts at the output of the choke and ends at the fence of the final destination (usually a refinery). Downstream is everything inside the area of the destination. The most important factor to consider when selecting a valve for a pipeline application is whether the valve is piggable – that is, the inside is designed to be cleaned or inspected.

  • Oil and Gas

The oil and gas industry is a subset of the pipelines category. Due to the high demand for oil and gas, deeper wells, longer pipelines, and lower production costs have become necessary. Along with the need for an inexpensive valve, the device must also be tougher, last longer, and perform better to meet the demands of the industry. Valve service environments and operating conditions are often extreme with high temperatures (greater than 1,500°F) and high pressure (greater than 25,000 psig) or cryogenic and very low pressure applications. Another feature important to valves used in the oil and gas industry is the capacity for remote control.

  • Food and Beverage

The food and beverage industry is a large and growing industry with an increasing need for parts and products that keep plants running smoothly .The industry’s many challenges, including safety concerns, have prompted strict material requirements for the valves used in these plants. There are two classifications for valves in the food and beverage industry: those in direct contact with food materials and those handling utility services (i.e. steam, water). For valves which come into direct contact with food, there are regulations in place (issued by such organizations as the FDA) which require that the inside of the valve be smooth enough to avoid trapping particles or bacterial accumulation. Valves made of a soft material must not absorb or hold any product going through the valve. These standards also specify that there should not be dead volume in the valve or crevices where material can be trapped to avoid decay or stagnate. Valves in the food and beverage industry do not face the high pressures or highly corrosive materials that are present in other industries.

  • Biopharm Industry

The biopharm industry is part of the larger chemical processing industry. The most important feature of valves used in this industry is their ability to be cleaned and sterilized. The chemical processing industry is responsible for processing raw materials into products. Since chemical processing often involves reactions using pressure and/or heat, and could cause toxic by-products, the media in this industry tends to be highly corrosive and abrasive. The valves need to be able to tolerate the nature of the media, as well as offer precise flow control and high leakage protection to protect against spills and cross-contamination.

  • Marine Industry

Valves play a critical role in the marine industry. As ships become larger and are used more frequently, they require the ability to generate power, treat and manage wastewater and control HVAC, as well as perform their required tasks. The size and application of the ship will determine the different types and number of valves on board. Valves are used to regulate the loading and storage of a ship’s power supply, provide water for fire-fighting capabilities, handle and processes wastewater and store any liquid cargo, among many other applications. Any valve that processes sea water must be durable, and all marine valves must be reliable due to lack of resources once out at sea.

 

005-installation-of-gate-valve.jpg

The closure element of a gate valve is a replaceable disk. To open the valve, the disk is completely removed from the stream and offers virtually no resistance. Therefore, there is little pressure drop across the open gate valve. A fully closed gate valve provides good sealing due to the 360° disk-to-seal ring contact surface. Proper mating of a disk to the seal ring ensures there is very little or no leakage across the disk when the gate valve is closed.

They are used to start or stop a flow completely. They should not be used to control flow rate. Using a gate valve in a partially open position can damage the valve. Fluid flow across the gate causes erosion to the gate making it impossible to seal well against its seat.
Fluid can flow through most gate valves in either direction.
The closing element in a gate valve is a wedge-shaped disc or gate attached to the end of the stem, as shown in Figure. The gate fits into a wedge-shaped seat in the valve body to stop flow through the valve, as shown in Figure.

 006-type-of-gate-valve
[current-page:title-plain]