Difference between dry gas seal and mechanical seal

They have the added feature of providing more positive sealing during shutdown. For turbocompressor applications, it is very common to specify dry gas seals instead of wet seals oil seals. Replacing wet seals with dry seals in centrifugal compressors epa. The system is not accepted, hence mechanical seal preferred as they tend to seal with no visible leak. A double seal costs less to purchase and install than a tandem seal, but as is the case most of the. Inboard of the dry gas seal is an inner labyrinth seal, which separates the process gas from the gas seal. Unlike an oring seal, the hydraulic diameter of a bellows seal is not a fixed geometric value. The terms gaskets and seals are often used interchangeably.

Key considerations for dry gas seal performance flow. Seal performance is determined primarily by the condition of the faces and the pressure applied to them. Function of mechanical seal the function of every mechanical seal is to prevent. For turbocompressor applications, the seal panel, the seal piping arrangements, and the seal vent system details are critical for reliability, performance, safety and operation of dry gas seals. So the question is why use the double seal arrangement at all. We are committed to providing the latest technologies and designs in order to provide our turbo machinery customers within global energy industries with the solution. Beyond gas savings, dry seals also yield significant operational and maintenance savings compared with wet seals. Type 2874ne noncontacting, nonelastomer metal bellows outward pumping dual gas seal for hightemperature applications. A labyrinth seal is a type of mechanical seal that provides a tortuous path to help prevent leakage.

The difference between single and double mechanical seals. This is essential when pumping or mixing a dangerous or toxic substance. Figure 1 shows an example of a modern centrifugal compressor. In this article, we will see the basic classification of mechanical seal that is the mechanical seal balanced and unbalanced type. Mechanical seals are typically used for pressures up to psi. The original gas seal, with a design pedigree stretching back over 30 years and evolving gradually. The biggest benefit of using mechanical seals is the drastic reduction in leakage. These seals have been designed and are manufactured using our unique modular system, which ensures product quality, continuity and reduced delivery times. Double dry gas seals require the simplest system design. Seals is a category that encompasses many types of seals.

The reliability of any component is directly related to the complexity of its supporting systems. Contrary to wet mechanical seals, in dry gas seals there is no contact between the faces so overheating, or actually, any frictional heat, does not occur. A new, highly reliable gas lubricated api 682 iso 21049 qualified hightemperature, noncontacting mechanical seal that utilizes internally pressurized outward. Double or dual mechanical seals are designed to ensure maximum sealing safety. The seal gas supply is piped to the gas seal control panel where it is filtered, dried and cooled and then connected to the flow control of the same differential gauge and differential regulator as the reference gas. This regulator will maintain the seal gas supply pressure to the seal at a higher pressure than the reference gas.

John crane gas sealsgas seals and their application for maximum reliability 2. Dry gas seal system centrifugal compressor, dry gas seals are an integral part of modern centrifugal compressors. Instead, the lubricating liquid will vaporize as it crosses the seal faces and the leakage is a gas or vapor. The difference between mechanical seal and gland packing. However, endusers should ask themselves several questions before deciding to retrofit. The difference between mechanical seal and oil seal. Mechanical contact face seal a typical example of a mechanical contact face seal is shown in figure 8. Dry gas seals dgs used in ultrahigh pressure gas reinjection systems are setting a new standard in offshore, deepwater applications. Difference between mechanical seal and gland packing. A dual mechanical seal offers a second outer seal to contain the pumped fluid by creating a cavity or chamber between the inner and outer seal that can be filled with a fluid.

Like packing, the mechanical seal faces must also be lubricated. Mechanical seals are devices that seal machines between rotating parts shafts and stationary parts pump housing and are an integral part to the pump. An unstable condition from thermoelastic instability could result in a high wear rate of the sealing surfaces. This video was made using our mechanical seal basics training software which covers a large range of seal types like pusher seals, nonpusher seals, cartridge seals, split seals, double seals. The mechanical seals are designed to minimize leakage of process gas, while the compressor is pressurized and in the. A sealing dam maintains uniform pressure distribution between the seal faces and helps to provide the hydrostatic lift that results in a low startup. Even when leakage isnt visible, harmful vapors could be escaping. This has produced a range of compressor dry gas seals and pump gas seals. The clearance between rotating shaft and the passage way through the wall of a housing casing or pressure vessel. They rely on the continuous contact between a rotating and fixed seat that are separated by a carbon ring refer to fig. Dgs support systems are less elaborate and less expensive than older systems that almost always use oil as a coolant or separating layer in the narrow clearance between stationary and rotating seal components. Buoyancy seals use a couple of concentric baffled cylinders in the path of the purge gas as indicated in figure1. The use of dry gas seals has also expanded into a number of seal arrangements for liquid sealing.

Dry gas seals are noncontacting, dryrunning mechanical face seals that consist of a mating rotating ring and a primary stationary ring. The problem with an ordinary contacting mechanical seal or wet seal is the risk of seal faces overheating at. As gas seals become more common, it s important that users understand the differences between them and liquid lubricated seals. The separation gas should be filtered to 5 microns solid particles and should be 99. This results in a less complex system of potentially higher reliability than tandem seals. Dry gas seals are noncontacting, dry running mechanical face seals that consist of a mating rotating ring and a primary stationary ring. Use double seals, with clean gas buffer systems if required, if sufficient n2 pressure is available and it is compatible with the process. Centrifugal compressors require seals around the rotating shaft to prevent gases. A dry gas seal is a type of seal used in large rotating equipment to keep the. A dry gas seal is a mechanical seal that uses a sealing gas to create a barrier between the process gas and the atmosphere. Dry gas seals operate very similar to a contacting oil seal and pump mechanical seal, except they. The dry gas seals are shown at both ends of the rotor. For a more complete description of dry gas seal principles of operation, see shah 1988. Depending on the application and users needs, different seal types.

Although gland or packing seals have been the default sealing method of choice for many years, mechanical seals provide many operational benefits and should also be considered. What is the difference between a gasket, an oring and a seal. A clean and dry separation gas is continuously injected into the barrier seal to protect the migration of lube oil from the outboard bearing housing. Outboard of the dry gas seal is a barrier seal, which separates the gas seal from the compressor shaft bearings fig. If the load at the seal faces is too high, the liquid film between the seal rings could be squeezed out or vaporized. When operating, lifting geometry in the rotating ring generates a fluiddynamic lifting force causing the stationary ring to separate and create a gap between the two rings. Figure 3 shows a tandemtype dry gas seal with an intermediate labyrinth configuration for a centrifugal compressor application. This article will explain what a mechanical seal is and the key design features that make them work. John cranes comprehensive range of dry gas mechanical seals are designed to provide you with the correct seal solution suited for your specific application, to ensure optimal reliability, safety and performance. A mechanical seal is simply a method of containing fluid within a vessel typically pumps, mixers, etc. These seals virtually eliminate leakage of the fluid or gas being handled in pumps or mixers. Small shallow grooves on seal faces pump the gas into the area between the stationary face and the rotating face, increasing the pressure. With proper application and design however, the leakage is so minute that actual droplets of liquid are not detected.

Heres an example where a paper mill replaced packing with a mechanical seal to stop leakage. Mechanical seals consist of two seal rings mated together to create a seal at their interface. A dry gas seal is a type of seal used in large rotating equipment to keep. Mechanical seal balance is used to refer the load act across the seal faces. An example of such a seal is sometimes found within an axles bearing to help prevent the leakage of the oil lubricating the bearing a labyrinth seal may be composed of many grooves that press tightly inside another axle, or inside a hole, so that the fluid has to pass through a. However, it can be a very costly venture over time as they require more maintenance, and also allow more product loss than mechanical seals. With a lower k value, the safety against thermal overload will increase, but the mechanical seal may also lift off more easily. Mechanical seals and gland packing are the toprated and mostpreferred sealing mechanisms. Packing seals use ropelike materials that wrap around the shaft of a pump, filling in dead space and minimizing fluid loss. Key considerations for dry gas seal performance flow control. Compressors in a natural gas transfer and distribution network is a common example where dry gas seals are routinely used.

Is there actually a difference between arco gas and brand name gas like. Mechanical seals consist of a rotating element and a stationary element, each with a lapped, precisionsmooth mating face see figure 1. Other key factors are vibration, heat and pumpage characteristics. The benefits of dry gas seals are such that conversions from traditional oil seals to dry gas seals may be advantageous to compressor operators. These seals are typically provided with labyrinth seals inboard of the sealing surfaces for use with optional buffer gas. Double seals provide a level of safetyzero emissions compliance not possible with single seals. Describe difference between mechanical seal and oil seal whether it is a mechanical seal or oil seal, it prevents the fluid seeping the liquid to other parts of the machine, or it keeps the rotating parts lubricated both sealing types are popularly used in different mechanical engineering applications. A major survey into the reliability of drygas seals in the united kingdom 24 highlighted three key causes of. The fundamental difference is that a gasket is a physical piece that goes between two flanges to create a seal at a joining point between two components. As nouns the difference between seal and gasket is that seal is a pinniped pinnipedia, particularly an earless seal true seal or eared seal or seal can be a stamp used to impress a design on a soft substance such as wax while gasket is any mechanical seal that serves to fill the space between two objects, generally to prevent leakage between the two objects while under. Mechanical seal technology and selection eagleburgmann.

Mechanical seal basics and seal selection process training. The seals are located between the process section and the bearing. Common dry gas seal failures are discussed below along with their causes and remedies. A mechanical seal, and more specifically a double mechanical seal, should always be used when the pumped fluid presents a safety, health, or environmental hazard. What is the difference between mechanical seal and gland. Dry gas seals are noncontacting, dry running, mechanical face seals comprising a rotating mat.

Dry gas seals are basically mechanical face seals, consisting of a mating rotating ring and a primary. Sealing is accomplished by vertical contact between the carbon ring and the rotating and stationary seat. Dry gas seal systems for centrifugal compressors page 4. Here is a comparison between gland packing and mechanical seals, and how you can decide which one is right for you. For compressors, the two points where the rotating shaft passes through the. Tandem seal with intermediate labyrinth and separation seal.

One seal ring rotates with the shaft and the other is stationary. We are committed to providing the latest technologies and designs in order to provide our turbo machinery customers within global energy industries with. Floating seal mechanical face seals is a simple product made up of two components. Buoyancy seal typically uses the difference in densities of the purge gas and ambient air to keep the air from entering flare system. For compressors, the two points where the rotating shaft passes through. They are used directly as dry gas seals, as a backup seal to a standard liquid seal and also as a gas barrier seal for hazardous or toxic products. A clean and dry sealing gas is injected between the inner labyrinth seal and the gas seal, providing the working fluid for the seal running gap. Dgs application rangejohn crane dgsoperating range temp. Normally oil seals cannot with stand more pressures. Difference between mechanical seal and gland packing packing seals have been the most widely used sealing solution for many years. Dry gas seals are mechanical facetype seals available as single, double. Dry gas seals are generally noncontacting, dry running face seals, mainly used in high speed applications. Inadequate fuel gas pressure during start up typical conditions on inboardoutboard seal will include running. What is difference between mechanical seal and oil seal.

When this fluid is unpressurized, it forms a buffer between the pumped fluid and atmosphere and is commonly referred to as a buffer fluid. Basically oil seal is used to seal oil chambers of rotating equipments like pump, agitator, gear box bearing housings. Dry gas seal systems for centrifugal compressors page 3. A dry gas seal control system must have an adequate range and controllability to maintain a minimum 16 fps 4. Drygas mechanical seals set a new standard in deepwater. What is the difference between mechanical seal and oil. Dry gas seals are mechanical facetype seals available as single, double and tandem models. Describe difference between mechanical seal and gland packing seal and packing are integral and essential elements in a pump system, shaft, and several other mechanical engineering applications. If purge gas is lighter than air it accumulates at the top of the inner cylinder and forms a seal. Their main job is to prevent the pumped product from leaking into the environment and are manufactured as single or double seals. Aesseal has invested heavily in the development of gas seal technology, that we believe will revolutionise the industry.