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. Centrifugal compressors require seals around the rotating shaft to prevent gases. Dry gas seals operate very similar to a contacting oil seal and pump mechanical seal, except they. Dry gas seal system centrifugal compressor, dry gas seals are an integral part of modern centrifugal compressors. Type 2874ne noncontacting, nonelastomer metal bellows outward pumping dual gas seal for hightemperature applications. The terms gaskets and seals are often used interchangeably. Dry gas seals are noncontacting, dry running mechanical face seals that consist of a mating rotating ring and a primary stationary ring. Difference between mechanical seal and gland packing packing seals have been the most widely used sealing solution for many years. Mechanical seal balance is used to refer the load act across the seal faces. Normally oil seals cannot with stand more pressures.
As gas seals become more common, it s important that users understand the differences between them and liquid lubricated seals. Dry gas seals are noncontacting, dry running, mechanical face seals comprising a rotating mat. Mechanical seal technology and selection eagleburgmann. Mechanical seals are devices that seal machines between rotating parts shafts and stationary parts pump housing and are an integral part to the pump. These seals have been designed and are manufactured using our unique modular system, which ensures product quality, continuity and reduced delivery times. However, it can be a very costly venture over time as they require more maintenance, and also allow more product loss than mechanical seals. The difference between mechanical seal and oil seal. For compressors, the two points where the rotating shaft passes through the. Outboard of the dry gas seal is a barrier seal, which separates the gas seal from the compressor shaft bearings fig. 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. The use of dry gas seals has also expanded into a number of seal arrangements for liquid sealing. A labyrinth seal is a type of mechanical seal that provides a tortuous path to help prevent leakage. Dry gas seals are basically mechanical face seals, consisting of a mating rotating ring and a primary.
Other key factors are vibration, heat and pumpage characteristics. This article will explain what a mechanical seal is and the key design features that make them work. Drygas mechanical seals set a new standard in deepwater. Mechanical seals and gland packing are the toprated and mostpreferred sealing mechanisms.
A new, highly reliable gas lubricated api 682 iso 21049 qualified hightemperature, noncontacting mechanical seal that utilizes internally pressurized outward. The problem with an ordinary contacting mechanical seal or wet seal is the risk of seal faces overheating at. Depending on the application and users needs, different seal types. What is the difference between a gasket, an oring and a seal. Double seals provide a level of safetyzero emissions compliance not possible with single seals. A dry gas seal control system must have an adequate range and controllability to maintain a minimum 16 fps 4. This regulator will maintain the seal gas supply pressure to the seal at a higher pressure than the reference gas. 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. The difference between mechanical seal and gland packing. Dry gas seals are generally noncontacting, dry running face seals, mainly used in high speed applications. For a more complete description of dry gas seal principles of operation, see shah 1988. Difference between mechanical seal and gland packing. What is the difference between mechanical seal and gland.
A dry gas seal is a type of seal used in large rotating equipment to keep. Dry gas seals are mechanical facetype seals available as single, double. Here is a comparison between gland packing and mechanical seals, and how you can decide which one is right for you. Mechanical seals consist of two seal rings mated together to create a seal at their interface. Dry gas seals dgs used in ultrahigh pressure gas reinjection systems are setting a new standard in offshore, deepwater applications.
Dry gas seal systems for centrifugal compressors page 4. A major survey into the reliability of drygas seals in the united kingdom 24 highlighted three key causes of. 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. Mechanical seals consist of a rotating element and a stationary element, each with a lapped, precisionsmooth mating face see figure 1. 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. Compressors in a natural gas transfer and distribution network is a common example where dry gas seals are routinely used. 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. Key considerations for dry gas seal performance flow control. In this article, we will see the basic classification of mechanical seal that is the mechanical seal balanced and unbalanced type. With a lower k value, the safety against thermal overload will increase, but the mechanical seal may also lift off more easily. With proper application and design however, the leakage is so minute that actual droplets of liquid are not detected. 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. 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.
Function of mechanical seal the function of every mechanical seal is to prevent. Tandem seal with intermediate labyrinth and separation seal. One seal ring rotates with the shaft and the other is stationary. The seals are located between the process section and the bearing. For turbocompressor applications, it is very common to specify dry gas seals instead of wet seals oil seals. A sealing dam maintains uniform pressure distribution between the seal faces and helps to provide the hydrostatic lift that results in a low startup. Inboard of the dry gas seal is an inner labyrinth seal, which separates the process gas from the gas seal. A mechanical seal is simply a method of containing fluid within a vessel typically pumps, mixers, etc. Is there actually a difference between arco gas and brand name gas like.
Replacing wet seals with dry seals in centrifugal compressors epa. Sealing is accomplished by vertical contact between the carbon ring and the rotating and stationary seat. 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.
Dry gas seal systems for centrifugal compressors page 3. Aesseal has invested heavily in the development of gas seal technology, that we believe will revolutionise the industry. The separation gas should be filtered to 5 microns solid particles and should be 99. Double dry gas seals require the simplest system design. What is difference between mechanical seal and oil seal. These seals virtually eliminate leakage of the fluid or gas being handled in pumps or mixers. Buoyancy seal typically uses the difference in densities of the purge gas and ambient air to keep the air from entering flare system. A dry gas seal is a mechanical seal that uses a sealing gas to create a barrier between the process gas and the atmosphere. 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. 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. Common dry gas seal failures are discussed below along with their causes and remedies.
Their main job is to prevent the pumped product from leaking into the environment and are manufactured as single or double seals. The clearance between rotating shaft and the passage way through the wall of a housing casing or pressure vessel. 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. A dry gas seal is a type of seal used in large rotating equipment to keep the. Seal performance is determined primarily by the condition of the faces and the pressure applied to them.
These seals are typically provided with labyrinth seals inboard of the sealing surfaces for use with optional buffer gas. Packing seals use ropelike materials that wrap around the shaft of a pump, filling in dead space and minimizing fluid loss. Mechanical seal basics and seal selection process training. We are committed to providing the latest technologies and designs in order to provide our turbo machinery customers within global energy industries with. The original gas seal, with a design pedigree stretching back over 30 years and evolving gradually. This is essential when pumping or mixing a dangerous or toxic substance. The benefits of dry gas seals are such that conversions from traditional oil seals to dry gas seals may be advantageous to compressor operators. 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. Dry gas seals are noncontacting, dryrunning mechanical face seals that consist of a mating rotating ring and a primary stationary ring. If purge gas is lighter than air it accumulates at the top of the inner cylinder and forms a seal. An unstable condition from thermoelastic instability could result in a high wear rate of the sealing surfaces. Beyond gas savings, dry seals also yield significant operational and maintenance savings compared with wet seals. This results in a less complex system of potentially higher reliability than tandem seals. However, endusers should ask themselves several questions before deciding to retrofit.
Figure 1 shows an example of a modern centrifugal compressor. 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. The system is not accepted, hence mechanical seal preferred as they tend to seal with no visible leak. 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. This has produced a range of compressor dry gas seals and pump gas seals. 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. 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. Like packing, the mechanical seal faces must also be lubricated. What is the difference between mechanical seal and oil. Floating seal mechanical face seals is a simple product made up of two components. Mechanical contact face seal a typical example of a mechanical contact face seal is shown in figure 8. John crane gas sealsgas seals and their application for maximum reliability 2. Seals is a category that encompasses many types of seals.
The mechanical seals are designed to minimize leakage of process gas, while the compressor is pressurized and in the. Unlike an oring seal, the hydraulic diameter of a bellows seal is not a fixed geometric value. Heres an example where a paper mill replaced packing with a mechanical seal to stop leakage. The biggest benefit of using mechanical seals is the drastic reduction in leakage. 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. Dgs application rangejohn crane dgsoperating range temp. 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. Mechanical seals are typically used for pressures up to psi. They rely on the continuous contact between a rotating and fixed seat that are separated by a carbon ring refer to fig. Dry gas seals are mechanical facetype seals available as single, double and tandem models. Inadequate fuel gas pressure during start up typical conditions on inboardoutboard seal will include running. Even when leakage isnt visible, harmful vapors could be escaping. The reliability of any component is directly related to the complexity of its supporting systems. They have the added feature of providing more positive sealing during shutdown.