Double or dual mechanical seals are designed to ensure maximum sealing safety. The use of dry gas seals requires a system designed to supply sealing gas to the seal as a working fluid for the running gap. Stahley published 2002 engineering dry gas seals have been applied in process gas centrifugal compressors for more than 20 years. Aug 02, 2017 a continuous supply of the seal gas at steadystate conditions is essential to proper functioning of the dry gas seal. Aug 02, 2017 dry gas seals are an integral part of modern centrifugal compressors. Dry gas seal arrangement typical dry gas seal seal face of dry gas theory of noncontact lift off of stationary ring achieved by increased pressure at the taper. Dry gas seal technology has demonstrated reliability and cost savings for most applications of new compressors.
Recovery system that separates gas from the exiting sealoil before routing to the degassing tank recovered gas sent to various outlets. Gas seal vendors have strict requirements for the seali ng gas quality. 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 are becoming the most popular shaft seals for centrifugal gas compressors as they do not require a supply of oil either as a lubricant or sealing medium. Because of this, most dry gas seals have a maximum operating temperature of 177c. Dry gas sealing system retrofit boosts performance, lowers. Dry gas seal dgs systems are used throughout the process industry to provide positive shaft sealing on compressors and other rotating machines in order to prevent the release of potentially harmful gasses or substances into the surrounding atmosphere. Apr 02, 2020 a new system can be fitted with a dry gas seal from the start, if desired. The benefit of dry gas seal reduce leakage gas process reduce the complex of system support reduce failure of mechanical system reduce amout of seal oil 4. The dry gas seals employed in dresserrand centrifugal compressors represent a significant advance in shaft sealing.
Dry gas seals have been applied in process gas centrifugal compressors for more than 20 years. These standards are based on over 20 years of experience in the area of gas seal system design, drawing from actual field experience of thousands of compressors. The dry gas seal was marketed as a simple solution to seal oil system reliability issues, but in reality, when one considers all the possible process and operational related. Apr 27, 2011 common dry gas seal failures are discussed below along with their causes and remedies. Dry gas seals dgs used in ultrahigh pressure gas reinjection systems are setting a new standard in offshore, deepwater applications. These boosters meet applicable international standards e. More than 80% of centrifugal compressors today are manufactured with a dgs stahley 2001. In case of the existing compressor equips oil film seal, seal oil console shall be replaced with dry gas seal control system. A sealing gas is injected into the seal, providing the working fluid for the running gap and the seal between the atmosphere or flare system and the compressor internal process gas. This technology provides 100% sealing of the pumped. Dry gas seals 101 presentation gas compressor scribd.
The whole system for the distribution and control of the seal gas, the buffer and the separation gas is arranged in the dry gas seal control rack, containing the. Over 80 percent of centrifugal gas compressors manufactured today are equipped with dry gas seals. Dry gas seals can eliminate some of the conventional prob lems associated with seal oil systems. The backup seal may show reasonable performance under low pressure but may fail to perform under higher pressure if the primary seal fails. The application of dry gas seal system is recommended. Rely on excellence competence in compressor sealing. Dry gas seal systems for centrifugal compressors page 2 of. Dgs, the correct operation of the sealing system is. With no contacting surfaces, dry gas seals are extremely reliable, reducing downtime and unplanned maintenance expenses. Every component of a dry gas seal is designed to manage exposure to extreme conditions. Dry gas seals handbook presenting a complete guide to the technology, from gas seal operation to lessons learned from actual field experience, this practical text will help you make informed decisions regarding application, operation, and maintenance of dry gas seals.
Compressor was stopped and performed static test with low pressure nitrogen to confirm the nde seal health condition before change out as the last dry gas seal was changed one year back due to the same problem. Also, some modifications are required for the existing rotor and casing. The horsepower of the pumps vary from 25 hp to 2500 hp. A variety of sizes are made with different components to handle conditions with extreme heat or cold, unusually small contaminants, and other challenges. Process design considerations for a compressor drygas sealsystem interface.
A dry gas seal consists of a rotating, hardface mating ring with either a machined or etched circumferential spiral groove pattern and a primary stationary ring in softer ma terial. These gas seal systems are normally supplied by the compressor oem mounted adjacent to the compressor. All dry gas seals need additional protection from the process and the bearing lubrication sides of the seal history. A continuous supply of the seal gas at steadystate conditions is essential to proper functioning of the dry gas seal. Mar 23, 2019 dry gas seals may or may not provide positive gas sealing if the seal faces are damaged or distorted. The quality and composition of the sealing gas is an other issue of concern in the gas seal system design. Forsthoffer, in forsthoffers best practice handbook for rotating machinery, 2011. The seals can be arranged in single, double or tandem arrangements according to the application. Dry gas seal system design standards for centrifugal.
A convergence of technologies and experience from the trusted names in gas seal and system manufacture, application, and retrofitting, our heritage durametallic. Dry gas seals are part of our manufacturing range which are used on high speed compressors in gas and oil industries. Figure 1 from dry gas seal system design standards for. Dry gas seal manual valve bearing mechanical scribd. Dry gas seal systems the use of dry gas seals requires a system designed to supply sealing gas to the seal as a sealing and working fluid for the running gap. Liquid or dirt should not be allowed in a dry gas seal. It is a very common practice to use seal gas tapped from the compressors discharge. In some cases a retrofit to a dry gas seal can easily be justified. These mechanical seals are being installed on compressors at the tupi 4 floating production site in the lula field in. The facility has a total of 95 type 2800 dry gas seals in. Dry gas seals were introduced in the late 1960s but did not gain wide acceptance until 20 years later as the ultimate solution to compressor seal oil system problems. Dry gas seals, an alternative to isosleeve and isocarbon seals, eliminate the need for oil supply systems. Dry gas seals for compressors and auxiliary equipment, sms.
Cobey has manufactured nearly 500 dry gas seal panels and has participated as a member of the api task force responsible for writing the 1st edition of api692. Whenever a gas seal system is utilized, the design of the critical equipment by definition incorporates a separate lube oil and seal system. Processdesign considerations for a compressor drygas. 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. We are committed to providing the latest technologies and designs in order to provide our turbo machinery customers within global energy industries with. Specifying engineers sometimes do not give enough attention to the scope, definition and selection of the most appropriate gas seal type, its control system and auxiliaries for a given service application. Compressors built prior to the 1980s used earlier seal technology with varying amounts of success. Apr 15, 2008 the quality and composition of the sealing gas is an other issue of concern in the gas seal system design. The nde primary vent high pressure indicated the high leakage of the dry gas seal. We are the leadingedge service provider for dry gas seal retrofits, high end compressor seal troubleshooting, seal support engineering and world class gas conditioning systems. Dry gas seals do not require a seal oil system, eliminating both the adverse environmental impact of contaminated oil and the maintenance costs associated with oil seals. Consideration must be given during the design or retrofit phases to the separation between the liquid lube and gas seal system.
It is acknowledged that the additional equipment will increase the complexity of the system and the overall maintenance workload and this should be taken into account by individual operators when making the. The information found in dry gas seals handbook will help you make informed decisions regarding the application, operation, and maintenance of dry gas seals. In fact if oil from the shaft bearings is allowed to enter the seal it is likely to cause seal failure. A clean and dry sealing gas is injected between the inner labyrinth seal and the gas seal, providing the. Such seals are available for use with a variety of compressed systems, including in harsh environments where other seals might be prone to failure. Dry gas seal systems for centrifugal compressors page 2. Dgs application rangejohn crane dgsoperating range temp. 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. Key considerations for dry gas seal performance flow. Gaslubricated used for twenty years ago almost of the compressor use them 3.
This is essential when pumping or mixing a dangerous or toxic substance. Dry gas seal features eliminates seal oil support system reduces maintenance costs saves energy. These seals virtually eliminate leakage of the fluid or gas being handled in pumps or mixers. Dry gas seals for pumps instead od usual end seals in pumps, we propose to install dry gas end seals. Alternative solution sealoilgas separation and recoveryuse simple process of separating sealoil and entrained gas with the gas routed to recovery andor use. There are two basic types of gas seal systems differential pressure d p control and flow control. Jun 19, 2014 cobey has manufactured nearly 500 dry gas seal panels and has participated as a member of the api task force responsible for writing the 1st edition of api692. As a result, both the refinerys initial investment and its ongoing operating costs were reduced. Transitions to a traditional liquid seal in the event of the loss of barrier gas and recovers to a gas seal upon restoring the barrier gas compact flush mount design that does not require modification of the stuffing box. Dry gas seals are an integral part of modern centrifugal compressors. The alarm and shutdown devices of the seal oil system must be of reasonable range and sensitivity and. Dry seals on new compressors are now more prevalent in industrytypically cheaper than wet seals dry seal retrofits on older compressors very high in cost. A dry gas seal is in the form of a selfcontained cartridge which must be installed as a complete unit. There are two basic types of gas seal systems, differential pressure.
The dry gas seal contains temperaturelimited static seals between the seal cartridge and the casing and between the shaft sleeve and shaft. Drygas mechanical seals set a new standard in deepwater. Gas seals eliminate the need for complex and costly seal oil systems, and the ongoing maintenance associated with them. Process design considerations for a compressor drygas. Dry gas seals are noncontacting, dryrunning, mechanical face seals comprising a rotating mat ing ring and a stationary primary ring. It is also possible to retrofit to replace a seal on an existing system with this design. There are two basic types of gas seal systems differential pressure d p control. Pdf improving dry gas seal reliability researchgate. The seal gas supply pressure should be at least 50 psi 3.
Centrifugal compressor wet seals seal oil degassing and. Therefore, in hightemperature sco 2 turbines, the seal buffer gas also serves to cool the seal. What is a double seal and when to use one double seals. What is api 692 1st edition, compressor dry gas seals. The seal on the bearing side is intended as a safety seal. Dry gas sealing systems for oil sands pumping applications. A sealing gas, typically filtered process gas, is injected between the inner labyrinth seal and the gas seal, filling the liftoff void. The original patent was for kaydons tapered ramp lift geometry, a constant diameter variable depth dynamic lift design. Feb 14, 2017 every component of a dry gas seal is designed to manage exposure to extreme conditions. Drygas seals dgs used in ultrahigh pressure gasreinjection systems are setting a new standard in offshore, deepwater applications.
The oilfilm seal commonly used in earlier compressor designs has been mostly phased out by dgss. Each aesseal gas conditioning system contains the key api modules plus various enhancements derived from our own field experience, to ensure the highest degree of compressor dry gas seal reliability and longevity. In most cases the buffer gas is process gas tapped from the compressor discharge and then filtered before being fed to the seal chambers. Despite the 20year trend of increasing dry gas seal applications, and industry accepted standard for gas seal support system design does not exist. Dry gas seal technology for compressors equipped with dry gas seals dgs, the correct operation of the sealing system is mandatory.
High quality compressor dry gas seal support systems engineered to customer requirements for all seal configurations and applications. The function of a gas seal system is naturally the same as a liquid seal system. Centrifugal compressor wet seals seal oil degassing and control. This book presents a complete guide to the technology, from the principle of gas seal operation to lessons learned from actual field experience. The function of a gas seal system is to continuously supply clean and dry seal gas to each dry gas seal. Inadequate fuel gas pressure during start up typical conditions on inboardoutboard seal will include running.
Dec 28, 2006 the dry gas seals employed in dresserrand centrifugal compressors represent a significant advance in shaft sealing. Prevents oil contamination dry gas seal features operation seal reverse rotation short periods of reverse rotation can be tolerated without damage but should be avoided bidirectional seal designs are available. Centrifugal compressor wet seals seal oil degassing. Double seals provide a level of safetyzero emissions compliance not possible with single seals. The primary ring is radially restrained but can move in the axial direction. Pdf dry gas seal system design standards for centrifugal. A dry gas seal is a type of mechanical seal used to contain gases without incursion from contaminants or inadvertent release of the gas into the surrounding environment. Inboard of the dry gas seal is an inner labyrinth seal, which separates the process gas from the gas seal. The function of a fluid seal system, remembering that a fluid can be a liquid or a gas. John crane gas sealsgas seals and their application for maximum reliability 2. Flowserve also gave support control back to the customer by providing stepbystep guidelines, enabling the refinery to directly manage the entire process. The parasitic power losses caused by oil shear and drag are also absent with gas seals. Compressed gas properties and conditions should also be carefully considered when specifying a dry gas seal and designing the seal system. These gas seal systems are normally supplied by the compressor oem mounted on the compressor base plate.
Processdesign considerations for a compressor drygas sealsystem interface chung leong, independent consultant, and sanjiv goyal, fluor enterprises ments. Field applications of dry gas seal designs were completed in 1952. Despite the 20year trend of increasing dry gas seal applications, an industry accepted standard for gas seal support system design does not exist. Dry gas seal mechanical seal manufacturers seals leak.
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