This chart shows an example of one type of tandem seal with leak rates ranging between 0. 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. Outboard of the dry gas seal is a barrier seal, which separates the gas seal from the compressor shaft bearings fig. Key considerations for dry gas seal performance flow. Centrifugal compressor wet seals seal oil degassing and control. Dgs application rangejohn crane dgsoperating range temp. Symbols a area of sliding face a h area hydraulically loaded by medium pressure b width of sliding face.
This greatly increases reliability and reduces seal maintenance to a minimum. The outboard labyrinth reduces warm seal gas leakage to the process side. Dry gas seals operate with clearances measured in microns, much less than the thickness of a human hair. On the rotating ring surface instead we find some grooves having a particular shape. Many continue to operate well with wet seals as originally specified.
This was the firstradial lip seal to be press fitinto an outside diameter od bore. Generalized dry gas seal dgs as used in process gas compressors. The seal faces are the elements that define the sealing interface. Apr 27, 2011 common dry gas seal failures are discussed below along with their causes and remedies. A booster package provides a small amount of gas flow when the. For a more complete description of dry gas seal principles of operation, see shah 1988. Dry gas seals handbook top results of your surfing dry gas seals handbook start download portable document format pdf and ebooks electronic books free online rating news 20162017 is books that can provide inspiration, insight, knowledge to the reader. The seal faces must allow for rotation as well as other motions experienced in the pump. 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 noncontacting, dry running, mechanical face seals comprising a. However, dry gas seals figure 1 are prevalent in new installations.
The inboard labyrinth, on one hand, provides an additional seal between the process and. If r744 is at a pressure higher than the triple point and it reduces to a pressure below the triple point for example to atmospheric pressure, it will deposit directly to solid. Typical wet gas seal leakage ranges from 40 to 200 scfm for a beam type compressor. These gas seal systems are normally supplied by the compressor oem mounted adjacent to the compressor. Seal face stationary seat secondary seals spring other metal parts except seal cover and shaft sleeve direction of rotation of the mechanical seal type n and k type c is also the spring winding direction r clockwise looking from the stationary seat toward the seal face looking from the drive side with the shaft. Dry seals, which use highpressure gas to seal the compressor, emit less natural gas up to 6 scfm for a two seal system, have lower power requirements, improve. Suited for engineers, operators, maintenance personnel, purchasing personnel and technical management,this book presents a complete guide to the technology, from the principle of gas seal operation. John crane training john crane mechanical seals, seal. Turbomachinery sealing solutions flowserve corporation.
In the late 1920s, a self contained shaft seal was created from oil resistant leather assembled into a metal case. Dgs, the correct operation of the sealing system is. The dry gas seal and compressor manufacturers instructions should be strictly followed when installing, commissioning, operating, and maintaining dry gas seals and their support systems. Engineers operators maintenance personnel purchasing personnel technical management the information found in dry gas seals handbook will help you make informed decisions regarding the. Aug 02, 2017 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. This book presents a complete guide to the technology, from the principle of gas seal operation to lessons learned from actual field experience. The separation gas should be filtered to 5 microns solid particles and should be 99. Aug 02, 2017 the materials for the dry gas seal faces, secondary sealing elements and metallic components must be suitable for all operating conditions and the gas composition of the application. 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.
Dry gas seals are noncontacting, dryrunning, mechanical face seals comprising a rotating mat. The other seal face will be mounted into and stationary with the gland. Scribd is the worlds largest social reading and publishing site. John crane gas sealsgas seals and their application for maximum reliability 2. Dry gas seal systems for centrifugal compressors page 3 of.
Dry gas seals, an alternative to isosleeve and isocarbon seals, eliminate the need for oil supply systems. 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. As an example, the following factors deserve consideration when selecting the dry gas seals for centrifugal compressors in liquefied natural gas lng service. The installed separation seal is not securely separating the bearing oil from the dry gas seal. The information found in this handbook will help to make informed decisions regarding the application, operation, and maintenance of dry gas seals. It is a book which should be at the fingertips of all engineers concerned with mechanical seals. While primary function carried out by the two options is almost the same, there are diversifications in the scope of the search performed by each. In some cases a retrofit to a dry gas seal can easily be justified. The turboexpander dry gas seal consists of the conventional dry gas seal mating ring and primary ring, an outboard labyrinth, an inboard labyrinth, and the cavity to be vented, if desired. The following procedures are provided as general guidelines only.
Dry gas seals dry gas seals, an alternative to isosleeve and isocarbon seals, eliminate the need for oil supply systems. Dry gas seal handbook is a practical text which provides a vast amount of solid and well tested guidance. Pdf dry gas seals handbook download read online free. Inboard of the dry gas seal is an inner labyrinth seal, which separates the process gas from the gas seal. Dry gas seals are in used in compressor stations, processing plants, refineries, chemical plants, and more. Mechanical seals according to en 12756 code system for single mechanical seals there is a distinction drawn between standard n and short k types. Such seals are available for use with a variety of compressed systems, including in harsh environments where other seals might be prone to failure. Alternative solution sealoilgas separation and recoveryuse simple process of separating sealoil and entrained gas with the gas routed to recovery andor use. The sationary ring has a flat and smooth inner surface which is located just opposite to the rotating one. Dry gas compressor seals piyush shah group manager, type gas. Robert flitney, in seals and sealing handbook sixth edition, 2014.
Dry gas seal applications for high pressure youtube. Dry gas seals are designed with many of the basic characteristics of liquid mechanical seals and can therefore be potentially subject to similar failure modes. Dry gas seal manual valve bearing mechanical scribd. Learning is through an effective blend of classroom theory sessions and practical handson exercises. One seal face will be mounted onto and rotating with the shaft. Features of our gaspac dry gas seal line include innovative solutions to hang up, reverse rotation, reverse pressurization, and centering of rotating components. Inadequate fuel gas pressure during start up typical conditions on inboardoutboard seal will include running. Recovery system that separates gas from the exiting sealoil before routing to the degassing tank recovered gas sent to various outlets. Elliott dry gas buffer systems are designed to api 614 standards. 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 issues, its complexity rivals that of the oil systems. A safer alternative to natural gas is dry, inert nitrogen gas which can be generated on site from standard compressed air. The most significantdevelopment in the evolution of the radial lip seal happened toward the end of world war ii. Compressors built prior to the 1980s used earlier seal technology with varying amounts of success.
It is not unusual to find large process gas machines still in service four or more decades after commissioning. Mechanical seal technology and selection eagleburgmann. Feb 14, 2017 a dry gas seal creates a film of gas between a rotating seat and a stationary face. Double dry gas seal systems as compared to tandem systems eliminate the following. The advantages of dry gas seals over wet seal systems can be defined as follows. Despite the fact that the use of dry gas seals in process gas centrifugal compressors has increased dramatically over the last. Dry gas seals are noncontacting, dryrunning, mechanical face seals comprising a rotating mat ing ring and a stationary primary.
Dry gas seal technology has demonstrated reliability and cost savings for most applications of new compressors. The nde primary vent high pressure indicated the high leakage of the dry gas seal. For double mechanical seals backtoback en specifies the short type only. An stable and complete layer of lubrication greatly affects the performance. Components dry gas seals dry gas seals, an alternative to isosleeve and isocarbon seals, eliminate the need for oil supply systems. Replacing wet seals with dry seals in centrifugal compressors pdf.
For example, the lubricating gas that is normally used to pressurize the seal is natural gas. Dry gas seals for compressors and auxiliary equipment, sms. May 11, 2020 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. 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. Dry gas seal systems for centrifugal compressors page 5 of. Feb 01, 2017 multistage pumps for light hydrocarbons how to ensure you get the best pump for the service duration. Forsthoffers best practice handbook for rotating machinery. While dry gas seals can be very problematic if not. Seal faces can be lubricated by the process fluid or, with double mechanical seals, by a proper auxiliary fluid see chapter relevant to configurations. When the compressor is not running and depressurised the two rings touch each other because the springs behind. Ebook dry gas seals handbook as pdf download portable. Despite the fact that the use of dry gas seals in process gas centrifugal compressors has increased dramatically over the last 20 years, the technology remains misunderstood by many in the industry. Download as pdf report of dry gas seals handbook to search for words within a dry gas seals handbook pdf dossier you can use the search dry gas seals handbook pdf window or a find toolbar.
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