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Dry Gas Seal

dry gas seals for high-pressure gas injection compressors.

by:Lepu Seal     2019-11-06
The growing global demand for oil and the continued rise in oil prices have prompted oil companies to develop new oilfield resources.
However, exploration has also increased costs in terms of technology.
Many of these projects have a common demand that natural gas related to crude oil must be redeveloped
Inject thereservoirs.
The required injection pressure can reach a value of up to 800bar (11,600 psi).
Advanced Superhigh-
The pressure centrifugal compressor covers this application.
Sealing Solution for machine spindle seal based on well-
Verified dry gas seal (DGS)technology.
This article describes the use for extremely high-
Gas injection pressure service.
It provides a summary of the R & D and qualification program for these als and explains the design features and operational limitations.
In order to meet the global demand for energy, leading oil companies are increasing their investment.
A typical example is the exploration of the tenggzi and kasagan fields in the Caspian Sea region.
The Kashagan field, one of the largest in nearly 30 years, is estimated to have an oil recovery rate of 13 billion barrels.
The technical challenge of Onemajor is to compress the relevant highly corrosive acidic gas to the ultra-high-Re-stressinjection.
Compressor set consisting of three centrifugal compressors driven by 30-
MW gas turbine to ensure high
Pressure service.
Based on expectations of growing demand for supermarketshigh-
Pneumatic shaft oil seal, EagleBurgmann, 1996, started the anR & D project to develop the dry gas sealing technology extremepressures, 2000, a joint project sponsored by the European Union, the theMethod project.
The project partners include the Royal University of England, GE Oil and gas and igbergman.
The purpose of this method is to evaluate the feasibility of apressure operating DGS at 560 bar (8,120 psi).
Gained valuable insights from this project on the special requirements of DGS operating under extreme conditions.
On 2005, EagleBurgmann, at the invitation of GE Oil and Gas, participated in the DGS qualification program operated at the 425 bar (6,160 psi).
Gas-operating conditions
The compressor group consisting of three centrifugal compressors performs jet service at extremely high pressure (LR MRHP)
Driven by a gas turbine.
Table 1 shows typical design conditions for dry gas seals.
Seal design status-of-the-
The artistic sealing system of the natural gas compressor is a series dry gas seal with an intermediate maze. The seal (Figure 1)
Consists of two continuous single seals.
In normal operation, the pressure is reduced through the sealing surface of the main seal (1)
The torch pressure is slightly higher than the atmospheric pressure.
Secondary seal (2)
Run under torch pressure, but can run under full process pressure in case of failure.
Main seal supply filter process gas (Connection A).
Inert gas (N2)
Connect the C application.
The pressure to block the gas is slightly higher than the pressure of the torch (Connection B)
, Thus obtaining the flow of gas through the maze along the direction of the torch.
The leakage of the main seal is directed to the torch, which prevents the leakage of the process gas into the atmosphere. [
Figure 1 slightly]
In order to prevent the sealing element material from squeezing, the extrusion gap should be as small as possible.
The function ap is the gap between the balance sleeve and the support ring (Figure2).
However, free movement must be ensured under all operating conditions.
The design of the function gap must not exceed the weight of MM.
This very small gap value is a severe challenge in manufacturing, as changes in clearance height must be ignored under the influence of temperature and pressure.
In order to achieve this goal, a wide range of FE-
Calculations were made before the design was finalized. [
Figure 2:At ultra-
Under high pressure, not only in the radial direction, but also in the axial direction, the action of the Pneumatic load on the DGS will produce great force.
To ensure the maximum stability of DGS under such a high load, Cross
The part of the metal sleeve in the sealed box must be greater than the part that works under lower pressure.
Low standard design
And intermediatepressure-
Range DGS, using a sleeve design with an adapter sleeve assembled above the sleeve (Figure 3a).
If only one sleeve is usedhigh-
Pressure DGS, relatively small crossover
The section is too weak for high axial loads.
Therefore, in the Superhigh-
Pressure design with separate sleeves (Figure 3b)
Ensure maximum stability of DGS. [
Figure 3a omitted][
Figure 3b omitted]
The final seal design is shown in figure 4.
The seal is designed with the shaft diameter of 140mm. [
Figure 4 slightly]
Theoretical Evaluation has carried out extensive calculation and analysis in the process of development
Pressure compressor seal.
Focus on three different areas: 1)
Detailed features of sealing surface design related to primary ring and mating ring (e. g.
Make taper, Groove design, tuning steps, etc. ); 2)
Structural Analysis of main sealing parts under sealing gas pressureand3)
Define the detailed design of the two component support rings and carbide sleeves for the extrusion clearance.
Some of the detail features of the rotating and stationary rings are essentially the result of the computational analysis, specifically the design of the grooves, tuning steps, and the manufacture of cones.
The basic analysis tool is a coupled fluid-
Structural Solver designed for mechanical seal analysis.
In any sealing design, the overall goal is to maintain optimal sealing performance and safe operation under all operating conditions.
However, sealing design can be a problem when there are extreme operating conditions and a large number of design parameters must be handled.
Also, there are very few isolated influences on me. e.
Single change-
Design parameters usually affect all important performance parameters.
Moreover, the effect is often contradictory.
For example, while increasing the initial taper will essentially improve the lift-
At the same time, the thermal film stiffness and sealing performance will deteriorate at the maximum speed.
Figure 5a and 5b in p-
Ndomain, for the operation of using methane as a sealed gas.
Only a comprehensive view can provide the necessary information to confirm or exclude the design.
This visualization of the results data provides a comprehensive investigation of the behavior of the most relevant sealing parameters or sealing performance.
Therefore, it is easy to find weak points and insufficient security.
It is clear that a single outcome parameter is not sufficient to evaluate a proposed design.
Obviously, start.
Rising at maximum pressure is the most serious running state since the running gap reached its lowest value.
The test must prove that the design value is still large enough to avoid the radial friction marks caused by the small gap size. [
Figure 5a omitted][
Figure 5b omitted]
Essentially, the groove design controls the properties of the housing.
Unfortunately, one may not just choose a design with considerable safety margin at low speed and under maximum pressure.
This design will definitely lead to high speed and high leakage rate. Pressure level.
Anyseal design, which is especially suitable for high
Therefore, the performance seal must consider all the necessary operating conditions as well as possible.
By comparing the leakage values calculated and measured, the predicted high accuracy is proved.
The predicted leakage value under the main operating conditions is very good compared to the leakage value measured in the actual test.
Deviation less 【+ or-]15%.
In order to prove their structural integrity, a wide theoretical evaluation of their core parts was carried out. TheFinite-Element-
Analysis using ANSYS. Axis-
Symmetric modeling is applied. Inboard seal (IB)
And outboard seal (OB)
Single configuration is analyzed using linear and nonlinear
Linear material models, respectively.
The goal is to evaluate the stress distribution and deflection under several loads such as \"static conditions\", \"normal dynamic operation\" and \"failure operation of sealing surface.
For example, Figure 6 shows the yon Misesstress distribution for \"running normally.
\"It was found that the stress levels in all regions were significantly lower than rp0. 2 (
[ForInconel 850 N/mm2R]
718 under precipitation heating conditions).
A small area with a high stress level was found at the inner flange angle of the shaft sleeve.
However, it does not damage the mechanical stability of the sleeve. [
Figure 6 slightly]
Pay special attention to the extrusion gap behavior at the dynamic secondary seal (Figure 2).
The extrusion gap is the radial distance between the outer diameter of the carbide sleeve and the inner diameter of the support ring corresponding to the hydraulic diameter (Figure 7).
On the one hand, this gap must be small enough to avoid the extrusion of the four fluorine element, on the other hand, it must be large enough to avoid the contact between the two parts, the sleeve and the support ring. [
Figure 7 Slightly]
Since the sleeve and the bracket use the same material, the thermal expansion rate of the two components will be the same.
The goal now is to find an optimal design that allows for a minimum change in the gap size under all loading conditions.
Two important facts must be considered for this design: 1)
There will be a relative axial movement between the sleeve and the support ring, which will change the direction on the sleeve and significantly affect the deflection; and, 2)
The tensile stress inside the sleeve must not exceed the defined limit.
According to the customer\'s specifications, the sealed box was tested in the EagleBurgmann test facility with a maximum pressure of 425 bar.
Different operating conditions were simulated in several test steps.
After each test step, check the seal. As a follow-
EagleBurgmann store test, one month-
Daily verification and endurance testing were carried out at the facility of the compression manufacturer.
Two seals in a superhigh-
Pressure compressor.
Table 2 shows the entire qualification process.
The test at the EagleBurgmann store is at a high
The maximum pressure is 425 bar, the maximum speed is 12,373 r/min, and the speed test is strict.
The test gas is a mixture of air and Helium/air.
Slow scrolling test at 1,000 r/min.
To simulate the axial displacement between the sealing housing and the shaft, the hydraulic piston is integrated.
The sensor measures the axial displacement.
To monitor the temperature in the sealed box, a thermocouple wire was installed in several locations.
The typical test results of the in-board sealing test are shown in figure 8. [
Figure 8:
Extensive validation tests were carried out in the facilities of the compression manufacturer.
The compressor is operated with pure methane. During the 16-
During the day test, including several downtime and start-up of the compressor, the performance of the seal has been within the expected range and is very stable.
Summary of the test procedure performed on the dry gas seal designed for ultra-high-
The pressure compressor shows the challenge in this high seal
Pressure levels can be achieved with DGS technology.
Based on this experience, seals can be manufactured for the design pressure of 450 bar.
However, EagleBurgmann is there to develop the high quality of the project
The pressure seal raises the maximum pressure limit to 550 bar, ensuring optimal reliability even within this pressure range.
Bibliography: A. calculation and analysis method of dry gas sealLaxander, K. Lang, R. Johannes (2005)
, Dynamic Sealing, advanced topics and technical solutions for Poitiers workshops.
A. principle and design of mechanical sealO. Lebeck (1991)
Published by John Willie & Sons, New York.
\"2005 financial and operational reviews\", ExxonMobil (2006)
Irving, Texas.
\"Size of the seal--
Bergman DGS for compressors (2001)
\"The brochure of Bergman Industry Co. , Ltd.
Wolfratshausen, KG. By Drs.
Peter Droescher Sattler, Andreas Schruefer andArmin Laxander, EagleBurgmann industries, Dr, Germany.
Peter Droescher is the engineering compressor seal manager.
He received a degree in mechanical engineering from Munich University of Applied Science.
During his 20 years at EagleBurgmann, he has gained a wealth of knowledge in mechanical sealing technology.
Contact viaAnita la fond for constructive communication, Inc. , 973-992-
0715, alafond @ building communications. com. Dr.
Michael Sattler is vice president of Global Application Engineering.
He has 20 years of professional experience including all aspects of dry gas sealing and sealing control units for compressors such as product management, marketing, Application Engineering, commissioning and trouble shooting.
In 1989, he joined EagleBurgmann after receiving a degree in industrial engineering from the University of Applied Science in Munich. Dr.
Andreas Schruefer is a senior R & D expert. He has a Ph. D.
Degree in dry gas sealing technology.
He was employed by atEagleBurgmann for the month.
He is good at mechanical seal development, from pump seal, mixer/mixer seal to compressor seal.
In the past few years,
Schruefer has been focusing on high
Development of crystal diamond coating for pressure drying gas sealing technology and mechanical sealing. Dr.
Amin Laxander is a senior engineer in R & D. Dr.
He received his PhD. D.
Received a degree in aerospace engineering at Stuttgart University in 1996.
After holding multiple positions in the aerospace industry, he joined EagleBurgmann in 2002 for numerical analysis of dry gas seals.
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