Compressor Seal Research Articles

Compressor seals for hydrogen recycle service

Hydrogen recycle service has presented a special challenge for centrifugal compressors and particularly the casing seals, mainly because of contamination from process gas. This feature, reproduced with permission from the Turbomachinery Laboratory, reviews a simplified process to identify the sources of contaminants affecting both dry and wet seals. It lists precautions for the application of dry seals in this service, and discusses improvements to materials used for a wet seal design. Finally, it highlights two case histories where retrofits with the improved liquid film seal have significantly reduced sour seal oil leakage rates.

An air and refrigeration machine oil console fire

An incident due to the ignition of a fire at the top of an oil console of air and refrigeration compressors caused the shut down of an ammonia plant for five days. The cause: failure of refrigeration compressor seals resulted in the lowering of the oil level in the console. This caused cavitation in the oil pump suction resulting in high vibration in the pump discharge piping which led to the snapping of a 3/4'' diameter interconnection line weld joint. Oil splashing from the snapped joint to the nearby steam header with improper insulation caused a serious fire above the oil console.

Evaluation of Floating Ring Seals for Centrifugal Compressors Using the Finite Element Method

The use of liquid ring type oil seals in centrifugal compressors was essential for high pressure applications dating back to the early 1960’s. The analysis of high pressure oil seals was first documented in the literature in the mid-1970’s following a series of compressor instability problems that made it clear that a better understanding of how seals influence the overall rotor stability was necessary. To produce compressor designs at higher speeds requires that an adequate method of predicting the oil seal influence on rotor dynamic stability be available for the designer. With the enhanced capability of personal computers and improved finite element models of the oil film thermal and hydrodynamic solutions, it is now possible to more accurately predict the dynamic characteristics of the oil seals. This paper presents a series of predicted results from a currently available advanced state of the art computer analysis for high pressure oil seals. The evaluation of several high pressure compressor seal designs illustrates the current capability for analytical predictions for various seal bore geometries. Conclusions and recommendations for the design of liquid ring seals are presented, which can give the compressor designer guidance for application to future high performance compressor liquid seal designs.

TWO- DIMENSIONAL ANALYSIS OF THIN SHELL- OR PLATE-LIKE MUFFLER ELEMENTS OF NON-UNIFORM THICKNESS

A general procedure for the analysis of curved, thin muffler elements, which can efficiently utilize the limited space in hermetically sealed compressors or compact engine installations [1], is extended to take non-uniform thickness into account. The inhomogeneous 2-D wave equation for the non-uniform thickness case is derived in two dimensional curvilinear coordinates defined on a curved surface by the application of Hamilton's principal. Four pole parameters are formulated form the pressure response solutions using the modal series expansion method and orthogonality property. The analyses of two types of curved, thin muffler elements with thickness variation in only one direction are demonstrated as examples. Analytical results are verified by comparison with the results obtained from a finite element program. Good agreement was achieved as long as the thickness of the muffler element is sufficiently small compared to the wavelength range of interest.

TWO DIMENSIONAL ANALYSIS OF THIN, SHELL OR PLATE LIKE MUFFLER ELEMENTS

A general procedure for the analysis of curved or flat, thin two dimensional muffler elements is developed. These thin elements can efficiently utilize the limited space of hermetically sealed compressors or small engine compartments. The two dimensional inhomogenous wave equation is developed in two dimensional curvilinear co-ordinates by the application of Hamilton's principle. Four pole parameters are formulated form the pressure response solutions using the modal series expansion method. The eigenvalues and transfer functions of three types of thin muffler elements connected to an anechoic pipe are given as examples: the flat rectangular box, the thin annular cylindrical shell, and the flat circular box. A verification is made by comparing results for an annular cylindrical muffler element with results obtained from a three-dimensional model; good agreement was achieved as long as the thickness of the muffler element is sufficiently small compared to the wavelength range of interest.

Dry gas seals for low and high pressure

The following article reviews test results accumulated on gas lubricated seals for compressors. The influence of various combinations of materials on the operating behaviour of the seals is also analyzed.

AE ANALYSIS OF DESTRUCTION BEHAVIOR DURING THERMAL CYCLING ON FLAME SPRAY COATINGS

Abstract Acoustic emission characterization (AE) is receiving considerable attention from the industries, due primarily to the current progress in advanced materials for using under severe environmental conditions. Recently much application has been done on wear and corrosion resistant coatings for aeroplane turbine engines, boiler tubes and so on. Especially high toughness chromium carbide coating containing nickel and chromium matrix is widely used for seals in compressors, turbines and bores of hydraulic cylinders. Till now, the coating has been performed with D-gun (detonation gun) and plasma spraying for high temperature seal. With the development of high velocity flame spraying (600m/sec. particle velocity), it has become important to compare its coating characterization with D-gun under wear and thermal cycle uses. We have used METCO DIAMOND-JET system gun to compare with D-gun system. For high velocity flame spraying, propylene as fuel and oxygen mixed gases were used. Movable electric furnace with sensor which could adjust moving velocity was used. AE signals of each and total thermal cycling were measured. Also amplitude distribution analysis was carried on. Result obtained by high velocity flame coating was better than those by D-gun on thermal cycle use.

Implanted Component Faults and Their Effects on Gas Turbine Engine Performance

Under the sponsorship of the Canadian Department of National Defence, the Engine Laboratory of the National Research Council of Canada (NRCC) has established a program for the evaluation of component deterioration on gas turbine engine performance. The effect is aimed at investigating the effects of typical in-service faults on the performance characteristics of each individual engine component. The objective of the program is the development of a generalized fault library, which will be used with fault identification techniques in the field, to reduce unscheduled maintenance. To evaluate the effects of implanted faults on the performance of a single spool engine, such as an Allison T56 turboprop engine, a series of faulted parts were installed. For this paper the following faults were analyzed: (a) first-stage turbine nozzle erosion damage; (b) first-stage turbine rotor blade untwist; (c) compressor seal wear; (d) first and second-stage compressor blade tip clearance increase. This paper describes the project objectives, the experimental installation, and the results of the fault implantation on engine performance. Discussed are performance variations on both engine and component characteristics. As the performance changes were significant, a rigorous measurement uncertainty analysis is included.

Transient Response of Floating Ring Liquid Seals

The design and analysis of pressure balanced seals are important to the designers and users of turbomachinery which require floating element seals. The design objective for compressor seals differs from that of the engineered pump seal but the common factor includes the ability to predict the dynamic response of the floating ring seal relative to the rotor shaft. Steady-state calculations can be used to study possible operating conditions for compressor designs, but they do not include accurate account of rotor shaft response and ring spin torque. In addition, engineered pump seal applications are such that the ring is expected to track shaft movement during start-up and shut-down transients when reduced pressures and leakage produce laminar flow sealing conditions. The analysis presented in this paper gives the designer the ability to evaluate seal ring dynamic transient response, including friction stick-slip on the axial sealing face and the ring spin torque interaction with the antirotation element. The analysis results presented in this paper were obtained from a personal computer program written specifically for seal transient analysis.

Determination of the fatigue resistance characteristics of valve strip for sealed compressors

Determination of the fatigue resistance characteristics of valve strip for sealed compressors

A study on the dynamic characteristics of an oil system for turbocompressors. 1st Report. Header pressure control by a new-type oil hydraulic valve.

An oil system is the equipment used to control the flow of hydraulic oil to the bearings and seals in process compressors and steam turbines. The conventional oil system, in many cases, has been controlled by pneumatically operated process control valves. It is generally difficult, however, to control the relatively rapid response of an oil hydraulic system by a pneumatically operated control system. A new-type of control valve for header pressure control was developed. The dynamic characteristics of the oil system using the new-type of valve was examined theoretically and experimentally. The effect of parameter variations on the pressure response and stability of the control valve were clarified. As a result, the stable region of this system increases with the increase of valve flow force.

SEAL OIL CONTAMINATION

OFFSHORE and remotely located gas compression trains have brought to light peculiar problems of contamination in compressor seal oil systems and, to a lesser degree, compressor lubricating oil systems. A more complex situation exists in the event that the lubricating and seal oil systems are one.

Improving the tightness of end-face seals in compressors

The working surfaces of the stationary and moving rings in end-face seals are usually finished by lapping, because other finishing processes do not ensure the desired surface characteristics -- nonparallelism within 1.5 ~ and surface finish within Ra = 0.16-0.04 p. The stationary rings are usually made of antifriction graphite-base material while the moving rings are made of 20Kh steel with a hardened case-carbufized surface of up to 0.8 mm thickness. The lapping process results in impregnation of the rings with abrasive particles (from the lapping paste) and swarf from wear of the lapping plates. Our studies showed that the depth of impregnation was 15-30 ~ for steel rings and 5-60 ~ for graphite rings. In our opinion, the abrasive particles impregnated in the ring surface during lapping cause periodic loss of tightness in end-face seals during operation. Friction and wear of the stationary and moving rings in operation result in periodic displacement of the abrasive particles. Thus, a gap is created between the mating surfaces of the rings and the Khladonoil mixture starts to leak out. The extent of leakage is usually higher than that specified by the USSR standard GOST 7475-77. After some time the dislodged abrasive particles get thrown out of the contact area under the influence of frictional and centrifugal forces, the gap between the mating surfaces is reduced, and steady-state operation with minimal leakage of Khladon-oil mixture is reestablished. The cycle is repeated when new abrasive particles are once again dislodged and start to move freely at the ring interface. At the Odeskhoiodmash plant a new process of finishing [i, 2] has been developed and introduced for machining the mating surfaces of sealing rings. This process ensures the desired parallelism and surface finish while avoiding impregnation of the machined surface with abrasive particles. The new process of finishing the working surfaces of sealing rings (microgrinding)is done with the help of an abrasive stick 4 (Fig. i) which has an oscillating motion in the direction B and a reciprocating motion in the direction C parallel to the surface which is to be machined. The stick is also given a rocking motion (in the direction A around the pivot 5) perpendicular to the directions of oscillation and reciprocation so that the tip of the stick wears out to a curved surface 3. The line of contact 2 between the stick and the component moves along the curved surface 3, while the stick rocks in the direction A. At the same time, the stick moves along a chord of the component i as a result of the reciprocating motion. The high unit pressures at the contact zone and favorable conditions for cleaning the surface by means of a cooling-lubricat

The J-Seal - Novel concept for a resilient noncontacting face seal

Turbine engine compressor seals must survive a severe environment of pressure and temperature while minimizing leakage. In addition, these seals must be tolerant to uncertainty and fluctuation in relative location of stationary and rotating members. Resilient seals overcome this uncertainty by making the stationary member flexible. Any interference is temporarily accommodated by elastic deformation, and, when the rotating member subsequently moves away, the stationary member springs back to follow it. The problem with resilient seals is to combine flexibility with strength. The J-Seal is a concept which supports the steady pressure load by membrane action, and minimizes the bending stresses which have to be supported when accommodating relative motion between stator and rotor. A design study has been performed and the resultant configuration is now at the fabrication stage. This paper describes the concept and the tradeoffs involved in its design, and presents the performance to be anticipated.

Effect of the microrelief of rubbing faces of sealed refrigeration compressors on their working life

Effect of the microrelief of rubbing faces of sealed refrigeration compressors on their working life

Lubrication of reciprocating compressor seals : P. Hanlon, Lubrication Eng., 22 (2) (1966) 50–56; 8 figs., 9 refs.

Lubrication of reciprocating compressor seals : P. Hanlon, Lubrication Eng., 22 (2) (1966) 50–56; 8 figs., 9 refs.