Mechanical Engineer''''s Reference Book 2011 Part 13 pot

Dynamics of floating systems 14/31 conditions. Now, the solution for scattered wave potential due to the stationary floating body, subjected to incident waves of potential, ~$2, is identical to that described in Section 14.5 for fixed structures. A set of linear simultaneous equations are obtained by equating the flow due to the local source plus the additional flow due to all other sources to the negative of the flow due to the undisturbed wave for each facet on the body surface. Solutions of these equations yields the unknown source strengths and, therefore, the velocity potential, bs, which is used to derive pressures and wave forces by integra- tion over the body surface. Thus the wave force vector, F, of equation (14.46) may be obtained for an incident wave of specified frequency and direction. The velocity potentials, +f> are obtained in a way similar to that above except for the use of a different boundary condition which reflects the fact that bf arises from body motions in otherwise still water. Thus, at all facets, the source strengths, +fi> are such that the flow due to the local source plus the flow due to all other sources equals the velocity component of the body along the facet normal. This velocity component will depend on the mode of motion (surge, sway, heave and SO on) in which the body is moving. All of this can be represented by equating the normal velocity of the fluid and of the jth facet for the vessel moving in its kth mode of motion. This yields the equation (14.53) where v,k is the normal velocity of the jth facet with the vessel moving in its kth mode of motion. Furthermore, nj is the normal to the jth facet, a+,lanj is the normal fluid velocity at the jth facet due to a unit source at the itb facet, and utk are the unknown source strengths required in the kth mode. Application of equation (14.53) for all facets produces a system of complex equations to be solved for the source strengths. Once these are known, the pressures at the facets are evaluated and their effects integrated over the vessel surface to yield forces in each mode of motion to unit motion in the kth mode. These forces may be written as a complex square matrix, G(w) which can be decomposed into its real and imaginary parts through the equation G(w) = w2 MA (w) - i~ BJw) (14.54) to yield frequency-dependent added mass and damping ma- trices MA(w) and Bp(w) which are required for equation (14.46). The inclusion of physical mass, hydrostatic and mooring stiffness matrices, M, K and K, completes derivation of all of the coefficient matrices of equation (14.46). The hydrodyna- mic coefficient matrices are, however, frequency dependent and require carrying out a diffraction analysis at all frequen- cies at which motions are required. Equation (14.46) is linear and can readily be solved to yield the displacement vector X. The exciting force vector F(w) and the coefficient matrices MA(w) and BJw) can also be derived using finite-element methods in a way analogous to that for the boundary-integral approach described above. There is one further point of interest regarding the relation- ship between the scattered and forced wave potentials (rnS and rnf) for a floating vessel problem. The use of equations called Haskind relations (see Newman3') enables the scattered wave potential, rnS, to be expressed in terms of the incident and forced wave potentials, I$,, and +f. Thus, once 6f is calculated, need not be computed by diffraction analysis but can ?stead be derived using the Haskind relations. $ (Tik = Vjk linearity around resonance with the heave response amplitude per unit wave amplitude reducing from 4.88 mim at 1 m wave amplitude to 1.26 mim ai 6 m wave amplitude. The vessel motion response away from resonance is not significantly affected, although there is some increase in response around 16-19 s due to the corresponding increase in wave force amplitude at these periods. The large change in the unit heave response at and around resonance is to be expected, since the damping force in a vibratory system is dominant at resonance. 14.6.6 Diffraction theory Calculations of wave-induced motions of a large non-space frame structure in gravity waves requires a solution of the wave problem with no flow boundary conditions at the moving body surface in addition to the free surface and sea-bed boundary conditions. The solution can be split into two related problems - the scattering wave problem defines wave forces on a floating body when fixed in space and with waves incident on it in an identical manner to the technique for computing wave forces on a fixed body described in Section 14.4. The radiation wave problem is concerned with defining forces on the body (added mass and damping) due to its oscillation in otherwise still water. These oscillations will induce wave potentials such that the total wave potential in the fluid is the sum of the incident, +,,,> scattered, &, and forced wave potentials. rnf2 so that 4 = $w + dh + rnf (14.50) and these must satisfy the boundary conditions at the body surface given by (14.51) where V,q is the velocity of the body surface in the direction n normal to the surface. This boundary condition can be applied at the mean body surface since the theory is applied for small motions. +> together with its three components. It must also satisfy thle Laplace equation and the free surface and sea-bed boundary conditions. Furthermore, and $f must satisfy the radiation conditions. Boundary conditions for the scattering and radiation wave problem:j can be split up from equation (14.51) as a@,, J0s 1 -+-=o aH oln and d@f dn respectively, both being applied on the body surface. The scattering problem is identical to the application of diffraction theory on fixed structures as described in Section 14.4. The radiation problem can also be solved by using either boundary-integral or boundary-element techniques. For brev- ity, only the solution using boundary-integral techniques is describesd here. As in Section 14 4, the analysis assumes inviscid, irrotational flow and that wave amplitudes are small. The unsteady flow around the floating vessel is calculated by introducing oscillating sources of unknown velocity potential on the vessel's submerged surface that is discretized by a mesh of facets with an oscillating source on the surface of each facet. A Green's function is used to represent the velocity poten- tial of each source which, because of the form of the Green's function. satisfies Laplace's equation, zero flow at the hori- zontal sea bed, the free surface and radiation boundary (14.52) ~ __ - "in 14/32 Offshore engineering 0.6 - Figure 14.32 Facet discretization of a submerged ship hull for diffraction theory -0.6 Typical results of a boundary integral diffraction analysis for a ship-shaped hull are shown in Figure 14.33. The discretiza- tion of the submerged hull geometry is shown in Figure 14.32 using 277 triangular facets on the ship half-hull. The vessel is of 263.7 m overall length, 40.8 m beam and 145 937 t displacement with 14.80 m draught floating in deep water. Figure 14.33(a) presents the variation of added mass and radiation damping coefficients with frequency for heave and pitch motions. Note that the variation in added mass is relatively small but the radiation damping shows large changes with very small values at some wave periods. Wave-induced heave force and pitching moments and the resultant motion responses for head seas are presented in Figures 14.33(b) and 14.33(c). 14.7 Design considerations and certification It is important to appreciate that the design procedures for jacket structures outlined in the previous three sections are - I e I C Y I E P x I U m > I 0 5 10 15 20 Wave period (5) (a) BO 48 36 24 12 0 Heave exciting force Pitch exciting mom amplitude (MN/m) amplitude (GN m/r ‘4 32 4 Wave period (s) (b) Heave amplitude/ wave amplitude (m/m) 1 1.01 o.*i It 4.0 3.2 2.4 1.6 0.8 0 I Pitch amplitude/ wave amplitude Wave period (5) (C) Figure 14.33 Variations of heave and pitch added masses, wave-excitation forces and motion response with wave period for ship hull Design considerations and certification 14/33 I Basic definition of configuration and marine operations procedures Naval architecture Marine operation I Procedures Routes Service fleet Fittings, etc. 1 Bids, evaluations, contractors, selection I 1 Fabrication documents I I Technical assistance at yard Figure 14.34 Design procedure for jacket structure Technical assistance at field only a small part of the total design process. In order to illustrate this point, Figure 14.34 presents a flow chart showing the design procedures that need to be followed, from the initial specification through to commencing operation of a typical offshore structure. The jacket has to have sufficient strength, as it is assembled during the fabrication stage and loaded lout of the yard. It has also to meet the naval architec- tural an,d structural requirements of tow-out, up-ending and installation as well as surviving for a 20-40-year life. Some of the supplementary design tasks not covered ifi this chapter include the response of the structure to earthquakes, the provision of corrosion protection and in-service structural monitoring. The design procedure for iarge jackets invariably contains a model test phase for critical operations such as up-ending during installation. The documentation of the material, structural and welding details of the design during its certification, fabrication and service life pose an engineering management problem. Certifying authorities play a key role in the design proced- ure for an offshore structure. The major certifying authorities in the United Kingdom, Norway and the United States have built up extensive codes of practice which reflect research 14/34 Offshore engineering work, in-service experience and the results of failure investi- gations over many years of operation (see Lloyd’s Register of Shi~ping,~’ Department of Energy,j‘ Det Norske Verita~,~~ and American Bureau of Shipping36). Certifying authorities also provide an independent check of many of the calculations and decisions that need to be made during a typical design. There tends to be close technical collaboration between research establishments, designers and the operators of off- shore structures. References 1. Department of Energy, Offshore Installations, Guidance on design and construction, Part 11, Section 4.3, HMSO, London (1986) 2. American Petroleum Institute, Basic Petroleum Databook, Volume VI, No. 3, September. API, 1220 L Street NW, Washington, DC 20005, USA (1986) 3. Lee. G. C., ‘Recent advances in design and construction of deep water platforms, Part l’, Ocean Industry, November, 71-80 (1980) platforms: design and application’, Engineering Structures, 3, July, 140-152 (1980) 5. Thornton, D., ‘A general review of future problems and their solution‘, Proceedings of the Second International Conference on Behaviour of Offshore Sfructures, 28-31 August, Paper 88, BHRA Fluid Engineering, Craufield, Bedford, UK (1979) 6. Hamilton, J. and Perrett, G. R., ‘Deep water tension leg platform designs’, Proceedings of the Royal Institution of Naval Architects International Svmuosium on Develooments in Deeoer 4. Fumes, 0. and Loset, O., ‘Shell structures in offshore 7. 8. 9. IO. 11. 12. 13 14 15 16 17 Waters, 6-7 October, Paier‘no. 10 (1986) Meteorological Office. Meteorology for mariners, 3rd edition, HMSO. London (1986) Strahler, A. N. and Strahler, A.H., Modern Physical Geography, Wiley, New York (1978) Airy, Sir G. B ‘Tides and waves’, Encyc. Metrop., Art. 192, DD. 241-396 (1845) I LI Patel, M. H.: Dynamics of Offshore Structures, Butterworth Scientific, Guildford (1989) Morrison, J. R., O’Brien, M. P., Johnson, J. W. and Schaaf, S. A., ‘The forces exerted by surface waves on piles’, Petroleum Transactions, 189, TP 2846, 149 (1950) Sarpkaya, T.; ‘In line and transverse forces on smooth and sand roughened cylinders in oscillatory flow at high Reynolds numbers’, Report No. NPS-69SL76062, Naval Postgraduate School, Monterey, California (1976) Sarpkaya, T. and Isaacson, M., Mechanics of Wave Forces on Offshore Structures, Van Nostrand Reinhold, New York (1981) Sommerfield, A,, Partial Differential Equations in Physics, Academic Press: New York (1949) Stoker, J. J., Water Waves, Interscience, New York (1957) MacCamy, R. C. and Fuchs, R. A,, ‘Wave forces on piles, a diffraction theory’, US Army Corps of Engineers, Beach Erosion Board, Tech. Memo. No. 69 (1954) Garrison. C. J. and Chow, P. Y., ‘Wave forces on submerged bodies’, Journal of Waterways, Harbours and Coastal Division, 18. 19. 20. 21. 22. 23 24 25 26 27 28 29 30 31 32 33 34 American Society of Civil Engineers, 98, No. WW3. 375-392 (1972) Eatock-Taylor, R. and Waite. J. B., ‘The dynamics of offshore structures evaluated by boundary integral techniques’. International Journal for Numerical methods in Engineering, Zienkiewicz. 0. C., Bettes, P. and Kelly. D. W., ‘The finite element method of determining fluid loading on rigid structures - two and three dimensional formulations’: in Zienkiewicz, 0. C Lewis, P. and Stass, K. G. (eds). Numerical Methods in Offshore Engineering. Wiley, Chichester ( 1978) Penzien, J. and Tseng, W. S., ‘Three dimensional dynamic analysis of fixed offshore platforms’. in Zienkiewicz, 0. C. et al. (eds). Numerical Methods in Offshore Engineering, Wiley, Chichester (1978) Bathe, K. J. and Wilson, E. L., ‘Solution methods for eigen-value problems in engineering‘, International Journal for Numerical Methods in Engineering, 6, 213-216 Malhotra. A. K. and Penzien, J., ‘Nondeterministic analysis of offshore tower structures’, Journal of Engineering Mechanics Division, American Society of Civil Engineers, 96. No. EM6. 985-1003 (1970) Poulos, H. G. and Davis, E. H., Pile Foundation Analysis and Design, Wiley, New York (1980) Reese, L. C., ‘Laterally loaded pile; program documentation‘, Journal of the Geotechnical Engineering Division, American Society of Civil Engineers. 103, No. GT4, 287-305 (1977) Focht, J. A., Jr and Kock, K. J., ‘Rational analysis of the lateral performance of offshore pile groups’, Proceedings of the Offshore Technology Conference. OTC 1896 (1973) O’Neill, M. W., Ghazzaly, 0. I. and Ho, Boo Ha, ‘Analysis of three-dimensional pile groups with nonlinear soil response and pile-soil-pile interaction’. Proceedings of the Offshore Technology Conference. OTC 2838 (1977) American Petroleum Institute, Recommended practice for planning, designing and constructing fired offshore platforms, Dallas, Texas, Rpt No. API-RP-2A (revised annually) (1987) British Standards Institution, Code of practice for fixed offshore structures, BS 6235: 1982, BSI, 2 Park Street. London, WIA 2BS Dover, W. D. and Connolly, M. P ‘Fatigue fracture mechanics assessment of tubular welded Y and K joints’, Paper No. C141186. Institution of Mechanical Engineers. London (1986) Dover, W. D. and Wilson, T. J., ‘Corrosion fatigue of tubular welded T-joints’, Paper No C136186; Institution of Mechanical Engineers, London (1986) Warburton, G. B., The Dynamical Behaviour of Structures, 2nd edition, Pergamon Press, Oxford (1976) Newman. J. N., ‘The exciting forces on fixed bodies in waves’, Journal of Ship Research, 6, 10-17 (1962) Lloyd’s Register of Shipping, Rules and regulations for the classification of mobile offshore units, January, Part IV, Chapter 1, Sections 2, 3, 4 and 5, Lloyd’s Register of Shipping, 71 Fenchurch Street, London EC3 4BS (1986) Department of Energy, Development of the oil and gas resources of the United Kingdom. Appendix 15, Department of Enerzv. HMSO (1986’1 13. 73-92 (1978) 35. Det Korske VerGas. Rules for classification of mobile offshore units, Det Norske Veritas, PO Box 300, N-1322. Hovik, Oslo, Norway (1957) 36. American Bureau of Shipping, Rules for building and classing mobile offshore drilling units, ABS, 45 Eisenhower Drive, PO Box 910, Paramus, New Jersey, USA (1987) 15 Plant engineering I L S Ernie Walker and Ronald J. Blaen (Section 15.3) John S. Bevan (Section 15.4.3) Roger C. Webster (Section 15.7-1 5.9) Conte 15.1 Compressors, fans and pumps industrial boilers 15/80 15.1.1 Design principles 15/3 15.3.4 Terminology 15/83 15.1.2 Machine selection 15/13 15.3.5 Waste-heat boilers 15/84 15.1.3 Performance monitoring and prediction 15/14 15.3.6 Economizers 15/84 15.2 Seals and 15.2.1 15.2.2 15.2.3 15.2.4 15.2.5 ct requirement for chimneys and 15.3 Boilers and waste-heat recovery 15/75 flue designs 15/89 15.3.1 Types of boilers 15/75 15.3.2 Application an pressure vessels, pipes 15.4 Heating, ventilation and air conditioning 15191 15.9.3 Sound power 151139 15.4.1 Heating 15/91 15.9.4 Addition and subtraction of decibels 15/139 15.4.2 Ventilation 15/97 15.9.5 Addition of decibels: graph method 151139 15.4.3 Air conditioning 151106 15.9.6 The relationship between SPL, SIL and 15.5 Refrigeration 151114 15.9.7 Frequency weighting and the human response SWL 151139 15.5.1 Vapour compression cycle 151115 to sound 15/140 15.5.2 Pressure-enthalpy chart 151115 15.9.8 Noise indices 151140 15.5.3 Gas refrigeration cycle 151115 15.9.9 Noise-rating curves 15/141 15.9.10 Community noise units 15/141 15.6 Energy management 151116 15.9.11 Road traffic 151141 15.6.1 The energy manager 15/116 15.9.12 Air traffic 151142 15.6.2 Energy surveys and audits 151116 15.9.13 Railway noise 151142 15.6.3 Applications 1511 18 15.9.14 Noise from demolition and construction 15.6.4 Waste-heat recovery 151122 sites 151142 15.6.5 Control systems 151123 15.9.15 Noise from industrial premises 151142 15.6.6 Summary 151124 15.9.16 Measurement of noise 151142 15.7 Condition monitoring 15/124 15.9.18 The sound-level meter 151142 15.7.1 Preventive maintenance 151124 15.9.19 Digital signal analysis 151143 15.7.2 Predictive preventive maintenance 151124 15.9.20 Noise control 15/143 15.7.3 Condition monitoring 151125 15.9.21 Noise nuisance 151143 15.7.4 The parameters 151125 15.9.22 Health effects 151144 15.7.5 Vibration monitoring for machine 15.9.23 Damage to plant/machinery/building 15.7.6 Vibration analysis techniques 151126 15.9.24 Legislation concerning the control of 15.9.17 Microphones 15/142 condition 151125 structures 151144 noise 151144 15.8 Vibration isolation and limits 151129 15.9.25 British Standard 4142: 1990 151145 15.8.1 Introduction 151129 15.9.26 Noise-abatement zones 151146 15.8.2 Damping 151130 15.9.27 Planning application conditions 151146 15.8.3 Multi-degree of freedom systems 151130 15.9.28 The Health and Safety at Work etc. Act 15.8.4 Vibration isolation 151130 1974 151146 15.8.5 Shock isolation 151131 15.9.29 The Noise at Work Regulations 1989 151146 15.8.6 Vibration attenuation 151132 15.9.30 Noise control engineering 151147 15.8.7 Measurement of vibration 151133 15.9.31 Noise-reduction principles 151147 15.8.8 Vibration limits 15/136 15.9.32 Absorbers 151148 15.9.33 Vibration isolation 151148 15.9 Acoustic noise 151138 15.9.34 Practical applications 151149 15.9.1 Introduction - basic acoustics 151138 15.9.2 Sound intensity 151139 References 151150 15.1 Compressors, fans and pumps 15.1.1 Design principles 15.1 .I .1 General Compressors, fans and pumps are all devices for increasing the pressure energy of the fluid involved. Two basic types are used: rotodynamic, where flow is continuous, and positive displacement. where fluid is worked on in discrete packages defined by machine geometry. Compressors, fans and pumps may be rotodynamic, and compressors and pumps positive displacement. In general, the positive displacement machines give low mass flow and high pressure rise. 15.1.1.2 Rotodynamic machine principles These can be discussed together as the Euler equation applies to all types, differences being due to the fluid involved and the flow path. Figure 15.1 illustrates flow path differences. 15.1.1.3 Forms of the Euler equation Standard turbomachinery textbooks (see Turton') derive this equation, so it will be applied here to centrifugal and axial machines. Considering Figure 15.2 (a simple centrifugal pump) the specific energy increase is given by the Euler equation gH = 112vu2 - UlVU, (15.1) where u,, u2 are peripheral velocities (=wr) Vuz, Vu, are the peripheral components of the absolute velocities V2 and V,, respectively (see Figure 15.3). Vul 11s usually considered as zero in design flow conditions, gHIDEAL = u2 Vu2 (15.2) SO Radial Mixed Axial Figure 15.1 Flow paths used in rotodynamic machines Compressors, fans and pumps 1513 Figure 15.2 A simple radial outflow machine Inlet velocity VI = vR1 u1 curved blade / blade % Outlet velocity triangles v 0 (b) Figure 15.3 The effect of outlet angle on machine performance 15/4 Plant engineering or (15.3) Qu2 '42 or when rotational speed is constant, gH1DE.u = Ki - K2Q (15.4) with K2 depending on pz. Figure 15.3 shows how varying p2 affects both velocity diagrams and the gH to Q plot of performance plots, compressors being affected at lower flows by surge as discussed later. A simple axial machine is shown in Figure 15.4, with typical general velocity diagrams, which define the geometry and terms used: gHIDEAL = u[vuZ - vull (15.5) or if Vul = 0 (zero inlet whirl) as assumed for pumps of fans: gHIDEAL = uvu2 (15.6) gHlDEAL = U'i - - cot& or gHIDEAL = uvA2 (15.7) VA2 is a function of Q and flow area and pz is related to blade angles. For compressors, as Horlock' and Turton' show, (15.8) and for axial machines, this is usually written (15.9) _- A' - Cp AT = u (~VU) P and the velocity diagrams combine, as shown in Figure 15.5, on a common base. 15.1.1.4 Definitions of efficiency In all these machines efficiency statements are used: Power to fluid Power to shaft Overall efficiency vo = (15.10) Actual energy rise Euler energy rise Hydraulic efficiency vH = (15.11) Delivered flow Flow passing through rotor Volumetric efficiency 7" = (15.12) Mechanical efficiency qM = (15.13) Thus 70 = vM vV vH (15.14) Fluid power Input shaft power 15.1.1.5 Reaction This is defined for a compressor as: Energy change due to or resulting from static pressure change in the rotor Total change in the stage R= (5.15) For an axial compressor 50% reaction means a symmetrical velocity diagram as shown in Figure 15.5. Figure 15.4 Axial flow pump or compressor stage and the 'ideal' velocity triangles Figure 15.5 Axial velocity triangles based on a common base for an axial stage with 50% reaction (Vl = W,; V, = Wl) Compressors, fans and pumps 15/5 If a simple pump is considered, it is possible to state that there must be a working relation between the power input P, the flow rate 0, energy rise gH, fluid properties p and p, and size of the machine D. If a dimensional analysis is performed it can be shown that a working relation may exist between a group of non-dimensional quantities in the following equation: Term (1) is a power coefficient which does not carry any conventional symbol. Term (2) can easily be shown to have the shape V/Uand is called a flow coefficient, the usual symbol being 8. Term (3) similarly can be shown to be gH/U2 and is usually k.nown as a head coefficieat (or specific coefficient) 4. Term (4) is effectively a Reynolds number with the velocity the peripheral speed wD and the characteristic dimension being usually the maximum impeller diameter. Term (5) is effectively a Mach number, since K is the fluid modulus. Since these groups in the SI system are non-dimensional they can be used to present the results of tests of pumps in a family of pumps that are geometrically similar and dyna- mically similar. This may be done as shown in Figures 15.6 and 15.7 and Figure 15.8 shows how the effect of changing speed or diameter of a pump impeller may be predicted. using the scaling 1,iws: P p3D5 ~ Const Q wD3 = (:Onst (15.17) t 02 Qi a Figure 15.8 Prediction of speed change effect using equations (1 5.17) In Figure 15.8 points A define the energy rise gHand power PI at a flow rate 01, when the pump is driven at speed w,. If equations (15.17) are applied, D and p being the same. QJwlD3 = Q2/w2D3; hence Q2 gHJw{D2 = gH2/w$D2; hence gH2 PJpw:D5 = Pdpw2Ds; hence P2 This approximate approach needs to be modified in practice to give accurate results, for using model tests to predict full size power, as discussed by codes such as the American Hydraulic Institute standard^.'^ The classical approach to the problem of characterizing the performance of a pump without including its dimensions was discussed by Addi~on,~ who proposed that a pump of standardized size will deliver energy at the rate of one horsepower when generating a head of one foot when it is driven at a speed called the Specific Speed: N-\/75 Ns= K- ~314 ( 15. 18) The constant K contains fluid density and a correction factor, and it has been customary to suppress K and use the equation: (15.19) Figure 15.6 A pump characteristic for constant rotational speed h Power coeff Pc Figure 15.7 A non-dimensional plo‘c lor a pump Caution is needed in using data as the units depend on the system of dimensions used, variations being litres/minute, cubic metres/second, gallons per minute or US gallons per minute as well a metres or feet. Plots of efficiency against specific speed are in all textbooks based upon the classic Worthington plot, and Figure 15.9, based on this information, has been prepared using a non-dimensional statement known as the characteristic number (15.20) This is based on the flow and specific energy produced by the pump at its best efficiency point of performance following the approach stated by Wisli~enus:~ ‘Any fixed value of the specific speed describes a combination of operating conditions that permits similar flow conditions in geometrically similar hydrodynamic machines.’ Figure 15.10 presents, on the basis of the Characteristic number, the typical impeller profiles, velocity triangle shapes and characteristic curves to be expected from the machine flow paths shown. In the figure the characteristic ordinates are [...]... also specify instrumentation and test rig layout BS 848: Part li4gives methods of standardized testing and also of prediction when models are used and of allowance for compressibility Since fan noise is important in ventilation systems BS 848: Part 214 lays down noise-testing techniques and gives details of test chambers and site provisions The two parts form an essential item of fan test provision, and... adjacent metal parts - particularly the dynamic surface The better the finish, the less wear will occur; 0.4 pm (16 p in) R, on the shaft and 1.6 pm (64 p in) R, on the stuffing box bore should be ideal for most applications The use of shaft sleeves can give considerable maintenance advantage when considering the question of surface finish 3 The danger of extreme running clearances at the gland particularly... thus propagates round the blade row, in the opposite direction to rotation, at about half the rotational speed Reference 2 gives more detailed discussion Figure 15.31 shows the total limitations on the compressor surge line and mass flow rate of stall and choking For detailed discussion, textbooks such as those by Horlock’ and Balje” may be consulted f / increasing air content Figure 15.28 Effect of... back-pull out pumps I S 0 519911 covers all aspects, including testing, seals, bearings, noise and vibration, and lists all the relevant I S 0 and related BS 5316 standards, among which Part 1 (for general-duty class C pumps) and Part 2 (for class B Compressors, fans CISCHARGE DISCHARGE CONNECTING CR t and pumps 15/15 / HYDRAULIC FLUID ADJUSTABLE BYPASS VALVE / PLUNGER (a) t DIAPHRAGM SUCTION (b) t Figure... or laminated elastomer proofed cloth, are still popular for relatively slow-moving, lower-pressure reciprocating pumps handling water or LP steam One particular design, with a moulded, doublebevelled section, made from semimetallic rubberized yarn, is particularly effective on rotary applications dealing with viscous media which solidify when the pump is idle and cause damage to conventional plaited... greater quantity The appropriate packing section to use in relation to diameter is open to a degree of individual preference but broad recommendations are shown in Table 15.5 To give an idea of the capabilities of the various materials and constructions of soft packings which are readily available, reference may be made to Table 15.6 (suitability in different media/speed and temperature limits) Table 15.7... up to 400°C may be considered If a good performance is to be obtained, then close attention must be paid to mechanical conditions such as shaft run-out and finish Care in fitting and running-in is also mandatory Expanded graphite foil is the most recent and significant application of graphite, particularly in the context of valve applications Expanded graphite materials combine the wellestablished thermal... for total head, +8% for flow rate and t8% for input power This allows customers to have confidence in the published curves Similar provisions will be found in the American Hydraulic Institute Standards .13 If the pump is to follow API 610 these standards must be satisfied Where the liquid to be pumped is not water it is common practice to test on cold water and to predict the performance to he expected... typical characteristics as a function of k, (Turton’) Compressors, fans and pumps 15/7 Crank Connecting Discharge Plunger 4 1 I ? Crokhead guide 90 r- / Take-up I Packing I Cylinder I t Suction Figure 15 .13 A plunger pump (or piston pump) of strokes per unit time Similarly, the spur-gear device (Figure 15.14) traps a fixed quantity in the space between adjacent teeth and the casing, and total flow rate... provisions for standardized rig layout and instrumentation and methods of presenting data in a standardized way Corrections for compressibility and methods of performance prediction are all given BS 1571: Part 116 lays down provisions for testing positive displacement compressors of all the common types in use, both in packaged form and other installations All the standards give lists of British Standards . oscillations will induce wave potentials such that the total wave potential in the fluid is the sum of the incident, +,,,> scattered, &, and forced wave potentials. rnf2 so that. the operators of off- shore structures. References 1. Department of Energy, Offshore Installations, Guidance on design and construction, Part 11, Section 4.3, HMSO, London (1986). Institution of Mechanical Engineers. London (1986) Dover, W. D. and Wilson, T. J., ‘Corrosion fatigue of tubular welded T-joints’, Paper No C136186; Institution of Mechanical Engineers,