2000 Hook-up Book - Spirax Sarco

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SYSTEM DESIGN 60 Steam Meters Density Compensation For accurate metering of compressible fluids such as gases and vapors, the actual flowing density must be taken into account. This is especially true in the case of steam. If the actual flowing density of the steam is different to the specified density for which the meter was originally set up or calibrated, then errors will occur. These errors can be considerable and depend on both the magnitude of difference between the specified density and the actual flowing density, and the type of meter being used. Example: The steam meter is set up and calibrated for 100 psig (specific volume = 3.89 ft3 /lb) The steam is actually running at a pressure of 85 psig (specific volume = 4.44 ft3 /lb). a. Differential Pressure Device (e.g. Orifice Plate or Gilflo Meter) Error = s.v. actual [ -1 x 100 √ s.v. specified Error = 4.44 [ -1 x 100 √ 3.89 Error = 6.8 Therefore the meter will over read by 6.8% b. Velocity Device (e.g. Vortex Meter) [ [ Error = s.v. actual -1 x 100 s.v. specified Error = 4.44 -1 x 100 3.89 Error = 14 Therefore the meter will over read by 14% [ In the case of saturated steam, pressure and temperature are related and therefore to establish the flowing density of saturated steam, either pressure or temperature should be measured. In the case of superheated steam, pressure and temperature can vary independently from one another and therefore to compensate for changes in density of superheated steam, both pressure and temperature must be measured. [ [ [ Installation Ninety percent of all metering failures or problems are installation related. Care should be taken to ensure that not only is the meter selected suitable for the application, but that the steam is correctly conditioned both to improve meter performance and provide a degree of protection, and that the manufacturer’s recommendations regarding installation are carefully followed. Steam Conditioning For accurate metering of saturated steam, irrespective of the meter type or manufacturer, it is important to condition the steam so that it is in the form of, or as close as possible to, a dry gas. This can be achieved by correct steam engineering and adequate trapping to Steam Separator Thermostatic Air Vent Figure 62 Steam Conditioning Station Isolating Valve Strainer reduce the annular film of water that clings to the pipe wall, and effective separation ahead of the meter to remove much of the entrained droplets of water. It is therefore recommended that a steam conditioning station (as shown in Fig. 62) is positioned upstream of any type of meter on saturated steam applications. This will enhance accuracy and protect the meter from the effects of water droplets impacting at high velocity. Good steam engineering such as the use of eccentric reducers, effective insulation and adequate trapping will also prevent the dangerous effects of high velocity slugs of water known as waterhammer which can not only destroy meters but will also damage any valves or fittings in it’s path. Float & Thermostatic Steam Trap Check Valve Steam to Meter
Meter Location Meters need to be installed in defined lengths of straight pipe to ensure accurate and repeatable performance. These pipe lengths are usually described in terms of the number of pipe diameters upstream and downstream of the meter. For example, an Orifice Plate with a Beta ratio of 0.7 installed after a 90° bend requires a minimum of 28 pipe diameters of straight pipe upstream and 7 downstream. If the pipe diameter is 6", this is equivalent to 14 feet upstream and 3-1/2 feet downstream. If the meter is located downstream of two 90º bends in different planes, then the minimum straight length required upstream of the meter is 62 pipe diameters or thirty one feet. This can be difficult to achieve, particularly in fairly complex pipework systems, and there may not in fact be a location that allows these criteria to be met. This is an important consideration when selecting a meter. Table 19 shows the minimum piping requirements for Orifice Plates as laid down in the US standard ASME MFC-3M together with the manufacturers recommendations for vortex and spring loaded variable area meters. See Figures II-93, 94, 95, 96 (pages 131 and 132). Steam Meters Table 19: Recommended Minimum Straight Lengths (D) for Various Meter Types On Upstream (inlet) side of the primary device Downstream Meter Type ß Single Two 90° Bends Two or more 90° Bends Reducer Expander Globe Valve Gate Valve All Fittings Ratio (3) 90° Bend Same Plane Different Planes 2D to D 0.5D to D Fully Open Fully Open in this table Orifice Plate 0.30 10 16 34 5 16 18 12 5 Orifice Plate 0.35 12 16 36 5 16 18 12 5 Orifice Plate 0.40 14 18 36 5 16 20 12 6 Orifice Plate 0.45 14 18 38 5 17 20 12 6 Orifice Plate 0.50 14 20 40 6 18 22 12 6 Orifice Plate 0.55 16 22 44 8 20 24 14 6 Orifice Plate 0.60 18 26 48 9 22 26 14 7 Orifice Plate 0.65 22 32 54 11 25 28 16 7 Orifice Plate 0.70 (4) 28 36 62 14 30 32 20 7 Orifice Plate 0.75 36 42 70 22 38 36 24 8 Orifice Plate 0.80 46 50 80 30 54 44 30 8 Vortex (1) N/A 20 - 40 20 - 40 40 10 - 20 10 - 35 50 20 - 40 5 - 10 Spiraflo (2) N/A 6 6 12 6 12 6 6 3 - 6 Gilflo (2) N/A 6 6 12 6 12 6 6 3 - 6 Gilflo SRG (2) N/A 6 6 12 6 12 6 6 3 - 6 Gilflo ILVA (2) N/A 6 6 12 6 12 6 6 3 - 6 Notes: 1. The table shows the range of straight lengths recommended by various Vortex meter manufacturers. 2. Downstream requirements are 3D and 6D when upstream are 6D and 12D respectively. 3. ß ratio = Orifice diameter (d) divided by Pipe diameter (D) 4. Most Orifice Plates are supplied with a ß ratio of around 0.7 which gives the best pressure recovery without compromising signal strength. 61 SYSTEM DESIGN
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DESIGN OF FLUID SYSTEMS HOOK-UPS
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Spirax Sarco Spirax Sarco is the re
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Section 1: System Design Informatio
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SYSTEM DESIGN 2 The Working Pressur
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SYSTEM DESIGN 4 Sizing Steam Lines
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SYSTEM DESIGN 6 Sizing Superheated
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SYSTEM DESIGN 8 Draining Steam Main
Page 16 and 17: SYSTEM DESIGN 10 Draining Steam Mai
Page 18 and 19: SYSTEM DESIGN 12 Steam Tracing The
Page 20 and 21: SYSTEM DESIGN 14 Steam Tracing Sizi
Page 22 and 23: SYSTEM DESIGN 16 Steam Tracing Trac
Page 24 and 25: SYSTEM DESIGN 18 Steam Tracing A si
Page 26 and 27: SYSTEM DESIGN 20 Pressure Reducing
Page 28 and 29: SYSTEM DESIGN 22 Parallel and Serie
Page 30 and 31: SYSTEM DESIGN 24 How to Size Temper
Page 32 and 33: SYSTEM DESIGN 26 Temperature Contro
Page 38 and 39: SYSTEM DESIGN 32 Makeup Air Heating
Page 40 and 41: SYSTEM DESIGN 34 Draining Temperatu
Page 42 and 43: SYSTEM DESIGN 36 Draining Temperatu
Page 44 and 45: SYSTEM DESIGN 38 Steam Trap Selecti
Page 46 and 47: SYSTEM DESIGN 40 Steam Trap Selecti
Page 48 and 49: SYSTEM DESIGN 42 Flash Steam Flash
Page 50 and 51: SYSTEM DESIGN 44 Flash Steam Flash
Page 52 and 53: SYSTEM DESIGN 46 Condensate Recover
Page 54 and 55: SYSTEM DESIGN 48 Condensate Pumping
Page 56 and 57: SYSTEM DESIGN 50 Clean Steam Printi
Page 58 and 59: SYSTEM DESIGN 52 Clean Steam Overal
Page 60 and 61: SYSTEM DESIGN 54 Clean Steam Figure
Page 62 and 63: SYSTEM DESIGN 56 Testing Steam Trap
Page 64 and 65: SYSTEM DESIGN 58 Spira-tec Trap Lea
Page 68 and 69: SYSTEM DESIGN 62 Compressed Air Sys
Page 70 and 71: SYSTEM DESIGN 64 Compressed Air Sys
Page 72 and 73: SYSTEM DESIGN 66 Compressed Air Lin
Page 74 and 75: SYSTEM DESIGN 68 Typical Steam Cons
Page 76 and 77: SYSTEM DESIGN 70 Specific Heats and
Page 78 and 79: SYSTEM DESIGN 72 Specific Heats and
Page 80 and 81: SYSTEM DESIGN 74 Conversions To Con
Page 82 and 83: SYSTEM DESIGN 76 Flow of Water thro
Page 84 and 85: SYSTEM DESIGN 78 Moisture Content o
Page 86 and 87: SYSTEM DESIGN 80 ANSI Flange Standa
Page 89 and 90: HOOK-UP APPLICATION DIAGRAMS Sectio
Page 91 and 92: Figure II-3 Draining and Air Ventin
Page 93 and 94: Figure II-8 Draining Steam Main whe
Page 95 and 96: Figure II-12 Typical Pressure Reduc
Page 97 and 98: Figure II-16 Installation of Pressu
Page 99 and 100: Figure II-20 Typical Pneumatic Sing
Page 101 and 102: Condensate Return Steam Supply Stea
Page 103 and 104: Steam Supply Steam Supply Figure II
Page 105 and 106: Figure II-31 Temperature Control of
Page 107 and 108: Elevated or Pressurized Return P 2
Page 109 and 110: Figure II-39 Controlling Temperatur
Page 115 and 116: Figure II-50 Trapping Small Utensil
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Figure II-55 Draining and Air Venti
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Figure II-59 Air Venting and Conden
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Evaporator Pressure Figure II-64 Dr
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Figure II-68 Installation of Pump/T
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Figure II-73 Draining Small Condens
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Figure II-78 Flash Steam Recovery a
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Figure II-80 Heating Water using Re
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Figure II-82 Recovery of Flash Stea
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Figure II-84 Flash Steam Condensing
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Figure II-87 Tank Sterilization Cle
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Steam Supply Figure II-93 Typical S
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Figure II-97 Hand Operated Rotary F
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Figure II-102 Freeze Proof Safety S
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Figure II-106 Continuous Boiler Blo
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Figure II-111 Controlling Temperatu
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141
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PRODUCT INFORMATION Section 3
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Steam Traps • Balanced Pressure T
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147
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Subject Index Safety...............
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Subject Index Radiation—Baseboard
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Argentina Spirax Sarco S.A. Ruta Pa
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2000 Hook-up Book - Spirax Sarco

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