Gas Proportioners - Back Pressure Compensated

Transcription

1 Gas Proportioners - Back Pressure Compensated G To blend two or three gases in homogeneous infinitely variable concentrations, directly at the end use point, this instrument is unsurpassed in convenience and economy. Gas Proportioners pay for themselves since they eliminate the need for expensive custom blended gas mixtures. They lend flexibility and economy to the utilization of component gas cylinders and piped-in supply lines. Another advantage in laboratory investigations is the freedom to reproducibility increase or decrease concentrations during the course of an experiment. The flowrates are not affected by downstream pressure variations as long as back pressures do not approach or exceed the input pressure. Input pressures of up to 200 psig (13.8 bars) can be used; however, customers very often find 50 psig (3.45 bars) a convenient setting to work with. Design Features * Blending of two or three gases with gas proportioners obviates the need for: -ordering fixed gas mixtures, -contamination from reusable gas cylinders, -potentially inaccurate mixtures by gas suppliers * Rib-guided or fluted metering tubes facilitate stable, accurate readings. * OPTIGRAD scales minimize parallax and eye fatigue. * Interchangeability of flowtubes and floats. Assorted flowtubes may be used in conjunction with a single mounting frame, an apparent benefit in many laboratory applications. * Simple means of panel mounting. Panel mounting is convertible to bench mounting through the use of an optional acrylic tripod base with spirit leveler. F L OW METERS F L OW C O N T RO L S

2 Built-in Valves Meters are available with built-in needle valves (CV ), high precision metering valves (MFV ) with non-rising stems, or with no valves. The higher cost of MFV valves is justified whenever high sensitivity control and resolution are desirable particularly in conjunction with metering tubes of very low flowrates. A choice of six MFV flow capacities are offered (see Table 10) to be matched with individual flowmeter ranges. Specifications Standard Component Materials of Construction s: Heavy walled borosilicate glass. Mounting fittings in contact with gases: Black anodized aluminum, or 316 stainless steel. Side Panels: Aluminum, black anodized. Front shield and back plate: 1/8 thick clear polycarbonate and white acrylics. G Accuracy: ±2% of full scale reading, from 10 to 100% of scale. Conforming to ISA RP Specification 2-S-10. Component Repeatability: ±0.25% Typical calibration curves for air at 50 psig/3.5 bars using glass floats are available. Consult the company on the availability of calibration data for non-hazardous gases and special individual calibrations. Max Operating Pressure: 200 psig/13.8 bars. Max Operating 0 0 Temperature: 250 F/121 C. s * Precision fabricated from heavy walled, shock resistant borosilicate glass. * Bores are uniformly tapered or formed with internal rib-guides or flutes. * Floats are retained by TFE plugs. * Self cleaning. * Low differential pressures that stay independent of flow rate changes. O-rings and packing: Buna-N O-rings in aluminum models. Viton-A O-rings in stainless steel meters. Viton packings. PTFE/Kalrez optional. Connections: 1/8 NPT female inlet and outlet connections. Optional hose and compression fittings are available(see page 16). Table 19 - Gas Proportioned Options Model Number of Material of Number* Component Valve Options End Fittings Gases CV MFV In Fluid contact 2G yes aluminum 2G04 2 yes -- aluminum 2G yes 316 stainless steel 2G24 2 yes stainless steel 3G yes aluminum 3G04 3 yes -- aluminum 3G yes 316 stainless steel 3G24 3 yes stainless steel *Select flowtubes from Table 20 and also Tables 4 and 6. Table 20 - Typical Flow Capacities at 50 psig/3.5 bars inlet pressure Air Air Number [std. ml/min] Number [std.ml/min] G G G G G G G G G 2008 Bench mounting acrylic tripod bases are optional. When ordering please specify: 1. Model number (see Table 19) 2. numbers. 3. Options, i.e. Acrylic Tripods: TPG for two and TPH for three component gases.

3 How To Order P xp T xt S G Select the desired flowmeters style, including the choice of end fitting materials and valve options from appropriate catalog pages. Flowmeters are shipped with optional built-in valves installed at the inlets (bottom blocks), unless otherwise instructed. For vacuum service it is recommended that the valves should be positioned at the outlets of meters. Gas proportioners are designed with valves in the upper blocks, downstream from individual flowtubes for component gases. In manifolded multiple tube meters, valves are in the block opposite from the manifolded one (i.e. if manifolding is at the inlet, valves are in the outlet block, and vice versa). Frame Typical 150 mm Frame and Assembly Select flowtubes from Tables 4, 5, 6, 7 or 8. For nonstandard conditions and fluids follow the sizing procedures outlined on page 7. If direct reading scales are desired, Table 8 (page 11) represents typical air and water direct reading flowtubes, consult the company for a complete listing of available direct reading scales. When ordering flowtube subassemblies only, indicate the flowtube numbers including the float suffix. When ordering complete flowmeters it is important to specify frames, flowtube numbers and floats as shown in example below. Two floats may be installed in a flowtube. Assembly Flowmeter Product Code: / Size Code: Make Selection From Catalog Material Code of Fluid Contact Fittings: Black Anodized Aluminum Chrome Plated Brass 316 Stainless Steel Teflon PTFE Valve Option Code: No Valve High Precision Metering Valve (MFV ) Needle Valve (CV ) Size Code: 150 mm 65mm Options: Select From Tables 4, 5, 6, 7 and 8 or list of Direct Reading Scales Scale Code: Select From Tables 4, 5, 6, 7 and 8 list of Direct Reading Scales Float Code: Glass (black) Sappire (red) 316 Stainless Steel Carboloy (tungsten carbide) Tantalum G S ST C T Example: P 0 4 / G Teflon - Reg. trademark of DuPont Carboloy - Reg. trademark of General Electric Co.

4 Meter Sizing Flow capacity tables 4, 5, 6 and 7 are based on calibrations at standard conditions, meaning psia (1 atm) pressure and 70 F (21.1 C). Tables list maximum flow rates of flowtubes. The usable range of meters is at least 10:1, often more. Thus, as a rule of thumb, to estimate the minimum metering limit divide the flow rates listed, by ten. For gases or liquids with fluid properties not greatly different from the calibration media, tables apply directly, when working pressure and temperature are also approximately standard. Where the above conditions do not apply the maximum flow rates of the metered fluids are converted to equivalent standard flow rates of air or water. To do this calculate K as shown in charts, multiply the maximum flow rate with this factor, and select the appropriate flowtube size from the Flow Capacity tables 4, 5, 6 and 7. Calculation vs. Calibration It is very important that the correction factors as calculated from the accompanying equations are used for sizing only. These relationships are greatly simplified and will not provide precise predictable flow corrections. It is always best practice to calibrate meters for non-standard conditions on site, by using reliable means of calibration. In case of liquid flows at each major point along the scale, sample volumes are collected in a buret of a volumetric flask during measured time intervals. Volumes are interpolated to a unit of time such as for example [ml/min] or [cu. ft/hr] etc. A table or a graph is then constructed to establish a complete set of calibration data. In case of gas flows, calibration data can be similarly developed, except that collection of sample volumes is accomplished by means of gas sampling devices, the simplest of which is a soap bubble meter. Table 1 - Float Densities Material Density [g/ml] glass 2.53 sapphire 3.98 stainless steel 8.04 Carboloy tantalum Gas Flow Q air =K gas X Q gas K gas = Where: G x T act T o x P o P act Q air = equiv.air flow capacity at Standard Conditions (STP) Q gas = maximum flow of metered gas G = specific gravity of metered gas (from Table 3) T act = absolute tempure at flow conditions, deg R or deg K T o = absolute temperature at Standard Conditions (STP) deg R (530) or deg K (294) P act = pressure at flow conditions, psia P o = pressure at Standard Conditions (STP), (14.7 psia) Liquid Flow Q water =K liq X Q liq K liq = Where: (d F - d W ) (d F - d L ) x d L d W Q water = equivalent water flow capacity at Standard Conditions (STP) Q liq = maximum flow of metered liquid d F = density of float selected, (see table 2), (g/ml) d L = density of metered liquid, (g/ml) d W = density of water at Standard Conditions (STP) (1.0 g/ml) Table 2 - Conversion Factors Multiply By To Obtain atm lbs/sq. in atm kg/sq. cm lbs/sq. in kg/sq. cm ml/min liters/min ml/min X 10 cu. ft/min ml/min x 10 gal/hr cu. ft/hr 472 ml/min gal/min 3785 ml/min g/ml lbs/cu. ft g/ml lbs/cu. in Table 3 - Density, Viscosity and Specific Gravity of Gases Gas Density Viscosity Specific Gravity [g/ml] [centipols] G[air=1.0] acetylene air ammonia argon butane carbon dioxide carbon monoxide chlorine ethane ethylene helium hydrogen hydrogen chloride methane nitrogen nitrous oxide oxygen propane sulfur dioxide

5 Table of Standard Flow Capacities Table 5-65mm s (See Table 8 for Gas Flow Capacities) Maximum Flow Rate Number Air Water [sml/min] [scfh] [ml/min] [gph] G Table 4-150mm s S (See Table 7 for Gas Flow Capacities) ST Maximum Flow Rate C Number Air Water T [sml/min] [scfh] [ml/min] [gph] G G S S ST ST C C T ST G G S S ST ST C C T T G G S S ST ST C C T T G G S S ST ST C C T T G G S S ST ST C C T G G S S ST ST C C T G ST G G S S ST ST C C T T G G S S ST ST C C T T G G S S ST ST C C T T * Suffix refers to float materials; G = Black Glass, S = Sapphire (red), ST = 316 Stainless Steel, C = Carboloy, T = Tantalum

6 For direct reading (engineering units) scale flowtubes contact Muis Controls. Flow capacities shown in Tables 4, 5, 6 and 7 are based air or water at STP conditions see paragraph on o on calibrations at standard (STP) conditions (70 F METER SIZING on page 4. o /21.1 C and 14.7psia / 1 atm abs). For fluids other than Table 6-150mm flowtubes, gas flow capacities of routine gases Number Maximum Flow Rate Argon Carbon Dioxide Helium Hydrogen Nitrogen Oxygen [sml/min] [scfh] [sml/min] [scfh] [sml/min] [scfh] [sml/min] [scfh] [sml/min] [scfh] [sml/min] [scfh] G S ST C T G S ST C T G S ST C T G S ST C T G S ST C T G S ST C T G S ST C T G S ST C T G S ST C T *Suffix refers to float materials: G = black glass, S = sapphire (red), ST = 316 stainless steel, C = Carboloy, T = tantalum

7 Table of Standard Capacities Table 7-65mm flowtubes, gas flow capacities of routine gases Maximum Flow Rate Number Argon Carbon Dioxide Helium Hydrogen Nitrogen Oxygen [sml/min] [scfh] [sml/min] [scfh] [sml/min] [scfh] [sml/min] [scfh] [sml/min] [scfh] [sml/min] [scfh] G S ST C T G S ST C T G S ST C T G S ST C T G S ST C T G S ST C G S ST C G ST G S ST C T G S ST C T G S ST C T *Suffix refers to float materials: G = black glass, S = sapphire (red), ST = 316 stainless steel, C = Carboloy, T = tantalum

8 Table 8 - Partial List of Direct Reading Scales (Accuracy = ± 5% F.S.) Table of Standard Capacities Air-65mm Maximum Flow Air-150mm Maximum Flow Water 65mm Maximum Flow Water 150mm Maximum Flow G 7 sml/min S 25 sml/min G 0.5 ml/min S 1 ml/min ST 50 sml/min S 50 sml/min ST 6 ml/min C 10 ml/min G 100 sml/min C 100 sml/min ST 60 ml/min ST 20 ml/min C 250 sml/min S 500 sml/min ST 115 ml/min G 50 ml/min C 500 sml/min G 800 sml/min ST 150 ml/min G 60 ml/min G 1 sl/min C 1.25 sl/min G 250 ml/min G 100 ml/min G 5 sl/min G 2.5 sl/min G 500 ml/min C 200 ml/min ST 10 sl/min S 5 sl/min ST 750 ml/min ST 500 ml/min ST 25 sl/min C 10 sl/min S 1.0 L/min ST 1.2 L/min ST 40 sl/min ST 42 sl/min ST 1.5 L/min T 2 L/min Flowmeters with dual-floats have a turndown ratio better than 20:1 KA Aluminum Kit shown Three types of kits are offered: * Model KA Aluminum Flowmeter Kit. * Model KS Stainless Steel Flowmeter Kit. * Model KT Teflon PTFE Flowmeter Kit. F L OW METERS F L OW C O N T RO L S