Standardization of systems means good clarity and simple facilities for configuration. Different versions mean that it is possible to appropriately adapt the system to the requirements. The modules can be combined as desired. Standardization also means that not all imaginable versions are included, and that special requirements such as armored cables, customer-specific documentation, specific conductor labeling, or certificates such as CE or 31B cannot be implemented at all, or not without an extra charge.
The design is divided into the following standard modules: sampling, pressure reduction, sample preparation system, SITRANS CV, gas supply, calibration gases.
General information
The set can be dimensioned for a 230 V AC or 115 V AC power supply. It is not possible to switch between supplies.
The gas connections can be supplied with either metric or imperial dimensions.
On the metric line, the gas connections are in the form of metric clamping ring glands with a diameter of 3 mm. The imperial line contains gas connections in the form of imperial clamping ring glands with a diameter of 1/8 inch. The pipes between the sampling probe, pressure reduction, sample preparation device, and SITRANS CV are optionally available. The system is generally designed for temperatures between -20 and +55 °C, in Cenelec Category 2G, T3. When provided with heating, the system can also be used down to -30 °C. The natural gas to be measured should be in a stable gaseous form, dry and clean.
Sampling probe
The basic components of a sampling probe are a lance, process connection, process isolation and, if necessary, pressure reduction. They are supplied separately for the high-pressure version.
Lance
A representative sample should be taken from the central third of the pipeline. With a lance length of 1 m it is therefore possible to extract a sample from a pipeline with a diameter of up to 1 600 mm. In addition, two versions with different types of lance diameter are available. On the one hand, a pipe whose outer diameter is 6 mm and inner diameter is 2 mm. On the other hand, a pipe whose outer diameter is 12 mm and inner diameter is 2 mm. The lance can be supplied in a permanently installed or removable state.
Process connection
There are four versions for the flange connection to the pipeline. Flange DN 65 PN16 Form C and flange ANSI 2" 300 lbs RF for pressures up to 1 600 kPa, and flange DN 65 PN160 Form C and flange ANSI 2" 2 500 lbs RF for pressures up to 16 000 kPa.
Process isolation
It may be necessary to isolate the natural gas line from the system for maintenance and repair work. To do this, you can select either a simple stop valve or a double block and bleed structure. While the stop valve is a cost-effective solution for minimum requirements, the double block and bleed structure stands for enhanced safety, as it has two valves that prevent any gas from being transferred further.
High-pressure reduction on the primary side
Pressure can be reduced in three ways: directly at the probe (primary side), in an external casing with a pressure reduction unit (primary side), or in the sample preparation system (secondary side).
If the sample preparation system and the natural gas chromatograph are installed directly next to the sampling point, the high-pressure reduction can be implemented in the sample preparation system. The pressure should always be reduced as close to the sampling point as possible in order to keep the dead volume as small as possible. The sample and calibration gas pressures must be reduced to between 10 and 500 kPa. The sample gas pressure must be at least 200 kPa less than the carrier gas pressure. The carrier gas pressure should be between 600 and 700 kPa.
Heated and unheated pressure reduction units are available in the external casing for high-pressure reduction on the primary side. Pressure reduction in the external casing is suitable for combination with the permanently installed and retractable standard probe. The heated pressure regulators have a power consumption of 150 W, and reliably maintain the sample in a gaseous state.
Special probe with high-pressure reduction
A third option offers an alternative to the two standard probes: a permanently installed probe with integrated separation of aerosols (so-called BTU diaphragm) in the pipeline and a pressure reduction unit. The lance is integrated in this at a depth of 228 mm. The protection pipe has an outer diameter of 22.8 mm. The lance and pressure reduction do not need to be separately defined.
Heated sample gas line
To ensure that the sample is maintained in a gaseous state, it is recommendable to use a heated sample gas line – for example, between the sampling point and the sample preparation system. The sample gas line is encased in a PE corrugated hose with an outer diameter of 43 mm. The self-regulating maintenance temperature remains at approximately 80 °C. The electrical connection is in the terminal box.
The power consumption is approx. 38 W/m.
Pipe base for enclosure attachment
A hot-dip galvanized 2" pipe base, 1 700 mm high, with mounting brackets and joining sheet enables free-standing mounting of the protective casing.
Sample preparation
Generally speaking, the sample pressure must be reduced to between 10 and 500 kPa. The flow should be between 20 and 100 ml/min. It is important that the pressure is 200 kPa above the carrier gas pressure. The flow should be between 20 and 100 ml/min. The carrier gas pressure should be between 600 and 700 kPa.
The basic configuration of the sample preparation system for a stream includes a stop valve, 0.5 µm filter, flowmeter for the fast loop, pressure-relief valve set to 1 000 hPa, 3/2-way solenoid valve with sealed cable for automatic switching between calibration gas and sample gas, and a terminal box for connecting the solenoid valve. This valve must either be protected by the customer at 0.5 A, or a ready-assembled terminal box with power supply and fuses can be ordered from the list of supplementary items.
There are also a number of other options for modifying the basic configuration.
Secondary pressure adjustment
The pressure adjustment unit with unheated pressure regulators can be ordered for one, two and three sample flows. This type of structure meets the minimum secondary pressure adjustment requirements. Please note that a reduction in pressure cools the sample down considerably, which can cause moisture to condense if the dew point is fallen below.
Another alternative, however, is pressure adjustment with a heated pressure regulator (150 W) for one, two or three sample streams. Heating the sample ensures that it remains in a gaseous state. The Joule-Thomson effect is thus compensated. The regulators can reduce pressures from 160 to 1 000 / 1 700 hPa.
If the pressure is to be reduced directly at the sampling probe or in an external casing outside the sample preparation system, no further pressure reduction is required during sample preparation.
Sample injection
Where sample injection is concerned, straightforward and safety versions are available for between one and three streams.
Considered simply, sample injection is carried out for one, two or three streams using one solenoid valve per sample stream (cascade connection). Its job is to block any gas flows that are not required without preventing the desired gas from flowing. A 0.5 A fuse is required per solenoid valve and flowmeter. These are available in the ready-assembled terminal box.
The safety version of the sample injection system for one, two or three streams with double block and bleed technology enables the sample to be switched over, which in turn allows clean separation between gas streams by partially closing and venting the line. Since two valves are used to prevent the flow of gas that is not to be measured, rather than just one, the functional safety of the system remains at an optimum level for a long time. In addition, 0.5 A fuses are required for the sample valves and calibration valve. These are included in the electrical connection (supplementary item).
Monitoring the sample flow to the gas chromatograph
The sample flow to the SITRANS CV can also be monitored electronically as an option. An alarm signal is output when necessary. A switch disconnector for the power supply is also required; this can be ordered along with the ready-assembled terminal box.
Protective casing/mounting plate for sample preparation system
The sample preparation system is available mounted either on a plate, in the protective casing, or in the heated protective casing.
The stainless steel mounting plate, measuring 652 x 422 x 3 mm (H x W x D), is suitable for wall mounting. The system components selected are mounted on the plate and supplied with all pipes and wires installed.
The unheated protective transmitter casing, made from fiber glass-reinforced plastic and suitable for wall mounting measures 750 x 520 x 430 mm (H x W x D) and is fitted with stainless steel hinges, quick-release locks, safety glass windows and a stainless steel mounting plate.
The system components selected are mounted and supplied with all pipes and wires installed in the protective casing.
It is also possible to provide a heater in the protective transmitter casing which can be controlled between 10 and 40 °C in steps of 5. The system components selected are mounted and supplied with all pipes and wires installed in the protective casing. The heating has a power of 300 W.
Aerosol filter/glycol filter
These filters have the task of removing any impurities that may have been introduced into the natural gases by aerosols or glycols, thus providing an additional level of safety for the SITRANS CV and, therefore, the system functionality. The aerosol filter is supplied with 5 replacement membranes and the glycol filter with 10 replacement cartridges.
Manual laboratory sampling
An additional control valve permits manual laboratory sampling as an option. When not in use, it is fitted with a blanking plug on the output end.
Pipe base for enclosure attachment
A hot-dip galvanized 2" pipe base, 1 700 mm high, with mounting brackets and joining sheet enables free-standing mounting of the protective casing or the mounting plate as an alternative to wall mounting.
Protective top cover
Another option is a protective top cover made from fiber glass-reinforced plastic and supplied with mounting brackets, for protection against solar radiation and storms. It must be mounted to a pipe base.
Heated sample gas line
To prevent condensation of the sample, it may be necessary to use a heated prepared pipeline – for example, between the sample preparation device and SITRANS CV. The sample gas line is encased in a PE corrugated hose with an outer diameter of 43 mm. The self-regulating maintenance temperature is around 80 °C.
Example of single-stream sample preparation system: may deviate from the supplied system
SITRANS CV
The SITRANS CV natural gas analyzer forms the core component of the Set CV.
The analyzer measures the concentrations of the components C1 to C9 with N2 and CO2 in less than three minutes.
The valveless live injection method is not affected by fluctuations in the sample pressure, and ensures precise injection and repeatable results.
The SITRANS CV achieves a repeatability level that is 0.01 % for the upper and lower calorific values. In addition, the live injection system contains no moving parts and is, therefore, completely maintenance-free.
The narrow-bore capillary columns offer an extremely favorable ratio between volumes and active surface, yet only require a relatively low volume flow to achieve optimum separation. The result is fast and good separating properties.
Just like the live injection system, the patented live switching system contains no moving parts and is thus also maintenance-free. This column switching offers the facility for backflushing of higher hydrocarbons.
Unlike conventional gas chromatographs, the SITRANS CV applies the principle of in-line detection. The separation quality after practically every column can be checked. In addition, all gas outlets are monitored. Changes in the system functionality can be rapidly detected and compensated.
Miniaturization, which uses what is known as MEMS (micro electromechanical systems) technology, permits unusually low minimum detection limits, such as, for example, 5 ppm for neopentane. N2 can be exactly separated from CH4 even where the concentration ratios are unfavorable. Exact N2 concentrations of up to 25 % can be determined without any problems.
A high linearity throughout the measuring range allows extremely reliable measurements. The consumption of calibration gas is minimal since the SITRANS CV works with single-point calibration. Automatic optimization of the method provides an increased accuracy and longer service life.
The SITRANS CV uses the measured concentrations of the gas components to calculate natural gas parameters: the upper and lower calorific values, standard density and Wobbe index in accordance with DIN ISO 6976, GHOST 2267 or AGA 8. The unit stores the daily averages of all components and the calorific values over a period of up to 100 days.
Operating the SITRANS CV via the CV Control software is simple, clear and quick. This has been specially developed for the natural gas market.
The SITRANS CV must be ordered separately
You can find further information on SITRANS CV under "Process gas chromatographs".
SITRANS CV system components
Protective casing/plate for SITRANS CV
The SITRANS CV is available mounted either on a plate, in the protective casing, or in the heated protective casing.
The stainless steel mounting plate, measuring 652 x 422 x 3 mm (H x W x D), is suitable for wall mounting.
The unheated protective transmitter casing, made from fiber glass-reinforced plastic and suitable for wall mounting measures 750 x 520 x 430 mm (H x W x D) and is fitted with stainless steel hinges, quick-release locks, safety glass windows and a stainless steel mounting plate.
The protective casing can also be supplied with heating as an option. The heating can be adjusted between 10 and 40 °C, in increments of 5. The system components selected are mounted and supplied with all pipes and wires installed in the protective casing. The heating has a power of 300 W.
Terminal box
There are five connection options in total to choose from.
The simplest option is the interface in accordance with SITRANS CV (open cable end).
The terminal box measuring 340 x 170 x 91 mm (H x W x D) is made from polyester resin. The scope of delivery includes terminals, isolating terminals, cable glands and a PE rail. If ordered with the pipe base add-on part, the terminal box is supplied attached to the base, and the scope of supply includes 2.5 mm terminals for connection by the customer and M16/M20 cable glands. The voltage supply is 24 V DC. The terminal box is not suitable for connecting a heater, flow meter with limit value transmitter, and Double Block and Bleed (DB&B).
The terminal box measuring 360 x 360 x 190 mm (H x W x D) is made from painted sheet steel. The scope of delivery includes switch amplifiers, terminals, and cable glands. If ordered with the pipe base add-on part, the terminal box is supplied attached to the base, and the scope of supply includes 2.5 mm terminals for connection by the customer and M16/M20 cable glands. The voltage supply is 24 V DC. The terminal box is not suitable for connecting a heater and DB&B.
The terminal box, including switch amplifier and a power supply (115 V AC or 230 V AC, not switchable), measuring 360 x 360 x 190 mm (H x W x D), is made from painted sheet steel. The scope of delivery includes terminals, 0.5 A fuses, terminals, cable glands and a PE rail. If ordered with the pipe base add-on part, the terminal box is supplied attached to the base, and the scope of supply includes 2.5 mm terminals for connection by the customer and M16/M20 cable glands. The terminal box is not suitable for using DB&B.
The terminal box, including switch amplifiers and a power supply (115 V AC or 230 V AC, not switchable), measuring 360 x 360 x 190 mm (H x W x D), is made from painted sheet steel. The scope of delivery includes isolating terminals, 0.5 A fuses, terminals, cable glands, relays and a PE rail. If ordered with the pipe base add-on part, the terminal box is supplied attached to the base, and the scope of supply includes 2.5 mm terminals for connection by the customer and M16/M20 cable glands.
Gas supply
A gas chromatograph requires calibration and carrier gases. Therefore the set offers various options with regard to gas connection, gas cylinder design, and calibration gases. Either individual components or complete systems can be ordered.
Cylinder pressure reducer, separate
The cylinder pressure reducer for calibration gases is supplied separately. It is made from stainless steel and has a cylinder connection conforming to DIN 477 No. 14 (calibration gas). The cylinder pressure reducer is also fitted with a gauge for primary and back pressure.
Contact gauge for supply gases
Two gauges with a 50 mm diameter and mounted on the battery pressure reduction station can also be ordered. The intrinsically-safe slot initiators in accordance with NAMUR must be operated via a switch amplifier. This is not included in the delivery. The line is in the terminal box on the station panel.
Heated line
A heated prepared line is available for heating the calibration gas line from the cylinder cabinet to the sample preparation device. The power consumption is 38 W/m with an outer diameter of 45 mm on the corrugated hose. The integrated heating system is self-regulating with a maintenance temperature of approximately 80 °C.
Automatic cylinder changeover switch with separate coils
The stainless steel automatic cylinder transfer station, supplied on a mounting plate, is designed for back pressures of between 500 and 10 000 hPa, and contains two coiled pipes for helium that conform to DIN 477. The maximum permissible cylinder pressure is 200 000 hPa. This version also includes a gauge for measuring primary and back pressure. A contact gauge cannot be fitted when supplied separately.
Simple supply unit
This simple supply unit consists of a hot-dip galvanized 2-inch pipe base, 2 200 mm high, with a fiber glass-reinforced plastic protective top cover as well as two cylinder holders and a cylinder changeover switch. The gas cylinders are not included in the basic scope of supply.
Painted sheet steel gas cylinder cabinet
This version is supplied with the automatic cylinder changeover switch and coils, as well as the stainless steel calibration gas cylinder pressure reducer in a sheet metal cabinet.
The gas cylinder cabinet has room for two 50 l cylinders and one 10 l calibration gas cylinder. The dimensions are 2 050 x 1 250 x 400 mm (H x W x D). It contains the cylinder station, 1 stop valve for carrier gas, cylinder holder and pipe coils for the gas cylinders. The cabinet pipes are fully installed and the cabinet is equipped with bulkhead fittings for carrier gas, calibration gas and exhaust gas from the pressure relief valves.
As an option, this gas cylinder cabinet can also be supplied with a heating sleeve for a 10 l calibration gas cylinder at 20 °C retaining temperature. The cylinder head is heated separately, in a fiber glass-reinforced plastic enclosure. The cylinder pressure reducer is also located here. The heating sleeve prevents condensation from building up in the gas cylinder. To ensure seamless gas heating, a heated line for removing the calibration gas is recommended.
Calibration gases
Four different calibration gases are available as standard.
Gas mixture 1
Mixture 1 comprises the following components:
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10 liter cylinder for purchase with DIN 477 No. 14 connections |
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Filling (150 000 hPa) |
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15.5 mol% |
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0.5 mol% |
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8 mol% |
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0.5 mol% |
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0.15 mol% |
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0.15 mol% |
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0.08 mol% |
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0.08 mol% |
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0.08 mol% |
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0.05 mol% in methane (around 75 mol%) |
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± 5% in the range 0.1 ... 0.25 mol% |
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± 1% in the range 0.25 ... 1 mol% |
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± 0.5% in the range 1 ... 10 mol% |
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± 0.20% in the range 10 ... 100 mol% |
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Min. storage temperature |
-10 °C |
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Stability |
36 months |
Gas mixture 2
Mixture 2 comprises the following components:
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10 liter cylinder for purchase with DIN 477 No. 14 connections |
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Filling (76 000 hPa) |
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5 mol% |
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2 mol% |
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4 mol% |
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2 mol% |
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0.5 mol% |
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0.5 mol% |
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0.3 mol% |
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0.3 mol% |
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0.3 mol% |
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0.1 mol% in methane (around 85 mol%) |
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± 5 % in the range 0.1 ... 0.25 mol% |
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± 1 % in the range 0.25 ... 1 mol% |
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± 0.5 % in the range 1 ... 10 mol% |
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± 0.20 % in the range 10 ... 100 mol% |
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Min. storage temperature |
0 ... 5 °C |
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Stability |
36 months |
Gas mixture 3
Mixture 3 comprises the following components:
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10 liter cylinder for purchase with DIN 477 No. 14 connections |
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Filling (150 000 hPa) |
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2.5 mol% |
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0.1 mol% |
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0.5 mol% |
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0.15 mol% |
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0.03 mol% |
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0.03 mol% |
|
0.03 mol% |
|
0.03 mol% |
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0.03 mol% |
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0.015 mol% in methane (around 96.5 mol%) |
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± 5% in the range 0.1 ... 0.25 mol% |
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± 1% in the range 0.25 ... 1 mol% |
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± 0.5% in the range 1 ... 10 mol% |
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± 0.20% in the range 10 ... 100 mol% |
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|
Min. storage temperature |
-20 °C |
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Stability |
36 months |
Gas mixture 4
This gas mixture is composed individually. For this reason, a component range is specified below.
Mixture 4 comprises the following components:
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10 liter cylinder for purchase with DIN 477 No. 14 connections |
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Filling (exact composition specified) |
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2.5 ... 15.5 mol% |
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0.1 ... 2 mol% |
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0.5 ... 8 mol% |
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0.15 ... 2 mol% |
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0.03 ... 0.5 mol% |
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0.03 ... 0.5 mol% |
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0.03 ... 0.3 mol% |
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0.03 ... 0.3 mol% |
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0.03 ... 0.3 mol% |
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0.015 ... 0.1 mol% in methane (around 75 ... 96.5 mol%) |
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± 5 % in the range 0.1 ... 0.25 mol% |
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± 1% in the range 0.25 ... 1 mol% |
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± 0.5 % in the range 1 ... 10 mol% |
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± 0.20 % in the range 10 ... 100 mol% |
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The precise values for the composition within the specified limits is required.
PTB-certified version SITRANS CV Set
One version of the Set CV described above has been tested by the Physikalisch Technisch Bundesanstalt (PTB, German Technical Inspectorate) and approved for fiscal metering.
The SITRANS CV Set version approved for fiscal metering consists of a single-stream sample preparation system with stop valve, unheated pressure regulator, 0.5 m filter, DB&B 3/2-way solenoid valves, flowmeter with limit signal transmitter, fitted on a mounting plate and pipe base. The SITRANS CV is also fitted on a mounting plate and pipe base. Further components are a terminal box and the CV Control natural gas analyzer software. This certified version is also designed for indoor installation. The room temperature should not fall below 5 °C or exceed 55 °C. The certificate does not include a DSFG interface or mass storage unit.
The SITRANS CV must be ordered separately.