COMPACT MEASURING APPLIANCE AND METHOD FOR DETECTING HYDROCARBONS

Abstract

A measuring appliance for determining a hydrocarbon concentration in compressed air comprises a housing and the following components arranged in the housing: a main gas line with an inlet for the compressed air, and three additional gas lines, the first branching from the main gas line for compressed air to be measured, the first line connecting the main line to a first switchable valve. The second gas line branches from the main gas line, for reference compressed air, and connects the main gas line to the first switchable valve. The third gas line connects the first switchable valve to a sensor unit and includes copper. A reference gas unit is arranged in the second gas line and contains an oxidation catalyst in which the reference compressed air is produced from the compressed air. A pressure controller is arranged in the main gas line for ensuring a constant through-flow of the compressed air in the range from 3 to 16 bar. The appliance further includes a pressure measuring device arranged upstream of the sensor unit a temperature sensor arranged downstream of the sensor unit, and a cooling apparatus for cooling the reference gas unit.

Claims

1. A measuring appliance for determining a hydrocarbon concentration in compressed air comprising a housing and the following components arranged in the housing, the measuring appliance comprising: a main gas line with an inlet for the compressed air, a first gas line branching off from the main gas line for a compressed air to be measured, wherein the first gas line connects the main gas line to a first switchable valve, a second gas line for a reference compressed air branches off from the main gas line, wherein the second gas line connects the main gas line to the first switchable valve, a third gas line comprising copper connecting the first switchable valve to a sensor unit, wherein the sensor unit has a photoionization detector with a measurement chamber, a reference gas unit arranged in the second gas line containing an oxidation catalyst, in which the reference compressed air is generated from the compressed air, a pressure controller arranged in the main gas line for ensuring a constant through-flow of compressed air ranging from 3 to 16 bar, a pressure measuring appliance arranged upstream of the sensor unit for determining a pressure of the respective compressed air flowing into the sensor unit, a temperature sensor arranged downstream of the sensor unit for determining a temperature of the respective compressed air leaving the sensor unit, and a cooling device for cooling the reference gas unit.

2. The measuring appliance according to claim 1, further comprising a second switchable valve arranged in the third gas line downstream of the first switchable valve.

3. The measuring appliance according to claim 2, wherein the first and the second switchable valve are solenoid valves.

4. The measuring appliance according to claim 2, further comprising a pressure switch arranged in the third gas line between the second valve and the pressure measuring appliance.

5. The measuring appliance according to claim 1, wherein the measurement chamber is funnel-shaped.

6. The measuring appliance according to claim 1, wherein the cooling device for cooling the reference gas unit is configured as a fan so that ambient air flows into the housing and heated air flows out of the interior space of the housing.

7. The measuring appliance according to claim 1, wherein the measuring appliance further includes an evaluation unit.

8. The measuring appliance according to claim 1, comprising a further pressure measuring appliance arranged in the main gas line downstream of the pressure controller.

9. The measuring appliance according to claim 1, comprising a safety belt arranged in the main gas line downstream of the pressure controller, preferably of the further pressure measuring appliance.

10. A method for determining a hydrocarbon concentration in compressed air by means of the measuring appliance according to claim 1, the method including the following steps: guiding the compressed air containing hydrocarbons into the measuring appliance and configuring a constant through-flow at a pressure ranging from 3 to 16 bar, dividing the compressed air containing hydrocarbons into a compressed air to be measured and a reference compressed air, wherein the compressed air to be measured is applied directly to a sensor unit and the reference compressed air is initially oxidized, alternately supplying the compressed air to be measured in the reference compressed air into the sensor unit at a defined interval and determining a pressure of the respective compressed air flowing into the sensor unit, determining a measurement value from a signal difference between the compressed air to be measured and the reference compressed air, and determining a temperature of the respective compressed air leaving the sensor unit.

11. The method according to claim 10, wherein the compressed air to be measured is supplied at a factor ranging from 1.5 to 5 times longer than the sensor unit.

12. The method according to claim 10, wherein a mean value is formed from a multitude of detected measurement values.

13. The method according to claim 12, wherein a floating mean value is formed from a multitude of measurement values.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The disclosure is described in the following in detail with reference to the enclosed figures. Thereby, the figures only show favourable embodiments; however, the disclosure should in no way be limited to these. The figures show:

[0049] FIG. 1: a schematic diagram of an interior space of an embodiment of the measuring appliance according to the disclosure, and

[0050] FIG. 2: a functional diagram or schematic diagram of the fluid flows of the measuring appliance.

DETAILED DESCRIPTION OF THE DRAWINGS

[0051] FIG. 1 shows an interior space of an embodiment of the measuring appliance 20 according to the disclosure for the determination of a hydrocarbon concentration in compressed air with all components arranged in a single housing 68.

[0052] The measuring appliance 20 has a main gas line 28 with an inlet 31 for the compressed air. A first gas line 38 branches off from the main gas line 28 for compressed air to be measured, wherein the first gas line 38 connects the main gas line 28 to a first switchable valve 42. Furthermore, a second gas line 46 for a reference compressed air branches off from the main gas line 28, wherein the second gas line 46 also connects the main gas line 28 to the first switchable valve 42. Furthermore, the measuring appliance has a third gas line 37 comprising copper connecting the first switchable valve 42 to a sensor unit 26.

[0053] The sensor unit 26 has a photoionization detector 40 with a measurement chamber (not shown), to which the respective compressed air is supplied.

[0054] Furthermore, a reference gas unit 30 is arranged in the second gas line 46, thereby containing an oxidation catalyst (not shown). The reference compressed air, meaning compressed air free of hydrocarbons, is generated in the reference gas unit 30 from the compressed air containing hydrocarbons. Furthermore, a pressure controller 32 is arranged in the main gas line 28 in order to ensure a constant through-flow of compressed air ranging from 3 to 16 bar.

[0055] In order to determine a pressure and a temperature of the compressed air respectively flowing into the sensor unit 26 or flowing out of the sensor unit 26, the measuring appliance 20 has a pressure measurement appliance 56 arranged upstream of the sensor unit 26, as well as a temperature sensor 62 arranged downstream of the sensor unit 26.

[0056] Furthermore, the measuring appliance has a cooling device 51, 53 for cooling the reference gas unit 30.

[0057] In the third gas line 37, a second switchable valve 44 is arranged downstream of the first switchable valve, 42, and downstream of this, a pressure switch 54 is arranged.

[0058] The reference gas unit 30 also has a temperature controller 50 with an alarm function and a cooling device for cooling composed of a fan 51, as well as an air outlet 53.

[0059] The compressed air to be measured and the reference compressed air can leave the measuring appliance 20 via silencers 52.

[0060] From FIG. 2, the functionality of the measuring appliance 20 according to the disclosure is clarified. The compressed air containing hydrocarbons is guided through the inlet 31 into the measuring appliance 20. The pressure controller 32 regulates the inflow pressure. The safety valve 36, which opens, at a pressure of 4 bar for example, follows downstream of the pressure controller 32.

[0061] The compressed air to be measured is directly supplied from the compressed air containing hydrocarbons within the main gas line 28 to the sensor unit 26 via the first gas line 38 or to the photoionization detector 40 (PID) via the first switchable valve 42 and the second switchable valve 44.

[0062] A reference compressed air is initially supplied to the reference gas unit 30 via a second gas line 46, before this is also supplied to the PID 40 via the two valves 42, 44. Provided that no reference compressed air is required, this is discharged into the environment via a silencer 52.

[0063] The reference gas unit 30 has the temperature controller 50. If the temperature of the reference compressed air exceeds a limit value, the second switchable valve 44 is closed and an alarm is issued via an alarm device 61.

[0064] Downstream of the two switchable valves 42, 44, the electromechanical pressure switch 54 is arranged, which closes the second switchable valve 44 in the event of overpressure or a negative pressure and triggers an alarm.

[0065] The temperature sensor 62 monitors the temperature of the respective compressed air in the sensor unit 26 and outputs an alarm signal upon exceeding a limit value.

[0066] Furthermore, chokes 60 are provided within the measuring appliance 20 for regulating the through-flow of the respective compressed air. Furthermore, the measuring appliance 20 has a power supply unit 45 as well as a processor with a related printed circuit board.