Maintenance of M&C SP2006-H/DIL Sampling Probe

5.2 Supply of Dilution Gas

Open the main valve of the dilution gas source and adjust the precision pressure reducing valve to the pressure specified in the injector data sheet (for example, at a typical value of 3.0 bar, the corresponding dilution gas flow rate is about 490 Nl/h and vacuum degree is -0.8 bar).

Observe the low-pressure vacuum gauge: the pointer should point below -0.6 bar (e.g. -0.7 to -0.8 bar). If the vacuum degree is insufficient (e.g. -0.5 bar), the critical orifice plate cannot function properly and the dilution ratio will change. At this point, the dilution gas pressure should be gradually increased until the vacuum degree meets the standard.

If the vacuum degree still cannot reach -0.6 bar, possible reasons may include clogged injectors, excessive resistance in the sampling outlet pipeline (too long or too thin), insufficient dilution gas pressure, incorrect or missing orifice plate installation.

5.3 Connection process

If a manual ball valve (option VA) is installed at the front end of the probe, confirm that the ball valve is in the closed state. After the dilution gas injector has stabilized, slowly open the ball valve to allow the process gas to enter the probe. Observe whether the vacuum gauge reading is stable and should not show significant fluctuations.

5.4 Calibration and dilution ratio verification

Introduce a standard gas of known concentration (such as 100% O ₂ or 100% N ₂) into the test gas interface, and the pressure of the standard gas should be greater than 0.7 bar (overcoming the opening pressure of the one-way valve).

The standard gas flow rate should be at least 3 times the flow rate through the critical orifice plate (without bypass) to ensure complete replacement of the sample gas channel.

After the downstream analyzer reading stabilizes, calculate the actual dilution ratio based on the measured value and the theoretical diluted concentration. If there is a deviation, the dilution gas pressure can be adjusted slightly (within the allowable range of -5% to+30%) for correction.

Record the dilution gas pressure and vacuum degree at this time as a reference for future operation.

Daily maintenance and typical troubleshooting

The design of SP2006-H/DIL reduces maintenance frequency, but still requires the development of periodic inspection plans based on process conditions. The following are the most commonly encountered fault phenomena and solutions.

6.1 Filter blockage

Phenomenon: The vacuum gauge reading gradually increases (e.g. from -0.8 bar to -0.5 bar), and the downstream analyzer response slows down or the concentration decreases.

Reason: Particulate matter and viscous substances in the process gas accumulate on the surface of ceramic or glass fiber filters, increasing the suction resistance.

resolvent:

Close the front ball valve (if any) and cut off the sample gas.

Remove the filter chamber cover according to section 13.4 of the manual (use the handle to rotate and loosen the clamp, and pull out the cover).

Check if the compression screw of the filter is loose, and remove the filter element.

If there is visible dust accumulation on the surface of the filter element, compressed air can be used to blow it from the inside out; If it is severely blocked or broken, replace the spare filter element directly (recommended spare parts 90S0020 ceramic 2 μ m or 90F0125 glass fiber 0.1 μ m).

Simultaneously check the sealing ring of the filter element (93S0045, Viton) ®） Replace the O-ring (93S0020) inside the cavity cover if it is deformed or hardened.

After installation, re-establish the dilution gas and observe whether the vacuum degree is restored.

Preventive suggestion: If the concentration of process dust is high, a reverse blowing function (option/BB or/BB/F) can be selected. Regularly (such as every 4 hours), 6 bar compressed air can be introduced to blow the filter in reverse, which can greatly extend the life of the filter element.

6.2 Critical orifice plate or injector blockage

Phenomenon: The dilution gas pressure is normal or even high, but the vacuum degree is very low (such as -0.2 bar), and the dilution ratio is significantly abnormal (calibration failure of standard gas).

Reason: Ammonium salts, tar, polymers and other substances in the sample gas deposit on the micropores of the orifice plate (with a diameter of only a few tens of micrometers) or the nozzle of the injector after cooling.

resolvent:

Turn off the heating, cut off the dilution gas, and wait for the probe to cool down to room temperature.

Open the FRP shell, loosen the thermal clamp and clamp, and remove the dilution block (see Figure 16).

Carefully remove the critical orifice plate and/or injector using specialized tools (randomly provided). It is strictly prohibited to use metal needles or other hard objects for mechanical dredging, as it may damage the precision hole opening.

Place the orifice plate and injector into the ultrasonic cleaner and clean with a mild cleaning agent (such as deionized water or acetone, depending on the nature of the sediment) for 10-15 minutes.

After removal, dry it with clean compressed air, check the O-ring (93S0020 or 93S0025), and replace it if it is damaged.