Who has the specific operating procedures for dry gas sealing?

After the dry gas seal system is installed, before mounting the seal body, clean instrument air or low-pressure nitrogen at a pressure of 0.4–0.6 MPa should be supplied through the G1 and G2 flange ports for continuous purging for 4 to 6 hours or more. This process continues until a fine cloth is placed against the outlet and blown therefor for more than 5 minutes; if no dust, oil, moisture, or other impurities can be seen under close inspection, then the system is considered qualified. After purging, close all valves and put it in standby mode. 1. Open all normally open pressure tapping valves in the system, and activate on-site pressure gauges, transmitters, etc. 2. At least ten minutes before the start of oil transportation, please introduce the backflow isolation gas, and then turn on V8, V9 (or V10, V11) in sequence ； For the upstream and downstream valves of the S01 and S02 sonic orifice plate assemblies, isolate gas is supplied after they are put into operation. Similarly, the rear isolation gas can be turned off only after the oil transportation has stopped for ten minutes and there is no oil flow in the return oil line. 3. Before introducing process gas to the compressor or conducting a leak test, primary sealing gas should be supplied first; sequentially open valves V6, V5, V2, V1 (or V4, V3) to introduce the primary sealing gas source, and set PDICA-2882 to 0.2 MPa in the control system at the control room ； On-site observation shows that the reading of pressure gauge PI-2882 should be 0.2 MPa higher than the pressure in the balance line. When the compressor is shut down, the inlet to the primary seal can be closed only after all gas inside the machine has been exhausted. 4. After the primary seal gas is put into use, activate the flare or high-point vent line, and then introduce the secondary seal gas. Open valves V14, V18, V15, and V19 respectively to activate the flare lines for the primary seal discharge chamber ； Subsequently, the upstream and downstream valves of the SO3 and SO4 orifice plate assemblies were opened to introduce air under high and low pressure for secondary sealing. 5. Set the upper and lower limit alarm values for the flow rate of the primary sealing discharge pipelines at the high and low pressure ends of FIA-2881 and 2882 on the control system in the control room, as well as the interlock value for the high-limit alarm of the pressure switch (three-out-of-two) ； PDIA-2881: Upper limit alarm value for the differential pressure of the primary seal filter; PDICA-2882: Lower limit alarm value for the differential pressure between the primary seal gas and the balance tube, etc ； As well as the settings for starting the vehicle and interlock shutdown conditions, etc. (see the alarm and interlock condition logic diagram). (III) Alarm and handling measures: 1. After starting the machine, once the intake air under the secondary seal is stable, if the flow values indicated by the flow meters FIA-2881 and 2882 reach their upper limit, it indicates that there is excessive leakage from the primary seal. If such upper limit alarms persist and cause the corresponding pressure switches (using a three-out-of-two logic) to emit high-level alarm signals, it means that the primary seal at that end is damaged, and the machine should be shut down via interlock ； The appearance of a lower limit alarm indicates that the leakage rate of the secondary seal is too high. 2. When PDICA-2882 ≤ 0.08 MPa, it indicates that the inlet pressure for the primary seal is too low; the cause should be identified promptly and the air supply pressure increased to ensure the safe operation of the seal. 4. When the pointer on the header of filter F5 (or F6) is in the red area, it indicates that the filter element is clogged and needs to be replaced. Similarly, when the reading displayed by the PDT-2881 differential pressure transmitter is ≥60 KPa (triggering an alarm in the control room’s DCS), it means that the filter elements of F1, F3 (or F2, F4) are clogged and require replacement. (IV) Precautions: 1. At least ten minutes before the start of oil transportation, introduce the backpressure isolation gas ； Similarly, the backflow isolation gas can only be turned off after the oil transport has been stopped for at least ten minutes and it is confirmed that there is no oil flow in the return oil pipeline. Once oil transportation begins, the backflow isolation gas cannot be stopped, otherwise it will damage the seal. 2. Before introducing gas into the compression unit, primary seal gas must be supplied first to prevent unfiltered gas from escaping inside the unit and contaminating the primary seal surface ； Only after the compressor is shut down and the gas inside is completely exhausted can the inlet to the primary seal be closed. 3. When putting the filter into use, first slowly open the ball valve downstream of the filter, and then slowly open the ball valve upstream, to prevent rapid opening of the ball valves on either side of the filter from causing an instantaneous pressure surge that could damage the filter elements. Under normal operating conditions, the service life of the filter elements is up to one year. 4. When replacing the filter element, slowly open the ball valves upstream and downstream of the spare filter first to activate it. Then close the ball valves upstream and downstream of the filter that requires a filter element replacement, in order to replace the filter element. (Before replacing the filter elements of F1–F4 filters, which are used for filtering the primary sealing gas supply, it is necessary to open the bottom valve to release the pressure inside the filter chamber; thereafter, the terminal fitting must be loosened in order to remove the housing and replace the filter elements.) 5. Before starting the compressor, it is permissible to do so only when the values displayed by FIA-2881 and 2882 are greater than 4.5 Nm3/h, and the value displayed by PDICA-2882 is greater than 0.08 MPa; all other conditions must also be met. 6. When preparing to shut down the compressor, the primary seal gas supply should be switched as soon as possible to 10.5 MPaG of fresh hydrogen ； After the compressor is shut down, the pressure inside the unit should be released promptly to prevent the pressure from exceeding that of the primary sealing gas, which could lead to backflow of gas and contamination of the seals. 7. Regularly open the rear sealing condensate valves at P1 and P2 to check for any oil contamination and drain it, in order to ensure the safe operation of the seals. 8. Conduct at least two routine inspections of the sealing system devices daily. Pay special attention to whether the pressure of the primary sealing gas, as well as the pressures of the secondary sealing gas and the backflow isolation gas, are stable and meet the required standards; check whether the filters are clogged, whether the readings of the rotameters are stable, and whether the readings of the differential pressure transmitters are within acceptable limits or trigger alarm signals. 9. The spiral groove dry gas seal rotates in one direction only; therefore, reverse rotation must be avoided at all costs. At the same time, long-term operation at low speeds of less than 1000 RPM should be avoided. In both cases, it is possible to damage the seal. 10. Monitor changes in seal leakage levels at all times. Changes in the leakage rate directly reflect the operating condition of the dry gas seal. There are many factors that cause changes in the leakage rate, such as fluctuations in process gas, shaft movement, surge, and changes in pressure, temperature, and velocity. As long as it does not keep rising, the sealed operation is considered normal ； However, if the leakage rate shows an increasing trend, it indicates a failure in the dry gas seal. III. Handling of the dry gas seal during emergency shutdown: When the unit shuts down urgently, the pressure at the unit’s outlet quickly equilibrates with the system pressure, resulting in no pressure difference that can sustain the seal. This leads to a lack of supply of air for the first stage of the dry gas seal, which may cause contamination of the seal surfaces and ultimately damage the dry gas seal. 1. While installing a booster pump to increase the pressure difference between the primary sealing gas and the medium inside the machine is a good solution, it requires significant investment (the booster pump has to be imported, at a cost of around 350,000 RMB), and moreover, such pumps often fail. Recently, the booster pump for the dry gas seal of the hydrogen cracking unit at Zhenhai Refining & Chemical Plant failed after being used for only a short time. After several emergency stops, the dry gas seal was not damaged, and to date, there has been no damage to the dry gas seal due to the absence of a booster pump; therefore, after discussion, it was decided not to add one. 2. Change the nitrogen line in the machine room from 1.8 MPa to 3.0 MPa, so that once the unit is depressurized to an appropriate pressure, nitrogen can be used promptly as the primary sealing gas. 3. To ensure that the operator can maintain a pressure release rate of no more than 0.8 MPa/min, it is recommended to install an additional pressure gauge on the pipeline near the pressure release valve, so that the operator can easily monitor the pressure release rate.

Thank you to the original poster above for the very detailed information

The dry gas seals in our facility are from German company Bogmann; we can’t find the operating instructions right away. However, we are no longer using the first stage of process gas, and instead we are using nitrogen and air directly