====== Reactor loading ======
The loading of the reactor will inevitably deteriorate over time when solvents are used inside a glovebox even if a solvent filter is used. The solvent filter just slows this process down significantly and therefore needs regular maintenance itself to protect the reactor loading. The deterioration is due to the reaction of solvent molecules with the surface of the metal based getter material beads. This is especially true for halogenated solvents like dichloromethane. Unlike the normally formed oxide layer on the getter material these inactivated surfaces (e. g. halides, etc.) cannot be regenerated by hydrogen and therefore reducing the capacity for oxygen scavenging. A worn out reactor loading shows itself through a more frequqnet need for reactor regeneration cycles.
===== Replacement of the reactor loading =====
Manuals of the glove boxes usually call for a service technician to replace the loading of the reactor because this procedure requires the dismantling of the reactor from the gas purification unit. However if a service technician is not available or an option an exemplaric procedure is hereby presented. The glove box showed is a MBraun Labstar with the MB-10 gas purification unit.
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A 2003 MBraun LABstar glove box with a MB-10 gas purification unit.
First the circulation needs to be deactivated. This will stop the blower and close the pneumatic valves. Then the glove box has to be switched off using the main power breaker. After this disconnect it from the electrical grid. This is important for safety reasons. Next remove the back and top cover plates ({{ref>topcover}} and {{ref>blower}}).
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The big wrapped cylinder in the bottom left corner is the reactor. Attached to it are two pneumatic valves and the blower ({{ref>blower}}). The blower needs to be removed next. First disconnect the cable connected to it (red arrow). The connector is hold in place with a magnetic lock. The blower itself is only attached to the system via the two flanges (green arrows). So the blower is to be removed by opening the respective clamps on the flanges.
{{:wartung:kat:annotations:no_blower.png?direct&200 |title}}
Purifier unit without the blower and a plugged metal hose.
**Beware:** The moment the metal output hose (red arrow, {{ref>no_blower}}) is detached, the box will be open to air and the pressure inside it will drop. It is advisable to keep a plug nearby to immediately plug it. By doing so the introduction of air into the box will be minimal. In this case a proper plug was not at hand so the solution was improvised.
{{:wartung:kat:20260202_145243.jpg?direct&200 |pneumatic1_a}}
Next the first pneumatic valve hast to be removed. To do this unscrew the washer on the electrical connector to disconnect it ({{ref>pneumatic1_a}}). Disconnect the clamp at the flange and pull the valve carefully a little bit forward. You will notice the pneumatic connector with the pressure tubes at the back of the pneumatic valve ({{ref>pneumatic1_b}}). To disconnect the valve push and hold the blue ring while carefully pulling the tube out ({{ref>pneumatic1_b}}). Now you are able to remove the pneumatic valve ({{ref>pneumatic1_c}}).
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Before you remove the second valve, remove and plug the metal intake hose first ({{ref>pneumatic2_a}}). **Beware:** Again be quick while plugging the intake metal hose because the box will be open to air and the pressure inside it will drop like before in the case with the output metal hose. After this just remove the second pneumatic valve the same way like the first one ({{ref>pneumatic2_b}}).
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Reactor with disconnected metal tubes.
Next unscrew the two metal tubes next to the flanges at the reactor top ({{ref>metaltubes}}). These tubes are needed for the regeneration process.
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The mounting points where the reactor is fastened to the purification unit housing.
Unscrew the reactor from the mounting points and gently remove it from the purification housing ({{ref>mount}}). Be careful because there is still a cable attached to it.
{{:wartung:kat:annotations:cable1.png?direct&200 |cable_a}}
To detach the cable first remove the cover by loosening the two screws ({{ref>cable_a}}, red arrows). Now you can see the two powerlines (blue and brown) connected to the heater element and the ground (yellowgreen) connected to the reactor housing ({{ref>cable_b}}). These unprotected contacts are the main reason why you disconnect the entire system from the power grid. To remove the cable unscrew the washers so the entire contact housing can be detached ({{ref>cable_c}}).
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The reactor inside a fume hood (left) and respiratory protection gear (right).
The dust created by pouring out the reactor loading is harmful so the reactor needs to be moved to a well ventilated area, preferably a fume hood or outside ({{ref>fumehood_a}}). Additionally wear respiratory protection gear (e. g. FFP2 mask, {{ref>mask}}). **Important:** Provide a heat resistant container to pour the reactor loading into (e. g. metal container / buckets, {{ref>fumehood_a}}). Never dispose of it directly into the trash because the will be a fire hazard! Depending on the residual activity the reactor loading can generate quite a lot of heat when in contact with air. Thus the usage of a metal container.
{{:wartung:kat:20260202_162240.jpg?direct&200 |pour_a}}
Remove the meshed sealing rings ({{ref>pour_a}}) from the flanges of the reactor ({{ref>pour_b}}) and empty it into the container ({{ref>pour_c}}). The black pellets are the copper-based catalyst while the white ones are molecular sieves. For reasons mentioned before leave the old reactor loading to sit for a few days before you dispose of it.
{{:wartung:kat:20260202_162652.jpg?direct&200 |pour_a}}
After this prepare the new reactor loading. Usually the manufacturers of the boxes will provide refill sets for your specific systems ({{ref>refill_a}}). In this case there are two bags of molecular sieves, one bag of catalyst and two rubber gaskets for the meshed sealing rings ({{ref>refill_b}}). Replace the gaskets. To refill the reactor a suitable funnel is needed. For this purpose I 3D-printed a funnel with a KF40 flange which can be directly mounted onto the reactor ({{ref>refill_c}}). The model is provided [[https://www.thingiverse.com/thing:7319176|here (external link)]]. Mount the funnel on the same flange where the old loading came out. Refill the reactor in a specific order: First a bag of molecular sieves, then the bag with the catalyst and lastly the second bag with molecular sieves. The reason for this order is that the catalyst would be packed between the molecular sieves and therefore additionally protected. Now that the loading is replaced everything needs to be put together in reversed order.