Heat exchanger cooling fan problem

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16-025 and 16-050 radiator cooling fan

16-025 and 16-050 radiator cooling fan












The heat exchanger cooling fan used on the Physical electronics 16-025 and 16-050 heat exchangers which are used to cool the x-ray sources on an XPS system can run slowly as the fan motor ages once the bearing lubricant begins to dry up. The result of a slow fan is that the anode will run warmer than normal and possibly melt.  At a minimum reduced cooling will shorten the anode lifetime.  The 16-020 heat exchanger has a fan that is attached to the pump motor, so it will not have this problem unless the pump motor fails.

The symptom for a slow heat exchanger fan is that with the source at full power after 20 minutes of operation the water lines to the x-ray source will be very warm or even hot  rather than slightly warm.

To test the fan you can feel how much air is coming out the back side of the radiator when the 16-025 or 16-050 heat exchanger is on.  The radiator will slow down the airflow, but it should still be a reasonable amount of air that escapes out the back side of the radiator.  If the fan looks like it is spinning slowly and there is minimal airflow then the fan should be replaced.

If you want to test the actual RPMs of the fan you can use a non-contact laser tachometer (available for as little as $15.00).  Or you can use an audio method as shown in this video on YouTube that uses Audacity:



The fan motor should spin at 1650 RPMs.

If you determine that the fan should be replaced (or if you want to as a preventive measure if your heat exchanger is 20 years old), here is the model number information –

Manufacturer – Orion

Fan, AC, 230V, 254 X 89mm, Round, 547CFM, 35W, 55dBA, 1650RPM

Manufacturer part number: OA254AP-22-1TB

Allied Stock # 70103674

It is held in place with some radiator mounting rods that are available at most auto parts stores.  Look for Hayden Nylon mounting rods with vibration pads.

Nylon mounting rods

Nylon mounting rods














In addition to the cooling fan, if the pressure indicator on your 16-050 heat exchanger bounces during operation you should consider replacing the water pump as well.  RBD Instruments provides the water pumps.   The 16-020 and most 16-025 heat exchangers do not have a pressure gauge.

And of course, make sure that the radiator is free from dust as being covered with dust will also reduce the cooling efficiency of the 16-020, 16-025 or 16-050 heat exchangers.   Refer to the RBD TechSpot post Heat Exchanger Preventive Maintenance for more information on dust and the radiator.

Heat exchanger preventive maintenance will prolong the anode lifetime on your 10-610 mono chromator anode and prevent a costly and time consuming anode meltdown.

Kratos Monochromator adjustment

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This Kratos monochromator adjustment procedure is used on the Kratos Axis, 165, Ultra and Nova monochromators.

Steps involved in optimizing the performance of the Al Monochromatic x-ray source:

First, load a sample bar containing a grid alongside a clean Ag foil sample at the same height.

  1. Using the Mg source image the grid to locate the height of the auto stage that gives the best focus. Move across to the Ag foil sample.
  2. Using the Mg anode find the BE position of the Ag 3d 5/2 peak. This method requires that the calibration of the energy scale of the instrument is correct.
  3. Using the BE position obtained with the Mg dual anode switch to the mono source and begin tuning the source position in conjunction with the crystal settings as detailed below.
  4. The image below shows the mono crystal adjustment mechanism. First undo the locking screw. (Rather than just loosening the locking screw, it sometimes helps to use the locking screw as a counter drive against the micrometers to enable a finer adjustment on the crystal mechanism). Micrometer A tilts the crystal left and right moving the mono spot in the x-axis on the auto stage. This can be carefully adjusted to optimize the count rate on its own (no interaction with other parameters). Similarly, there is a tilt adjustment on the mono source that changes the source to crystal distance that can be adjusted for maximum count rate at this point.
  5. The micrometer on top of the mechanism (marked “Do not adjust” in the image) changes the distance between the crystal and the sample. (After initial factory set up …i.e. for normal maintenance procedures…anode changes etc… this will not need re-tuning).
  6. Micrometer B tilts the crystal to move the mono spot along the y-axis of the auto stage (towards and away from the dual anode source). This micrometer always needs to be adjusted in conjunction with the linear movement of the mono x-ray source itself. When the mono source position is changed it moves the refracted beam on the sample so the tilt adjustment is required to move the mono spot back to the analysis position to maximize the count rate.
  7. The linear drive on the mono source itself should be adjusted in small increments. At each new position micrometer B is used to move the beam spot back to the analysis position (by maximizing the count rate). The best method is to tilt the crystal carefully through the maximum once or twice and make a note of the best count rate obtained.

Next, move the mono source a short distance (this will decrease the count rate). Now repeat the adjustment on Micrometer B to bring the count rate to a new maximum. If the new maximum is higher than the previous one continue the process moving the source in the same direction until the new maximum is lower than the previous one. Then move the source back to the previous setting and re-optimize.

If at the start of the procedure the second maximum is lower than the first, reverse the direction of movement of the mono source and continue the process in that direction to find the best “maximum” count rate.

Once the set up is close to optimum performance more improvement can sometimes be obtained by setting up the tuning using the 110um selected area instead of large area “hybrid” mode. (Starting with the 110um aperture is sometimes difficult due to the lower counting rates).

The locking screw should finally be re-tightened in conjunction with small final adjustments of the micrometers to maintain the maximum count rate. The locking screw may push the crystal position slightly as it is tightened.


Installing parts using Au seals.

When installing using Au wire seals it is essential to locate the seal in the correct position. The seal should be resting snugly on the shoulder formed above the main flange.





This way when the 2 surfaces come together the Au wire is ‘boxed” in and compressed.




If the Au seal is stretched or is not a tight fit on the shoulder and therefore “hangs” over the edge of the shoulder above the flange it will be pinched as the flanges are pulled together and NO SEAL CAN BE ACHIEVED NO MATTER HOW MUCH YOU TIGHTEN THE BOLTS!

Since the seal cannot be seen after mating up the flanges the only indication of whether the Au seal is in place is the gap between the 2 flanges when they are pushed together. There should only be a very small gap between the flanges <~1mm. If the gap is larger it means the Au seal is pinched.





Water Box Maintenance


With 15kV applied at the anode the water lines act as a conductive path to ground. The first point of contact to ground is at the outlet pipe from the solenoid valve (above the valve in the water box. (The water tube goes from there to the supply pipe on the anode). The other point is where the return line from the anode attaches to the flow switch (below the flow switch)






These are the most like places for corrosion due to the voltage difference. Check and clean out or replace these fittings to bring up the flow rate.

Also remember to check the in-line filter. If there is a drop in pressure across the filter as indicated by the pressure gauges, the filter may need to be replaced.


Installing the Old Style Filaments in an 04-500 or 04-548 X-ray Source


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In my previous two posts about the 04-500 and 04-548 X-ray source I showed you all the steps necessary to completely disassemble and reassemble the source and also how to install the new style filaments. Old style or new style? … Continue reading