Presentation on theme: "TSI Nephelometer Zero Filter Assembly Zero filter valve Zero filter Zero filter motor Metal flange."— Presentation transcript:
TSI Nephelometer Zero Filter Assembly Zero filter valve Zero filter Zero filter motor Metal flange
Ball Valve Replacement (1) 1) Before disassembly, note position of ball valve (closed or open) and metal butterfly flange. Also, check the distance between the IR reflective sensor and the metal butterfly flange. You will try to duplicate these positions when finished. 2) Disconnect ribbon cable J17. 3) Disconnect tube from small filter to inlet block. 4) Remove large white HEPA filter because it gets in the way of this repair. This will involve loosening any of several nylon Swagelok nuts and then turning the filter off of the threaded stem.
Ball Valve Replacement (2) 5) Get a 9/16” wrench and start to remove the 4 long threaded bolts that secure the ball valve to the instrument housing. Get a feel for how tight they are screwed in. When finished, you will screw these bolts down but only so tight as to compress the o-rings and securely hold the ball valve in place. I believe it is possible to torque these bolts down too hard so that the valve does not turn easily, but unfortunately I don’t have a torque wrench reading to give you.
Ball Valve Replacement (3) 6) When you remove the bolts, the inlet block will come off and the coupler assembly will separate. Put the inlet block aside for now. Check the position of the coupler section that is on the shaft of the ball valve. In order to replace the old ball valve, you will have to remove this section of the coupler assembly from the old ball valve shaft. Note which groove on the valve shaft the Allen screws go into (there are 3 grooves on the shaft). If you have already removed the valve you may have to look at the marks on the shaft to see where the Allen screws were positioned. Get the new ball valve I sent and put this flange and coupler section on the new ball valve shaft exactly as it was on the old one. This will be a first guess as to the proper flange orientation and may be pretty close.
Ball Valve Replacement (4) 7) Make sure the new ball valve has o- rings at each end of the valve. If it does not, use the o-rings from the old valve. 8) Reposition the new ball valve on the instrument housing. Loosely tighten all four bolts to hold down the inlet block/ball valve assembly. When it will just hold itself, check the position of the coupler. Make sure the two ends are meeting nicely in the middle, that the shafts are more or less aligned, and that there are no big gaps lengthwise that could cause problems. Make sure the distance between the IR reflective sensor and the metal butterfly flange is about the same as it was before you started, generally < 1/8”.
Ball Valve Replacement (5) 9) This step is very important. You will need to make sure that the orientation of the ball in the valve is consistent with the flange position. The valve stops rotating just after the metal flange breaks the beam from the IR reflective diode. When the flange is in this position, the ball in the valve should be fully open or fully closed. You may need to adjust this several times to get a fully open or fully closed valve when the rotation stops. If you do not get this right your zero background checks will be bad because the valve will not be fully closed.
Ball Valve Replacement (6) 10) Tighten down the 4 threaded bolts. Make sure they are tight enough to compress the o-rings and that the valve body will not move around (even if you try to make it move by pushing it). Do not over tighten the bolts as this could cause the ball valve to deform and not turn smoothly. Tighten the bolts pretty tight but certainly not as tight as you could tighten them! 11) Re-install the HEPA filter. Use Teflon tape (recommended) or a flexible silicone sealant on the threaded stem. Tighten all nylon Swagelok nuts. Reconnect filter tube and ribbon cable.
When this replacement is finished, please perform a couple of tests. First, make sure the zero valve turns as it is supposed to. From the data collection program, go to the neph screen. Bring up the detailed menu for the neph. On this screen you should see choices for switching the zero valve to the zero state or the sample state. Toggle this software switch and make sure the valve turns as it is supposed to. When the software thinks the valve is in the zero state, look in the inlet and verify that the valve is closed. Next, perform one or more nephelometer zero background measurements. The software command can also be issued from the neph menu. This will take about 7 minutes including two 1-minute blanking periods and is all automatic. The zero values you come up with on this zero should be similar to those from the previous zero. You may have to perform several zero measurement cycles to achieve consistency between zeros. Depending on whether the nephelometer calibration has been compromised (i.e., if you performed a neph calibration when the old ball valve was broken you may have a bad calibration stored in the neph), you may need to recalibrate the neph. If so, perform the neph calibration as described in the neph manual or per specific NOAA instructions. If the new calibration is acceptable, store the new cal constants in the neph. Finally, perform a neph span check. Again, this command is on the nephelometer menu. Hopefully after all this you get a good span check with average errors at the few percent level or less. We will be able to see the results of the span check when it is completed. Good luck!