Second Booster Pump for the Main Compressor --------------------------------------------- Initial Rev. 12-May-2022 Current Rev. 18-May-2022 Because the cooling water flow for the main compressor, i.e. the Pulse Tube Compressor, in the Helium Liquefier was just barely sufficient it was decided to add a second booster pump. From the Cryo-Mech manuals we understand that they do not want the Helium Gas temperature to be above 70 deg C or the water Outlet temperature to be above 40 deg C. In the summer of 2021 we saw the Inlet water temperature as high as 29.7 deg C and it may have been warmer than that. In general Cryo-Mech assumes a lower cooling water Inlet temperature than that provided by the BPS Building's Process water system. The Cryo-Mech specification charts cover the cooling water Inlet temperature range from 10 to 27 deg C. Thus we need a cooling water flow rate that is high enough to keep the temperature difference between the Inlet and Outlet water to 10 deg C or less. This will require a flow rate above 12 Liters per Minute. This is the upper limit of what the cooling loop in the main compressor is designed to handle. From the Cryo-Mech charts a flow of 12 LPM will require an Inlet to Outlet pressure drop of about 24 psi. Because we have seen the static pressure in the building's Process Water System be as high as 100 psi in the Supply line in the sub-basement we do not want to use an arbitrarily high pressure boost at the Inlet to the main compressors cooling loop. The Cryo-Mech specification is that the pressure in this cooling loop should be 110 psi or less. Thus we will keep the current booster pump at the Inlet to the cooling loop and add a second booster on the Outlet side of the loop. Both the Inlet and Outlet booster pumps are Bell & Gossett model PL-36B. At a flow rate of 4 gpm which is at the low end of normal operation for these pumps, if everything is working correctly they should give a boost of about 15.0 psi. The second booster pump was installed on 12-May-2022. This installation included: - Removing the first booster pump (on the Inlet side of the main compressor) so that its motor could be rotated 90 degrees wrt its pump body to put them in correct alignment and so that a power cord with correct water resistant strain relief could be installed. Note that Bell & Gossett requires these pumps to be operated with their motor shaft horizontal and the motor connector box on top, i.e. the ventilation slots and weep hole facing down. - Adding a 4th pressure gauge to the setup for the main compressor so that we can see the cooling water pressure at the following points: supply / supply pump input, supply pump output / compressor inlet, compressor outlet / return pump input, return pump outlet / return. - Adding an electrical power wiring setup that will keep all connections up out of the water when there is a leak. - Cleaning the rust and sludge out of the cooling water circuit components that were being re-used, e.g. the inlet booster pump and the flow rate gauge. - Replace the filter element in the filter for the main compressor's cooling water. The installation work took about 4 1/2 hours. During this time the pressure in the storage dewar rose from 3.10 psi up to 9.69 psi. The liquid level in the storage dewar did not drop so I don't think that there was very much boil off. There was only 15 psi in the Recovery Tanks so no time was lost liquefying recovered gas. The main compressor was turned Off by setting its operation to Manual and then to Off on the Liquefier's control-display panel in B111 and then turning Off the breaker on the front of the main compressor. When the system was turned back On, the main compressor's front panel breaker is switched On and then on the control-display panel it was switched from Manual to Auto On/Off operation. Special Conditions Readings Before Resuming Normal Operation: ------------------------------------------------------------- After the water circuits had been completely reconnected the 4 pressure gauges were checked for equal readings by turning On the Supply and Return valves in Rm B111 one at a time. The pumps were also run one at a time to see their individual effect. Water Pressure Gauges ------------------------------------ Valve Settings -- Compressor -- Pumps On/Off Supply Inlet Outlet Return ---------------- ------ ------ ------ ------ Only Supply Open 80 80 80 79 psi Both Pumps Off Only Return Open 69 71 70 70 Both Pumps Off Only Supply Open 79 81 80 79 Both Pumps Off Both Valves Open 78 79 72 72 Both Pumps Off Both Valves Open 76 91 74 73 Only Supply Pump On Both Valves Open 76 76 60 73 Only Return Pump On Both Open 74 88 62 74 Both Pumps On Conclusions: - In the pressure range of interest the 4 gauges all seem to read within 1 psi of each other. - The pumps running individually each produce about the expected 15 psi boost in pressure. - Compared to the static no flow pressures, when we have both valves Open and both pumps running we loose about 5 or 6 psi in supply pressure and have about 4 psi of extra return pressure. Before vs After Pressure and Temperature Differences: ------------------------------------------------------ I averaged the main compressor Inlet vs Output pressure and temperature differences for 6 to 10 readings all taken when the compressor had been in operation for greater than 20 minutes so that things were presumably in equilibrium. The before readings are from the week before the second booster pump was installed. With Only With Supply Compressor Inlet-Outlet Supply Pump & Return Pumps ----------------------- ----------- -------------- Pressure Difference 15.5 psi 25.9 psi Temperature Difference 11.4 deg C 8.0 deg C Tentative Conclusion: We can now operate with 3.4 Deg C warmer Inlet cooling water. I have recorded the reading from the inline flow meter but I can not compare the before and after readings because I cleaned the brown / black rust like material from the flow meter while I had this cooling loop taken apart. There had been so much rust like material on the spring loaded slide in this meter that I think that all of my before readings were taken using the wrong reference point. You can even see the difference in the before after camera pictures. The spring loaded slide is now white and has a red ring around it that I now assume is the reference point for taking readings. Before the cleaning this ring was black and did not show up. My before readings were taking using the only part of the slide that was white at the time. This was a section of the slide closer to its input end and immediately adjacent to the now red ring. Age of the two Pumps: --------------------- Reza confirmed that the original booster pump for this system was purchased in about January or early February of 2021. So as of this writing in May of 2022 that pump has been in operation for about 15 months. That original pump was taken apart on 12-May-2022 to rotate the motor on the pump body by 90 degrees. At that time the rust or black/brown junk in it was cleaned out and a proper line cord and strain relief were installed. The pump's impeller and such looked in good shape. That pump was put back in service as the source side pump which is the side that it had originally been on. The new pump, which is on the return side, was purchased in late April of 2022 and started operation on 12-May-2022. It also was taken apart to rotate its motor by 90 degrees on the pump body to have things in the orientation required by Bell & Gossett, i.e. the motor's vent slots and the pump's weep hole facing down. During the daily walk through both pumps are checked for leaks and so far they look OK.