RIKEN Accel. Prog. Rep. 48 (2015)

Ⅳ. OPERATION RECORDS

Present status of the BigRIPS cryogenic plant
K. Kusaka,＊1 M. Ohtake,＊1 T. Kubo,＊1 K. Yoshida,＊1 M. Ohshima,＊2 A. Mikami,＊2 H. Shiba,＊2 H. Hazama,＊2

RIKEN Nishina Center＊2Nippon Kucho Service Co., Ltd.
＊2Mayekawa Mfg. Co., Ltd.
＊1250200150100
50002000

40006000

8000

10000 12000 14000

Operation Time of Coalescer Filters [h]Fig. 1. Oil contamination at the entrance of the secondcoalescer vessel (3SP).
Oil Contamination [wt. ppm]

In addition to periodic calibration of pressure andtemperature sensors, maintaining the oil-removal module in
the helium compressor unit is crucial to ensure long-term
continuous operations of BigRIPS1). The oil-removal
module comprises an oil vessel with a demister (1SP), threecoalescer vessels (2SP, 3SP, and, 3.5SP), and two adsorbent
vessels (4SP and 5SP). We replaced the activated charcoal
and molecular sieves in 4SP every year and the activatedcharcoal in 5SP every 2 years to ensure low oil
contamination in helium gas at the exit of the oil-removalmodule.
Before the adsorbent vessels, oil in the helium gas isseparated by coalescer filters in three coalescer vessels. The
drain oil separated from the helium gas is sent to thecompressor via a drain line with solenoid valves, dependingon the oil level in the coalesce vessel. By measuring theoperation interval of the solenoid valves, the oil
contamination level of the helium gas at the entrance of thesecond and the third coalesce vessel can be evaluated. The
expected oil contamination levels at the entrance of thecoalescer vessels are 15-50 and 0.75-1.25 wt. ppm for 3SP
and 3.5SP, respectively. The oil contamination level canalso be easily measured with an oil check kit2).
Each coalescer vessel contains four coalescer filters,
manufactured by Domnick Hunter3), and all the filters werereplaced every 2 years, since 2008. However, the filters
used for 6 years were discontinued and replaced with thesuccessive product of Domnick Hunter in 2014.
Figure 1 shows an estimate of the oil contamination levelat the entrance of 3SP as a function of the coalescer filter
operation time from the oil drain from the 3SP. The navyblue, green, and, yellow diamonds represent the estimates
for the 2008-2009, 2010-2011, and 2012-2013 operations,respectively. The estimate for the 2014 operation with newcoalescer filters is shown as pink diamonds. The estimates
increase to 50~75 wt. ppm up to an operation time of2000 hours for the period of 2008-2009 and 2010-2011 andthen stays constant. The estimate for the 2014 operationshows similar behavior. On the other hand, the estimate forthe period of 2012-2013 scatters largely and showsmonotonous increasing tendency. The oil check kit values
are also shown as open symbols in Fig. 1. The open
triangles, squares, circles, and diamonds represent results
for the 2008-2009, 2010-2011, 2012-2013, and 2014
operations, respectively.

Oil Contamination [wt. ppm]

H. Miura,＊2 H. Shiraki,＊2 H. Hirai,＊2 M. Haneda,＊2 M. Kubota,＊2 M. Noguchi,＊3 and N. Suzuki＊310864200

2000

4000

6000

8000

10000 12000 14000

Operation Time of Coalescer Filters [h]Fig. 2. Oil contamination at the entrance of the third
coalescer vessel (3.5SP).
In Fig. 2, we show a similar analysis of the oilcontamination at the entrance of 3.5SP. Symbols and colors
used in Fig. 2 are same as those in Fig. 1. A gradualincreasing tendency of the oil contamination is seen in all
operation periods. Following the large oil contamination at
the entrance of the 3SP, the results for the period of
2012-2013 are approximately twice of that for the otherperiod. Since the solenoid valve of 3.5SP was operated onlyonce since Sept. 2014, only one pink symbol is plotted inFig. 2. Although the performance efficiency of the newfilter elements seem to be similar to that of discontinued
ones, we shall continue observations and investigate
oil-removal modules carefully in the coming maintenanceperiod.
References

1) K. Kusaka et al.: RIKEN Accel. Prog. Rep. 41, 244 (2008).
2) K. Kusaka et al.: RIKEN Accel. Prog. Rep. 43, 309 (2010).
3) http://www.parker.com/- 330 -完全版2014_本文.indd 330

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