Ⅳ. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 47 (2014)

Present status of the BigRIPS cryogenic plant
K. Kusaka,＊1 M. Ohtake,＊1 T. Kubo,＊1 K. Yoshida,＊1 Y. Mori,＊2 M. Ohshima,＊2 K. Yamamoto,＊2 S. Watanabe,＊2Y. Tezuka,＊2 A. Mikami,＊2 H. Shiba,＊2 H. Hazama,＊2 H. Miura,＊2 M. Noguchi,＊3 and N. Suzuki＊3RIKEN Nishina Center
Nippon Kucho Service Co., Ltd.
＊3Mayekawa Mfg. Co., Ltd.
＊1
＊2Oil Contaminaon [wt. ppm]

160140120100806040200㻜㻞㻜㻜㻜㻠㻜㻜㻜㻢㻜㻜㻜㻤㻜㻜㻜㻝㻜㻜㻜㻜㻝㻞㻜㻜㻜㻝㻠㻜㻜㻜Operaon Time of Coalescer Filters [h]Fig. 1. Oil contamination at the entrance of the second
coalescer vessel (3SP).
10Oil Contaminaon [wt. ppm]

Periodic maintenance of the BigRIPS cryogenic plant isessential to ensure long-term continuous operations ofBigRIPS. In addition to periodically calibrating thepressure and temperature sensors installed in the system,
maintaining the oil-removal module in the helium
compressor unit is crucial1). The oil-removal module
comprises an oil vessel with a demister, which is used as abulk oil separator (1SP), three coalescer vessels (2SP, 3SP,and, 3.5SP), and two adsorbent vessels (4SP and 5SP) that
contain activated charcoal and molecular sieves. The
periodic replacement of coalescer filters and adsorbents
ensure the small oil contamination in helium gas. The
contamination ranges between 0.008 - 0.02 weight ppm(wt. ppm), depending on the quality of the coalescers used.
We replaced all the coalescer filters in three coalescer
vessels during the summer maintenance in 2008, 2010, and2012. Each coalescer vessel contains four coalescer filters,
manufactured by Domnick Hunter3), and the drain oil
separated from the helium gas is sent to the compressor via
a drain line with solenoid valves, depending on the oil levelin the vessel. The expected oil contamination levels at theexit of the coalescer vessels are 15-50 and 0.75-1.25
wt. ppm for 3SP and 3.5SP, respectively. The oil
contamination level can be easily measured with an oilcheck kit2).
Figure 1 shows the contamination measured at theentrance of 3SP as a function of the coalescer filter
operation time. The oil check kit values are shown as
open symbols in Fig. 1. The open triangles, squares, andcircles represent results for the 2008-2009, 2010-2011, and2012 operations, respectively. An estimate from the oildrain from the 3SP is also shown in Fig. 1. We estimate
the oil contamination level by measuring the operationinterval of the solenoid valve installed in 3SP. The navy
blue, green, and, yellow diamonds represent the estimates
for the 2008-2009, 2010-2011, and 2012 operations,respectively. The estimates of oil drain increase to 50~75
wt. ppm up to an operation time of 2000 h for the period of2008-2009 and 2010-2011 and then stays constant.
Corresponding oil check kit results show a similar
increasing tendency. On the other hand, the estimate fromthe oil drain for the period of 2012 shows monotonous
increasing tendency and does not stay constant for any long
period. We shall continue observations in the next
operation. This difference indicates the performanceefficiency of different coalescer filters.

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Operaon Time of Coalescer Filters [h]Fig. 2. Oil contamination at the entrance of the thirdcoalescer vessel (3.5SP).
In Fig. 2, we show a similar analysis of the oil
contamination at the entrance of 3.5SP. Symbols andcolors 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 less oil contamination at
the entrance of the 3SP, the results for the period of
2010-2011 are approximately half of that of the other period.
However, the oil contamination estimated from the oil drain
for the period of 2012 unexpectedly increased faster thanother periods. We shall continue observations in the next
operation and investigate the coalescer filters in themaintenance planned in the summer of 2014.
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/- 313 -