A furnace capable of generating temperatures of 100℃ and above is categorized as a high temperature furnace (or high-temp furnace). Prior to use in any beam experiments, the safety review must be conducted, including an on-site test at the MLF.
See Regulation (High-temp furnace) for details of the safety regulations.
Common points that are considered in the review process are described below.
・Cables and connectors should be of the proper specification, in accordance with the design requirements of the furnace.
・Wiring should be done properly (no unsealed connectors, etc.).
・All components should be properly grounded.
The furnace should be equipped with automatic interlock systems to prevent the improper operation of the equipment. The types of interlock systems that should be prepared are described below.
When the temperature control thermometer detects a temperature rise over the pre-set value, the control system should automatically shut-off the heater power output. Most commercially available temperature controllers are equipped with this function.
Apart from the temperature control, an independent temperature monitor is also necessary. As in the case of the temperature control above, heater power output should be shut-off when the monitoring thermometers detect a temperature rise above a pre-set value. Placement of the monitoring thermometers should take into account the safe operation of the heater and any nearby experimental equipment, as well as the safety of personnel. Ideally, the monitoring thermometers should be mechanically fixed. Most commercially available temperature controllers do not provide this function. Such an independent monitor helps to ensure the safety of the equipment.
In the near future, an independent temperature interlock system will be provided by the MLF.
The following are a few examples of equipment failure scenarios that might trigger the interlock systems:
・During sample exchange, a control thermometer is not replaced in the proper location, leading to excessive heating on the sample.
・During the experiment, a broken thermometer is replaced with one of improper type, leading to erroneous temperature readings.
・While the heater control works well, a temperature rise is detected on the heater support structure outside the sample region and near to other temperature-sensitive equipment.
As a matter of principal, we ask users to equip their high-temp furnaces with two interlock systems to guard against excessive temperature rise.
When using a water cooling system, the use of an interlock system responding to water pressure and water quantity is recommended.
When using equipment in vacuum or in some other specified pressure range, the use of an interlock system responding to the pressure value is recommended.
The interlock system should not include any automatic reset function. The reset of the interlock system should be handled manually by the operator after investigation of the cause and confirmation that normal operation can be safely resumed.
An emergency shut-off device (button/switch) should be installed in an easily accessible location to allow for the manual shut-off of the high-temp furnace upon detection of any defects or malfunctions by the operator.
It is recommended that an indicating lamp be installed for announcing high-temp operation and abnormality.
MLF adopts the following convention for the light color and corresponding meaning.
・High-temp furnace operation : Lighting RED.
・Abnormal operation detected : Flashing RED with beep.
MLF is planning to install such indicating lamps in the near future.
The stability of the equipment control will be tested at a temperature of 10 degrees Celsius over the maximum temperature to be used in the experiment.
When handling samples after the high temperature measurement, please adopt measures to avoid burns. It is advisable to install a monitoring thermometer near the samples and to prepare manuals describing the operation of the furnace.
The MLF requires the continuous monitoring of the furnace by an operator when in raised temperature operation. Personnel assignment should be arranged when the long monitoring time is expected.
The above discussions apply to general high-temp furnaces. Additional considerations for particular furnace types are described below.
A particular safety concern with lamp heaters is an unforeseen temperature rise at a place outside the sample region caused by errant thermal radiation light resulting from design flaws or equipment malfunctions. For the safety measures, we run an operation test prior to the experiment and monitor thermal changes at various parts of the equipment.
Laser heating furnaces have similar characteristics to furnaces with lamp heaters, but the directivity of the heating is higher. In addition to the MLF Instrumental Safety review, a J-PARC Safety Review is also required. 7.High-Power-Light Source
High temperature experiments using some atmospheric gas require safety reviews by both the Instrumental Safety Team and the Gas Safety Team. Please consult with the instrument scientist. Please be aware that using a flammable gas requires prior consultation.
大学共同利用機関法人 高エネルギー加速器研究機構 独立行政法人 日本原子力研究開発機構 J-PARCセンター