Quench

3 minutes to read

Definition: QUENCH

**Quenching’ is a term referring to the events that occur when the cryogenic liquids used to cool the magnetic coils boil rapidly, resulting in a very rapid escape of helium from the cryogen bath. This means that the superconducting coils cease to be superconducting and return to a resistive state. A ‘Quench’ will usually be accompanied by a loud detonation resembling a lightning sound, a hissing sound or an abrupt sound with the expulsion of cold gas.

Quenching can occur by activation of the magnet’s stop button, or spontaneously, following a defect in the magnet itself. The emergency stop button of the magnet should only be used in the event that the magnetic field causes injury to the patient or staff, then a static field shutdown is required, or if a fire or other unforeseen event requires rapid access of emergency personnel to examine the chamber. Note, however, that initiating a ‘Quench’ may not result in total magnetic field suppression, and a hazard may still exist. Some magnets seal only partially and the magnetic field is therefore not completely eliminated. In such cases, appropriate safety measures must still be taken when handling ferromagnetic objects near the magnet.

One of our magnet manuals suggests that the field strength is likely to be reduced to ~ 20 mT after about 20 seconds following the initiation of a Quench.

Kanal, MR Safety

http://www.revisemri.com/questions/safety/quenching

Emergency case: Quench

• In the case of a Quench in the MRI unit, the MRI staff should evacuate the magnet room if possible, and the UNF department.

If someone is in the MRI room (in the magnet) or in the MRI room during the QUENCH, get the person(s) out of the MRI room, and then assist the individual(s) using first aid responder principles.

• call 5555 for all emergencies; identify:

• What is the emergency situation :

  There is a Magnet Quench in MRI room C-0674

• Where you are:

  Functional Neuroimaging Unit

• Who are you :

  Your name

*- Once everyone is out of the magnet room, the door must be locked.

If the emergency response team is present, make sure they are aware of the residual magnetic field.

Inform the Functional Neuroimaging Unit staff of events.

UNF staff will inform management, Siemens service Uptime, etc.

Siemens Uptime Service 1-800-359-6709 Site #8010

You will also need to make a written summary of the incident (incident report).

The STOP button

This button de-energizes the superconducting magnet (Quench).

*- Press this button in case of emergency in the magnetic field and notify Siemens service immediately *- Only superconducting magnets are used.

*- Only superconducting magnets have a shut-off magnet switch - permanent magnets cannot be switched off. *

Quench

A Quench occurs when there is a sudden loss of superconductivity in the magnetic antenna as a result of the temperature increase in the magnet.

The cryogenic substances used for superconductivity have suddenly evaporated causing a change in the temperature of the magnet.

The cryogens used for superconductivity evaporate suddenly causing a change in the magnetic field of the magnet in less than 20 seconds.

A Quench can occur following the following events:

• Setting up the MR system (powering up or filling the magnet)

• Accident (earthquake, fire, etc.)

A Quench can be released by the user in a controlled manner by activating the Magnet Stop button.

*Siemens Healthcare_ Safety_Guide_AE_4c.pdf* p.15