HP 11744195 manual Description of Safety Features

Description of Safety Features

On each unit, there are a number of features, which help to ensure safe operation. These features are:

❏Temperature High/Low Limit Control:

A user-programmable limit control is provided as an independent measure of safety against thermal runaway (hot or cold), which could occur from, but not limited to, the following:

Programming error Primary controller failure Thermocouple breakage Heater SSR failure Circulation blower failure

The limit control is wired into the control devices to provide a totally independent safety system. A separate thermocouple is provided for the limit control and located inside the air plenum. If this device has reached an alarm condition, the system must be reset by pressing the “Chamber Reset” button on the control console.

WARNING!: The alarm set point of this device should never be set higher than +200°C or lower than –80°C as these are the maximum design temperature of the system.

It is important to note that this safety controller does not protect from a possible failure of the cooling solenoid valve. It is possible for this valve to fail and allow liquid nitrogen to continue flowing into the chamber, resulting in extremely cold temperatures. As a result, Chart recommends changing the solenoid valve on a regular basis as a preventative maintenance measure against such occurrences.

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