Fusible Link and Quartziodal Bulb - Deluge Valve

[rrkumar50]

We have Dry type Deluge Valve System for our hot air Oven with quartzoidal bulb rated at 93 degree Celcius, presently the system is having fusible link (rating 72 degree UL 555 certified) in the fire damper of hot air duct; due to frequent failure in the fusible link. it is suggested to for next higher rated fusible link that is above 100degree, our concern is whether higher rating of the fusible link have the posibility of attaining a temperature of above 93 degree of quartzoidal bulb which may activate the deluge valve?
the operating termperature of oven is 65degree.
some body throw more light on this issue
Thanks

[f81aa]

Hi rrkumar50:

Given that I have no experience with this type of protection system. I tried to find specific references to support what I´m about to say but failed. Anyway, I´ll venture an opinion at the risk of being rebuffed.

Years ago I read that there should be certain difference of temperature degrees between the temperature of activation of a heat detector and the normal temperature of the environment where the detector is located.

You mentioned that the operating temperature of the oven is 65 degrees Celsius whlle the fusible link has a rating of 72 degrees Celsius. You also said that the fusible link has frequently failed. Those 2 values look too similar to me. Minor fluctuations in the oven operating temperature could be having an effect on the fusible link. I´m not sure if the term for this is thermal creep.

IF I WERE YOU:

If the design basis for this protection system were available, I´d search for the reasons that support the value of 72 degrees Celsius for the fusible link. I´d also try to find if the oven operating temperature was increased and why. Any management of changed performed?

Choosing a higher rated fusible link seems a right move to me. I´d search for the value of the difference of temperature degrees between the temperature of activation of the fusible link and the normal temperature of the environment where it would be located.

It´s obvious that the protection system design intends the rated 72 degree Celsius fusible link to fuse sooner than the 93 degree Celsius quartzoidal bulb tripping the deluge valve. The proposed higher rated fusible link will reverse the intended sequence of events. So I´d think of also increasing the rating of the quartzoidal bulb.

Finally, I´d make sure that a management of changed is performed and that all decisions are technically supported.

I hope that other members will also throw some light on this issue.

Regards