Glass Bulb Sprinklers
I’m sure everyone is familiar with glass bulb fire sprinklers. So much so in fact that they may not be familiar with fusible link sprinklers. The glass bulb is considered the standard type of sprinkler operation today. But, us older folks in the sprinkler community remember a time when the fusible link sprinklers were the standard. But did you know that the glass bulb sprinkler has been around over 80 years!
Grinnell introduced the first bulb in 1921 known as the Quartz Bulb. It is described in the 10th edition of the NFPA Handbook as a silica bulb sprinklers and as late as 1948 still considered a reliable sprinkler. Grinnell followed this in 1933 with the Quartzoid bulb. Known as Grinnell C these stayed in the Grinnell product line for many years. These are still available today from Tyco. They are now known as Issue D sprinklers, and only available in temperatures higher that those offered by Job.
The other companies that I know of that attempted glass bulb sprinklers is “Automatic” Sprinkler, and Reliable. Central had one in the early 80’s but I understand it was imported from Germany. Other companies may have tried but I have no information on them. Only Grinnell has consistently kept them in production over the years. My knowledge here is limited to what I have in my collection.
JOB GmbH was formed in 1971. This company is the manufacturer of nearly all the glass bulbs used in fire sprinklers today. They offer a complete range of bulbs in both standard and quick response.
The only issue I have with the current glass bulb sprinklers is their delicacy. As sprinklers have gotten smaller, and with the introduction of the quick response bulbs, great care must be taken to protect the sprinklers during installation. The days when a fitter put the heads in a bucket to carry around are gone. At my last company you could get fired for not properly protecting the sprinklers until they were installed.
Now to protect these sprinklers they are shipped with orange plastic guards. The bright color should indicate to the installer that it is still in place and needs to be removed. But I have been to many facilities where I found the guard still in place years later.
And though rare, I have seen bulbs where there was no liquid in them. The one pictured below was found in a spare head box. It has a Job bulb in it. I have had field crews show me ones they removed from service. I always wondered it they were installed empty or if it had leaked out over time.
But despite their popularity and cost advantages, I don’t think the fusible link sprinklers will be relegated to the junk heap. Being a little more rugged I still see them installed in places where damage is a concern. In storage racks and low areas where head guards are necessary.