Bolted Pressure Switches

BLOG: Bolted pressure switches

A frequently used voltage level for industrial facilities is 480 volts.  At this voltage, hundreds or thousands of amps are needed to supply industrial electrical systems. These rely on switches and circuit breakers.

In this article, bolted pressure switches are discussed. 

Several bolted pressure switch designs were developed through the years as a safer means to turn power on and off.  

These designs work well when maintained and IF they are correctly installed.

Bolted pressure switches contain two major items: operators and blades.  Operators use large springs to the provide mechanical force needed to turn a switch on and off. Blades are designed to carry power, or interrupt it (turn on and off the power)

Near the leading edge of the blades, an “arc tip” may be found.  It’s purpose is to carry the high heat involved when a contact opens and closes.  Arc tips, generally made of tungsten, handle the extremely high and short lived heat when a switch opens and closes. The tungsten carries electrical current for a short time before the copper ( or aluminum) main blade fully close or open. 

The switchblades are opened and closed at approximately the same moment in time.  Equipment operating at 1000 volts or less the “same time” duration is less important. 

However, at medium voltage levels ( 1000-100,000) volts, this “same time” synchronization becomes more important; that’s another topic for another time. 

Bolted pressure switches may or may not have fuses. Never assume the fuses are safe to remove if the switch is open- in my 40 years  in electrical cabinets, I’ve seen plenty wired incorrectly!!

Bolted pressure switches require  maintenance. Without maintenance, they frequently fail, get hung up, open only one or two phases, overheat, burn, explode, catch fire and WILL put an entire facility in the dark.

Bolted pressure switches are not blister packed at Walmart, so it’s important they are maintained. There are hundreds of choices but very few can be retrofitted. 

Maintaining a bolted pressure switch needs done according to the original equipment manufacturers instructions.  In absence of those instruction’s, don’t guess.  

REMEMBER: Just because you haven’t seen problems doesn’t mean there are no problems!  These system’s do not announce failure. When called to operate, malfunction will put your facility without electrical power quicker than you can say “why didn’t I maintain this?”

WE routinely service bolted pressure switches.  Call or email us when we can help. 

Neil Volk

Electrical Engineer