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In my last post,I wrote about minimum safty switches required to be install on Air Compressor,that are LOPS,LCWPS,HDATS & Motor Overload Relay.It is also
important to protect your compressor from excessive vibrations developed due to operation or any other reasons.Unfortunately many plants are not using this
safty switch on their compressor.If you are using or interested to install Excessive Vibration switch,this post will help you to increase your knowledge.many
different Vibration Switches are available in market but in old days a very accurate switch”Robertshaws” made in USA make VIBRASWITCH is adopted by
various plants.The details is as below.
The switch is to protect the crankcase/crankshaft against any damage from malfunctions that can be detected as an increase in vibration.This is mounted on crankcase of compressor.It is sensitive to vibration in the direction perpendicular to its mounting base.
It contains a vibration detecting mechanism,which also function as a “Mechanical Amplifire” to activate a snap-action switch when the selected level of
vibration is exceeded and the detecting mechanism “Trips”.
The mechanism may be reset manually,by depressing the reset button to make the armature away from latching magnet until it is held against the stop pin.
Adjustment of operating set point.
The operating set point for the”Vibraswitch” varies with the type of Air Compressor & its location on the machine.The set point adjustment suggested here are
for machine which are working in good or normal condition.
The switch is adjusted by three step procedure,for making the adjustment, cover must be removed to gain access to the set point adjustment screw.
01)Zero Vibration Level Measurement:-
When the compressor on which the Vibraswitch is mounted,not operating,back-off the set point adjustment screw counter clockwise two turns & press the reset button.Then turn the set point adjustment screw slowly clockwise until actuation occurs.This is the zero vibration point or actuating point,when the
compressor not in running condition.A mark should made to permanently record this “Zero Vibration point”.Subsequent measurments are made relative to
this point.
02)Normal G-Level measurement:-
When the compressor is in operating condition,back off the set point adjustment screw one turn counter clockwise and reset.If it will not reset,back-off slowly until reset.Again turn the set point adjustment screw slowly clockwise until actuation occurs,mark the position.The difference between the two actuating points in step 01 & step 02 is the normal G-level of the Air Compressor,in scale divisions.One scale division is 0.1g & one full revolution is 1.0g
03)Fine Set Point Adjustment:-
Rotate the set point adjustment screw one full turn counter clockwise from the point where actuation occured in above step 02.
NOTE:-Use Ohm meter to observe the actuation of the Vibraswitch visually in noisy surroundings.
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