Field Application Note
`
`Accelerometer Installation Guide
`
`AIG
`
`Table of Contents:
`
`Section I:
`Introduction
`
`Section II:
`Mounting Accessories
`Installation Tools
`Adhesives and Sealants
`
`Section III:
`Preferred Mounting Locations
`Direct Mounting
`Adhesive/Stud Mounting
`Adhesive Mounting
`NPT Adapter Mounting
`Motor Fin Mount
`
`Section IV:
`Cabling
`Signal Interference Sources
`Sensor Wiring
`
`
`Section I:
`Introduction:
`
`There are three mounting methods typically used for
`vibration monitoring applications; stud mounting,
`adhesive bonding and magnetic mounting. Stud
`mounting
`is
`the preferred method
`for permanent
`mounting applications. This method is accomplished by
`securing the sensor directly to the bearing housing
`using a mounting stud. This method allows the sensor
`to measure vibration according to the manufacturer’s
`specifications. The mounting
`location
`for
`the
`accelerometer should be clean and paint free, also the
`mounting surface should be spot‐faced to a surface
`smoothness of 32 micro‐inches. The diameter of the
`spot‐face should be about 10% larger than the sensor
`diameter. Any irregularities in the mounting surface
`preparation will translate into improper measurements
`or damage to the sensor may occur. STI prefers that a
`mounting pad be placed between the machine and the
`sensor
`to provide a smooth surface
`for
`the
`accelerometer to attach to.
`
`Adhesive or glue mounting provides a secure attachment
`without extensive machining; however this method will
`reduce
`the operational
`frequency range since
`the
`adhesive will act like a shock absorber, this is also known
`as damping. The replacement or removal of the sensor is
`also more difficult than any other mounting method. The
`most important issue for using adhesives is surface
`cleanliness, without a clean surface the adhesive will not
`fully bond to the machine.
`
`The magnetic mounting method is typically used for
`temporary measurements with a portable data collector
`or analyzer. This method is not recommended for
`permanent monitoring. The sensor may be inadvertently
`moved and the multiple surfaces and materials of the
`magnet may interfere with or increase high frequency
`signals.
`
`As can be seen in the figure below, the mounting method
`has an effect on the operating frequency range of an
`accelerometer. By design, accelerometers have a natural
`resonance which is 3 to 5 times higher than the
`advertised high end frequency response. The frequency
`response range is limited so that a flat response is
`provided over the operating range. The advertised range
`is achievable only by stud mounting. Any other mounting
`method will adversely affect the natural resonance, and in
`turn
`the usable
`frequency
`response
`range.
`
`
`
`
`
`
`
`
`
`
`
`
`
`***STI’s preferred mounting method is the stud mount
`with mounting pad and epoxy.***
`
`
`
`1010 East Main Street, League City, TX 77573 Phone: 281.334.0766 Fax: 281.334.4255
`www.stiweb.com / www.stiwebstore.com
`Copyright © 2012 STI Vibration Monitoring, Inc.
`
`1
`
`APPLE 1039
`
`

`

`Section II:
`Mounting Accessories:
`
`Part Number
`
`Description
`
`Use
`
`CMCP‐200 Series
`CMCP200‐01
`CMCP200‐02
`
`Accelerometer Mounting Pads
`1/4” x 1” Dia.
`3/8” x 1” Dia.
`
`Provides Ideal Mounting Surface.
`Use 1/4” pad for stud/adhesive
`mounting and 3/8” pad for adhesive
`mounting.
`
`Pipe Thread Mounting Adapter
`1/2” NPT
`3/4” NPT
`3/8” NPT
`1/4” NPT
`
`Makes use of existing NPT
`threaded holes to mount sensors.
`Adapters are finished with a lapped
`surface and a 1/4”‐28 threaded
`hole.
`
`
`
`
`
`
`
`
`
`CMCP203 Series
`CMCP203‐01
`CMCP203‐02
`CMCP203‐03
`CMCP203‐04
`
`CMCP205 Series
`CMCP205‐01
`CMCP205‐02
`CMCP205‐03
`CMCP205‐04
`
`Motor Fin Mounts
`1.25” L x 0.50” W
`2.00” L x 0.50” W
`1.75” L x 0.25” W
`1.00” L x 025” W
`
`CMCP230 Series
`CMCP230‐01
`CMCP230‐02
`CMCP230‐03
`
`1/4”‐28 UNF Mounting Studs
`1/2” in Length
`3/4” in Length
`3/8” in Length
`
`Allows for mounting sensors in
`between motor fins when a flat
`surface is not available. Tips are
`angled to ensure contact with
`machine casing.
`
`Sold in packs of 10.
`
`
`
`Installation Tools:
`
`Part Number Description
`
`CMCP270
`
`Piloted End Mill
`
`CMCP271
`
`Piloted End Mill with
`Replaceable Cutting Tips
`
`Use
`
`Used to mill a 1” flat surface and also
`provides a guide hole for tapping ¼”‐ 28
`threads. Includes end mill, pilot, drill bit
`and Allen wrench
`
`Same as CMCP270 but provides
`replaceable cutting tips. Cost effective
`when mounting a large quantity of
`sensors.
`
`
`
`
`
`
`
`1010 East Main Street, League City, TX 77573 Phone: 281.334.0766 Fax: 281.334.4255
`www.stiweb.com / www.stiwebstore.com
`Copyright © 2012 STI Vibration Monitoring, Inc.
`
`2
`
`

`

`Adhesives and Sealants:
`
`Part Number Description
`
`Use
`
`CMCP206
`
`Adhesive Filler
`
`Used to fill voids when installing CMCP205 motor fin
`mounts. 2 Part Epoxy
`
`CMCP207
`
`Adhesive Dispenser
`
`Used to dispense CMCP206 Adhesive Filler
`
`CMCP208
`
`Mixing Nozzle
`
`Used to mix CMCP206 two part epoxy
`
`CMCP210
`
`Acrylic Adhesive Bypacs
`
`2 Part Epoxy for easier mounting of 1 or 2 sensors
`
`CMCP211
`
`Depend 330 and Activator 2 Part Adhesive with spray activator. Good for over 10
`installations
`
`CMCP212
`
`Silicone Dielectric
`
`Helps ensure transmittal of higher frequencies
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`CMCP213
`
`Silicone Sealant
`
`Used to “flood” connectors to eliminate moisture build up
`inside of sensor connector
`
`
`
`Section III:
`Preferred Mounting Locations:
`
`Preferred Mounting Locations
`
`1010 East Main Street, League City, TX 77573 Phone: 281.334.0766 Fax: 281.334.4255
`www.stiweb.com / www.stiwebstore.com
`Copyright © 2012 STI Vibration Monitoring, Inc.
`
`3
`
`

`

`Direct Stud Mount:
`
`Mounting Pad Mount w/Adhesive: (Preferred)
`
`1010 East Main Street, League City, TX 77573 Phone: 281.334.0766 Fax: 281.334.4255
`www.stiweb.com / www.stiwebstore.com
`Copyright © 2012 STI Vibration Monitoring, Inc.
`
`4
`
`

`

`Mounting Pad Mount w/Adhesive: (Preferred)
`
`Mounting Pad with Adhesive Mount:
`
`1010 East Main Street, League City, TX 77573 Phone: 281.334.0766 Fax: 281.334.4255
`www.stiweb.com / www.stiwebstore.com
`Copyright © 2012 STI Vibration Monitoring, Inc.
`
`5
`
`

`

`NPT Adapter Mount:
`
`Motor Fin Mount:
`
`1010 East Main Street, League City, TX 77573 Phone: 281.334.0766 Fax: 281.334.4255
`www.stiweb.com / www.stiwebstore.com
`Copyright © 2012 STI Vibration Monitoring, Inc.
`
`6
`
`

`

`Sensor Sensitivity
`
`Maximum Cable Length
`
`100mV/g
`
`500mV/g
`
`100‐150’
`
`150‐500’
`
`4‐20mA Velocity Sensors >1000’
`
`Sensor Wiring:
`
` A
`
` “Single Point Grounding” scheme must be utilized
`when installing a vibration monitoring system. All grounds
`must be connected at one location. It is recommended
`that the grounding point be at the transmitter/monitor end
`and not at the machine. On most machines or where
`other machines are being monitored significant ground
`differentials can be found between sensor locations and
`machines.
`
`All Instrument Wire shields must be grounded at one end
`of the cable, and the other end left floating or not
`connected. The Instrument Wire should be grounded at
`the Vibration Monitoring System. If the shield is not
`grounded, the shield will become an antenna increasing
`induced noise on the signal path. If the shield is grounded
`at both ends, it will allow ground current (ground loop
`noise) to flow through the shield, seriously increasing
`signal noise.
`
`Section IV: Cabling:
`
`The instrument wire from the vibration sensor to its
`transmitter or monitor should be either a twisted pair or
`triad cable depending on the sensors requirement. These
`cables should be stranded, twisted, individually insulated,
`shielded and with an overall jacket. The shields or drain
`wires must be insulated or isolated from each other and
`the conduit. The use of multi‐conductor cable with a
`single shield is not suggested due to its susceptibility to
`induced noise and line interference.
`
`The gauge or thickness of the instrument wire is
`determined by the distance between the sensor and the
`transmitter or monitor. Long
`lengths of cable will
`deteriorate the signal; this can be a problem when
`monitoring gear mesh
`frequencies, blade pass
`frequencies or rolling element bearing frequencies.
`
`Signal Interference Sources:
`
`Noise or Line Interference can be induced in a Vibration
`Monitoring System in a number of ways. However, there
`must first exist a source for the induced noise. There are
`numerous noise sources available in an industrial or
`power generation plant:
`
` •
`
` AC Power Transients
`• AC Power Transients
`• Ground Differentials
`• Switching Circuits
`• High Voltage Circuits
`• Improper Load Balance
`
`Noise can be induced in a Vibration Monitoring System
`through Electrostatic (Capacitive), Electromagnetic
`(Inductive) or Conductive Coupling (Direct Connection).
`All noise will be induced in the monitoring system through
`one or more of its external connections or Field Wiring.
`
`It is critical that conduit be utilized with the sensor cabling
`and its associated wiring. The use of conduit greatly
`reduces
`the possibility of
`induced noise or
`line
`interference on the signals path. The conduit system shall
`be dedicated to the monitoring system and no other
`wiring should be in the same conduit. Also, cable trays,
`wire ways, or instrument trays are an unacceptable
`alternative to dedicated conduit. Route the conduit as far
`as possible from any power cables, relay contact cables
`and motor control cables. If you must cross these cables
`do so at a 90° angle.
`
`The following table offers a guideline to determine the
`maximum cable length for different types of sensors. This
`is based on an ideal installation where the cable is
`properly grounded and installed in a dedicated conduit
`system.
`
`1010 East Main Street, League City, TX 77573 Phone: 281.334.0766 Fax: 281.334.4255
`www.stiweb.com / www.stiwebstore.com
`Copyright © 2012 STI Vibration Monitoring, Inc.
`
`7
`
`

`

`Sensors with Built In Cables:
`
`Cable Part Number
`
`Description
`
`Color Code
`
`CMCP1100‐XX
`CMCP1100S-XX
`
`CMCP1100HT‐XX
`
`Low Cost Accelerometer with Integral Cable Red (+)
`Black (‐) Shield/Drain
`
`High Temperature Low Cost Accelerometer
`with Integral Cable
`
`White (+)
`Black (‐) Shield/Drain
`
`Sensors with Built In Cables:
`
`Cable Part Number
`
`Description
`
`CMCP602L‐XX‐XX
`
`CMCP602H‐XX‐XX
`
`Accelerometer Extension Cable
`2 Pin, Standard Cable
`
`Accelerometer Extension Cable
`2 Pin, High Temperature Cable
`
`Color Code
`
`Red (A)
`Black (B) Shield/Drain
`
`White (A)
`Black (B) Shield/Drain
`
`CMCP603L‐XX‐XX
`CMCP603H-XX-XX
`
`Accelerometer Extension Cable
`3 Pin.
`
`Red (A)
`Black (B) White (C) Shield/Drain
`
`1010 East Main Street, League City, TX 77573 Phone: 281.334.0766 Fax: 281.334.4255
`www.stiweb.com / www.stiwebstore.com
`Copyright © 2012 STI Vibration Monitoring, Inc.
`
`8
`
`