Settings
Setting the Set-Point in Inches Per Second (IPS) Peak
NOTE: The unit must be set per the application upon installation.
Factory Settings:
- 1.5 IPS
- 1 sec. time delay
- 50% limit value
Figure 4 – EVS-2 Detail for setting IPS and Delay Set-points
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Procedure
Refer to the monitored machine recommended setting and mounting information and make appropriate adjustments. To adjust the setpoint, open the Murphy EVS-2 cover and follow these steps:
1.
Select the appropriate delay settings and ranges using the DIP switches.
2.
A. Time delays for each channel are set to either 1 second or 5 seconds via DIP switch 1 for
Channel 1, and DIP switch 5 for Channel 2.
(ON=1 sec; OFF=5 sec)
B. Select a range that allows normal vibration and preferred trip points to exist near mid range.
Range selection affects both channels. The measurement range in vibration velocity (in/sec peak) is established when:
DIP switch 2: ON=0.75 in/sec peak (DIP switches 3, 4=OFF)
DIP switch 3: ON=1.50 in/sec peak (DIP switches 2, 4=OFF)
DIP switch 4: ON=3.00 in/sec peak (DIP switches 2, 3=OFF)
Use a slotted, narrow blade screwdriver to adjust both of the Vibration Set Point potentiometers:
To increase the Vibration Set Point, turn the potentiometer clock-wise.
To decrease the Vibration Set Point, turn the potentiometer counter clockwise.
3.
Make sure that the machine to be monitored is powered on and in normal operation.
Determining & Adjusting the Delay Setpoint (1 or 5 Seconds)
The Delay Setpoint value can define the line between sensitivity and nuisance faults. A 1 second delay allows a potentially catastrophic failure to be detected quickly. A 5 second delay helps prevent normal start-up vibrations from triggering an alarm. An evaluation of these two conditions should be made for each unique installation before setting the Delay Setpoint.
If start-up vibrations exceed the established threshold limits and trigger the alarm at the desired delay set-point, wire the EVS-2 to a “Class B” input timer on a Murphy annunciator or controller. If used with a PLC system, the input can be timed out for startup.
There are two independently adjustable channels. Each channel has its own delay setting.
Useful Vibration Formulas
V =
πfD
V = 61.44 g/f g = 0.0511 f
2
D g = 0.0162 Vf
D = 0.3183 V/f
D = 19.57 g/f
2
D (displacement) = inches peak-to-peak
V (velocity)=inches/second=IPS g (acceleration) = 386.1 inches / second
2 f (frequency) = RPM/60 rms (root mean squared) = 0.707 x peak peak-to-peak = 2 x peak
π = 3.1416
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Pot Settings
The Vibration Setpoint potentiometers (pots) adjust the level detection based on the scale set in DIP switches 2 through 4. These pots adjust to a percentage of the scale (range) chosen. If
0 to 1.5 IPS is selected as the range, then a pot setting of 50% would cause the EVS-2 to trip at a vibration of 0.75 IPS.
Figures 5 and 6 illustrate these pot settings for the EVS-2.
Figure 5
Figure 6
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Setting of Alarms
The alarm values may vary considerably, up or down, for different machines. The values chosen will normally be set relative to a baseline value determined from experience for the measurement position or direction for that particular machine.
As shown in Figure 7, it is recommended that the alarm value be set higher than the baseline by an amount equal to 25% of the upper limit for Zone B. If the baseline is low, the alarm should be below Zone C.
Where there is no established baseline (for example with a new machine) the initial alarm setting should be based either on experience with other similar machines or relative to agreed acceptance values.
After a period of time, the steady-state baseline value will be established and the alarm setting should be adjusted accordingly.
Recommended Alarm Settings
The following are guidelines based on industry standards. Actual settings will vary depending on mounting and unit installation. (Note: Refer to the Appendix for recommended settings by specific manufacturers.) Experience with a given installation should be the major factor in deciding the settings.
It is recommended that the alarm value should not normally exceed 1.25 times the upper limit of zone B.
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Vibration Limits Based on Class of Equipment Based on ISO 10816-3
Figure 7 – Vibration Limits
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Typical Vibration Alarm Settings of Various Installations
THE VALUES LISTED BELOW ARE GUIDELINES ONLY – Actual vibration limits must be related to stress levels, which can be measured with strain gage equipment. In general, if vibration levels are below the guidelines mentioned below, the stress levels are well below the fatigue level of the equipment. If vibration problem is perceived, a spectral analysis should be performed on the unit by a qualified specialist.
Type of Equipment
Compressor, Centrifugal
Compressor, Reciprocating
Conveyors
Electric Motors
Engines
Fans, Blowers
Gear Boxes
Generator Sets, Electric Driven
Generator Sets, Engine Driven
Machine Tools (unloaded)
Pumps, Centrifugal
Pumps, Gear
Pumps, Reciprocating
Turbines
Velocity (IPS peak)
LOW HIGH
0.2
0.5
0.4
0.7
0.3
0.1
0.5
0.5
0.3
0.7
0.2
0.1
0.2
0.5
0.05
0.1
0.1
0.5
0.05
0.4
0.3
0.3
0.7
0.2
0.3
0.3
0.7
0.2
Reciprocating Compressor Vibration Setting Guidelines
THE VALUES LISTED BELOW ARE GUIDELINES ONLY – Cyclical failures generally occur in the range of 10 to 100 cycles. High velocity at high frequency will result in failure at a much greater rate than high velocities at a low frequency. Experience should also be a guideline in determining acceptance limits for a particular compressor package.
Type of Equipment
Motor Frame
Compressor Frame
Velocity (IPS peak)
(IPS) (mm/sec)
0.3 – 0.5 8 – 12
0.2 – 0.3 5 – 8
Compressor Cylinder (outer end)
0.5 – 1.0 12 – 25
Pulsation bottles (outer center) 0.5 – 1.0 12 – 25
Skid Frame (top) 0.1 – 0.3 2.5 – 8
Scrubber (6’-6” elevation) 0.8 – 1.0 20 – 25
Piping (saddles and 12” spans) 0.5 – 0.8 12 – 20
PSV’s (top of valves) 0.6 – 0.8 15 - 20
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Equipment Manufacturer Recommended Settings
ARIEL: SKID, FRAMES, CYLINDERS (provided by Ariel) MICROLOG CMVA60
SETUP: Velocity ins/sec, zero to peak
If a vibration problem is perceived, a spectral analysis should be performed on the unit by a qualified vibration specialist.
The following chart indicates overall average limits for various models of Ariel equipment.
THESE VALUES ARE GUIDELINES ONLY - Actual vibration limits must be related to stress levels, which can be measured with strain gage equipment. In general, if vibration levels are below the guidelines mentioned below, the stress levels are well below the fatigue level of the equipment.
Model
Skid
Compressor Frame
JG, A, M, N,
P, Q, R, W
<0.10 IPS
<0.20 IPS
JGJ, H, E, T,
K
<0.15 IPS
<0.40 IPS
JGC, D, B, V
<0.20 IPS
<0.20 IPS
Compressor Cylinder <0.45 IPS <0.80 IPS <1.0 IPS
Chart effective 10/01/00, Check latest limits on Ariel Web Site.
Other manufacturer’s data will be provided as authorized.
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