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11 - SPECIAL INFORMATION FOR ATEX ZONES
11.5 - Check - Periodic inspections
11.5.1 - Vibration of the unit
■ Dangers:
- The vibration check detects:
• Any wear to rotating parts. Any significant discrepancy in the vibration speeds may cause parts to come into contact with each
other, which may spark an explosion; it may even cause certain parts to break with the same result.
• An increase in the vibration speeds may also indicate that there is an accumulation of dust and an imbalance has been created.
An accumulation of dust can spark an explosion, by creating areas of contact or by reducing the ignition temperature of the gas.
■ Check:
- Users must ensure that the vibration levels of the fan motor assembly remain below the standardised levels, and that there are
no deviations in the vibration speed values.
- Application category BV3 according to standard ISO 14694.
■ Check frequency:
- Depending on the use (room temperature, and hourly rate of rotation of the unit) and the fluid circulated (from highly charged with
particles, to very clean), users must check the vibration speeds so that any discrepancy in the speed levels can be detected.
- The frequency of checks must be as follows:
• Every 150 hours, or weekly, during the first month of installation.
• Every 2000 hours, or every 3 months thereafter
■ Corrective actions:
- If a deviation in the vibration speed values is noted, the fan motor assembly must be stopped and inspected. If dust is found, all
the areas affected must be thoroughly cleaned. If the vibration speed level is still compliant with the standardised thresholds, the
fan motor assembly may return to normal operation.
- If the alarm level is reached, schedule a second inspection and return to checking every 150 hours, or weekly.
- If the maximum standardised vibration thresholds are exceeded, the fan motor assembly must be stopped, a record taken, and
a 2
nd
inspection must be performed.
- In all cases, a vibration check must be performed after the fan motor assembly is returned to normal operation.
11.5.2 - Checking the ground continuity
■ Dangers:
There is a risk of electrostatic discharge.
■ Check:
- For components fitted with straps:
• Perform a visual inspection of the ground straps (check they are present) and check that the ground strap terminal retaining
screws are correctly tightened.
• With the unit switched off, measure the resistance between one ground strap terminal on each component and the connection
terminal to the customer ground with a supply of 12 Volts. During the first check, this measurement must be noted on the
maintenance sheet (see § 11 -6 Inspection sheet) as well as the reference resistance. The resistance must not exceed 25% of
the reference resistance.
- If the resistance check exceeds 25% of the reference resistance:
• Dismantle each ground strap terminal individually. Only one terminal must be disconnected at a time (this operation must be
performed with the unit switched off)
• Check that there is no area of pitting corrosion on the grounding lug or strap terminal.
• Repeat the resistance measurement.
■ Check frequency:
- Elements ensuring ground continuity must be checked at the following intervals:
• Every 150 hours, or weekly, during the first month of installation.
- If any irregularity is detected during this period of observation:
• Every 5000 hours, or annually thereafter.
■ Corrective actions:
In the following cases:
- Ground strap terminal retaining screws incorrectly tightened:
• Retighten the screws, if the problem persists.
- Areas of pitting corrosion detected on the grounding lug
• Lightly grind the surface of the lug and carefully check the condition of the ground strap terminal.
- Areas of pitting corrosion detected on the ground strap
• Replace the ground strap.
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