Hazard Monitors for Grain Elevators

Johnny Wheat
Brian Knapp
4B
Components
Limited
PRESENTED BY:
Copyright 2012 © 4B Components Ltd. All Rights Reserved

Combustible Dust
(Fuel)
Dispersion
of Dust Particles
Ignition Source
(Heat)
Confinement
of the Dust Cloud
Oxygen in Air
(Oxidizer)
YOUR PROBLEM: Grain dust is explosive
YOUR SOLUTION: Remove one of the elements from
the dust explosion pentagon

Common Ignition Sources:
1. Belt Slip
2. Belt Misalignment
3. Hot Bearings

If you eliminate these ignition sources then you not only
considerably reduce your chance of having an
explosion, but you also realize every day values of:
1. Improved Preventative Maintenance
2. Smoother Running Equipment
3. Longer Service Life for Equipment

YOUR PROBLEM: Belts slipping on the head or drive pulley of a
machine is an ignition source
YOUR SOLUTION: Install a speed switch at the tail end of the bucket
elevator or conveyor to warn when the belt starts
to slip and automatically stop the machine
Sensor
M800 Elite Speed Switch

Standard 1910.272(q)(5)
The employer shall equip bucket elevators with a motion detection
device which will shut-down the bucket elevator when the belt speed
is reduced by no more than 20% of the normal operating speed.

YOUR PROBLEM: Belts misaligning and rubbing against a machine’s
casing is an ignition source
YOUR SOLUTION: Install belt misalignment sensors at the drive and
tail ends of the bucket elevator to warn when the
belt starts to rub and automatically stop the machine
Sensor
Sensor
Touchswitch

Standards 1910.272(q)(6)(i) & (q)(6)(ii)
Equip bucket elevators with a belt alignment monitoring device which will
initiate an alarm to employees when the belt is not tracking properly.

YOUR PROBLEM: Bearings overheating are ignition sources
YOUR SOLUTION: Install bearing temperature sensors on all critical
bearings such as the drive and tail bearings to warn
when a bearing reaches a high temperature and
automatically stop the machine
Sensor
Sensor
ADB Bearing Temperature Sensor

Standard 1910.272(q)(4)(ii)
Provide vibration monitoring, temperature monitoring, or other means
to monitor the condition of those bearings mounted inside or partially
inside the leg casing.

YOUR PROBLEM: Electrical equipment can itself, be an ignition
source for a grain dust explosion
YOUR SOLUTION: Only install equipment approved / listed and
certified by an NRTL (Nationally Recognized
Testing Laboratory)
Class II Division 1 Group G -
• For example, inside a bucket elevator or belt conveyor
Class II Division 2 Group G -
• For example, outside a bucket elevator or belt conveyor

YOUR PROBLEM: You are not confident that your local electrical
service supplier has the experience and knowledge
required to professionally install a hazard monitoring
system
YOUR SOLUTION: 1. Send your electrician to the manufacturers
facility for training on the equipment to be installed
2. Have the manufacturer install the system or
recommend a suitable installer

YOUR PROBLEM: Operators continue to operate equipment despite
hazard monitoring systems indicating that there is
a hazardous condition
YOUR SOLUTION: 1. Educate operators on the hazards of grain dust
explosions
2. Instruct operators of the severe penalties that
will be enforced if they do not follow company
policy
3. Automatically log all alarms and shutdowns so
that operators understand that there is a
permanent record and they are accountable

YOUR PROBLEM: Equipment does not perform to your expectations
YOUR SOLUTION: 1. Inspect the system and installation
2. Commission the system
3. Test the system, both initially and periodically
4. Train the operators and management on the
capabilities, use, maintenance and testing of the
system

YOUR PROBLEM: A sensor or control is damaged and the only way
to run equipment is by electrically bypassing the
hazard monitoring system
YOUR SOLUTION: DO NOT RUN IN BYPASS. Have spare sensors
and components available for immediate
replacement so that down time is reduced to a
minimum
! ! ! WARNING ! ! !

Standard 1910.272 App A
It is imperative that the prearranged schedule of maintenance be
adhered to regardless of other facility constraints. The employer
should give priority to the maintenance or repair work associated with
safety control equipment…
(See Actual Standard For Full Interpretation)

YOUR PROBLEM: 1. OSHA has stepped up its facility inspection and
audits in conjunction with their National Emphasis
Program (NEP) on dust explosions
2. OSHA is finding twice as many violations in
relation to the NEP inspections compared with all
other types of facilities. One such violation is that
bucket elevators and conveyors are not equipped
with bearing temperature, belt alignment and
underspeed detection monitors
YOUR SOLUTION: 1. Understand the dangers of grain dust, and
implement a program of compliance to not only
OSHA regulations, but also NFPA and other
standards
2. Install hazard monitors (as discussed earlier) to
help eliminate ignition sources

OSHA & NFPA STANDARDS
(See Actual Standard For Full Interpretation: OSHA 1910-272, NFPA 61, NFPA 654)
Hazard Requirement
Belt Slip Motion detection device to provide a shutdown and
alarm at 20% reduction in normal belt speed. Also
shutdown of feeding equipment.
Belt Misalignment Belt alignment monitoring devices at head and tail
pulleys, which initiate an alarm.
Bearing Failure Bearing temperature or bearing vibration monitors which
activate and alarm.
Pulley Misalignment Head pulley alignment monitors which activate an alarm.
Plugged Spout Sensors which provide a shutdown and alarm when there
is a plug condition. Also shutdown of feeding equipment.

o NFPA 61 Standard for agricultural and food
processing industry (rev. 2008)
o NFPA 68 explosion venting standard (rev. 2007)
o NFPA 69 prevention standard (rev. 2008)
o NFPA 70 NEC (rev. 2008)
o NFPA 77 static electricity (rev. 2007)
o NFPA 499 guide to combustible dust area
classifications (rev. 2004)
o NFPA 654 standard for general industry (rev. 2006)
NFPA STANDARDS

TYPICAL SENSORS FOR HAZARD MONITORING
Speed &
Belt Slippage
Belt Misalignment
Bearing
Temperature

TYPICAL CONTROLS FOR HAZARD MONITORING
Watchdog™ Elite
Single Machine
Hazard Monitor
PLC T500 Hotbus™
Multi Machine
Hazard Monitor

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Hazard Monitors for Grain Elevators

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