Industrial Plant Gas Detection - The Human Sensory Model

Human Sensory Model Gas Detection
(courtesy of MSA/GM)

At any of today’s chemical, refining, processing, or storage facilities contain large indoor and outdoor areas of plants present a congested array of complex equipment, such as tanks, pumps, pipelines, and valves. Your safety depends on sensors that alert you to the presence of gas or vapor hazards, that if left unchecked, could put lives in danger and bring productivity to a standstill.

Traditional sensors rely on a sense of smell to detect trace amounts of gas emanating from the leak. No matter how many of these smell based sensors you install, if a leak doesn't contact the sensor, it could go undetected leaving you oblivious to the potentially dangerous situation. Gas leaks are affected based upon density, ambient temperature, nearby air  ow including wind, and other factors. Despite the number of fixed gas and flame detectors installed within a given system, a leak or flame can still go undetected if it doesn’t reach a gas sensor or can’t be seen by a flame sensor.

Human Sensory Model

Given the difficulties faced by the best sensing technologies, a new strategy in gas and  flame protection has emerged for use within industrial plants. A better, more reliable system is to use the human sensory model to provide layers of protection when monitoring hazardous environments. With this approach smell based detectors are just the beginning.

To enhance detection, integrate optical open path infrared gas sensors, along with gas imaging and optical flame detectors. These allow detectors to actually see a gas leak or flame across wide areas that traditional sensors might miss due to environmental factors such as wind. Catalytic bead detectors“sniff” gases, infrared and optical type sensors “see” gases and flames and ultrasonic sensors “hear” gases. If detectors react in ways that resemble those of humans, that is, based upon intelligence and retained past memories, then layering sensor technologies throughout the plant can achieve a sensory chain of defense against hazardous gases and flames.

To complete the human sensory model add ultrasonic gas leak detectors that can hear the gas leak that might go unnoticed by traditional gas detectors. These sensors form a chain of defense against the hazardous effects of gas release, with the widest portfolio of gas flame detection products available, we are able to tailor a multi-layered solution optimized for your facility.

For more information, contact:

Instrument Specialties Inc.
3885 St. Johns Parkway
Sanford, FL 32771

www.isisales.com
phone 407.324.7800
fax 407.324.1104
e-mail: offices@isisales.com

Helpful Hazardous Area Definitions for Process Control Instrumentation

Courtesy of SOR Pressure, Temperature, and Level Instruments

SOR Explosion Proof
Pressure Switch

Hazardous Area Classification

Hazardous Areas are locations where the potential for fire or explosion exists because of gases, dust, or easily ignitable fibers or flyings in the atmosphere.

In North America, hazardous area classification is separated by classes, divisions, and groups to define the level of safety required for equipment installed in these locations. Classes define the general form of the flammable materials in the atmosphere. Divisions define the probability of the presence of flammable materials. Groups classify the exact flammable nature of the material.

In Europe and countries outside of North America, classification of hazardous areas is accomplished differently. Zones are used to define the probability of the presence of flammable materials. Protection Types denote the level of safety for the device. Groups classify the exact flammable nature of the material. These groups are separated differently than North American Groups. Temperature Identifications convey the maximum surface temperature of the apparatus based on 104° F (40° C) ambient. These temperature codes are selected carefully not to exceed the ignition temperature of the specific gas or vapor to be encountered in the application.

Some hazardous area classifications are not shown here. For further detailed information, see specific standards published by approval organizations.

Classifications Inside North America

Classes
Class I	Flammable gases or vapors are present in the air in quantities sufficient to produce explosive or ignitable mixtures.
Class II	Combustible or conductive dusts are present.
Class III	Ignitable fibers or flyings are present, but not likely to be in suspension in sufficient quantities to produce ignitable mixtures. (Group classifications are not applied to this class.)

Divisions
Division 1	The substance referred to by class is present during normal conditions.
Division 2	The substance referred to by class is present only in abnormal conditions, such as a container failure or system breakdown.

Groups
Group A	Acetylene
Group B	Hydrogen (or gases of equivalent hazard)
Group C	Ethylene (or gases of equivalent hazard)
Group D	Gasoline (or gases of equivalent hazard)
Group E	Metal Dust
Group F	Coal Dust
Group G	Grain Dust

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Classification Outside North America

Zones
Zone 0	Area in which an explosive gas-air mixture is continuously present or present for long periods.
Zone 1	Combustible or conductive dusts are present.Area in which an explosive gas-air mixture is likely to occur in normal operation.
Zone 2	Area in which an explosive gas-air mixture is not likely to occur, and if it occurs it will only exist for a short time.

Protection Types
		Zone
d	Flameproof (Explosion proof) Enclosure	1,2
e	Increased Safety	1,2
ia	Intrinsic Safety	0,1,2
ib	Intrinsic Safety	1,2
o	Oil Immersion	2
p	Pressurized Apparatus (Purged Apparatus)	1,2
q	Powder Filling (Sand Filling)	2
m	Encapsulation	1,2
n	Normally Nonsparking and/or Nonincendive Circuits)	2

Temperature Codes
	°F	°C
T1	842	450
T2	572	300
T3	392	200
T4	275	135
T5	212	100
T6	185	85

Groups
Group I	For application in below ground installations (mines) where methane (firedamp) and coal dust may be present.
Group IIA	For application in above ground installation where hazards due to propane may exist. This group most closely matches the North American Group D.
Group IIB	For application in above ground installations where hazards due to ethylene may exist. This group most closely matches the North American Group C.
Group IIC	For application in above ground installations where hazards due to hydrogen or acetylene may exist. This group most closely matches the North American Groups A and B.

Simple, Effective Shield Protects Against Hidden Level Gauge Glass Erosion Failures

Eroded glass in liquid
level gages.

It's no mystery why high pressure liquid should command your respect. when you've got 400, 500 or even 10,000 PSI in your process, you've got to pay close attention, even to instruments as trustworthy as your armored class level gauges.

Although armored glass liquid level gages are extremely reliable, leaks can occur due to deferred maintenance, or the rigors of continuous operation under high pressure. Erosion of armored gage glass, for example, is often invisible without inspection of the disassembled gage.

To add a new level of protection, the manufacturer Jerguson has introduced the SafeView safety shield. The SafeView shield made of tough polycarbonate can protect nearby operators from high pressure leaks.  In the video below you can see how it shields a direct hit from a 2000 PSI simulated leak. Additionally, it protects the gauge glass from accidental impact, deflecting even direct deliberate blows.

Installation is simple and takes only minutes per unit. The shield fits Series 20, 32 and 300L Jerguson flat glass gauges plus many gauges made by other companies, so you can retrofit your entire facility.

Let’s hope you never experience a high pressure leak, but using this type of device provides an extra level of safety and assurance just in case.