April 24, 2012

Safeguard Against a Dangerous and Often Undetected Visitor in Gas Compressor Stations

Lubrication oil is commonly circulated through natural gas compressors in order to facilitate cooling and to prevent engine wear. These systems are highly pressurized and thus create a high risk potential for leakage. When leaks occur the lube oil often sprays into the atmosphere producing an oil mist or atomized cloud. And often leaks will stream continuously undetected for hours or even days without the proper detection technology in place. The mist not only creates an expensive, time-consuming clean-up project, but more importantly, can produce highly toxic smoke or burst into explosive flame upon contact with hot surfaces or engine spark ignitions.

It is not uncommon that gas transportation companies can report dozens of oil leaks per year and some of these leaks have ignited into flame events causing significant damage and production loss. Numerous industry studies have verified that both smoke and oil mist will almost always precede flame prior to an explosive event and have been proven to obscure or blind some optical flame detectors preventing fire warning and potentially leading to disaster.

The solution in this application is an explosion-proof oil mist detector. An effective detector should be equipped with a powerful infrared optical sensor that monitors ambient air for the presence of particulate matter such as dust and oil mist, and for products of combustion like smoke and carbon. The Net Safety Millennium Oil Mist Detector (Airborne Particle Monitor – APM) is the only Class1 Div1 detector of this kind available on the market today.

The principle of operation is based on the reflection of infrared radiation by airborne particles. Field-adjustable zero level of obscuration as well as multiple sensitivity settings allows for fine tuning within specific application conditions to optimize performance and eliminate false alarms. Sensor performance is also not effected by high volume air velocity which makes it ideal for various duct monitoring applications as well. Responses from the APM include actuation of relays, LED indicators, LED alphanumeric display and 4-20mA DC output for transmitting information to other devices.

Oil mist detectors are critical in the previously described natural gas compressor station system where lube oil is used to cool and lubricate compressors in pipeline or processing applications. Advanced detection systems provide compressor buildings with fast, accurate detection of lube oil leaks manifested by smoke or oil mist, providing a proven source of protection for plant and personnel. Natural gas transportation companies worldwide and several offshore platform operators have successfully implemented the Millennium Oil Mist Detector to supplement protection provided by optical flame detectors and fixed gas sensors in these specialized applications.

Learn more about the Net Safety Oil Mist Detector.

April 4, 2012

Preventing Boiler Explosions with Combustion Analysis

Hello everyone. This is Doug Simmers, product manager for combustion analyzers, and today I’m talking about analytical methods for protecting electrostatic precipitators. While I’m using an example from paper mills, many boilers and industrial furnaces utilize electrostatic precipitators for removing fly ash and other particulate from flue gases.

Bark is burned in a bark boiler along with other waste wood products to produce steam that is used in the pulping process, to drive the paper machine, and for many other uses. After combustion, the flue gases from the boilers are often passed through an electrostatic precipitator that uses static electricity to gather the fly ash. An electrostatic charge is induced in the flowing particles and then the particles are collected onto the energized plates with a negative voltage through electrostatic attraction. The negative voltage on the collector plates can be several thousand volts and there is some potential for electrical arcing inside the precipitator. If a combustible gas mixture is allowed to flow through the unit, the result can be an explosion. Combustion analyzers can tell boiler operators when explosive gases begin rising in the boiler flue gases, so they can take action to modify the fuel/air ratios, bypass the flue gases around the precipitator, or power down the precipitator. Good flue gas analysis of O2 and CO also helps the operator to optimize efficiency, and balance the combustion inside of large furnaces.

If an operator sees the O2 going down and the CO going up, that indicates there is a problem developing. Most engineers prefer that the analyzers be placed just ahead of the electrostatic precipitator in order to ensure that flue gases flowing through the precipitator have a low level of combustibles (CO) and a sufficiently high level of O2. In some cases, extremely high particulate levels can negatively affect the optical measurement of the CO. If the IR source energy is blocked by the fly ash, the performance is degraded. In these cases, the CO instrument can be mounted downstream of the precipitator after the fly ash is removed. While the location prior to the precipitator provides the fastest speed of response, high levels of CO in the flue gases typically take many minutes to develop, and the downstream measurement can still provide timely indication of increasing CO.

The initial response to a situation of falling O2 and increasing CO is to correct the fuel/air ratio (more air, less fuel), since bypassing or unpowering the precipitator may result in opacity exceedences. A reliable set of O2 and CO analyzers is the key to assist the operator to make the proper decisions surrounding the operation of an electrostatic precipitator.

You can check out more details on this application in my article in Pulp and Paper International which can be accessed HERE.

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