Frequently Asked Questions

 

Is it possible to convert my existing diesel engine, so it can be used in potentially hazardous area?

In general, every diesel engine can be converted for operation in potentially hazardous area. Some conversions are easy and cost effective, while other can be extremely complex and expensive. Difficulty level is proportional to the amount of potential ignition sources present at the starting point of conversion. Engine with many initial ignition sources requires more work, so conversion is complex and expensive. On the other side are the engines with small amount of initial ignition sources. In this case, conversion is straight forward and down to installation of the SafeCooler Zone 2 protection kit and 3GHI Protection engine safety system.

There are two areas that determine the complexity of the conversion.

Exhaust system

Most common potential ignition source on the diesel engine is related to hot surfaces present in the exhaust system. Most of diesel engines in marine specification have water cooled (wet) exhaust manifolds and turbines, so external surface temperature of those components is controlled by water jacket. Engines in marine specification are preferred candidates for Zone 2 conversion, as hot surfaces in the exhaust system are already eliminated at engine production line. Diesel engines in industrial specification are more challenging as those are fitted with “dry” exhaust manifolds and turbines. During full load operation dry manifolds and turbines can be red hot, so those need to be coated, or replaced with water-cooled version before engine can be placed in Zone 2 potentially hazardous area. Thermal coating is a very time-consuming process, as complete coat layer needs to be durable and gas tight over the entire engine lifetime. This is the main reason why JB Safe Diesel do not offer thermal coating for engine exhaust system. Replacement of existing dry manifold and turbine with water-cooled version is also expensive, as parts need to be outsourced via engine manufacturer aftermarket channel. In addition, engine emission certificate is voided when aftermarket turbine of different type is installed.

Engine speed governing systems

Modern diesel engine is equipped with electronic speed governing system which ensure optimal fuel injection for better fuel economy and lower exhaust emission. Electronic speed governing system contains different sensors, electronic injectors, and main control unit (ECU, or ECM). All those components are considered as potential ignition sources, so they need to be assessed and tested according to specific certification scheme. Most common certification scheme according to series of EN60079 standards requires detailed information about all components and includes thermal endurance testing, electric strength test, IP testing and drop test. This is the main reason why such certification is time consuming and quite expensive. Certification can be justified in case when large amount of the engines will be subject to Zone 2 conversion, otherwise it is better to use engine with already ex-approved speed governing system.

Alternatively, engines with classic hydromechanical speed governing system can be used – such engines are often called “mechanical engines.” Hydromechanical speed governing system do not have any electronic components, so assessment is simplified.

cool  Marine engine with water-cooled exhaust manifold and turbine

frown  Industrial engine with “dry” exhaust manifold and turbine

cool  Engine with ex-approved speed governing system

cool  Engine with hydromechanical speed governing

frown  Engine with non-approved speed governing system

 

Is it mandatory to use exhaust flame arresters?

Exhaust flame arresters prevent flame transmission from exhaust system to surrounding atmosphere. Exhaust flame arresters shall be used when exhaust gases are discharged to potentially hazardous area, however there is one exception from this rule.

Appendix B in EN1834-1 standard contains exhaust flame arrester elimination test procedure. If test is passed, then exhaust can be discharged to potentially hazardous area without needs for using exhaust flame arresters.

3GHI Lite flame arrester elimination system from JB Safe Diesel allows to pass exhaust flame arrester elimination test procedure from EN1834-1 standard. System is shutting down the engine immediately after gas (10% LEL) is detected in the engine intake, so test requirements are fulfilled. In addition, 3GHI Lite system is type approved by notified body, therefore is not required to perform exhaust flame arrester elimination test procedure every time when system is installed on the engine.

Immediate engine shutdown caused by 3GHI Lite system is not allowed for emergency, or essential applications (i.e., fire pumps, emergency generators, crane drivers). In those cases, exhaust flame arresters shall be used when exhaust is discharged to potentially hazardous area.

 

Exhaust Flame Arresters decision tree

What is maintenance interval for exhaust gas cooler?

Exhaust gas cooler need to be cleaned periodically. Soot deposit decreases exhaust gas cooler efficiency. Soot deposit is increasing as engine is running, so exhaust outlet temperature is increasing proportionally. A 1 mm soot deposit is equivalent to a 10% efficiency loss, while 3 mm soot deposit can reduce efficiency by up to 50%. We recommend to clean exhaust gas cooler before exhaust outlet temperature reach warning limit of 190°C.

Exhaust gas cooler cleaning interval depends on soot emission. Engines running at optimal and constant load are low on soot emission, so cleaning interval will be long (1500 hrs, or more). On the other hand, are the engines which are subject to cold operation, low load, and rapid load changes. In this case, cleaning interval will be extremely short (500 hrs, or less) as result of high soot emission.

Extremely short cleaning intervals are often result of wrong engine application, or not responsible operation.

To increase gas cooler cleaning intervals:

  • Warmup engine before applying load.
  • Avoid rapid load changes.
  • Periodically run engine at rated load, so soot contamination is burned out.
  • When possible, periodically inject catalytic powder to burn soot at lower temperatures. Contact us for more info.

What is change (cleaning) interval for exhaust flame arrester?

Same as for exhaust gas cooler – change, or cleaning interval for exhaust flame arrester depends on soot emission from the engine.

Engines running at optimal and constant load are low on soot emission, so cleaning interval for exhaust flame arrester will be longer. On the other hand, are the engines which are subject to cold operation, low load, and rapid load changes. In this case, cleaning interval will be shorter as result of high soot emission.

Typical change / cleaning interval for exhaust flame arresters is between 6-8 hours.

Engines fitted with exhaust flame arrester shall be equipped with exhaust backpressure monitoring device to indicate when flame arresters’ elements need cleaning. (i.e., pressure gauge, or pressure transmitter with automatic alarm). Running engine with clogged exhaust flame arrestors may lead to decreased power performance, increased fuel consumption, or even engine failure.

3GHI Protection engine safety system provides dedicated exhaust backpressure monitoring for applications fitted with exhaust flame arresters.

Operation guidelines when using engine equipped with exhaust flame arresters.

  • Warmup engine before applying load.
  • Avoid rapid load changes.
  • Monitor exhaust backpressure
  • Never run engine with clogged exhaust flame arrester

 

Can I free issue diesel engine for Zone 2 conversion at JB Safe Diesel?

Yes, we accept free issued engines for Zone 2 conversion at our specialized workshop. Diesel engine can be in used condition, or brand new. Check our SafeCooler portfolio to see which engines are currently supported with generic Zone 2 conversion kits. If your engine is not on the list, please contact us for custom made solution.

What is operational ambient temperature limit for Zone 2 diesel engine?

Ambien operational limits are given on engine data plate, and/or Declaration of Conformity document. If no information is provided, then standard operational temperature range of -20°C…+40°C shall be assumed.

Lower temperature limit is normally related to engine starting capability. Most of the diesel engines will start down to -10°C ambient. Cranking at lower temperatures requires starting aids like oil, or coolant heaters.

Upper temperature limit is driven by explosion protection, and/or engine performance. Some hot spots on the engine may become active only at higher ambient temperatures. One of the most common ambient dependent hot spots is present on the turbocharger. In this case engine need to be power derated, or upper ambient temperature limit need to be decreased to assure hot spot free operation. Always check provided documentation to see if engine power output is not affected while operating in high ambient temperatures.

Is it possible to convert diesel engine for operation in Zone 1?

EN1834-1 provides design guidelines for 2G category engines suitable for operation in Zone 1, so conversion is allowed and technically possible. Operating diesel engine in Zone 1 is not recommended, because as per definition “explosive atmosphere in Zone1 is likely to occur occasionally in normal operation.” Operating diesel engine in such condition may lead to unstable operation, or even engine runaway. At JB Safe Diesel we always recommend placing diesel engine in Zone 2. Placement in Zone 1 shall only be considered when no other option is available.

Can rig safe diesel engine be placed in Zone 2?

Rig safe diesel engine units cannot be used in potentially hazardous area (Zone 2). As per definition, Zone 2 is an area where explosive atmosphere can be present for the short period of time as result of abnormal operational conditions. Every equipment placed in Zone 2 area must be free from any potential ignition sources during operational and standby conditions. Rig safe diesel engine units provide enhanced level of safety features, but they are not free from the potential ignition sources. For example, surface temperature of the exhaust channel on rig safe engines is far above safe limit defined by temperature class. More important, high surface temperature is still present after engine shutdown. This is the main reason why rig safe engine units and generator shall not be used in potentially hazardous area (Zone 2), even when they are connected to external shutdown system.

Rig Safe diesel engine units shall always be placed in adequate distance from potentially hazardous area with prior approval from the installation manager.

Please check range our SafePack and SafeGen product lines if you need diesel engine package, or generator set intended for operation in Zone 2.