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AREA CLASSIFICATION AND STE EQUIPMENT ZONING

GENERAL DISCUSSION

When we speak of zone 1 or zone 2 equipment we mean that the equipment is rated foruse in areas classified to either zone 1 or 2. So first thing we need is the definitions ofZONE Areas:

ZONE 0 AREA : Area where explosive gas-air mixture is continuously present orpresent for long times

ZONE 1 AREA : Area where an explosive gas-air mixture is likely to occur in normaloperations

ZONE 2 AREA : Area where and explosive gas-air mixture is not likely to occur, and if it occurs, it will only exist for a short time

SAFE AREA : All other areas than those mentioned above

Above definitions from DNV Tech Notes for Fixed offshore Installations... but an old copy... I reallyneed to update my library.

In addition to the above classifications as ZONE, there also exist the definitions as Class 1 Division 1,Class 1 Division 2 that are broadly similar to Zone 1 & Zone 2 respectively.

Based on the above ZONE definitions we must then look to see how far the ZONEClassification extends from the source.

The area extent depends upon whether you have a Primary or Secondary grade source hazard and

also whether the gas is heavier or lighter than air. Air is Molecular weight 28 and gases betweenMolecular Weight 21 to 35 should be considered to fall in both categories. We would mostly fall intothe category where gases are lighter than air but if the gas gravity, as determined by Ranarexmeasurement is greater than 0.75 we need to consider the heavier than air category as well. (Notethat H2S is heavier than air but is not a factor as Zone classification covers explosive mixtures).

"Primary Grade Source" - machinery or plant that can release a flammable substance into theatmosphere during normal operation. Typical sources: open tanks, sample and draining outlets, pumpglands where leakage may be expected to occur...etc.

"Secondary grade Source" - machinery or plant that can release a flammable substance into theatmosphere during abnormal situation or infrequent operations. Typical sources pump glandsdesigned and maintained to prevent leakage, sample or drain outlets operated infrequently, valves,fittings, gauge glasses etc.

As you may have determined from the above the extent of the classification area can be somewhatopen to individual interpretation. I consider that our pumps are designed and maintained to preventleakage and that operation of drains and outlets is infrequent so our equipment is a "SecondaryGrade Source".

Since we do not typically have the Gas Gravity from the Ranarex until the test is ongoing there is aconsideration to classify the gas as both heavy & light which will affect where on the rig you can place

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certain items. Erring on the side of caution is recommended but if we can get expected Gas Gravityinfo up front then we can stay in "lighter than Air" category. Separation efficiency will also affect ourmeasured gas gravities... if there is liquid carryover due to poor mist extractor performance orexcessively wet gas then the gas gravity from the Ranarex will read high.

FOR OUTDOOR AREAS, GASES LIGHTER THAN AIR, AND SECONDARY GRADESOURCE OF HAZARD:

Following 1965 edition of IP Electrical Code and area within a vertical cylinder with a radius 3 metermeasured from the source and a height 4.5 meter above and 4.5 meter below the source has to beclassified.

For a Secondary Grade Source this area will be classified as ZONE 2.

In case of a Primary Grade Source the above area will be classified as ZONE 1 and an area of 3meters horizontal and vertical from the ZONE 1 area will be classified as ZONE 2.

THAT'S THE END OF THE DEFINITIONS.

Now that we have the definitions we now talk about what equipment can go where with the primeconsideration being that equipment in the zone classified area should not produce a spark ortemperature surface high enough to cause ignition of the potentially flammable gas-air mixture. Thereare different degrees of electrical and temperature protection required based upon whether you are tobe operating in a Zone 1 or Zone 2 area.

HOW DOES OUR EQUIPMENT STACK UP?

Sometimes we talk about our separator being Zone 2. Perhaps a terminology error as the separatorwould really be ZONE 0 rated, as it does not have electrical or temperature sources to produceignition. The separator does produce a ZONE 2 area due to infrequent releases from Sight Glasses,Daniels Orifice box, Shrinkage Tester and Sampling ports.

Everything within 3 meters horizontal and 4.5 meters above & below must therefore be rated ZONE2. This means pump drivers, lights - if we install them on the separator skid, the lab etc.

It also limits where you can place the equipment on the rig as some areas are classified to prohibitthe equipment. Example ... you couldn't place a separator, choke, or flange connection within 3meters of a rig vent or air intake to pumps and compressors.

The above applies in general to our equipment.

SPECIFIC CONCERNS:

LIGHTING / ELECTRICAL

Zone 1 & Zone 2 compliance specifications usually aren't that much different so not much of astep to go to Zone 1 spec from Zone 2. Last Lab I built I asked for a Zone 2 spec on the outercabin and the Vendor went to Zone 1 because it was the same cost and fit easier into his productline. Both Zone 1 & Zone 2 are protecting the same thing... one just deals with more frequent orexpected occurrences.

Lighting placed in our area should be rated Electrical Class for Zone 2.

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Temperature Class runs from T1 through to T6 and these correspond to temperatures, forexample on the glass surface of a floodlight. T4 is ok for Zone 2 - Don't have the book with me totell you the other T* ratings that are suitable.

PUMPS

Electrical Pumps with Zone classified motor, starter box are fine.

Diesel Pumps - Trickier. You need : Anti Static Drive belts, Anti Static Fan for the radiator, a water-cooled exhaust for surface temperature

need to cool to 200F... this means an oversizedradiator

Spark Arrestor on exhaust Shutdown on air intake

If you have a very long shaft... to get the driver 3 meters or more away from the fluid end thenyou meet zone requirements. Even if you could find a set-up like that though I still wouldn't

recommend it for our operation and doubt that customers such as the IOC's would accept it.

HEATERS

Steam type not a problem but the Steam generator needs to be remote, as this is an open flamediesel burner. You do of course need to protect against hydrocarbons, resulting from a coilfailure, from reaching the Steam Generator.

Gas or Diesel Fired - Trickier. These of course have an open flame in the fire tube and anexhaust stack.

The open flame within the heater we can argue is isolated from the coils by the water bathsurrounding the fire tube but we should have a low water Alarm and shutdown incorporated onthe shell side. The fire tube should be fitted with a flame arrestor to atmosphere but even at thatthere will be an area that is "open" to atmosphere for monitoring the flame. If the heater is 3meters or more in length one can argue that this source is outside the Zone 2 area created by thefront-end heater piping.

The Vertical Exhaust is a source of both surface heat and spark or ash fallout. Spark arrestor onthe Exhaust is recommended.

Gas or diesel fired heaters can be equipped with various safety systems such as Flame Detectorand temperature Sensors that will control fuel supply to the firetube.

LABS

Here we have a choice, to set them close to the equipment. In which case they should meetZone Classification requirements, or set them remote of the equipment in a safe area.

Lab Electrics can be installed that meet Zone Classification requirements however the Computerequipment is not able to meet Zone Classification requirements.

To overcome the difficulty of computer equipment, resident in a Zone Classified area the Labshould be fitted with:

Air Purge System

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Internal Cabin Pressure Sensor/Shutdowns Internal Cabin or Air Purge Supply Lower Explosive Limit (LEL) / Higher Explosive

Limit (HEL) and H2S Gas Sensors for Alarms and shutdowns. Alarms and time delay shutdowns for Open doors Multi cable Transit (MCT)

Usually an offshore lab as described above will have two compartments, separated by an internalAir Lock Compartment. The full Zone Classified version has sensors for Cabin pressure. Apositive pressure supply to the Cabin prevents ingress of Hydrocarbon and/or H2S gases. If thepressure drops below set point an alarm sounds, if pressure drops further the electrics may beshut down.

Common Mistake in Air purge is the set up of supply. The safe method is a Blower set in aremote area to supply fresh air to the lab. The feed line has positive pressure so that if puncturedit will not allow ingress Hydrocarbon or H2S gases. The method sometimes used in error is tohave suction in the lab and run a hose to a safe area. If the hose is punctured then the suctionwill draw from atmosphere at the puncture, which may have hydrocarbon or H2S gases.

Alarms and Time delay shutdowns for the internal air lock doors - sound if both doors are openand shutdown if both are open for a set period of time.

MCT is used for feeding cables (SCAN2) into the lab. Lycron insert blocks are removed, cablesrun into the lab, then the blocks re-installed to form a compression seal around the cables.

Often you may also find labs equipped with an Uninterrupted Power Supply (UPS) so that if wedo lose power the SCAN2 system doesn't shut down. This would make the alarms andshutdowns of no value, as do computers that would have their own battery power to keeprunning. These need to be shutdown manually if the alarms shutdown the lab power.

Labs should be equipped with an Emergency Light, rated for Zone Classified areas. Theemergency light plugs into the sockets in the lab and if power is lost the Zone 2 light comes onautomatically so we are not lost in the dark.

That's it.

Probably more than you wanted to know. There will be more to this that can be picked up fromreading the various regulations but for what we do I hope this covers and explains the basics.

Now that I've got it written I'll look to get it on the web.