security systems of gasThe plant security system is designed with the objective of preserving the plant equipment and facilities, through ongoing monitoring and early detection of causes of risk that may affect the safety of equipment, plant facilities and personnel. Primarily, the system consists of electronic detection equipment, control and action, additional redundancy nature has hydraulic / pneumatic, working somewhat independently of the plant control system.
As elements of detection (ED) in the primary monitoring system must: transmitters explosive mixture, flame detectors, pressure transmitters, cuff buttons, smoke detection, level transmitters. These elements feed control logic resident in the area drivers who take decision to make, for example:

• Locking gas input to the plant.
• Lock and depressurization gas entering the plant.
• Stop a process train independently.
• Stop equipment.
• Blocking production wells.
• Stop power plant.
• Trigger alarms.

The logic is deterministic type which gives repeatability and simplicity to the system, making it reliable, has a development of concurrency or simultaneous approach «that provides an effective arrest of explosive mixture or flame, and, for the protection of pipelines, detection pressure early on in them, is via the detection of growth pressure gradient described as «Shutdown of pipeline protection.» All this to lead to a safe condition of equipment, facilities and protect personnel as may be in the catchment areas of risk.

The final control elements which will be described below are solenoid valves, relays and converters mainly IP. Each of the primary detection component and system action have been continuous verification of component failure and the entire communication path (circuit) associated with it, including a self function test can quickly determine what a system failure. The detection of a communication failure of some component of the security system is clearly indicated on the display station system operation and automatically generates a report on the fault detected.

The system can be summarized daily in a file all events related to these faults. Changes of states of variables (valves, equipment failure, «trip» level 1 shutdown, etc..) Are given on the operator stations, the system also has an alarm feature audible and visual field. In conclusion, with reports that the system must issue to take action. These reports are simple and objective way that the operator can make a quick decision on contingency measures to be taken in plant after a «trip.» They should be detailed to allow subsequent detailed analysis of what happened.

The operation of the system is always in automatic mode or normal, ie without intervention of the Plant Operator to implement the different logics of «trip.» Operate the security system involves manually disabling it, for what it takes different authorization levels in the hierarchical structure of the company.

Maintaining the security system is one of the most care and is performed rigorously, it is noteworthy that each component of the system is disconnected for maintenance disables it. With respect to the wellhead facilities, this electronic system performs monitoring, and «shut down» only by order of the plant operator. Given the hydraulic linkage between the rush to plant and the output of the wells, it was felt unnecessary intervention of the security system for remote transmission. These facilities also have remote on location security system redundant.

The plant security system is designed with the objective of maintaining equipment and plant facilities through ongoing monitoring and early detection of causes of risk that may affect the safety of equipment, facilities and protect personnel that may be in the catchment areas of risk. Primarily, the system consists of electronic and nature has redundancy hydraulic / pneumatic, working with some independence from ground control system. In the following paragraphs describe the operation of security system based on electronic controller Ramos Plant.

Ramos Field

The Ramos Field is located in the province of Salta, 70 km southwest of the city of Tartagal, in northern Argentina, on the hills of San Antonio. With a reserve of more than 100 m3 of gas Mstd MM is the second largest gas reserves in Argentina. The left figure shows the location.

The site has 16 productive wells linked to the conditioning plant for a collection system. This collection system is divided into two parts: South and North. The wells of the southern bloc entering a primary separation station (ESP) in compression through a manifold, since there is linked to the process plant through two pipelines of 12 «and a pipeline of six» was the length of these 5,500 mts. The northern block wells are connected to the manifold gas plant for its straight. The pot plant is farther from the R-1008, with a distance of 15,000 meters of pipeline.

Safety gas plant

The figure shows the «Collection System» Reservoir where you can view the location of the wells in the South Block North Block, ESP and linking to Plant Ramos (VNP).

The gas conditioning plant consists of four trains of the type of independent processes with dehydration LTS Mono Ethylene Glycol (MEG) as a chemical absorbent. The gas processing capabilities are:

• Train A: 1500 MSMCD
• Train B: 2500 MSMCD
• Train C: 3000 MSMCD
• Train D: 3000 MSMCD

Plant Ramos is orchestrated in large part by using a control system and electronic monitoring, supplemented by tele-control system for remote stations such as wells, ESP, meter bridge, Plant, Compressors, etc.,. This control is combined with redundant nature pneumatic and hydraulic equipment considered critical.

Plant Security System Ramos
The plant safety system Ramos is thought to work independently on the criterion of plant operations and automatically. Acting in accordance with the conditions of risk and implementing action logic that will lead to a safe condition or lower risk to set the operation of the plant (equipment, facilities and people).

The elected detection system consisting of field transmitters as explosive mixture, flame detection, liquid level, gas pressure, smoke or buttons of «Shutdown» virtual field and plant operator station.

The electrical circuits are independent of the control system in most cases. This is due to changes in the Reservoir and increasing the processing capacity at the plant. The strategy of the security system lies in two primary and two redundant controllers, who can work independently of the data servers and programming. That is if there is a separation of the monitoring network controllers are field the system in Control Room operation of plant or data servers and programming, these drivers by itself maintain and implement the strategy of «Shutdown» if necessary, keeping the performance for which it was conceived. It has a logic of deterministic type, ie all possible system state, according to its inputs and outputs, have not produced results and indeterminate states. For example, send the command to close a valve, it takes longer than expected, the system displays
failure of closure and continues with the logic to verify the second stop valve to continue the process of «sutdown.» Another case that occurs frequently is double shutdown command, the case for which logic takes only one and starts the shutdown sequence. It should be noted that once initiated the shutdown command logic does not accept any duration of this process, that is not possible to reverse a running shutdown. Only after the security system goes to reset state can take control again.

In the photo above shows one of the drivers of the security system with its power supply and its input and output boards.

One of the biggest weaknesses of the electronics is the power, so the power system is 24 volts and is based on batteries and chargers. Inside the cabinets of the drivers, using distributed voltage converters 12 and 220 DCV ACV. The decision was made not to use UPS because of the failure statistics carried in the reservoir and reduced risk of interrupting the power supply to perform maintenance on the battery-charger configuration. This configuration had no power failures since mid-2003 to now. Including the annual plant shutdowns plant out of service.

The security system is always operating on automatic. Skip to manual system involves
disabling it. Disabling the security system is governed by a process of successive authorizations for the weather that he remain in that state. Up to 8 hours of daytime ban can only authorize the plant manager Ramos, up to 24 hours can only authorize the Super-intendant of the Reservoir, up to a week can only operate if the district manager authorizes it for further periods of operating time Plant Ramos disabled the security system for the operations manager for Argentina. The example is to show the importance and high availability that has the security system of the Ramos Field.

Hardware and architecture is based on a Delta V. The «Simplified Architecture» is shown below:

Elements of detection (ED)
Described below detection elements of the system:

Explosive Mixture transmitters.
Allow continuous monitoring of the percentage of explosive mixture in air its signal being proportional to the lower limit of explosion. These transmitters are strategically located on the ground, sending the information to the electronic controllers. In order to improve the sensing of mixing, built an enclosure that cuts the speed of the gases and spent more time on the sensor.

The states may adopt the sign of these instruments are:
Normal State: The transmitter sends a signal between 0 and 50% of LEL. (4-12 mA)
Alarm Level 1: The transmitter sends a signal between 50% and 75% of LEL. (12-16 mA)
Alarm Level 2: The transmitter sends a signal of more than 75% of LEL. (> 16 mA)
Failure Transmitter: Sends a signal to 0% or less than 100%. (<> 20 mA)

The «transmitter failure» simply refers to the reading of an inconsistent or erroneous signal involves decalibration «down» less than 0% (<> 20 mA) of explosive mixture. This involves regular maintenance and carry a documented history of each of the sensors explosive mixture.

To detect explosive mixture is defined as the maximum value of sensing the threshold for which the air / fuel gas can start and maintain combustion called LEL (low explosive limit), mixed with 5% methane and 95% air) , the signal generated by the transmitter is sent to the system to be monitored and processed from zero percent of gas / air LEL value to one hundred percent of this measurement.

Note: You mentioned that this method of detection, the system can operate with a safety margin than the alarm values mixing rates have not become explosive or produce combustion. An explosive mixture transmitter shown in the photo on the right.

Flame Detectors (UV-IR)
Allow the detection of outbreaks of calls by detecting the combined emissions of ultraviolet light and infrared radiation produced by a flame. These two issues are compared and in the presence of the two activates a discrete signal which is sent to the drivers. Also show the level reached in 4-20 mA loop. They are located mainly in a manner to cover risk zone furnace hot-oil (natural draft cabinet-type and Radial Venting), compressors (propane and recycle gas), Electro-compressors (propane and recycle gas) oil tanks, gasoline Reboilers, glycol regenerators Moto-generators. In the photo below shows a mounted equipment, these are generally high.

The states may adopt the sign of these instruments are:

Normal State: The transmitter sends a signal of 4 mA.
Alarm Call: The transmitter sends a signal of 20 mA.
Fault Detector: The transmitter sends a signal less than 4 mA or greater than 20 mA.
Reset Detector: The DeltaV open a contact sensor power for 5 sec.
Detector Test: The DeltaV closes a contact detector test.

The failure detector is a signal coming from a routine autotesteo the instrument and it takes a value less than 0% (<4> modifiable only from the programming mode of the security system.

Level Transmitters
Detection of high-level vent separator. These are redundant and different technology. One is by differential pressure and one guided wave radar. Any of them can produce «trip» the system after a maximum of 30% of the separator vent. In addition to a level of 20% of these transmitters computer automatically activated electro-pump drainage. This pneumatic pump has redundancy, ie failure of the electric pump, pneumatic pump is operated. The level is shown by signals of 4-20 mA. A difference in measurements in both displays alarm priority. The failure criteria are the same as those described for the detection of explosive mixture.

Pressure Transmitters
Allow continuous monitoring of pressures in the circuit of high pressure gas and detection of high growth pressure. These are redundant and the pressure is shown by signals of 4-20 mA. Since downstream of the plant Ramos is a Compressor Plant, about 30 km distant, pressure transmitters in conjunction with logic block and vent cause plant to avoid over pressure in the pipeline Ramos-Compressor Plant Plant. The verification of the integrity of the loop is similar to the explosive mixture detectors.

Smoke Detectors
Allow the detection of fumes in closed sectors of the combustion product of elements in these areas, the alarm signal is also sent to different controllers for logical processing.

Signals sent to the system: Presence of Smoke detected, 2.0 Amp Dry Contact. Normal Open.
Sensor Reset: By cutting for 10 sec. food.

These detectors are located mainly in the CCM’s, trenches, electric conduits, control room and control room. No cause «trip» of the security system, alarms emit only.

ShutDown buttons
Distributed field buttons that when pressed cause «trip» Security System. They are located in accessible locations are operated by hand and will of the operator in case that according to its criteria identifies an emergency situation. They also have signs. They are placed at a discrete input module controller input as expected. These have a short-circuit resistance allows a continuous current flow and are therefore placed at the analog input module. The states can take the signal circuits of the buttons are:

Normal State: For the emergency stop circuit circulates a signal of 4 mA.
Pushbutton operated: For the emergency stop circuit circulates a signal of 20 mA.
Circuit fault button: The button signal is less than 4 mA to 20 mA or greater.

The check circuit continuity between the DeltaV controller and Shut Down buttons is guaranteed by the permanent measurement of the current signal. The circuit of the punch buttons (shut down) has a dedicated circuit for continuous verification of the integrity of this circuit. If this circuit has disadvantages electric power system operator to give notice to the plant without causing the shutdown of the station (currents below 4 mA or greater than 20 mA). There is also a Shutdown button on the screens of the stations of plant operation which can be actuated by the operator and produce the «trip» the system.

Final Action Items (EAF)
The final action items that handle safety system drivers are mainly:

Solenoid Valves: Used to link the pneumatic and hydraulic and pneumatic control valve / hydraulic, and other redundant systems locking gas income.
IP Conversion: Used in gas pressure controller output plant pipeline.
Relays: used as intermediate outputs to produce failure of equipment, exits visual and audible alarms, etc.

All these elements have continuity check loop similar to those described in transmitters of explosive mixtures and flame detector, which ensures a continuous checking of the state of the electrical circuit.

Simultaneous activity concept
All elements of detection (ED) above; meters explosive mixture, flame detectors, pressure transmitters, etc., Are continuous monitoring. When reading values casts performing below the «trigger», the security system constantly check pending state of emergency.

If you send an item worth more than the acceptable limit, the security system
consider their status as «ON» and will meet during the time that it is actually activated more time from the instant-off, known as dwell time.

After this time the security system enables the possibility to change the state of the sensor (within the program that runs the system) to assess the real indication of the sensor at that time. This concept in the security system is done through the implementation of the following premise: «An active sensing element may change the indication of status (within the program that runs the system) to OFF if and only if readings are obtained the sensing element below the trigger levels for more time spent provisions. » The dwell time is a parameter that can be modified only from the programming mode by personnel authorized to do this.

It follows that the concept of simultaneity that appears in the logic of emergency not only covers the actual existence of simultaneous activation conditions, but also:

1) The detection of an emergency event.
2) Their disappearance.
3) The occurrence and detection of another event of emergency in a time less than or equal to the dwell time since the demise of the event referred to in item 1.

In this regard, and taking an example for transmitting explosive mixture in order to keep operating the criterion of simultaneity, these transmitters will remain for a time of 20 seconds (these times are programmed into the DeltaV controller and can be modified only from the Programming Mode DeltaV system by authorized personnel) asset after the completion of its detection, hoping that another detector or group of detectors triggered by what starts the «trip» the system for detection of explosive mixture.

This concept applies to cuff buttons, which when activated instantly trigger the system.

Manual Mode Operation
The system is not running Shutdown logic to events detected, with the exception of the buttons of Shutdown. That is the output action of the system remains inhibited by detection sensor (flame, explosive mix, level, pressure), but not for ShutDown buttons.

It also allows the display of all associated variables as the firing of the alarm set, as proper operation of the controllers, communication status and normal functioning of the sensors and equipment.

In this mode the operator can change the state Board of valve outlet individually or stop any team in particular Shutdown. Shown in the picture above lay out a security system A & B Train Station Operation room security system. You can change the state individually from manual or automatic station operation room for each plant.

Auto Mode
In this mode the system performs the actions planned for each case without operator intervention. The system checks the conditions through the detection elements and the logic and I xecutive following:

• Plant Shutdown: There are two conditions:

1) Level 1: Blocking entry of gas to the plant, equipment and stop controlled depressurisation process train D, C, B and A.
2) Level 2: Blocking entry of gas plant and equipment trains stop process D, C, B and A.

• ESP Shutdown remote station.
• Shutdown of pipeline protection.
• Well Shutdown South Block.
• Wells Shutdown of North Block.
• General alarm system.
• Closure of production wells by high pressure (hydraulic transmission), a consequence of blocking entry of gas plant.

All actions are informed by alarms at the operator station.

In this mode the operator can also perform manual command to run each train individually shutdown process, and also can take action on the following equipment:
Close block valves.
Open vent valve closure upon verification of block valves. In the right figure shows a graph of the plant operator station vent valve in the open state of all process trains.
Stop Compressors.
Stop pumps.
Paro Horn.
Arrest Generator Plant.
Valve opening pressure controller output plant.

Reset Mode
Produced an event of shutdown, the system remains in that state until the conditions that produced it have disappeared, after which the system must return to rearm Reset by it on behalf of the operator. With this condition may return to operating condition of equipment or block valves and venting plant. The rearming of any manual action item is, therefore, despite the rehabilitation is done with the RESET from the control room and be a change of state command of the elements of action, it will not really be made if not carried out the operation on the local computer system or valve.

It should be noted that the entry of gas valves must be enabled to plant locally. That is to open them should go to the bottom of it and enable the «pilot» tire.

If the condition does not disappear shutdown, the system remains in that state until the item is restored was the «trip», meanwhile you can not change state any valves or equipment, as these remain suppressed.

All variables operational security system are represented in the corresponding screens in the implementation of the security system on workstations Plant Ramos.

Logic Operation
The guidelines for designing the logic of action were, seeking simplicity with early detection via continuous monitoring of causes of risk. Beyond providing maintenance and troubleshooting of the system effectively. Another important aspect is taken into account the information provided to the plant operator, since this depends on further action, as a result of a «trip.»

Summarized the criteria previously applied to deterministic logic, which contributes to a highly reliable system.

Level 1 Shutdown Conditions
Plant Shutdown for Operator action:
• Field ShutDown button: Activate any button (these are not inhibited when
the system is in manual mode).
• Station Operation button from the control room (virtual).

Plant Shutdown caused by flame detection:
• Two flame detectors activated simultaneously, these detectors are called
• A flame detector logic of simultaneity of a minute.
• A flame detector and an explosive mixture detector simultaneously.

Action sequence shutdown Level 1:
1) «Trip» alarm Plant.
2) Blocking or closing valves shutdown input SDV’s gas plant. Pneumatic actuators are controlled directly by the solenoid valves from the controller of the security system via relays. In series with these valves occurs closure or blockage of the second line, but these are controlled by a pneumatic controller, so that the solenoid valves operated security system controller driver mentioned.
3) Turn on Red Moto-pump fire.
4) Shutdown Primary Separation Level 2 Remote Station compression «Southern Bloc» (command sent from the plant controller Ramos ESP controller for telecommunication system).
5) Stop hot-oil furnaces.
6) Stop ovens Mono-ethylene glycol regeneration of train A and train B.
7) recycle compressor stop, blocking and depressurization of «Recycling System.»
8) Stop propane compressors, Lock and depressurization of the «cooling system».
9) Stop electro-pumps.
10) Verification of proper closing of gas valves income dual-income gasping
gas (state control).
11) Vent plant by opening pressure control (PCV’s). The opening order
depends on the place where it started the shutdown condition.
12) Open vent valve (BDV’s) train D, C, B and A. The order of opening depends on where it originated shutdown status.
13) Reset Standby condition.

Shutdown Level 2 conditions
Plant Shutdown caused by detection of explosive mixture:
• Three sensors explosive mixture simultaneously with level 2 criterion of simultaneity.
• Five explosive mixture sensors simultaneously with level 2 criterion of simultaneity.
• High level of venting separator (KOD).

Shutdown action sequence Level 2:
1) «Trip» alarm Plant.
2) Blocking or closing valves shutdown input SDV’s gas plant.
3) Turn on Red Moto-pump fire.
4) Shutdown Primary Separation Level 2 Remote Station compression «Southern Bloc» (command
sent from the plant controller Ramos ESP controller for telecommunication system).
5) Stop hot-oil furnaces.
6) Stop reclamation furnaces ethylene glycol mono-rail train A and B.
7) recycle compressor stop, blocking and depressurization of «Recycling System.»
8) Stop propane compressors, Lock and depressurization of the «cooling system».
9) Stop electro-pumps.
10) Verification of proper closing of gas valves income dual-income gasping
gas (state control).
11) Reset Standby condition.

Pipeline Shutdown Protection
This logic was developed primarily to protect the pipelines to Ramos-Cornejo
unplanned shutdowns of the compressor Cornejo (distant 30 km), avoiding the pressure in the same reach critical values.

The variable that controls the pressure pipeline header in the output of the measuring bridges PM-21 PM-30 and PM-40 plant output. This logic also has a manual mode (can be operated only by the operator) and automatic mode or normal. In figure
left screen shows the operation in which one can select the option of blocking and blocking 3 Million 11 Million as described below.

This protection has two conditions:
a) Block 3 million (3MMMCSD):
When there is an increase of 2.2 lbs / min (pressure gradient) and Superalloys 1145 Lbs (80.5 Kg/cm2). The double lock system activates the gas entry manifold plant only for wells R-1001 R-1002 and R-1004. Shooting shutdown train level 2 only D (ability to process 3 million Sm3 / D).
b) Block 11 million (11MMMCSD): When there is an increase of 4.3 lbs / min (pressure gradient) and more than 1160 lbs (81.5 Kg/cm2). Shoot total shutdown level 2 (ability to process 11 million Sm3 / D).

Report Master Alarms and Events
In implementing the security system includes a Palm Plant report all alarms and events occurring during system operation.


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