The Logic Behind The Magic. “Control Function Block "

Process quantities (level, flow, pressure, ..etc) in plant need to be maintained at target value and a difference from these values could result in a dangerous condition arising or loss production.

To maintain these process quantities condition over an extended period of time without any operator involvement. Automatic control system is usually installed and used.

The element of these control system (loop) are:

1. Transmitter: Process variable is measured by the primary element of the transmitter and the measured signal is converted to electric 4 to 20 mA signal.
2. Controller: Controller receive a signal from the transmitter and compares this value with the set point and computes the output signal to achieved the set point.
3. Final Control Element: Correction device in the control loop. Usually a valve

The Logic Behind The Magic. “Production Well"

A well drilled to find and produce oil or gas in an unproven area  to find a new reservoir

Reservoir development process is comprises of 5 phase:

1. Well construction

2. Drilling

3. Casing

4. Cementing

5.  Completion

The Logic Behind The Magic. “Line Monitored Signal conditioning"

Signals from the various field F&G detectors and push button are processed by the Safety Shutdown System by means of dedicated functions implemented as standard within the Safety Shutdown System.

The line monitoring facility discriminates between open-circuit, short-circuit and true alarm conditions.

the  line monitoring faults is handled as follows:

The Logic Behind The Magic. “Emergency Shutdown System (ESD) Operating Philosophy 3"

Start-up and Maintenance inhibit/ Override

In order to be able to start-up equipment or sections process, it is necessary to inhibit some inputs to the ESD system, as sensor signal may be in abnormal state prior to start-up and could cause a shutdown. Such inhibits are designated as "start-up inhibits".

While Maintenance inhibits are set from the  maintenance / inhibit console for maintenance purpose

Each inhibit function is reset automatically either by the sensor signal reverting to normal state or after a predetermined time delay. The automatic resets are achieved by the Safety Shutdown System.

The Logic Behind The Magic. “Emergency Shutdown System (ESD) Operating Philosophy 2"

Resetting philosophy

Further to a shutdown, the related ESD levels need to be individually and manually reset by the Operation Console operator. The ESD level can be reset only if the upper ESD level is in normal condition.

Resetting sequence is as follows :

·         The operator is informed on the ESD and process displays that the ESD level can be reset

·         ESD level alarm return to normal conditions only when all ESD causes have disappeared or have been inhibited and the ESD level reset is carried out on the ESD display of theOperation Console

The Logic Behind The Magic. “Emergency Shutdown System (ESD) Operating Philosophy 1"

The Emergency Shutdown (ESD) System is designed to protect the personnel, plant, equipment and the environment against pollution. The purpose of the ESD system is to monitor process safety parameters and activate or shutdown the process system and/or the utilities if these parameters deviate from normal conditions.

Usually there are several levels of shutdown:

·         ESD 0 :                       Total emergency shutdown  with abandon of platform

·         ESD 0.1 :                    Black shutdown

·         ESD 1 :                       Total plant emergency shutdown

·         ESD 2 :                       Total process shutdown

·         ESD 3 :                       Local unit shutdown

The Logic Behind The Magic. “Blow Down Valve"

Blowdown valve (BDV) is a block valve that is actuated through the ESD system which is situated in the system requiring pressure depressurisation during plant emergeny or shutdown. BDV is not used in process control.

BDV is typically with shutdown valve but in the reverse condition.(BDV is Fail Open valve, SDV is Fail Closed valve)

The Logic Behind The Magic. “Shut Down Valve".

The isolation of sections of plant will typically be an engineering judgement based on:
1. The purpose for the isolation; either maintenance/operation or shutdown
2. The design condition of the section, particularly pressure
3. The nature of the fluid in the section, e.g. flammability, toxicity etc

Isolation of a section for shutdown purpose will always consist of a single, actuated valves on the perimeter, which will respond to a shutdown signal(s) from ESD systems. Single shutdown valves are normally sufficient for the event initiating the shutdown and associated risk

The Logic Behind The Magic. “Smoke and Heat Detectors"

There are two types of smoke detectors, each having different applications

Ionization Smoke Detectors detect the presence of smoke by means of a small ionization chamber and a source of ionizing radiation. Ionization Smoke Detectors are generally better at detecting smaller smoke particles such as that produced by rapidly burning fires, but are less sensitive to the larger smoke particles generated by smouldering fires, etc.

Photoelectric (Optical Point) Smoke Detectors detect the presence of smoke by means of a small light source and a separate photoelectric light sensitive cell housed within a sensing chamber. Photoelectric Smoke Detectors are generally more sensitive to larger smoke particles such as that generated by dense smoke or smouldering fires, but are less sensitive to small particles of smoke found in rapidly burning fires.

The Logic Behind The Magic. “Open Path Type Gas detector”

Open Path type gas detector devices measure the sum of the hydrocarbon molecules along a narrow beam, the configuration for displaying the reading from an IR beam gas detector is as follows:

Display in LEL-meters which is an integral of percentage LEL as multiplied by the length of the beam.  This is in effect a direct reading of what the device is measuring i.e. the total number of hydrocarbon molecules along the length of the beam.

Alarm levels should be set at a low level but such that spurious alarms are avoided, typically:

·         High level gas – 1 LEL.m,

·         High-High level gas – 2.53 LEL.m 

The Logic Behind The Magic. “IR Flame Detectors" The Logic Behind The Magic. “IR Flame Detector”. ”.

Fire detection is required for process equipment and heat generating utilities, specifically where liquid hydrocarbons may accumulate.  For areas where there is a significant fire risk, additional detectors employing diverse techniques may be considered.

The fire detectors should be selected to suit the conditions and to provide the earliest reliable warning. The suitability of the fire detector is dependant upon the characteristics of the fire, which are determined by the materials involved and their rate of combustion.

Triple Band IR Flame Detectors are considered best practice for flame detection.

Sample of IR Flame Detectors criteria and requirement is shown below.

The Logic Behind The Magic. “Hydrogen Sulphide detectors”

Fixed toxic gas detection is usually provided throughout the platforms due to the significant levels of H₂S in the process fluids being handled and the need to ensure the rapid detection of H₂S gas hazards to warn personnel.

Electrochemical type is widely used and installed in areas where the accumulation of H₂S is likely and at all ventilation intakes

High or High High gas detection by a single H₂S gas detector shall only initiate alarms whereas a coincident High High gas detection by two or more detectors shall initiate a confirmed gas condition with subsequent actions in accordance with F & G Cause & Effect Matrix.

The Logic Behind The Magic. “Gas detector”.

Gas detectors is installed in the platform according to the type and nature of perceived hazard. For example, IR point type gas detector only measure flammable gas concentrations at certain points and there is no way of knowing the composition of the gas cloud between the point detectors, it is therefore necessary to initiate alarms and executive actions well before the concentration at any point reaches 100% of the LFL. The settings shall be as follows:

·         High level gas (process areas) – 20%LEL,

·         High-High level gas (process areas) – 50%LEL,

These type of detector usually have 7 signals and status that are shown in the control room,

1. Faulty Status
2. Calibrate alarm
3. High gas alarm
4. High  gas exec action
5. High-high alarm
6. High-high gas exec action.
7. Inhibit signal

Pipe Reducing Factor

Holden wants to install 1" valve in 2" size pipe. But he wonder what are the reducing factor that he needs to consider. So he began to make the calculation.


Cv with piping geometric factor consideration equations are:



         
             Where Fp (R)

 

Where:

 d :           Valve inlet diameter 

D            :           Internal diameter of the pipe 

K            :           Head loss coefficient of a device, dimensionless

N2           :           constant to suit the measurement unit, 890