Thermocouple Calibration

            A thermocouple can be any junction between two different metals and may be used to measure temperature. Each metal produces a different electrical potential that varies according to changes in temperature. This rate of change is different for each of the metals in the thermocouple, so a thermocouple produces a voltage that increases with temperature. You can calibrate a thermocouple by plotting the thermocouple's voltage-temperature curve.

Apparatus: 
Thermocouple; 
Temperature controllable bath (thermo bath)
Digital Thermometer;
Multimeter.

Procedure: 

Step 1
         Fill the thermo bath container with water and turn the thermo bath on. Heat the water to 30 degrees Celsius and turn the thermocouple device on. Connect each lead of the multimeter to one end of the thermocouple. This multimeter should be able to measure a voltage of 1 microvolt.

Step 2
         Place one junction of the thermocouple into the water and allow the voltage to stabilize. This occurs when the voltage stops fluctuating except for the last digit. Record the stable portion of the voltage from the multimeter.

Step 3
         Increase the water temperature to 35 degrees Celsius and record the stable voltage on the multimeter again. Repeat this procedure for each 5-degree increase in temperature from 35 to 60 degrees Celsius.

Step 4
         Measure the room temperature and look up the voltage for your thermocouple type at the room's temperature. For example, the voltage for a type K thermocouple at a temperature of 25 degrees Celsius is 1 millivolt. Add this value to each of the voltages you recorded in Steps 2 and 3.

Step 5
         Use the curve-fitting method of your choice to find the line that best fits your recorded data. The slope of this line provides the voltage increase for each degree of temperature increase. The voltage on a standard type K thermocouple should increase about 40 microvolts for every degree Celsius increase in temperature.

(As mentioned in the theory, the multimeter reading corresponds to the difference in temperature between the surroundings (room) and the bath. To calibrate the thermocouple, we have to take the room temperature into consideration to get the absolute value of temperature measured. Find the equivalent millivolt value for the room temperature from the corresponding Thermocouple table (E_RM). Then, add that millivolt value, corresponding to the room temperature, to every multimeter reading (E_MM). Tabulate the values.)

Observations (Type-K thermocouple used):
Room temperature : 20.5° C = 66.2° F; corresponding mV reading from tables E_RM = 0.818 mV

Bath Temperature,TB [° C]	Bath Temperature, TB [° F]	MM reading, EMM [mV]	Total emf, E = EMM+ ERM [mV]	Temperature corresponding to E, TTC [° C]	Temperature corresp. to E, TTC [° F]
30		0.361	1.179	29.4
35		0.579	1.397	34.8
40		0.788	1.606	39.9
45		0.995	1.813	44.9
50		1.202	2.020	49.9
55		1.407	2.225	54.9
60		1.613	2.431	59.8

Plot the measured bath temperatures values (T_B) on y-axis against the corresponding thermocouple emf (millivolt) values (E) on x-axis. Find the slope, intercept and the correlation coefficient of the curve-fitted line by any method. If the correlation coefficient is not very close to one, curve fit with higher order polynomial. Calculate the 95% uncertainty in temperature measurement of the calibrated thermocouple sensor if the obtained curve-fit correlation is used.

NOTE: 
The multimeter voltage reading should be zero when you measure room temperate without the reference junction (the thermocouple connected directly to the meter) Then the reference temperature is the same as measured temperature, both equal to the room temperature, therefore the temperature difference and generated voltage should be zeros. However, your reading will never be exactly zero due to many reasons:

1.     if the tip of the thermocouple is wet it may be sub-cooled due to evaporation;

2.     the room temperature is non-uniform;

3.     the meter is not perfect (make a short-circuit to check its zero),

4.     the measured circuitry may be picking up some "noise," since it acts as an antenna; etc.

Cantrol Valve Benchset and Stroking

Benchset are the actual pressure ranges for travel of the actuator with no friction. These are the actual maximum and minimum pressures that move the actuator from end to end of its range of operation. This is typically performed on the actuator before it is mounted onto the valve.

Stroking is the pressure range for the operation with friction. Stroking takes into account the added pressure required to overcome friction forces when the actuator is connected to the valve assembly.

When stroking a valve, two sets of pressure ranges are produced. There is one pressure range that actuates the valve from fully open to fully closed. The other range is generated from actuating the valve from fully closed to fully open.

The operational stroking range adds pressure and flow effects.

With any type of friction, the problems arise where the pressure to drive the device in one direction will be different to that required to drive it in the other direction. To move the valve in the positive direction, then the force has to exceed the benchset pressure by the amount of the friction. To drive the actuator in the opposite direction, the force has to go below the benchset pressure by the amount of the friction. This is the hysteresis and applies when friction is present.

The amount of friction determines the amount of variation from the benchset pressure range.

RTD Wiring Arrangements(2 Wire,3 Wire,4 Wire Systems)

RTD connection to a Wheatstone Bridge:

• Two-wire
• Three-wire
• Four-wire

Two-wire measurement:

         This is the most basic type of connection for an RTD device. It is used in very simple, cheap applications. They minimize cost at the expense of accuracy. 

         The main problem with two wire measurement is that there is no accounting for the resistance, or even change of resistance in the sensing leads. The measuring device cannot differentiate between the RTD resistance and lead resistance.

Three-wire measurement:

         Three-wire measurement with an RTD device balances the resistances in the lead wires within the bridge. Even though this is a simple modification to the two-wire device, it has the added cost of requiring three wires to obtain the measurement.

         The concept of operation is quite simple in that one lead is measured in the top half of the bridge, with the other lead in the bottom half. Since the sensing distance and other effects are the same, the lead resistance from both sensing leads cancel.

Four-wire measurement - Switched:

         One of the limitations with the three-wire measurement, is that if the lead resistance is not the same or suffer different effects, then the measurement will be erroneous. The Four-wire measurement takes both sensing leads into account and alternates the leads into the upper part of the bridge.        

           By alternating, the lead resistance is effectively measured in both sensing leads, but is then cancelled out by taking the average of the two readings. This level of complexity does make four-wire sensing more expensive.

control Valve Leakage Classifications

          In many process applications, it is important that the control valve be able to completely stop fluid flow when placed in the “closed” position. Although this may seem to be a fundamental requirement of any valve, it is not necessarily so. Many control valves spend most of their operating lives in a partially-open state, rarely opening or closing fully. Additionally, some control valve designs are notorious for the inability to completely shut off (e.g. double-ported globe valves). Given the common installation of manual “block” valves upstream and downstream of a control valve, there is usually a way to secure zero flow through a pipe even if a control valve is incapable of tight shut-off. For some control valve applications, however, tight shut-off is a mandatory requirement. For this reason we have several classifications for control valves, rating them in their ability to fully shut off. Seat leakage tolerances are given roman numeral designations, as shown in this table

Seat Leakage Classifications

There are actually six different seat leakage classifications as defined by ANSI/FCI 70-2 2006 (European equivalent standard IEC 60534-4).

The most common used are

• CLASS IV
• CLASS Vl

CLASS IV is also known as metal to metal. It is the kind of leakage rate you can expect from a valve with a metal plug and metal seat.

CLASS Vl is known as a soft seat classification. Soft Seat Valves are those where either the plug or seat or both are made from some kind of composition material such as Teflon or similar.

Valve Leakage Classifications

Class I - Valve Leakage Classifications

Identical to Class II, III, and IV in construction and design intent, but no actual shop test is made. Cass I is also known as dust tight and can refer to metal or resilient seated valves.

Class II - Valve Leakage Classifications

Intended for double port or balanced singe port valves with a metal piston ring seal and metal to metal seats.

• 0.5% leakage of full open valve capacity.
• Service dP or 50 psid (3.4 bar differential), whichever is lower at 50 to 125 ^oF.
• Test medium air at 45 to 60 psig is the test fluid.

Typical constructions:

• Balanced, single port, single graphite piston ring, metal seat, low seat load
• Balanced, double port, metal seats, high seat load

Class III - Valve Leakage Classifications

Intended for the same types of valves as in Class II.

• 0.1% leakage of full open valve capacity.
• Service dP or 50 psid (3.4 bar differential), whichever is lower at 50 to 125 ^oF.
• Test medium air at 45 to 60 psig is the test fluid.

Typical constructions:

• Balanced, double port, soft seats, low seat load
• Balanced, single port, single graphite piston ring, lapped metal seats, medium seat load

Class IV - Valve Leakage Classifications

Intended for single port and balanced single port valves with extra tight piston seals and metal to-metal seats.

• 0.01% leakage of full open valve capacity.
• Service dP or 50 psid (3.4 bar differential), whichever is lower at 50 to 125 ^oF.
• Test medium air at 45 to 60 psig is the test fluid.

Typical constructions:

• Balanced, single port, Teflon piston ring, lapped metal seats, medium seat load
• Balanced, single port, multiple graphite piston rings, lapped metal seats
• Unbalanced, single port, lapped metal seats, medium seat load
• Class IV is also known as metal to metal

Class V - Valve Leakage Classifications

Intended for the same types of valves as Class IV.

• The test fluid is water at 100 psig or operating pressure.
• Leakage allowed is limited to 5 x 10^-4 ml per minute per inch of orifice diameter per psi differential.
• Service dP at 50 to 125 ^oF.

Typical constructions:

• Unbalanced, single port, lapped metal seats, high seat load
• Balanced, single port, Teflon piston rings, soft seats, low seat load
• Unbalanced, single port, soft metal seats, high seat load

Class Vl - Valve Leakage Classifications

Class Vl is known as a soft seat classification. Soft Seat Valves are those where the seat or shut-off disc or both
are made from some kind of resilient material such as Teflon. Intended for resilient seating valves.

• The test fluid is air or nitrogen.
• Pressure is the lesser of 50 psig or operating pressure.
• The leakage limit depends on valve size and ranges from 0.15 to 6.75 ml per minute for valve sizes 1 through 8 inches.

Typical constructions:

• Unbalanced, single port, soft seats, low load

                   It is from this leakage test procedure that the term bubble-tight shut-off originates. Class VI shut-off is often achievable only through the use of “soft” seat materials such as Teflon rather than hard metal-to-metal contact between the valve plug and seat. Of course, this method of achieving bubble tight shut-off comes at the price of limited operating temperature range and the inability to withstand nuclear radiation exposure.

Turbine flow meter:

• The flow of the liquid caused the rotor to spin at an angular velocity which is proportional to the velocity of the liquid. The speed of the rotor is detected by a pickup on the outside of the tube.
• The liquid may be swirling when its enter the meter which may speed up or slow down the meter. This can be corrected by using flow straightner (bundle of tubes element or radial vane elements). Straightening elements consist of a cluster of vanes or tubes inside a piece of straight pipe. This is placed at upstream of the meter. If a plain straight piece of pipe is before the meter, it should be about 20*diameters equivalent in length minimum.
• The vane is made of ferromagnetic material.
• A high frequency Ac voltage (10KHz) is applied to the coil.
• Generally turbine meters perform well, if the Reynolds number is greater than 4000 and less than or equal to 20000. Because viscosity, temperature variation affects accuracy.
• The turbine meter operating temperature ranges from -200 to 450 0C.
• Density changes do not greatly affect turbine meters.
• The number of pulses per unit volume is called the meters K-factor (pulse/gallon)
• Available in sizes from 5 to 600 mm.

Four main types of pickups:-

• Magnetic reed switch: magnets in the rotor cause the reed switch to on and off giving a digital output this device needs a power supply.
• Optical pickup (photo electric): A beam of light (usually infra red) is interrupted. ( the problem with this method is that the windows tend to become fouled, and so light transmission through the liquid is not to be recommended in many application).
• Inductive pickup: work on the principle of a moving magnet producing a flux which produces a voltage in an inductive pick up.
• Reluctive pickup: it works similar to inductive but the magnet is in the pickup ant rotor in magnetic.
• Radio frequency (RF): an oscillator applies a high frequency carrier signal to the coil in the pickup assembly, an passing of the rotor blades modulates the carrier.

Coriolis mass flow meter

·         The measuring principle is based on the controlled generation of coriolis forces. These forces are always present when both translational and rotational movements are superimposed.

·         The amplitude of coriolis force depends on the moving mass.

Notes:- The fluids fights against this rotation because it wants to keep traveling in the straight line. For any given rotational velocity, the amount of fight will be directly proportional to the product of the fluid velocity and fluid mass. This is the basis of a “coriolis mass flowmeter”. The magnitude of the coriolis force will be directly proportional to the fluids mass flow rate.

Measuring principle:

·         When the mass flows through a vibrating pipe coriolies forces exist which bend or twist the pipe.

·         These very small meter tube distortions are measured by optimally located sensors and evaluated electronically

·         This measuring principle is independent of pressure, temperature, density, viscosity and conductivity.

Tube designs:

·         The tube can be curved or straight form.

·         When the design consist of two parallel tubes, flow is divide into streams by a splitter near the meters inlet and outlet its recombined at the exit.

·         The single continuous tube design (or in two tubes joined in series), the flow is not split inside the meter.

·         In either case, drivers vibrate the tube, these drivers consist of a coil contacted to one tube and a magnet connected to the other. The transmitter applies an alternating current to the coil, which cause the magnet to be attracted and repelled by turns.

·         If the electromagnetic sensors are used, the magnet and coil in the sensor change their relative positions as the tube vibrate, causing change in the magnetic field at the coil.

·         The main difference between the force coil and the sensor coil is that the force coil is powered by an AC signal to impart a vibratory force to the tubes, where as the sensor coils are both unpowered so they can detect tube motion by generating AC voltages to be sensed by the electronics module.

·         When there is no flow in the two tubes, the vibration caused by the drive results in identical displacements at the two sensing points.

·         When the flow is present, coriolis force act to produce a secondary twisting vibration, resulting in a small phase difference in the relative motions. This is detected at the sensing points.

·         Meters are available in size from 6mm or less to 200mm or more and for flow ranges from 0-3kg/hr upto 0-680,000kg/hr.

·         Accurate measurement of both liquids & gases.

·         Ranges cover from less than 5g/m to more than 350 ton/hr.

·         Mass flow, density and temperature can be accessed from the one sensor.

·         Many models are affected by vibrations.

·         The upper pipe line diameter is 150mm

Pitot Tube

           In its simplest form the Pitot tube comprises a small tube inserted into a pipe with the head bent so that the mouth of the tube faces into the flow. As a result, a small sample of the flowing medium impinges on the open end of the tube and is brought to rest. Thus, the kinetic energy of the fluid is transformed into potential energy in the form of a head pressure (also called stagnation pressure).
           

            The simplest pitot tube consists of a tube with an impact opening of 3.125 mm to 6.35 mm diameter pointing towards the approaching fluid. This measures the stagnation pressure. An ordinary upstream tap can be used for measuring the line pressure.

            The velocity equation for the pitot tube is given by
            v = Cp 2gh
            Where: Cp is the pitot tube constant.

            Pitot tubes are generally used only in low-to-medium flow gas applications where high accuracy is not required.

Dall Tube

      It is a modified version of venturi tube. It produces large differential pressure with low pressure less than the conventional venturi tube.

      It consists of a flanged spool piece body with a short, straight inlet section terminating in an abrupt decrease in diameter or inlet shoulder. This is followed by a conical restriction and a diverting outlet separated by a narrow annular gap. The high pressure tap is a hole drilled through the body tangent to the inlet shoulder. The low pressure tap is drilled through the body so as to connect with an annular slot in the throat.

      It is not suitable for measuring the flow of fluids containing solids which could settle out in the throat slot. The Dall tube is used for water, sewage, air and steam flow measurement. The Dall tubes are normally cast in gun metal. But for 450 mm and larger sizes, high grade cast iron is used. When it is required to protect the tube from corrosion, it may be lithcote lined.

Advantages

1. Low head loss

2. Short lying length

3. It is available in numerous materials of construction.

Disadvantages

1. Pressure difference is sensitive to up-stream disturbances.

2. More straight pipe required in the approach pipe length.

3. It is not considered for measuring flow of hot feed water.

Positive Displacement Meters

Positive Displacement Liquid Meters:

• Nutating Disk Meter
• Oscillating Circular Piston Meter
• fluted rotor meter or rotating impeller meter or helical rotor meter
• Oval Gear Meter
• Sliding Vane Meters or (rotating vane)
• Reciprocating Piston Meters
• Rotating lobe
• Precision Gear Flow meters

Positive Displacement Gas Meters:

• Wet Gas Meter 
• Diaphragm Meter
• Rotary Positive Displacement Gas Meter

Nutating disk meter:
          In this type of meter, an inlet chamber is formed by the housing, a disk, and a partition between the inlet and outlet port. Water is prevented from leaving the chamber by the disk, which maintains line contact with the upper and lower conical surfaces of the housing. When the pressure is reduced on the outlet side by a demand of water, the difference causes the disk to wobble (but not rotate) about the vertical axis and thus provide a passage for the flow around the partion. The wobble of the disk causes a small pin attached to its spherical mount to trace out a circular path about the vertical axis of the device. This motion of the pin is used to drive the recording mechanical.

Oscillating circular piston meter:
           It is similar to the nutating disk meter. Its center is constrained to move in a circle by the transmission so that the radius of the cavity is essentially the sum of the radii of the rotary piston and the circle on which its center moves. When the center of the rotary piston is at the top of its travel, the piston forms a closed compartment with the cavity. One rotation of the shaft will cause the rotary piston to return to its starting place and so to discharge the volume of one compartment.

Fluted rotor meter or rotating impeller meter or helical rotor meter:
         The axial and radial fluted rotor meters work on the same principal. The axial fluted rotor meter makes use of two aluminium spiral fluted rotors working within the same measuring chamber — with the rotors maintained in a properly timed relationship with one another by helical gears. As the product enters the intake of the measuring unit chamber, the two rotors divide the volume being measured into segments; momentarily separating each segment from the flowing inlet stream and then returning them to the outlet of the measuring unit chamber. During this ‘liquid transition’, the segments of flow are counted and the results are transferred to a totalising counter or other flow recording device by means of a gear train.

Oval gear meter:
            The oval gear meter is a special form of a multiple rotor meter in which each oval rotor is toothed, and sealing between the rotors is enhanced by the resulting labyrinth. Each rotor transmits fluid from inlet to outlet and forms a closed compartment when its major axis is aligned with the flow direction. The volume passed per revolution of each rotor is four times the volume between the rotor and the oval housing when the rotor is confining liquid [Figure 9.4(a)]. In place of the leakage paths between the rotors of multi rotor meters, there will be, for this meter, extremely small leakage where the rotors mesh, and the tolerances for the other surfaces are likely to be to a high standard, giving a very small value for the overall leakage.

Sliding vane:
            Consists of a cylindrical rotor from retractable vanes protrude. The fluid flow against the vanes causes the rotor to rotate. As the rotor rotates, the trapped fluid between vanes is swept around and out of the chamber. The number of revolution of the rotor is thus a measure of the amount of fluid that has been passed through the meter. Accuracy is high, about 0.1%.

Reciprocating piston meter:
            Reciprocating piston meters are probably the oldest PD meter designs. They are available with multiple pistons, double-acting pistons, or rotary pistons. As in a reciprocating piston engine, fluid is drawn into one piston chamber as it is discharged from the opposed piston in the meter. Typically, either a crankshaft or a horizontal slide is used to control the opening and closing of the proper orifices in the meter. These meters are usually smaller (available in sizes down to 1/10-in diameter) and are used for measuring very low flows of viscous liquids.

Lobed impeller or Rotating lobe:
              In the rotating lobe design, two impellers rotate in opposite directions within the ovoid housing (Figure 3-3B). As they rotate, a fixed volume of liquid is entrapped and then transported toward the outlet. Because the lobe gears remain in a fixed relative position, it is only necessary to measure the rotational velocity of one of them. The impeller is either geared to a register or is magnetically coupled to a transmitter. Lobe meters can be furnished in 2-in to 24-in line sizes. Flow capacity is 8-10 gpm to 18,000 gpm in the larger sizes. They provide good repeatability (better than 0.015% AR) at high flows and can be used at high operating pressures (to 1,200 psig) and temperatures (to 400¡F). The lobe gear meter is available in a wide range of materials of construction, from thermoplastics to highly corrosion-resistant metals. Disadvantages of this design include a loss of accuracy at low flows. Also, the maximum flow through this meter is less than for the same size oscillatory piston or nutating disc meter.

Precision Gear Flow meters:
           The spaces between the gears and the chamber wall form the fluid transfer compartments. In this version, rotation is sensed by two electromagnetic sensors operating through a pressure-resistant and nonmagnetic element in the housing. Two sensors can be arranged to allow better resolution than one and to determine flow direction. Measurement uncertainty of ±0.1% rate is claimed. It is also claimed that rapid flow reversal can be followed (e.g., 801/min in about 0.01 s). Meters for flow range of as low as 0.001 1/min and as high as 1,000 1/min may be available with temperature ranges of -30 to 150°C and pressure up to 300 bars or more

Wet Gas Meter:
            The wet-type gas meter (Figure 2.11) comprises a gas-tight casing containing a measuring drum, with four separate compartments, mounted on a spindle that is free to revolve. The casing is filled to approximately 60% of it’s of volume with water or light oil. Under normal operation the gas passes through the measuring drum so that each compartment of the drum must, in turn, be emptied of water and filled with gas ⎯ thus forcing the drum to rotate. In an alternative arrangement the gas is introduced into the space above the water in the outer casing and then passes through the drum to the outlet of the meter. The spindle on which the measuring drum is mounted is connected through gears to record the quantity of gas passing through the meter. Such meters are available in capacities ranging in size from 0.25 to 100 dm3 with accuracy down to ±0.25%.

Swirl flow meters (vortex precession)

• The swirl meter is based on the principle known as vortex precession.
• The swirl meter can be used with both gases and liquids, its main application as a gas flow meter.
• The major advantage of the vortex precision technique over that of vortex shedding is, only three diameter of straight line required upstream of the meter (3D/1D)
• A inlet guide body whose shape is similar to a stationary turbine rotor is located in the inlet of the measuring device.
• The fluid entering the meter to spin about the center line this swirling flow passes through a venture, where it is accelerated and then expanded in an expansion chamber.
• The expansion changes the direction of the axis about which the swirl is spinning- moving the axis from a straight to a helical path. This spiraling vortex is called vortex precision.
• A flow straighter is used at the outlet from the meter.
• The rotation (swirl) is measured with pizeo sensor.
• The vortex shedding frequency is between 1 and 2000Hz, the higher.

High integrity pressure protection system (HIPPS)

           

               A High Integrity Pressure Protection System (HIPPS) is a Safety Instrumented System (SIS) designed to prevent an unsafe condition caused by pressure arising (e.g. due to separator outlet blocked in the choke valve downstream, blocked pipeline, etc).

               The decision to utilize a HIPPS in addition of utilize a PSV shall be based on the study of risk. The aim of this study is to determine a certain SIL requirement.

               This study will conclude whether some process condition need to have a HIPPS or its ok to protect it by a PSV valve only.

               A High Integrity Pressure Protection System typically is a complete functional loop consisting of:

• The initiators which detect the high pressure.
• A Logic Solver, which processes the input from the initiators and transmits an output to the final elements.
• The Final Elements, which consists of a valve actuated by solenoids.

                In general, the HIPPS required a minimum SIL 3 certification for a complete loop above (sensor, logic solver, and final element). Therefore the HIPPS architecture of the initiators, logic solver, and final elements shall be determined by using a SIL calculation. But in typical the architecture of the HIPPS will consist of 3 pressure transmitter, redundant logic solver, and 2 shutdown valve to achieve SIL 3 requirement. See VOTING LOGIC for more detail information about loop architecture selection to achieve certain SIL requirement.

                Another unique design of the HIPPS valve is the closing time of the valve that must be as fast as possible. In general application the HIPPS valve closure time requirement is calculated and simulated by using a dynamic simulation. The aim of the fast closure time in the HIPPS valve is to protect the downstream of the valve from a very high pressure condition that can happen in a very fast time.

                As an example and illustration, let’s say we have a separator downstream of the production manifold that needs to be protected from a high pressure due to separator outlet blocked. The separator design pressure is 800 psig, and the pressure downstream of the choke valve through the production manifold can be as higher as 1500 psig. With this condition and known flow rate to separator, the pressure arising time can be calculated. If the normal operating pressure of the separator is 600 psig, then time pressure arising from 600 psig to 800 psig must be calculated. Lets say, after some calculation the time needed by the separator to arise it pressure from 600 psig to 800 psig is 4 second, then this 4 second will be the minimum closing time of the HIPPS valve. If the closing time of the HIPPS valve is more than 4 second, the pressure inside the separator will arise more than its design pressure when the outlet is blocked and will endanger the platform (event though there will always be a PSV installed in the separator).

source:- instreng

Emergency Shutdown (ESD) System Philosophy

There are several purposes of the ESD System which is:

• Protection of personnel
• Protection of the environment
• Minimize loss of production and damage to plant assets

Typically, the ESD System could fulfill the above objective by the following implementation:

• Monitoring of an operational or equipment condition
• Automatic action in case of process hazardous conditions is exist by de-energizing electrical equipment, shutting down and/or isolating process equipment and, isolating and depressurizing the installation.
• Enabling manual initiation of ESD actions through ESD push button all around the plant.
• Monitoring the Fire & Gas conditions (F&G) by the F&G System
• Automatic action in case of F&G hazardous conditions exist by providing audible and visual alarms for personnel.

Typical ESD System Component

• Dedicated process transmitters
• Logic Solver
• Shut-Down valves (SDV), Fail to Close type, the purpose of this valve is to isolate.
• Blowdown valves (BDV), Fail to Open type. The purpose of this valve is to depressurize.

In practice the plant is usually divided into several isolable units that can be depressurized and isolated.

Deluge Valves

Deluge systems deliver large quantities of water, over a large area, in a relatively short period of time. They are commonly used in fixed fire protection systems whose pipe system is empty until the deluge valve distributes pressurized water from open nozzles or sprinklers.

Deluge systems contain more components and equipment than wet pipe and dry systems. So for that matter they are more complex. Detection systems can include heat, smoke, ultraviolet (UV), or infrared (IR).

Applications for Deluge Valves

Deluge systems are used in conditions that require quick application of large volumes of water. They create a ‘buffer zone’ in hazardous areas or in areas where fires can spread rapidly. They can also be used to cool surfaces to prevent deformation or structural collapse. Or to protect tanks, transformers, or process lines from explosion.

Other examples include: tanks containing combustible solutions; equipment pits; storage or process areas containing substances with a low flash point; or product handling systems.

The Inbal Deluge Valve is FM and VDS approved to 300 psi (21 bar) in sizes 3″, 4″, 6″, and 8″ (80, 100, 150, and 200 mm). It is compact, lightweight, and comes provided with a preassembled trim – all of which simplifies and speeds up installation. The Inbal Valve opens quickly, yet smoothly, preventing water hammer and is designed to prevent false tripping. Plus, it can be reset by a thumb-activated knob.



Cla-Val Hydraulic and Electronic Deluge Valves offer superior performance and durability in the most critical of fire protection applications. The electric/solenoid-operated Series 134 is an on-off valve that automatically opens upon receiving an electrical signal, to the solenoid pilot control, to rapidly fill fire protection piping. They are available in a wide range of materials that are poured in Cla-Val’s own onsite foundries for quick delivery.

Advantages and disadvantages of Deluge Valves

Advantages
Less expensive than other methods,
Uses water for extinguishing.

Disadvantages
Can damage sensitive or electronic equipment,
Longer clean-up time than powder and gas systems,
Requires a large water reservoir to operate.

Segmental wedge flow meter

                  The segmental wedge element has a V-shaped restriction cast or welded into a flanged meter body that creates a differential pressure. The restriction is characterized by the h/D ratio, corresponding to the β ratio of an orifice plate, where (h) is the height of the opening below the restriction (the only critical dimension) and (D) is the inside diameter of the pipe. It can be used for a variety of corrosive, erosive, and highly viscous fluids and slurries. The discharge coefficient (Cd) is a stable for Reynolds numbers of less than 500 – allowing it to be used down to laminar flow regimes.

                    The upstream and downstream pressure taps are usually in the form of remote diaphragm seals eliminating the need for lead lines.

Averaging Pitot Tube (Annubar)

             To obtain a better average value of flow, special two-chamber flow tubes with several pressure openings distributed across the stream are available, as shown in Fig. These annular averaging elements are called annubars. They consist of a tube with high- and low pressure holes with fixed separations.

             On a conventional integrated Pitot tube, the alignment can be critical. Misalignment causes errors in static pressure since a port facing slightly upstream is subject to ‘part’ of the stagnation or total pressure. A static port facing slightly downstream is subjected to a slightly reduced pressure.

Level measurements using Bubbler system:-

Bubbler tubes provide a simple and inexpensive but less accurate (±1-2%) level measurement system for corrosive or slurry-type applications. Bubblers use compressed air or an inert gas (usually nitrogen) introduced through a dip pipe. Gas flow is regulated at a constant rate (usually at about 500 cc/min). A differential pressure regulator across a rotameter maintains constant flow, while the tank level determines the back-pressure. As the level drops, the back-pressure is proportionally reduced and is read on a pressure gage calibrated in percent level or on a manometer or transmitter. 

The dip pipe should have a relatively large diameter (about 2 in.) so that the pressure drop is negligible. The bottom end of the dip pipe should be located far enough above the tank bottom so that sediment or sludge will not plug it. Also, its tip should be notched with a slot or ÒVÓ to ensure the formation of a uniform and continuous flow of small bubbles. An alternative to locating the dip pipe in the tank is to place it in an external chamber connected to the tank.

In pressurized tanks, two sets of dip pipes are needed to measure the level. The two back-pressures on the two dip pipes can be connected to the two sides of a u-tube manometer, a differential pressure gage or a d/p cell/transmitter. The pneumatic piping or tubing in a bubbler system should be sloped toward the tank so that condensed process vapors will drain back into the tank if purge pressure is lost. The purge gas supply should be clean, dry, and available at a pressure at least 10 psi greater than the expected maximum total pressure required (when the tank is full and the vapor pressure is at its maximum). An alternative to a continuous bubbler is to use a hand pump (similar to a bicycle tire pump) providing purge air only when the level is being read.