Side Mount vs. Top Mounted Level Instrument

 

Side Mount vs. Top Mounted Level Instrument

What should be considered when deciding whether a level device (transmitter or switch) should be top or side mounted with an external cage?

Top mounting means that the sensor or measuring element of the level gauge is inserted into the container or tank from above. Side mounting with an external cage means that the sensor or measuring element is integrally installed in an external cage prefabricated by the manufacturer.

The price of the external cage leveler is higher than the top mount type. This is due to the cost of the cage, in addition for a special material such as Duplex Stainless Steel. However, an external cage level gauge may have an isolation valve installed between the tank and the cage. This arrangement allows maintenance of the device without the need to shut down the process. Therefore, an external cage level measurement tool is preferred in most applications.

In some cases, a top mount tool is used, such as:

A buried ship because it has no side access.

A semi-submersible tank such as a caisson.

A liquid that can change properties/form due to temperature change and the use of steam or electrical auxiliary heating is not possible.

Why must the cable shield not be grounded on the instrument field device?

Grounding of the device cable shield

Why must the cable shield not be grounded on the instrument field device?

Cable shielding protects the signal transmitted by the conductor from external interference. The cable screen blocks external interference and noise and then directs it to the ground.

The screen must be grounded to only one source. Grounding is usually done in the equipment panel or cabinet, while the field equipment point is left ungrounded and isolated. This eliminates the ground loop current that can occur if the shield is grounded at both ends. In this case, the ground loop current becomes noise for the signal wire itself.

The following wiring diagram shows the ungrounded instrument cable shield on the operating device.

INSTRUMENT RANGE SELECTION

 Choice of instrument range

The range of the instrument is chosen based on the operating range of the process to be measured. In common practice, it is recommended to select a full-scale instrument that can provide an operating reading between 30% and 70%, especially for a pressure gauge. The following is an example of selecting a pressure gauge range

Given process data:

Minimum operating pressure: 5 kg

Maximum operating pressure: 9.5 kg

Maximum design pressure: 25 kg

Available standard pressure gauge range: 0-10 kg, 0-16 kg, 0-25 kg

[X] A selection of 0-10 barg will provide a 95% reading during maximum operating conditions. The device has only a small reserve above the maximum operating pressure.

[√] Selecting a range of 0-16 barg will provide the best reading during operating conditions. However, the maximum gauge pressure is normally 1.3x the maximum scale, which is only 16×1.3 = 20.8 barg. In such a case, the gauge must be equipped with over-range protection to withstand the design pressure.

[X] The 0-25 kg selection can withstand up to 32.5 kg (25 x 1.3) without using overrange protection, but under normal operating conditions this would give a poor reading indication.

Shutdown logic diagram

 Schematic of shutdown logic

A shutdown logic diagram (also known as an ESD logic diagram) shows the shutdown level hierarchy within a plant or platform. The shutdown logic diagram starts by telling the big picture of the shutdown level, usually the level starts from 0 and continues with a higher number (1, 2, …). A lower number represents a more critical shutdown. The following sheets continue with a hierarchy of details for each process unit.

A trip logic diagram describes the 'cause' that can trigger a trip and the effect that can occur after the signal is activated. This diagram also shows the action such as time delay, start inhibit, reset that will be performed for each action.

The location of each instrument acting as a trigger/cause must be clearly specified.

Reference document: SAFE Chart, philosophy

The SAFE table lists the required safety devices for each process device. The SAFE table must ensure that all safety requirements have been met and what executive actions the safety device must perform.

The philosophy provides the narrative and the engineer translates it into cause and effect interaction so that the plant works as the intended philosophy.

Purpose of the Shutdown Logic Diagram

The shutdown logic diagram can be used as a reference when preparing a cause and effect diagram.

Sensing Elements for pressure measurement

 Elements for pressure measurement

Bourdon tubes

A Bourdon tube is a metal coil made of a metal tube that is closed at one end and attached to a pressure source at the other. It has the required elasticity, due to which the pipe tends to deform in order to straighten itself under pressure. Applied pressure will result in movement at the free end causing the mechanical linkage to move the pointer. Bourdon tubes come in several forms, i.e. C tube, spiral or helix.

Bellows

The pressure element of the bellows is made of seamless tubes that are rolled. It looks like thin-walled corrugated cylindrical containers. The corrugator is flexible along its axis so that it changes its length in proportion to the applied pressure.

Diaphragm

A diaphragm sensor is a thin flexible metal disc. Pressure applied to one side of the disc causes a deflection that activates the pointer. To measure very low pressures, the diaphragm must be very thin. In this case, it is difficult to manufacture and its stability is poor. Capsules can be used for this application. It is made of two diaphragms welded together, so it doubles the deflection of the diaphragm, allowing smaller pressures to be measured without reducing its performance.

Use of temperature transmitters

Use of temperature transmitters  

In order to create a temperature measurement system, an electronic temperature measuring device must be connected to the control system. The RTD and thermocouple can be connected directly to the I/O card of the control system or through a temperature transducer for signal conversion. In most applications, a temperature transmitter is used to convert the RTD / thermocouple signal and transmit the 4-20 mA signal, rather than connecting the RTD or thermocouple directly to the I/O card

Choosing to use a temperature sensor over directly connecting an RTD or thermocouple to the control system provides many advantages:

Signals generated by a resistance temperature detector or thermocouple are categorized as a low-level signal and are therefore more susceptible to noise compared to a conventional 4-20mA signal generated by a transmitter.

Reduce the device cable type. It also means less type for a replacement cable.

The junction box for temperature sensor cables can be combined with cables from other 4-20 mA sensors.

There is no need to provide a special I/O card for the thermocouple/RTD. Just connect the transmitter to the analog input I/O card.

It provides a maintenance facility such as a diagnostic function in a smart transmitter.

Temperature element Instrument

 Temperature element Instrument

There are several types of temperature elements widely used to measure the temperature of a process substance. These types are divided into mechanical temperature elements and electronic temperature elements. The mechanical thermal element uses the principle of thermal expansion, that is, the element expands when the temperature increases and vice versa. The electronic temperature element uses the principle of changing electrical properties following a change in temperature.

Mechanical temperature element

Solid element

A bimetallic is a thermal element created from two types of metals that have different thermal expansion properties. The two metals are joined together to form one strip. Metal strips bend when the temperature changes. An indicator is attached to the free end of the bimetal to indicate the result of the temperature measurement.

Gas element

A gas-filled system is a temperature element based on the principle of the ideal gas law. It consists of a bulb/stem, a capillary and a Bourdon tube. The sensing element is a solid bulb or spindle containing gas. If the temperature rises, the volume remains constant because the flask is rigid, while the pressure of the gas increases proportionally. The change in gas pressure is measured by a pressure element such as a Bourdon tube.

The flask and bourdon tube are connected by a capillary tube allowing the placement of a temperature indicator that is not directly connected to the pipe/vessel being measured. These advantages allow the thermometer indicator to be mounted in a convenient location, while the sampling point of the measured process fluid is not permanently inaccessible.

However, the capillary can lose heat, so compensation must be added to eliminate the error. www.instrumentationportal.com

Liquid element

The liquid temperature element uses mercury in the bulb/stem. Mercury is no longer preferred in most process applications, although it provides fast response and good accuracy. Mercury is mostly used in a glass stem thermometer for non-process industries such as measuring body temperature.

Electronic device for measuring temperature

The two most commonly used electronic temperature elements are the resistance temperature detector (RTD) and the thermocouple. To indicate the temperature measurement, these elements need to be connected to the control system by cable directly or by means of a temperature sensor.

Resistance temperature detector

The Resistance Temperature Detector (RTD) works on the principle that the resistance of a metal changes with its temperature. RTD is the most commonly used type in process measurement due to its good stability, accuracy, repeatability.

Thermocouple

A thermocouple consists of two different metals, the transition of which generates a voltage proportional to the transition temperature. The thermocouple is selected for operation that requires a wide range (very high - low temperature). Other advantages of a thermocouple over an RTD are that it has a more durable construction and also provides a faster response.

ESD transmitter with voting logic

 ESD transmitter with voting logic

The ESD transmitter serving the critical trip level in the Safety Instrumented System is recommended to have a polling logic configuration. Election logic is used to minimize the occurrence of total loss of production due to a single transmitter failure or false trip. The voting configuration can be 2oo3 or 1oo2D based on SIL assessment and verification.

When using voting logic in a process, consider:

The transmitters should not have a common connection to the process line/equipment.

Transmitters forming the same voting logic must not be assigned to the same Safety Instrumented System I/O module.

Each instrument cable is routed differently.

The transmitters are set to the same calibration range.

It is also recommended to have third-party converters to avoid a manufacturing defect causing common mode failure. Also in this polling logic configuration, the SIS must compare the transmitter value and trigger an alarm on the Human Machine Interface (HMI) for any measurement deviations between transmitters.

                      ESD transmitter voting

On the 2oo3 polling transmitter, any one abnormal process variable detection by one transmitter will trigger an alarm. Shutdown will be initiated if two transmitters reach the shutdown set point.

Here are some examples of applications where an ESD transmitter is used with polling logic, usually part of a higher level in the shutdown hierarchy level:

Air instrument head

Export pipeline

KO drum

Instrument specification document vs instrument data sheet

 Instrument specification document vs instrument data sheet

What is the difference between a device specification and a device data sheet? The terms instrument specification and instrument data sheet are used interchangeably by some practitioners. Both are referred to as documents or information sheets that specify details about the device. You often see manufacturers use the word "specification" in their product sheet, and sometimes you get a "data sheet" in another manufacturer's product sheet.

For those involved in the project, the instrument specification and the instrument data sheet are two different documents. A device specification is a document that limits the boundaries of a device. It tells the general rule how to specify the tool to use. Meanwhile, the information in the data sheet is much more detailed and much more specific to suit the application.

The following example shows how the specification and data sheet talk about the scope of the device:

Specification: "The range of the instrument must be chosen so that the maximum value of the process variable does not exceed 90% of the calibrated range"

Data sheet: "0 - 100 barg" (in which case the maximum process pressure is 90 barg)

First, the device specification is generated and based on this document we can derive the data sheet and obtain additional information from other documents when preparing the device data sheet.

Cause and consequence in instrumention

 Cause and consequence in instrumention

Some projects categorize cause and effect as part of a process document, and some other projects consider cause and effect as part of tool outputs. Literally, "cause" means something that causes something else to happen, and "effect" is what happens as a result of the cause.

The interaction between cause and effect can be simple or complex. For a simple example in process control: the cause can be a high liquid level alarm in the tank and the consequence can be the opening of the outlet valve of the tank. A complex example could look like this: If at least two flame detectors detect a fire in area 1 and coincide with one flame detector detecting a fire in area 2, then it should close valve A, close valve B, open valve C, disconnect power. outlet etc.

Cause and effect are presented as a matrix form. Causes are listed on the left while effects are listed on the top, both described in the form of a tag number with their description (other supplementary information such as P&ID may be added). A marked intersection between the two means they are cause-and-effect related. Markers can be "X" which means the effect will be activated, "T" which means the effect will be activated with a time delay, "P" which means the cause will enable the effect.

There are two categories of cause and effect diagram:

ESD C&E diagram

C&E Fire and Gas Scheme

Reference Document: SAFE Chart, ESD Logic Diagram, Philosophy

The SAFE Chart presents the required safety devices for each process device. The SAFE table must ensure that all safety requirements are met and what powerful actions the safety devices perform.

The philosophy provides the narrative and the engineer translates it into cause and effect interaction so that the plant works as the intended philosophy.

The ESD logic diagram shows the plant shutdown hierarchy and describes the input that initiates the shutdown and the output as the results after the shutdown.

Purpose of the document Cause and effect

The cause and effect document will be translated into a programming language by the control system engineer and implemented into the control system as logic. This logic will always monitor the device during operation and operates if predetermined conditions are met.

PIPING AND FITTING DESIGN GUIDE

PIPING AND FITTING DESIGN GUIDE

The following points provide a brief guide to tubing and fitting design for instrument tubing and fittings. Selection preferences may vary between projects.

The selection of connection materials must take into account the process fluid pressure and pressure rating to ensure good sealing and integrity.

The pipe thickness must be selected based on the nominal application pressure. Consult the manufacturer for the pressure rating for each thickness of tubing.

Dual compression hose fittings are preferred.

For the entire project, it is absolutely necessary to use typical components of hoses and fittings from one manufacturer.

Mixing different threaded fittings from different manufacturers is not allowed, as this could lead to poor sealing of the fitting.

CONTROL SYSTEM ARCHITECTURE

CONTROL SYSTEM ARCHITECTURE

Control system architecture The system architecture depicts the architecture of the plant's management systems and also the interfaces between the systems needed for the general operation of the process plant.

> The required system is set by the extent of practicality, quality and safety of the instrumentality. this might embrace method system, safety instrumentation system, HIPPS, fireplace and installation, packaging unit system. 

> The system design drawing will show superior level instrumentality like operator digital computer, engineering digital computer, HMI server, OPC server, historical server, panel like ESD panel (button and lamp), fireplace and gas matrix and conjointly network instrumentality. 

> The system design should clearly outline the situation, each main locations, remote I/O location, indoor/outdoor location, control room/building limit. 

> The main management, local area network and communication cables also are shown and such as. The system design is abstract in nature and serves to specify the system needs for the DCS provider. This drawing is provided as supporting documentation for the method system demand.

Tubing schedule

Tubing schedule

A tubing schedule is a document listing tubing for equipment that serves as impulse piping, hydraulic/pneumatic supply and return piping, process piping such as chemical injection piping, melt loop. This document also shows details of the hoses required to connect the two points.

The minimum information provided in the pipeline plan must include:

Tube label number

Description of source and destination points

Tube size

Pipe wall thickness

Tube material

The length of the tube

Rating of hoses. 

Reference drawing:

The following document should be used when preparing a tubing plan:

Tool connection drawing

Block diagram of instrument tubing

Device piping network diagram

Arrangement of tool pipe lines

Layout of the fusible loop.

Purpose of pipe layout

The pipeline schedule is a reference when preparing material collection for material procurement. The pipe schedule will also be provided as a complete installation list during the construction phase, however the pipe lengths shown in this document should be verified on site prior to any cutting.

INSTRUMENT DATA SHEET

INSTRUMENT DATA SHEET

An Instrument Data Sheet is a document containing specification and information about an instrument. Specifies general instrument information such as tag number identification, service description, location (line number/equipment number), P&ID number or drawing number reference, process data (if applicable), calibrated range (if applicable), material , performance details (such as accuracy, linearity - if applicable), hazard certification (for electrical equipment), required accessories, etc. The details of information in the data sheet may vary from device to device, such as transmitter, switch, meter , control valves.

Reference Document: Piping and Instrumentation Diagram (P&ID), Heat and Material Balance (HMB), Line List, Instrument Specifications, Piping Specifications, Calculation, Supplier Catalog.

The preparation of the data sheet requires certain references to documents/drawings. The following steps describe the workflow:

The P&ID provides general information such as device tag number, service description, line number/device number, P&ID number.

Process data. Any of the following process data should be available for tool selection; liquid type, liquid state (gas/liquid), design pressure, operating pressure, design temperature, operating temperature, flow rate, density, viscosity, specific gravity, specific heat ratio (gas), molecular weight (gas). However, the process data information that needs to be included in the data sheet varies by instrument type. For example, a pressure gauge data sheet does not require a specific heat ratio. Based on the knowledge of this process data, the instrument engineer can select the instrument material, calibrated range, physical characteristics, etc. The process data can be obtained from the process discipline document called "Thermal and Material Balance". Alternatively, the instrumentation engineer can look at the line list, also issued by the process discipline, to obtain general process data. However, compared to HMB, only limited process data is provided in the linelist document.

Project specifications. The company has a specification that details the minimum instrumentation requirements. In addition, it also provides a standard that should be applied to the instruments to ensure a uniform specification for a particular instrument throughout the plant. This is intended to minimize spare parts and tools as well as ease maintenance.

Calculation. Some tools need to be calculated to be the correct size. This calculation is required before preparing the data sheet. Control valve, safety pressure valve, diaphragm, sump are some of the devices that need to be calculated.

Dealer catalog. When preparing a data sheet, it is recommended to refer to the supplier's catalog to ensure the availability of the equipment in the market. Failure to do so could result in difficulty finding the tool in the market at the procurement stage. If the device is not available in the market, it can change the design, not only the device design, but also go back to the process design. Not only rework, but it can also lead to project delays.

Code and standard. Last but not least, cross-checking of the related code and standard is necessary, although this issue was mostly covered in the project specification.

Purpose of the device data sheet

The purpose of instrument datasheet

Once completed, the data sheet is attached to an application to be sent to multiple vendors. Dealers will offer their offer with different models and manufacturers between offers. It is the Instrumentation Engineer's responsibility to evaluate all bids and determine which bid is technically acceptable.

After considering the technical and business aspects, the tool is purchased. After the purchase order, the supplier submits a supporting document and drawing. Based on supplier information, the instrument data sheet may be updated to include details to make the data sheet "as built".

Finally, the data sheet, along with its supporting contractor data, is stored in a library or document control and will be referenced during construction, operation, and maintenance

Heat detector: Fusible Loop System

Heat detector: Fusible Loop System

In addition to the flame, fire also produces smoke and heat. So a heat detector can be used to detect a fire. Compared to a flame detector and a smoke detector, a heat detector is slow in detecting a fire because it only activates when the fire produces enough heat for the heat detector to respond to. However, a heat detector can provide a useful backup or alternative to flame and smoke detectors. One way to sense heat is to use a fusible loop system.

The fusible loop system consists of the following parts:

- A fusible plug that melts at a set temperature

- Pipe network

- Charging panel with fusible loop

During startup, the fusible loop fills to allow air from the instrument air system to pressurize the loop. During normal operation, the pressure remains constant. If a fire occurs and the ambient temperature rises, the fusible plug will melt. The air in the loop is released and the pressure inside the tubing is reduced. A loss of loop pressure will be detected by a pressure transmitter in the fusing loop charging panel and signaled to the control room. Another action in the control system can be fire alarm activation, ESD activation, flood valve opening, etc.

The fusible plug is a non-resettable type. Restoring the system to normal after activation will require replacement of parts, i.e. fusible plugs.

Another disadvantage of the fusible loop is that the plug can be melted by a heat source other than fire, such as hot surfaces, motors, etc.

coaxial cable

Coaxial cables

 

Coaxial cables are cables intended for radio frequency and have two conductors in the same axis, that is why they are called coaxial cables. Internal conductor

Construction:-

Inner Conductor – Conductor consists of solid or stranded copper wires. These fine strands are twisted to form a junction-free conductor. Depending on the specifications, the shape of the conductor varies, ie.

A common copper conductor

Tinned copper conductor

Silver plated copper conductor

Copper-plated steel wires

The above conductors are provided according to resistivity, tensile strength, conductivity etc.

 

Dielectric:-

Said conductor is insulated with insulating material without air bubbles or air films and should maintain the center of the conductor exactly. Generally used insulation materials are…

Rigid polyethylene

Semi-rigid or foamed polyethylene

Synthetic rubber

PTFE

 

Outer conductor:-

The conductor laid in a common axis with the central conductor is called shielding, which is provided by lapping or cross braiding. The shielding should have no breach for less than 300mm. The outer conductor consists of the following material according to construction specifications.

Annealed bare copper.

Annealed tinned copper.

Silver plated copper.

 

Outer shell:-

The outer casing of such product is provided with a general coating of PVC compound as per IS 5831 OR synthetic rubber or PTFE casing to ensure a uniform casing. For PTFE, the overlap should not be less than 125%. Other types of cladding materials are also specified depending on the specifications.

 

Quality control: -

A number of tests are performed to create the perfect cable and provide accurate results

on advanced electronic testing equipment.

Conductivity tests.

Insulation resistance.

Spread speed.

Capacity

Corona tests etc.

Instrumentation cable

Instrumentation Cable

General Construction and Material Details The
cable is manufactured with the following components. Brief form details of the basic raw materials used are given as customer general information.

CONDUCTOR:
The conductors used are of high purity. H. 99.99% Electrolytic (EC) Copper. Copper is annealed to the standards specified in IS:8130 for best results in terms of conductivity, expandability, flexibility, brightness and oxygen scavenging properties. Generally, ANEALED Tinned Copper is used for electrical cables, and ANEALED BARE COPPER TYPE is used for wires.

INSULATION:
Unless otherwise specified, the following types of insulation are used.
1. PVC (Polyvinyl Chloride) Temperature 70°C
2. PVC (Polyvinyl Chloride) Temperature 85°C

Polyester tape in various thicknesses from 20 microns up to 70 coils 50 microns. These tapes protect cables from moisture and temperature.

SHIELDS:
Cables thus formed are shielded or shielded in the following versions. The entire
copper braid is shielded.
all poly aluminum tape shield
The twisted pairs are individually shielded and covered with poly aluminum tape throughout. Individually
twisted pair and copper braid shield.

INNER JACKET: 

Cable bundles and polyester bandages formed 

after laying are protected with an armored cable by an intermediate layer of PVC. The thickness of the inner jacket is different for each size. The minimum thickness of the inner sheath must be 0.3 mm.

ARMOR:
Armor is provided to protect cables from mechanical damage such as drilling, heavy material damage and being run over by vehicles. The type of armor offered is galvanized iron wire (GI) for diameters less than 13mm or GI strips for diameters greater than 13mm.

 Outer jacket
Cable bundles shielded in this way are protected by an outer jacket made of:
PVC (polyvinyl chloride) Temperature range -15°C to +70°C.
PVC (polyvinyl chloride) temperature range -15°C to +85°C

Instrument cable layout shows instrument cable routing according to plant or platform layout. In addition, Instrument Cable Management displays details related to instrument cables such as:

Location of field devices to be connected

Junction box location

Cable number

Cable goes up/down

Reference Drawing: Instrument Location Plan

In the instrument location plan, ignore the instrument that does not require wiring, such as pressure gauges, pressure relief valve, etc.

Accordingly, direct the electronic device to the nearest junction box (make the necessary separation from the junction box for analog or digital, SIS or BPCS or Fire & Gas, IS or Non-IS).

Route the multi-pair/multi-core cable from the junction box to the control room/other rooms.

Cable runs should be as short as possible, but consider some factors to avoid, such as high interfering noise, hot source, etc. See API 552.

Purpose of device cable arrangement

The instrument wiring arrangement together with the wiring block diagram are to be used as a reference for preparing the instrument wiring schedule when determining the following:

List of required cable and its length

Source and destination connection point of the end of the cable

The arrangement of instrument cables is also a reference to identify the existence of all instrument cables in a plant or platform.

No example is given here because the arrangement of the instrument cables depends on the layout of the plant or platform. However, the symbols below may be used for items related to the device's cable management.

Thermocouple cable

Thermocouple cables

> We manufacture wide selection of transmission line similarly as Electronic Cables together with of Thermocouple Cables like Grounded Thermocouple Cables, Ungrounded Thermocouple Cables and Exposed Thermocouple Cables that area unit offered at cheap prices with superior quality by optimizing with the newest technology that area unit been widely used in core industries like petrochemicals, steel and aviation all over India.

> Our highly affordable Thermocouple Cables are necessary for transmitting signals from the thermometer to the control unit. we have a tendency to use various conductor materials for this purpose. They carries with it the same e.m.f. output which varies with the thermocouple unit. Our cables area unit widely standard Mostly used in core industries like petrochemicals, steel and aviation.TC5-20 five Zone Hot Runner Controller thermometer Cable - 20' O.A.L.

> This hot runner controller thermometer cable is 20' in overall length and can monitor five zones.

> Our normal thermometer cables area unit created of high quality, durable and versatile 105°C PVC jacketed cable.

Conductors area unit #20 AWG solid sort "JX" extension grade thermometer, twisted pairs with overall foil protect and drain.

> Thermocouple Cables area unit used for signal transmission so as to control systems with unequaled performance, efficient building operations.

>Thermocouple Cables square measure obtainable with one amongst 3 junction varieties like

Grounded

Ungrounded or

Exposed

> By the aspect of the position of a grounded junction investigation, the thermometer Cables and Wires square measure physically hooked up to the encircling of the probe wall. This leads to smart heat transfer from the surface, through the probe wall to the thermocouple.

In AN ungrounded thermometer cables, the thermocouple is disconnected from the probe wall. Relevant time is caught up from the grounded vogue, however the ungrounded thermometer cables offers electrical isolation everywhere India.

 

What is level measurement?

Level Measurement

Q. What is level? 

> difference between two height of liquid in tank or vassel. 

UNIT

> Percentage ( o to 100 % ) 

> meter

> Feet

> inch

Q. What are the instruments used for level measurement? 

> types of level measurement

1.Dpt type Lt or Hydrostatic Head type Lt

2.Radar type Lt or Non contact type Lt

3. Level tro Or displacer type Lt

Sight glass method

Dpt level measurement

>Dpt type Lt work on the basic principle of " Pressure produced by the height of liquid which is measured in terms of level. 

> pressure is depends on two factor that is height and specific gravity of liquid, it does not depends on diameter of tank. 

DPT : DIFFERENTIAL PRESSURE TRANSMITTER

There are two types of leg , 

1.Wet leg 

> when process vapor is condensable ( liquid- vapour- liquid) then wet leg is used. 

2.Dry leg

> when process vapour is non condensable ( liquid- vapour×liquid) then dry leg is used. 

Calibration of dpt type level transmitter

> Take  a work permit. 

> Take loop in manual from dcs. 

> isolation dpt from process liquid by using 3 way manifold. Close both isolation valvevand open both drain valve. 

> Connect Hart at supply or connect multimeter at test point. 

> check zero ( 4.00 ma)  , if it is disturbed than adjust it using zero pot or push button and Hart. 

> connect pneumatic pressure source at high side and low side open to atmosphere. 

> Apply pressure at high side according to upper range value. 

>check span ( 20.00 ma) . if it is disturbed then adjt it using span pot or push button or Hart. 

> check linearity( 12.00ma)  by applying 50 ℅ input pressure. 

> Reduce pressure to zero. Remove pressure source. 

> close both drain valve and open both isolation valve. 

> Take loop in auto from dcs. 

Calibration Diagram

4 to 20 ma system

4 TO 20 MA SYSTEM

> 4 TO 20 ma system communicatt is analog 

> 4 To 20 ma system use one Instrument one cable

> 4 to 20 ma require general purpose supply

 ( smps) 

> 4 to 20 ma requires safety barriers to connect field instruments. 

> 4 to 20;ma use i/o cards ( AI, AO) to connect field instruments. 

> more cable is used

> more wiring and cabling termination costing. 

ZB= Safety barrier ( zener barrier) 

PS= Power supply 

CPU= Central processing Unit

AI = Analog input

AO= Anlog output

DI= Digital input

DO= Digital output

TB= Terminal block

SMPS= switch more power supply

                 |                 |                |               |

Transmitters         control    Switch     Relay card

                               Valve            TS         Alaram

                                                     PS          sov    

                                                      LS         contactor                                                        FS          

HART COMMUNICATOR

Highway Addresable Remote Transducer

Q. What are the used of HART comunicator in industries? 

>  Hart  comumunicator is used to communicate with transmeters and instruments which is SMART Hart communicator is connected at (+) and (-) at 24 v dc supply terminal. 

> To change the range of Transmitter. 

> To change the unit if Transmitter

> for loop checking 

> To check process value (pv) and ma output of Transmitter. 

  > To change sensor type from RTD to Thermocouple and Thermocouple to RTD. 

> zero trim function. 

> to change transmitter output from linear to squre root and squre root to linear. 

> To check configuration of Transmitter. 

> check comunicator ( 4 to 20 ma) function. 

All of about control valve

 CONTROL VALVE

> Control valve is the final control element which is used to regulate material flow in the process.  

                          OR

> control valve it used to control the flow of pipelines.

Company: Fisher

                     Masoneilan

                      Ratark

                      Demla

                      Samson

                      Valtek

                      Mil control

Types of control valve depending on body

1.Single seated valve

2.Double seated valve

3.Angle valve

4.globe valve

5.Butterfly valve

6.Ball valve

7.three way valve

8.Needle valve

9.Pinch valve

Depending on action

1.Air to open ( fail to close) 

2.Air to close ( fail to open) 

Types of Actuator

1.Pneumatic ( single acting & double acting) 

2.Pneumatic piston Actuator

3.Hydraulic Actuator

4.Electric Actuator

Parts of control valve

1.positioner

2.Actuator

3.diaphragm ( rubber) 

4.spring

5.stem

6.yoke

7.scale

8.Travel indicator ( indicating edge) 

9.feedback link 

10.valve body

11.plug

12.plug seat

13.gland packing

14.gland pusher

15.gland nut

16.Bonnet

17.stem connector

18.stem nut

19.cage

Accessory of control valve

1.Positioner

2.Air filter regulator

3.Solenoid valve

4.Volume Booster

5.Hand wheel

6. Limit switch

7.Air lock Relay 

8.I to P converter

Types of valve positioner

1.Pneumatic positioner

2.Electro Pneumatic positioner ( E/P) 

3.Electro pneumatic smart positioner

Control valve with positioner

Use of valve positioner

1.zero and span can be adjust using positioner

2.quicj action of control valve stem traveling will be fast

3.valve Hydterisis will be zero ( error zero) 

4.valve can be used for viscous liquid

5.if line pressure change there will be no effect on control valve. 

6.valve action can be change from Fc to found Fo to Fc

Calibration of control valve

> Connect ma source at (+) and (-) terminal of positioner

> Apply Air supply to positioner

>Apply 4.00 ma and check 0℅ at control valve. If it disturbed than adjust is using positioner. 

> Apply 8.00 ma and check 25℅ at control valve. 

> Apply 12.00 ma and check  50℅ at control valve. 

> Apply 16.00 ma and check 75℅ at control valve. 

>Apply 20.00 ma and check 100℅ at control valve. If it disturbed than adjust it using positioner. 

In field /online calibration

> Take a work permit. 

> Take a loop manual from dcs

> Take control valve by pass from line. 

>Remove cable which is coming from dcs. 

>connect ma source at positioner. 

>Apply 4.00 ma and check 0℅  at control valve. If it is dusturbed adjusted using positioner. 

>Apply 8.00 ma and check 25℅ at control valve

> Apply 12.00 ma and check 50℅ at control valve. 

> Apply 16.00 ma and check 75℅ at control valve. 

> Apply 20.00 ma and check 100 ℅ at control valve. If it disturbed than adjust by using positioner. 

> Take loop  in auto from dcs

commissioning in proces plant by instrumentation & control engineer, technician

 COMMISSIONING IN INSTRUMENTATION

> commissioning is the formal process of varifying and documenting that the installed field instruments and control system comply with and performance in accordance with the design intent. 

   CONTROL VALVE

                        

 TRANSMITTER

CHEMICAL PLANT

 

    CONTROL ROOM

 

 DCS PANEL

Work to be done while commisioning in process plant by instrumentation engineer. 

1.instrument take in line(process) Transmitter, pressure, pressure swich. 

2.As per commisioning list checked all point of instrument. 

3.checked interlock whenever aplicable. 

4.commisioning transmitter one by one in process line. 

5.Transmitter range to be changed as required by commissioning team also actual pressure flow to be given for calibration. 

6.Pressure switch set point to be checked as per datasheet while running line. 

7.checked zero before start commisioning. 

8. Wet to be filled while commisioning level transmitter. 

9.impulse line require any modifications to be changed

10.As per datasheet all alaram range to be checked by commisioning team. 

WHAT IS PIPING INSTRUMENT DIAGRAM?

PIPING AND INSTRUMENT DIAGRAM

Q. What is P& ID? 

>  Piping instrument Diagram. 

>  P & ID  shows Specification of the process instrument, equipment, piping, valves, fittings. 

> How to chose suitable symbol in control system

> detailed graphical represention of a process       including the hardware and software 

( I. e piping ,instrumentation, equipment) necessary to design construct and operate the facility. 

> common synonyms for p & id include engineering flow diagram( EFD) , utility flow diagram ( UFD) and Mechanical flow diagram(MFD) . 

                           P&ID

FOUDATION FIELDBUS SYSTEM

FOUNDATION   FIELDBUS

Q. What is FieldBus? 

>   Field Bus is a Digital, Two way, multi Drop dat bus For communication with field instrument. 

                HISTORY OF 

         INSTRUMENTATION

         Pneumatic instruments

         Output 3 to 15 psi

                         |

         Electronic Instruments

          4 to 20 ma ( non smart) 

                         |

           4 to 20 ma dc 

             Hart Smart

                          |

           Wireless Hart

         Wireless instruments

                           |

                 Fieldbus (FF) 

>Fiedbus was first introduced in the year of 1996 by instrument society of Automation. 

> Fieldbus is a one type of communication protocol to communicate with field instruments. 

> Fieldbus is a digital, two way, multi drop data bus fir communication with field instruments. 

> Output of field instruments ( transmitter) is Digital ( not a 4 to 2o ma) 

 > field bus data transfer speed is 31.25 kbps

> like a 4 to 20 ma system, fieldbus is also used two wire for power and signal ( output) but signal is digital. 

> Field bus allows Multiple instruments to use single cable. Single wire pair carries Both power and digital communication signal. 

> Instead of running individual cable in 4 to 20 ma system, fieldbus allow multiple instruments to use single cable. 

> Fielbus use twisted single pair cable. 

>Field cable colour is orange. 

> field bus use fieldbus power supply ( Fbps( that is 24 v dc. 

Top 100 industrial instrumention and control full form asked in interview

 

Top:100  INSTRUMENT FULL FORM

1.ISA:Instrument society of America

2.DCS:Distributed control system

3.PLC:Programable logic controller

4.SCADA:Supervisory control and data acquisition system

5.HMI:Human machine interface

6.HART:Highway addressable Remote Transducer

7.LRV:Lower Range value

8.URV:Upper Range value

9.FF:Foudation Field Bus

10.PROFIBUS:Process Fieldbus

11.I/P:i to p converter

12.ILD:Instrument loop diagram

13.ESD:Emergency shutdown

14.IP:Ingress protection

15.P&ID:Piping and instrument diagram

16.PPE:Personal protective equipment

17.EX:Explosive layer

18.NO:Normally open

19.NC:Normally closed

20.P/P:Pnematic poditioner

21.E/P:Electro Positioner

22.IS:Intrisically safe

23.TT:Tempreture Transmitter

24.LT:Level Transmitter

25.FT: Flow Transmitter

26.PT:Pressure Transmitter

27.DPT:Diffrential pressure Transmitter

28.TI:Tempreture Indicator

29.PI:Pressure indicator

30.LI:Level indicator

31.FI:Flow indicator

32.TIC:Tempreture indicating controller

33.LIC:Level indicating controller

34.PIC:Pressure indicating cocontroller

35.FIC:Flow indicating controller

36.TCV:Tempreture control valve

37.FCV:Flow control valve

38.PCV:Pressure control valve

39.TE:Tempreture element

40.PE:Pressure element

41.RTD:Resistance Tempreture Detector

42.T/C:Thermocouple

43.TW:Thermowell

44.FE: Flow Element

45.C/V:Control valve

46.AS:Air supply

47.AFR: Air filter regulator

48.FC:Fail to close

49.FO:Fail to open

50.SOV:Solenoid valve

51.SDV:Shut down valve

52.PSV:Pressure safety valve

53.MOV:Motor operated valve

54.TSO:Tight shut off

55.LSC:limit switch close

56.LSO:Limit switch open

57.PSI:Pounce per square inch

58.MNWC:Mili Meter Water column

59.PV:Process value

60.SP:Set Point

61.PTW:Permit to work

62.PID:Proportional integral Derivative

63.FBM:Field Bus module

64.PG: Pressure gauge

65.JB:Junction Box

66: ZB:Zener Barrier

67.I/O:Input/output

68.AI:Analog input

69.AO:Analog output

70.DI:Digital input

71.DO:Digital output

72.TAH:Tempreture alaram High

73.TAL:Tempreture Alaram Low

74.TALL:Tempreture Alaram low low

75.RCM: Reliability Central Maintainance

76.MM: Multimeter

77.HSE:High speed ethernet

78.SMPS:Switch more power supply

Industrial instrument

𝟭.𝗪𝗵𝗮𝘁 𝗶𝘀 𝗶𝗻𝘀𝘁𝗿𝘂𝗺𝗲𝗻𝘁? 

>   Instrument is a device which is used for measurement, controlling, monitoring and display of process. 

2.What is instrumentation? 

> Instrumentation is branch of engineer which is deals with measurement, controlling, monitoring and display of process variable. 

 

>Kind of process we show in industry. 

                       Cruide oil

                             |

                       Process

                            |

                         Heat

                             |

                        Petrol, diesel, neptha, 

                        Gasoline, Kerosine

3.What are the process variable? 

 > Tempreture

>  Pressure

>  Flow

>  level

4.What are the jobs for instrumentation engineer in industry? 

>  control and instrumentation engineers are responsible for designing, developing and operating control devices and system with an industrial facility.