what is loop testing in instrumentation

Basics of Loop Checks

Submitted by Katherine Bonfante on Thu, 10/04/ - Everybody knows that loop checking and field instrument testing is the last piece of the puzzle in each project before commencing the commissioning of any system. It is time-consuming and depends upon the completion of other systems like piping, electrical equipment, control valves etc. Sep 25, Loop Checking is defined as the checking for correct operation of all instrument systems and loops and the preparation of all instrumentation for commissioning.

Instrumentation Loop What happens when you heat gas Loop Checking. With this method cost and time will onstrumentation minimized and safety integrity will be maintained.

Loop Checking is defined as the checking for correct operation of all instrument systems and loops and the preparation of all instrumentation for commissioning. One group to be in the field Field Technician and the other group to be positioned whxt the control room or front of local panel Operator Station Technician. There are two types of loops are in the field of instrumentation. Open loop: It has no feed back. Close loop :It has feed back. In instrumentation a Close loop is consist of 3 basic Parts.

Input device pressure ,level ,flow ,temperature transmitters 2. Output device Control valve 3. To minimize overlaps and duplicate efforts, it is very important that the loop check team be prepared and are aware of their responsibilities. All required documentation drawings are assembled within each package. The components within the loop have been installed in accordance with process piping, instrument instrumenfation piping, mounting details and Instrument drawings.

During early commissioning or pre commissioning instrumehtation like flushing and blowing it must be ensured that the operational commissioning crew is fully equipped with means of communication. Actuate the switching action and check all the related system such as alarms,trip signal, indicating testinv etc. Check for the valve stroke and tight closing of control valve.

Check the fail-safe position of the valve after completing the test by removing the air supply to the valve. Like this: Like Loading Tags: Instrumentation Articles.

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Basics of Loop Checks

This tutorial explains the common principles of loop checking as they apply to various kinds of Smart devices. The detail procedure varies slightly depending on the manufacturer. Refer to the device instruction manual. But once the common principles in this tutorial are understood, the product manual becomes easier to understand. For this reason a loop check is done at commissioning to verify the integrity of the mA current loop. The loop check is typically done in 5 points to verify linearity; at 4 mA, 8 mA, 12 mA, 16 mA, and 20 mA And these may be checked in reverse order also.

It may be good practice to periodically perform loop check to verify the integrity of the current loop has not degraded over time or range mismatch as a result of device replacement etc. All signal loops should be checked.

A fundamental property of digital technology is that digital signals can be transmitted perfectly, without error and that digital signals can be replicated infinitely. There is no analog mA and therefore a traditional loop check need not be made for digital communication. During Transmitters configuration, we have to look after Device address very carefully otherwise it may mapped in a wrong way or some devices readings may swapped in control systems graphics.

The digital signal is rejected if it has been distorted. As a result, if the signal is received, it is received correctly, if not, somebody is notified. So if a transmitter using only digital communication measures This is why a loop check is not required for digital communication. It should be noted that there is no ranging in the transmitter when only digital communication is used, so there is no chance of range mismatch between a bus device or wireless transmitter and system causing an error.

Therefore physical input need not be injected, a simple plausibility check based on the prevailing condition is made; such as ambient temperature, atmospheric pressure, empty tank, or no flow etc. It is the nature of digital signals that if one value comes through correctly, then other values will also work. In most plants the system is using the real-time mA signal, and therefore analog loop check should be carried out to ensure the mA is functioning properly.

It is possible for the digital HART signal to give a correct indication while the analog mA signal is in error due to excessive load or ground loop etc. In some applications such as remote wellhead monitoring where fast updates are not required, HART devices may be used in a pure digital multi-drop topology using only the digital HART communication, no analog mA. In such applications, a mA loop check is not required since the current signal is not used.

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Accept Read More. Primary Menu Inst Tools. Search for: Search. Home Basics of Loop Checks. Previous Article. How a mA Transmitter Works? Next Article. What is Loop Checking? Related Articles. Babu KR December 11, at am Mr Bharadwaj, my appreciations for your valuable efforts to share the knowledge. Dan Warren December 13, at am Great link to many useful tools. Would be highly grateful. Aung April 20, at am Thanks Sir. Aung April 20, at am Thank you very much Sir. Belfar Salah June 25, at pm very important subject ,i would like to put them in PDF format.

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