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insteng
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Join Date: Jul 2011
Posts: 2

Flow Transmitter Installation Method for SIL-3 Requirement

08/17/2011 4:46 AM

Hi.

Are there anyone who can tell the installation method of three(3) flow transmitter on venturi tube to meet the SIL-3 requirement?

Which is the correct between individual installation from three(3) sets of tapping point on venturi tube and three(3) flow transmitters installation from one tapping point with T-branch?

Best Regards,
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PWSlack
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United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

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Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
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#1

Re: Flow transmitter installation method for SIL-3 requirement.

08/17/2011 5:00 AM

How about the equipment manufacturer?

http://en.wikipedia.org/wiki/Safety_Integrity_Level

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insteng
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#2

Re: Flow Transmitter Installation Method for SIL-3 Requirement

08/17/2011 9:24 PM

The manufacturer of the venturi tube is SAMIL Industry in South Korea.

To meet SIL-3 requirement, device from sensor to final element shall meet SIL-3 requirement. But unfourtunately there is no SIL-3 D/P flow transmitter so we install three flow transmitters to configure 2 out of 3.

So my question is that to install 3 sets of flow transmitter on a venturi tube, do we need three(3) sets of tapping point on venturi tube or only one tapping point is engugh?
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PWSlack
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#3
In reply to #2

Re: Flow Transmitter Installation Method for SIL-3 Requirement

08/18/2011 4:02 AM

SIL cannot be applied to a single instrument or even multiples of them. It can only be applied to the anticiapted failure rate and mode of a safety-critical system. Without knowing what this instrument is supposed to do and what it is connected to, the concept is meaningless. So far, the forum doesn't know what is in the line, what temperature and pressure, and what is supposed to happen to it in the event of a shutdown.

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Iris
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#4

Re: Flow Transmitter Installation Method for SIL-3 Requirement

08/19/2011 11:33 AM

Here's a quote from a white paper on Safety Instrumented Systems (SIS)

"In the real-world, as opposed to the laboratory, there are many factors that can cause a transmitter to read either dangerously high or dangerously low, that might not be detected during normal operation. Some obvious examples include:
- Pressure: plugged sensing lines, power supply variations, hydrogen permeation of diaphragm, severe over-pressure (pressure hammer) causing zero shift, mis-installation causing zero shift
- DP-Flow: eroded or mis-aligned primary element (orifice plate),

You might want to read the entire white paper, because it addresses the issues raised by PWSlack.

http://www.isa.org/Content/Microsites838/Safety_Division/Home818/ISA_2005_Safety_Papers/Measurement_Best_Practices_for_SIS.pdf
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Iris
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#5

Re: Flow Transmitter Installation Method for SIL-3 Requirement

08/20/2011 1:31 PM

Here's an engineering spec that understands the nature of DP measurement in ESD service: (note that the DP is primarily concerned with level measurement)

http://webcache.googleusercontent.com/search?q=cache:v2th-dg2gqMJ:igs.nigc.ir/IGS/SAMSS/SAES-J-601.PDF+%22SIL+3%22+redundant+DP+venturi&cd=12&hl=en&ct=clnk&gl=us&source=www.google.com

6.2 Process Taps and Connections

An ESD sensor shall have its own dedicated process tap or connection separate from a process control or monitoring instrument. Each transmitter shall be capable of being calibrated in-service independently.

ESD level inputs shall have separate process taps located at the same elevation as the process control and monitoring transmitter taps. ESD level transmitters shall be calibrated for the same range as the process control level transmitter and designed with its own local level sight gauge and drain/vent valves.

Exceptions:
Differential pressure transmitters used for ESD and process control service may be installed in parallel using the same primary element (e.g., orifice plate, venturi,and flow nozzle) provided they have independent process isolation valves. Individual transmitters shall be capable of being isolated while the other remains in service.

ESD Level transmitters may use the same process taps as the process control or monitoring transmitters when the tap nozzle size is at least 2 inches, the process is non-plugging and the common isolation valves on the tap nozzle are car sealed open. In addition, ESD and process control level transmitters shall have independent level bridle isolation valves and shall be calibrated for the same range. The ESD and process control/monitoring level transmitters shall be designed with local level sight gauge and their own drain/vent valves to allow independent isolation and calibration while the other remains in service. See SAES-J-300 for additional level requirements

http://webcache.googleusercontent.com/search?q=cache:v2th-dg2gqMJ:igs.nigc.ir/IGS/SAMSS/
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