Castello di Belgioioso – Pavia – July 5 and 6, 2017

AUTOMATION INSTRUMENTATION SUMMIT

The benefits of sample handling system design, related to the integrity and

reliablility of on-line process analyzer.

G.Severi

G.Tani

Summary

1. Fores Engineering Overview 2. Sampling System Architecture 3. Sample Conditioning 4. Compatible Sample 5. Timely Sample 6. Representative Sample 7. A Real Project

7.1 Critical Issues 7.2 Process Analisys 7.3 P&ID 7.4 Sample Control

8. Conclusions

1.Fores Engineering Overview

Worldwide

Expertise

Reliability

Team

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Petrochemical

Chemical

Power Plant

Inte

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Engineering Procurement Construction

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Tele

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Fores Engineering Srl is an Italian company part of the Rosetti Marino Group, founded in 1992, specialized in the design, integration and construction of different EPC System and Products for Oil & Gas, Petrochemical, Chemical and Energy industry. The production structure of the company is divided in three main operative units: • Skid & Packages • Automation, Telecom and Security • Industrial Service All the units operate both independently and in complete synergy, allowing the company to focus its attention on maintaining a high level of customer satisfaction.

The main activities are Project Management, Engineering, Procurement, Integration, Construction, Testing and Commissioning of its products. In addition, Fores Engineering provides Technical Supervision Services and After-sale Technical Assistance Services, such as Assistance and Supervision to the construction activities, commissioning activities and start-up activities, supply of spare parts and training in the field.

1.Fores Engineering Overview

1.Fores Engineering Overview

Collection of the sample from the

take-off point

Sample Preconditioning

Sample Transport Line

Sample Conditioning

Sample

Analysis Exhaust Sample

Outlet

Analysis of the Sample.

• Pressure Regulation • Vaporization

• Transport to the Analyzer • Temperature Control

Collection of a significant and useful amount of sample to be analyzed.

• Fast Loop • Sample Flow Control

• Exhaust sample to flare • (or) Return to the process

Analyzer

2.Sampling System Architecture

The good design of this chain is critical as the analyzer choice

A sample handling system, throught a pre-conditioning and conditioning subsystem, is necessary to guarantee a fluid sample compatible with the requirements of the Analyzer. That means:

• Compatible Sample >>> ensures the analyzer will work.

• Timely Sample >>> ensures a current measurement result.

• Representative Sample >>> ensures the right answer.

3.Why a Sampling System ?

Often, a considerable amount of attention is normally given to the choice of the most suitable type of analyzer to perform the analytical task, whereas no similar care it’s given to the sample handling system.

The analyzer is unable to detect the bad sample or to correct the inconsistency of the analysis.

The purpose of sample conditioning is to modify and control the condition of the sample to ensure that it is always compatible with the analyzer:

• A compatible sample will not harm the analyzer.

• A compatible sample prevent the analyzer from producing a reliable analytical result.

It may be necessary: • Remove excess solids • Remove liquid drops from gas • Remove bubbles from liquid

• Adjust temperature, pressure and flow • Set pressure and temperature to avoid a two-phase sample • Ensure wet materials are compatible with the sample

4.Compatible Sample

A timely sample is one that provides an analysis with an acceptable delay from real time of the sample collection at the take-off.

Time Lag: time between the collection of the sample at the take-off point and the analyzer inlet.

The standard transport time is 1 minute maximum.

Some point where time delay happens:

• Sample transport line • Sample pipe or vessels • Sample conditioning • Sample extraction • Sample stream selection by the control system

5.Timely Sample

Why a sample is not representative? Composition Change

• Contamination

• Two-phase sample due to a not well controlled temperature and pressure

• Chemical Reaction between sample molecules or between sample molecules and wet materials of construction

Precise Result is one that carries a high degree of confidence.

Accurate Result is one that closely represents the true value of the measurement.

Representative Sample is one that provides a meaningful analytical result useful for its intended purpose.

6.Representative Sample

Supply of Analyzer Shelters and ancillaries to be installed in EAU composed by the following main items:

• No. 2 Gas Chromatographs with two different ovens for each one: H2S analisys and Hydrocarbons analisys.

• No.2 Sample Streams for each Gas Chromatograph to be collected to both the ovens.

• Sample Transport Lines.

• Pre-Conditioning Systems for each sample stream.

• Sample Conditioning System for each analyzer.

7. A Real Application – Scope of work

• Critical composition, temperature and pressure of the sample fluid. [Tdp=43°C > Tamb]

• Ambient temperature range. [ Tamb = -5 ÷ +40 °C ]

• Sample streams selection to the desired oven. [ No. 2 Streams to No. 2 independent Ovens ]

• Long distance from the sample collection point and the analyzer inlet. [ Lstl > 80 m ]

• Analyzer requirements: flowrate, temperature and pressure of the sample.

[ Qs = 6 Nl/h , +30°C < Ts < +120°C , Ps < 3 barg ]

Some critical issues of the project:

7.1 A Real Application – Critical issues

Sample composition

Component Molar Fraction

CH4 74,86%

C2H6 7,38%

C3H8 4,85%

C4H10 1,07%

CO2 4,85%

H2S 32,38%

T, P, Flowrate required by the

Gas Chromatograph

Sample Temperature and Pressure at the Take-off

Point

Sample Transport Line lenght

Sample Chemical Properties

Pre-conditioning system Conditioning System Sample Transport Line

Heated transport line to maintain the sample

temperature

Sizing of the line

Fast Loop

Flow to Analyzer

Sample Stream Selection

Pressure Reduction

Vaporizer

7.2 A Real Application – Process Analysis

Take-off Point

Pre-Conditioning System

Sample Transport Line

Sample Conditioning System

Analyzer

Calibration

Utilities

Fast Loop

Control of the sample streams

7.3 A Real Application – P&IDs

With this solution it’s important to be careful to the analyzer control system time delay!

Pneumatic actuated three way valves with single and double effect have been used for the sample streams and calibration gas selection with double block & bleed configuration:

Stream 1 to Analyzer Stream 2 to Analyzer Calibration Gas

to Analyzer

7.4 A Real Application – Multistream System

8. Conclusions

A good and reliable Analyzer System should not ignore a careful and correct design of overall chain from process stream to analyzer, given the importance of sample compatibility, timing and representativeness, before it could be analyzed.

Often there’s a lack of understanding the importance of this pretreatment, jeopardising the correct analsyis and making more difficult the operation and maintenance activities as well.

It's not just important the Analyzer, but also how the sample arrives to it.

THANK YOU ALL!

For info: gabriele.severi@fores.it gioele.tani@fores.it salvatore.mecca@fores.it