Using ESD Valves as Safeguards

8/10/2019 Using ESD Valves as Safeguards

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"Using ESD Valves as Safeguards, Myth or Reality?"

German Luna-Mejias, P. Eng.

ACM Facility Safety

Suite 700 940 6th

Ave SW, Calgary, AB, Canada

[email protected]

[email protected]

Prepared for Presentation atAmerican Institute of Chemical Engineers

2013 Spring Meeting

9th Global Congress on Process Safety

San Antonio, TexasApril 28 May 1, 2013

UNPUBLISHED


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AIChE shall not be responsible for statements or opinions contained

in papers or printed in its publications


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"Using ESD Valves as Safeguards, Myth or Reality?"

German Luna-Mejias, P. Eng.

ACM Facility Safety

Suite 700 940 6th

Ave SW, Calgary, AB, Canada

[email protected]

[email protected]

Keywords: Process, Safety, Emergency, Shutdown, valve, bypass

Abstract

An Emergency ShutDown (ESD) valve is a safety device to be actuated during an emergency

situation to prevent hazardous consequences. The ESD valves are to be designed not to createadditional hazards when actuated. Sometimes, due to operational constraints ESD valves are

bypassed which contradicts best practices and creates an incremental risk for the facility, people

and environment. Lack of regulations sometimes drives ESD valves users to overlook or ignore

best practices with the associated incremental risk. This paper presents experiences duringHAZOPs/field observations where installed ESD valves are claimed as safeguards but are not(can be bypassed). The intent of this paper is to call the attention of designers, operators and

managers of the potential hazardous consequences they may face if ESD valves are not used as

per recommended practices.

1. Introduction

Our police force has to be right every time to prevent worst case scenarios, the bad guys only

have to be right once for a major impact to occur. Exactly the same happens with safety; safetydevices have to work when required; only one failure is enough to cause a major impact.

The use, absence or abuse of safety devices e.g. emergency isolation valves- have been thecause of several accidents in the industry:

A.P. Green Refractories Company Explosion at Brick Kiln during start-up due to a

main gas isolation valve bypass line leaking with 2 injured. Georgia, USA 1985. [1]

Oil & Gas, Sonat Exploration Company - Explosion and fire due to misalignment of

manual valves when feeding a low pressure system with HP Gas with 4 fatalities.

Louisiana, USA. March 1998.[2]


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Ammonia Plant: Fire and explosion with substantial damage to a reformer-furnace due to

bypass of control valve -with shutdown function- inadvertently open. No injuries, India,

May 1998.[3]

Esso-Australia Gas Plant Explosion due to the improper use of bypass valve aroundsafety valve as the safety valve was not operable with 2 fatalities and substantial public

welfare impact. Victoria, Australia. Sept 1998.[4]

As per these four examples, problems can happen anywhere in the world. In the last 3 years,

when performing Process Hazards Analyses (PHA), the PHA teams indicated no concerns aboutbypasses around ESD valves, because there are no regulations that prevent this. Common

responses were: this is not regulated, why worry about it or even worse: recommended

practices are recommendations, they are not mandatory. These practices are not onlyrecommended practices but common sense. Additionally, as AIChE members (including

professional denominations), the Code of Ethics indicates that welfare of the public and

environment is paramount.

2. Definitions

Emergency isolation valves, emergency block valves, Emergency Shutdown valves or

Automated Shutdown valve are different names for the same type of function valve.

A paper presented to GCPS in 2012 [5] indicates that the Emergency Block Valves (EBV) arenamely different as per different codes, regulations and companies.

2.1 Additional definitions:

Emergency Block valves are used to control a hazardous incident. These are valves for

emergency isolation and are designed to stop the uncontrolled release of flammable or toxicmaterials [6]

The ASV (Automated Shutdown Valve) is most commonly use in the Pipeline Safety Act 2011

[7]. The concept of the ASV is to mitigate the release of flammable or toxic materials, not theprevention of it. Pipeline Safety concern is H&SE not Process Safety.

2.1 ESD valve:

A valve with the following characteristics:

Actuated valve

Actuate upon a detection of a dangerous event defined by designers/operators and

confirmed during PHA study.

Provide protection against possible harm to people, assets or environment.

Not used for control


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An Emergency Shutdown valve for the scope of this paper- is a valve that will prevent a

hazardous situation from occurring (i.e. closing to prevent the overpressure of the vesseldownstream of the valve) or mitigating the impact after the situation occurred.

2.2 Bypass valve:

Definition of bypass:

go around something

channel carrying a fluid around a part and back to the main stream

In the oil and gas industry is sometimes common to find bypasses around control valves; this

situation is commonly used when it is expected that the valve may need maintenance during theoperation of the plant. The plant can continue to run for a short period of time with a manual

controlled function using a globe valve. This is a common accepted practice.

In this paper, the word bypass is a key element of the study, and follows the second definition:channel carrying a fluid around a part and back to the main stream; more specific: around the

ESD valve.

2.3 Norms and Standards

Depending on the system under review, there are several norms, recommended practices,regulations, etc. associated with the operation and installation of ESD valves.

Nevertheless, none of these documents indicates or dictates providing a bypass around an ESD

valve. A list of these documents is provided in the appendix A.

3. Installation and Use of ESD valves

In Vivianos work [5], the use of the 5W (What, Who, When, Where and Why) helps to

identify the need for emergency isolation valves. In this paper, it is considered that all 5W are

being taken in consideration and the evaluation is moving onto the next questions: Is it correctly

installed? It is a valid layer of protection? Does it protect against a hazardous event? Does itmitigate the impact?

Is my safeguard device reliable? In the O&G business a spurious trip is also a problem, but doesnot affect public welfare. Once the ESD valve is included in the detail design, how do we ensure

it is going to work in the different scenarios that led to the installation of the ESD valve?

The first phase of the analysis it to perform the risk evaluation or risk assessment.

3.1 Risk Analysis

During a PHA, analysis will be done to ensure the different ESD valves are valid safeguards to

prevent the hazardous event from happening. In this phase of the study a qualitative analysis is


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performed and team members will agree, or disagree, on the protection being used for

prevention. A good facilitator should challenge the team about the effectiveness of the safeguard(e.g. is there enough Process Safety Time, Is the actuation of the ESD valve creating another

hazardous condition(s)?).

On the other hand, since the PHA is a qualitative analysis, each safeguard is considered to be ofthe same weight or of the same importance. If required, an additional safeguards evaluation

may be carried out: LOPA.

LOPA (Layers of Protection Analysis) is a semi-quantitative analysis to determine the PFD

(probability of failure on-demand) of the safeguards to meet the tolerable frequency requirements

of each company.

Based on LOPA an Emergency Shutdown Valve may require being a SIL rated device to achieve

the tolerable frequency for a specified event. SIL rated means that the associated elements of the

safety device has to be designed, constructed and maintain to a minimum level of probability offailure when demanded to operate [8]

Previously it was mentioned that ESD valves should not be used to perform a control function asthe reliability or SIL rating of the ESD valve may be compromised. The PFD of a typical BPCS

(Basic Process Control System) is 0.1 (1 failure every ten times it is demanded) and the ESD

valve may require a higher reliability (e.g. SIL 2).

3.2 Use of ESD for Accident/Incident Prevention

When referring to Emergency Block Valves or Emergency Shutdown valves, two functions (or

purposes) should be studied: 1. Use of ESD valves for preventing the hazardous situation fromhappening (preventive barrier). 2. Mitigating the consequence (acting after the hazardous event

happens).

3.2.1 Accident/Incident Prevention

Valves in this category are mainly used in industries (e.g. Oil & Gas) to prevent the hazardous

event from happening.

In several scenarios briefly described in the introductory section of this paper, ESD valves were

installed to prevent a hazardous incident from occurring as per the original plant design concept.

3.2.2 Accident/Incident Mitigation

Valves in this category are mainly used to prevent public exposure to a hazardous event, after the

initiating event occurs. These scenarios are largely described and analyzed in documents such as

Pipeline Safety Act 2011 [7].


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The concerns of the regulator are focused more on spurious trips that may create a public impact

due to the effect of cutting the gas supply to communities. In this case, the regulator mayrecommend a manually activated Isolation Valve. For this scenario, a LOPA is recommended to

ensure that the Isolation valve will have a low PFD (probability of failure on demand).

4. ESD Valve Configuration

Sometimes for ease the operation the bypassing of ESD valves are permitted as there are noregulations or norms against it but common sense. These ease operation scenarios may

remove the protection intent of the ESD valve.

4.1 Creating additional hazards.

Installing an ESD valve to reduce the risk is a good idea unless this addition creates additional

hazards. If the ESD valve closes, it will isolate two systems: one at high pressure and other at

lower pressure. What happen if the high pressure system cannot withstand the pressure? Thisanalysis should be part of the PHA analysis.

Sometimes, a risk analysis is improperly done just to complete a check mark in a paper that

means the activity was performed. Therefore a proper evaluation is not accomplished and the

operator may believe the facility is safe to operate and it is not.

Unfortunately in many projects the PHA is just a check mark to achieve the project approval

and the PSM is not strong enough to ensure a proper PHA is accomplished. In an evaluation

done by OSHA [9] it has been found that improper or inaccurate hazard assessment is one of themain deviations from the safety programs.

In many PHAs studies it has been found that as no regulations mandate the owner to avoidbypassing the ESD valves they are frequently bypassed as it makes the start-up much easier and

faster.

If the ESD valve is designed to Provide protection against possible harm to people, assets or

environment or actuated upon a detection of a dangerous event it should not be bypassed. A

general rule of Safety indicates that: the important thing to do is to be safe when nobody is

watching

4.2 Bypassing ESD valve for start-up.

After the PHA and LOPA team agrees to install an ESD valve with specific SIL rating and

confirms that no added risk will be created if valve is actuated, what is next?

Even if no regulation mandates it common sense indicates that if a bypass is required around

an ESD valve the bypass has to be equipped with similar protection or equivalent to prevent theinadvertent operation of bypass or minimize the possibility of leaking.


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What are the problems associated with improper bypassing of ESD valves?

Operator error may remove protection

Valve leakage may remove protection

Any of these scenarios will invalidate the PHA previously performed and due diligence

may be difficult to justify if an accident happens.

Filling the lines with products before start-up is a common practice, occasionally done byopening the bypass around the ESD valve. The filling of lines is not a problem but the increased

pressure on the downstream side of the ESD valve may be a problem. That is what happened in

the Esso accident (Victoria, Australia) as a valve misalignment created an overpressure of the

receiving vessel.

Use of CSC (car seal closed) valves in the bypass around ESD valves is a partial protection as

the isolation valve may leak overtime without the operator knowing it. Pressure equalization is abigger issue than flow.

In the incident that occurred in the Brick Kiln the bypass valve around the main isolation valvewas somehow inadvertently open; it means that to start-up the facility the protection was

removed.

5. Conclusions

Potential damages to public and environment can be serious, including fatalities, as it has beenshown in several accidents around the world.

In the Pipeline Safety Act 2011 [7], the major concern is the amount of gas release and theimpact on public after the incident happens. It does not direct the users to provide preventive

safeguards.

As there are no specific regulations or codes, the bypassing of safety devices is a concern that isvery likely to be overlooked.


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6. Recommendations

6.1 General

Accident prevention requires ACTIVE leadership by management of safety issues.

Effective implementation of the right controls to manage, mitigate or eliminate hazards

and reduce risk.

Management systems and attitudes towards safety go hand-in-hand in creating robust

defenses.

This paper is written with the intention that the reader perform due diligence to make sure the

area under his/her responsibility is safe.

6.2 Safe Design

As a general rule, ESD valves should be installed based on PHA/LOPA

The actuation of ESD valves must not create additional hazards.

The required reliability of an ESD valve (PFD) must be evaluated by a LOPA or similar

analysis.

Bypass around ESD valve should only be permitted if an additional ESD valve with the

same functionality is installed in the bypass.

6.3 Operating practices

In the accidents reviewed at the beginning of this paper, in most of the cases the inadvertent

opening or closing of a valve was a key element to the problem. It is highly recommended toimplement a PSSR (Pre Start-up Safety Review) before any start-up.

7. Final Remarks

Bypass of a safety device may save time for operator, but may cost lives!

Follow PSM or equivalent because you want to be safe, not because a regulation requires

it!

A general rule of Safety indicates that: the important thing to do is to be safe when

nobody is watching


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8. References

[1] OSHA. Accident Report: Explosion in Brick Kiln. Accident # 14542070, report ID 0418100.

Washington, DC. 1985

[2] CSB. Investigation Report: Catastrophic Vessel Overpressurization (4 deaths). Report #

1998-002-I-LA; Chemical Safety Board, Washington, DC. 2000

[3] R.M. Chopde & K.M. Patel ., Ammonia Plants: Past accidents and lessons learnt, Krishak

Bharati Cooperative LTD, India. Presented at International Fertilizer Industry Association (IFA)

Technical Conference, Louisiana, 2000.

[4] A. Hopkins, PhD ., Lessons from Essos Gas Plant Explosion at Longford; Australian

National University, 2000.

[5] J. Viviano ., Emergency Block Valves; presented at VIII Global Congress on ProcessSafety, 2012.

[6] API Recommended Practice API RP-553:Refinery valves and accessories for Control and

Safety Instrumented Systems, Chapter 7. American Petroleum Institute, 1998.

[7] Pipeline Safety Act 2011 U.S. Congress, Law 112-90 Jan 3, 2012.

[8] CCPS., Layer of Protection Analysis: Simplified Process Risk Assessment, Center for

Chemical Process Safety. New York, NY.2001.[9] Jordan Barab., "Learning from Industry Mistakes" presented at NPRANational SafetyConference, May 2010


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APPENDIX A

Regulations, codes and recommended practices for the installation of emergency block

valves.

API RP-553 Refinery valves and accessories for Control and Safety Instrumented Systems

American Petroleum Institute, 2007.

NFPA 30 Flammable and Combustible liquid Code, National Fire Protection Association, 2012

NFPA 497 Recommended Practice for the Classification of Flammable Liquids, Gases, or

Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process

Areas National Fire Protection Association, 2012

API RP-500 Electrical Area Classification American Petroleum Institute, 2000

NFPA-58 Liquefied Petroleum Gas Code National Fire Protection Association, 2011

API RP-2510 Design and Construction of LP-Gas Installations at Marine and PipelineTerminals, Natural Gas Processing Plants, Refineries, Petrochemical Plants, and Tank Farms, 4th

Edition, 1978. American Petroleum Institute; recommended practice.

NFPA 85 Boiler and Combustion System Hazards Code, National Fire Protection Association,

2011

API RP-560 Fired heaters for General Refinery Services American Petroleum Institute, 2001

API RP-556 Instrumentation, Control and Protective Systems for Gas Fired Heaters, American

Petroleum Institute, 2000.

API RP-520 Part I: Sizing, selection, and installation of pressure-relieving devices in

refineries. Part II Installation American Petroleum Institute, 2000

API RP-521 Guide for pressure-relieving and de-pressuring systems,American PetroleumInstitute, 1998

Pipeline Safety Act 2011: U.S. Congress, Law 112-90 Jan 3, 2012.

Documents

Using ESD Valves as Safeguards