Section 3 — Process Safety & Loss Prevention

Emergency Isolation

IPE Engineering Practice IPE-EP-3-3-1

Document number: IPE-EP-3-3-1 · Section: 3 — Process Safety & Loss Prevention

SCOPE

• This document covers the minimum requirements and conceptual design criteria for safe and reliable installation and application of EMERGENCY ISOLATION valving and associated equipment. This specifically includes manually and remotely operated emergency isolation systems. This document also addresses the process facilities for which emergency isolation shall be considered including fired heaters, pressure vessels, etc. This document does not specifically cover normal isolation provisions for:
• on-line maintenance
• scheduled shutdown maintenance
• the isolation of utility lines after start-up (e.g. natural gas, nitrogen purges)
• The following subjects which are related to EMERGENCY ISOLATION are alluded to, but not specifically covered, under this document:
• safety alarm and process interlock (i.e. shutdown) facilities,
• depressurizing valves along with piping, primary/secondary containment, incineration, and flaring facilities.
• liquid pull-down facilities
• The section is intended to provide guidance to IPE personnel, consultants and contractors on the conceptual design of EMERGENCY ISOLATION valving and associated equipment for new plant construction or modification-to-existing projects as described in the following.
• It is intended to help identify and specify emergency isolation applications for new construction or modification-to-existing of process facility components, units, or transfer areas. Such process components include, but are not limited to:
• pressure vessels
• compressors
• low-pressure and atmospheric storage tankage
• fired heaters
• pumps
• battery limits piping
• marine facilities
• For existing components whose design intent is being significantly changed by proposed modifications, this document is intended to assist existing plants in identifying the need for emergency isolation.
• Wherever possible, this document states or references the corporate minimum requirements for the location and type of emergency isolation required for the process components identified above. Wherever possible, typical applications of such requirements are given.
• It is also intended to cover the conceptual design of new or modification-to- existing EMERGENCY ISOLATION facilities in general; rather than for specific application to process components such as fired heaters, compressors. etc. The document is based on current industry standards; codes, guidelines, recommended practices and lessons learned within the petrochemical industry.

• This document is intended to help existing Plants in their process hazard analysis (PHA) activities associated with OSHA 1910.119 in identifying the need for emergency isolation facilities as well as any process safety management activities in order to mitigate any potential loss of containment hazards that might occur. This document is intended to serve as a standard in the identification and assessment of emergency isolation needs. However, this document shall serve as both standards and guidelines in the implementation of emergency isolation facilities, in the same capacity as EP 3-1-1 for new or modification-to-existing projects. The interpretation of this document for existing Plants is also outlined in EP 3-1-1.
• This document is intended to cover EMERGENCY ISOLATION criteria for loss of containment of all dangerous materials as defined in 3.0 below. This document is intended to provide guidance for hazards involving releases of hydrocarbons from the process as well as high toxic hazard materials (HTHM's).
• This document is intended to be used as a reference document by IPE plants to provide sufficient detail in order to define a design scope so the detailed engineering for new or modification-to-existing projects can be completed.
• Other appropriate Industry and IPE mechanical, instrumentation and electrical design criteria, as referenced in Section 2.0 shall be followed in the development of the conceptual design scopes and detailed engineering design packages for EMERGENCY ISOLATION equipment and associated systems.

2.0 REFERENCES

The latest edition of the following specifications as well as industry codes, standards, regulations, and guidelines shall be referred to in the development of the conceptual and detailed design of EMERGENCY ISOLATION SYSTEMS:

STANDARDS AND PUBLICATIONS

STANDARDS AND PUBLICATIONS (CONT.)

DEFINITIONS

• Autoignition Temperature – the temperature at which hydrocarbons will spontaneously combust under laboratory conditions without the presence of an ignition source. IPE has adopted 410F as the lower boundary auto-ignition temperature of a standard hydrocarbon that is considered severe service. This 410F criteria is based on the worst case refining non-LPG material, kerosene.
• Combustible and Flammable Liquids:
• Combustible liquids are all liquids with a flashpoint above 100F .
• Flammable liquids are all liquids with a flashpoint below 100F and with a vapor pressure not exceeding 40 psia at 100F.
• Complementary Mitigation – Activities or facilities which are intended to reduce the consequences of a gaseous or liquid release, which are in addition to the primary mitigation measure covered in this document, namely emergency isolation. Such complementary measures are not intended to replace or supercede the use of emergency isolation. They are intended to enhance or augment the entire leak mitigation system, which includes facilities and activities.
• Dangerous Materials – Materials as defined below:
• High Toxic Hazard Materials such as phenol, hydrogen sulfide, chlorine, and others according to regulatory and local health practice.
• Highly corrosive materials, such as acid, caustic, and other materials recognized as injurious to personnel.
• Flammable and combustible fluids with operating temperatures above there flash points.
• Light hydrocarbons, lighter than 68 degrees API gravity (0.709 specific gravity).
• Boiler feedwater and steam, ASME/ANSI B16.5 Class 300 rating and higher.

• Demand – a valid emergency situation that requires a correct response by the operator intervention along with the successful functioning of the safety system. A pipe rupture results in a loss of containment and fire is considered a demand. A failure by the operator and/.or the safety system to respond to the demand is considered a covert or unrevealed failure if the system is considered fail safe
• Emergency Block Valve (EBV) Types – The description of the emergency block valve types, their similarities and their differences is provided in Table 1. It should be noted that "Emergency Block Valve Types" and "EBV Systems" and "Emergency Isolation Systems" is synonymous. However, reference to the emergency block valve or emergency isolation valve specifically refers to the valve itself, and not the actuation/instrumentation system.
• FAH, FAHH, FAL and FALL – Flow Alarm High (FAH) and Flow Alarm High (FAHH). Both process conditions initiate a high-pressure alarm; however, FAHH initiates an alarm that a shutdown action has been initiated. Similarly, FAL and FALL signify Flow-Alarm Low and Flow Alarm Low.
• Fire-Safe Valves – soft-seated valves tested under fire conditions equivalent to API Std 607 or all metal-metal seated valves, regardless of whether or not they have been tested to a manufacturer's equivalent test to API Std 607. Refer to paragraph 8.5.1 for acceptable fire safe valves for emergency isolation service. In the context of this document, the only acceptable fire safe valve for emergency isolation service is a metal-metal seated valve.
• High Toxic Hazard Materials (HTHM) – HTHM materials include Hydrofluoric (HF) Acid, Hydrogen Sulfide (H2S), and chlorine gas. Deciding whether these and other materials meet HTHM criteria is very subjective. However, a good example of a HTHM is a highly toxic material that is highly mobile, which can mean high volatility for liquids. Formal classification of materials that are HTHM's has been simplified, but not limited to, in this document to be HF acid, H2S, chlorine, and benzene.
• High Performance Check Valves – a high performance check valve is defined as an "equivalent to" fire-safe valve which provides a tight shut-off design which can maintain seating capability in normal service and during process upsets. (Note: there are no "fire-safe" industry standards for check valves; hence, the "equivalent to" reference is made.)
• Inherent Safeguards – these are design, operations, and maintenance related hardware and management systems which are primarily focussed on preventing a loss of containment situation. However, secondary hardware and management safeguards are also needed to mitigate a loss of containment situation should it occur .
• PAH, PAHH, PAL and PALL – Pressure Alarm High (PAH) and Pressure Alarm High (PAHH). Both process conditions initiate a high-pressure alarm; however, PAHH initiates an alarm that a shutdown action has been initiated. Similarly, PAL and PALL signify Pressure Alarm Low and Pressure Alarm Low.
• Process Hazard Analysis (PHA) – Qualitative and quantitative risk analysis techniques as applied to refining and chemical processes.
• Safety Systems – protective systems that can be internal or external to the process. Examples of internal safety systems include PAH, PAHH, PAL, PALL alarms and interlocks. Examples of external safety systems include gas and fire detection systems, fire water systems, water curtains. Such systems are typically used in loss of containment situations. Such systems can initiate an operator response or automatic intervention through interlocks.

• Severe Service – are defined as hydrocarbon duties above 410 of and/or 500 psig.
• Special Fire Risk Area is defined as any one of the following:
• All areas within 50 feet of a severe service plant equipment, and all hydrocarbon duty fired heaters (this latter point would exclude boilers).
• All areas within 50 feet of inventories in excess of 2,000 gallons of flammable.
• Liquids, or Combustible Liquids held above their flashpoint in process vessels, storage tanks/spheres, or transport containers, all areas within dikes and low lying areas designed to contain flammable liquids.
• Where flammable materials are being handled in enclosed buildings.

THE PURPOSE OF EMERGENCY ISOLATION

• Emergency isolation is intended to be used to reduce the consequences of a dangerous material loss of containment. Emergency isolation is considered a demand safety system that can be either manually or motor / pneumatically / hydraulically operated. By isolating the dangerous materials source from the leak / rupture source, the consequences of the release would be reduced.
• Emergency isolation shall be considered an integral part of the design of a process unit or facility . Achieving optimum emergency isolation may require careful location of equipment and should therefore be taken into account when developing plant or unit layouts.
• Emergency isolation shall be considered for:
• protection of individual pieces of critical equipment in the event of a fire
• preventing loss of containment of flammable/combustible or toxic fluids
• isolation of sections of process units for defined upset or emergency conditions
• isolation of complete process units for defined upset or emergency conditions
• isolation of whole plants from pipelines or public environments for defined upset or emergency conditions

DISTINGUISHING BETWEEN EMERGENCY ISOLATION TYPES

• There are four groups of emergency isolation systems: Type 1, 2, 3 and 4. These valve types have similar and differentiating features which are outlined in Table 1. The purpose of this table is to illustrate that the different valve types can be categorized several different ways. By showing these similarities and differences, the limitations and capabilities of each valve type is simply presented.
• There is often confusion as to the difference-between a Type 1 and 2 valve, as they are both manual block valves. The distinguishing feature is their location relative to the release source. Consider a manual block valve (BV) located on a fuel gas knockout drum vapor outlet that feeds a fired heater. This valve would be a Type 2 valve relative to the protection being provided to the Fired Heater. However, the same BV is also considered Type 1 as it also provides emergency isolation protection for small hydrocarbon releases at the fuel gas KO drum as the valve is located adjacent to the KC drum. Therefore, one valve can be considered as being two emergency isolation types. (Note: for the Type 1 valve relative to the KO drum, it would only be effective for minor leaks. This block valve may not be acceptable for more catastrophic scenarios.)

SELECTION OF EMERGENCY ISOLATION TYPES

• Isolation guidelines for all new process components for the following equipment are shown below:
• fired heaters
• pumps
• compressors
• pressure vessels
• pressurized and atmospheric storage tankage
• battery limits piping
• This section is applicable to existing plants and the above components which have been deemed necessary as a result of PHA or some other safety audit to require new EBV's where there currently are none, or where current EBV's require upgrading to improve hazard protection.
• The standards and guidelines within this section only pertain to emergency isolation hardware. Other hardware mitigation measures (e.g. process detection alarm and interlocks; fire, toxic gas and combustible gas detection) are covered outside this document. PSM mitigation measures such as procedures, personnel training, subsequent testing, and refresher training are also not specifically covered within this document.
• The Table 2 series of standards and guidelines uses knowledge-based criteria to assist in determining whether or not Type 1, 2, 3, or 4 emergency isolation systems are required. Standards and guidelines cannot be written to cover all design situations, as each process component must be evaluated in context with upstream and downstream equipment, physical criteria (e.g. spacing, layout), and human factors (e.g. response time, access, egress, operator safety, etc.). Consequently, the Table 2 series shall be used in conjunction with PHA for a new construction as well as for modification-to-existing cases.
• "Inherent Safeguards" are also discussed in Table 2. These safeguards are good, basic design features which are associated with the safe design, operation, and maintenance of the above process components. If these features are not in place, then the lack of these features may over-shadow the necessity and urgency for emergency isolation. The interpretation of the preventive safeguard deficiencies should be that the inherent process safety safeguards should be addressed as well as emergency isolation, as these safeguards prevent or inhibit the release from actually occurring. The secondary, mitigative measure deficiencies should be interpreted as hardware and controls that should or must be implemented. These hardware and controls, along with emergency isolation, can help reduce the consequences of a loss of containment situation.
• Should deficiencies in the inherent safeguards presented be discovered as a result of using any of the Table 2 series, or by using PHA, then the associated EP's dealing with the design of the above process components shall be reviewed. It should be noted that the intent of the list of inherent safeguards presented in Appendix A, Table 2 series is to identify common design issues addressed in other EP's. This list serves as a tool to help indicate where deficiencies may exist in the current design.
• It is strongly recommended for PHA activities involving emergency isolation that an experienced member of the fire department be present at the reviews. They will be able to provide guidance as to what reasonable actions could be taken in the event of a loss of containment.

COMPLEMENTARY MITIGATION ACTIVITIES AND FACILITIES

• Paragraph 6.0 along with the information in Table 2 provides a decision criteria for helping the designer decide which type of emergency isolation is necessary. Paragraph 6.0 also identifies complementary engineering, operating, and maintenance practices, called "inherent safeguards". These inherent safeguards focus on both preventive and mitigative activities and facilities. Paragraph 7.0 expands on the complementary mitigation facilities and activities identified in paragraph 6.0 and the Table 2. Specifically, paragraph 7.0 addresses those mitigation activities and facilities that are not directly associated with emergency isolation.
• Other Measures in Mitigating Liquid and Gaseous Releases – the preferred mitigation activity is to provide emergency isolation in the process to minimize the quantity of material released. Emergency isolation is used to: extinguish ignited materials by fuel isolation, to isolate hydrocarbons prior to ignition, or to isolate HTHM's. However, there are other complementary mitiqation activities available for vapor and liquid releases in the event that early detection and isolation is not probable, or that these activities will be necessary due to the inventories involved, the toxicity/flammability of the materials, their release rates, employee/societal risks. or any other dominant factor.
• For vapor releases. complementary mitigation can be provided through:
• fire-fighting that may include water sprays/curtains
• water sprays
• water curtains
• steam curtains
• air curtains
• deliberate ignition
• control of ignition sources
• Liquid releases can addressed through:
• fire-fighting
• drainage and containment
• dilution
• neutralization
• blankets or covers involving liquids, foams, solids
• minimizing vaporization through proper response techniques
• However, when one compares the above complementary mitigation options to emergency isolation, the most effective method in directly mitigating the effects of a loss of containment event is to provide isolation at or upstream of the leak source. None of the above options minimize the quantity of materials released; they only indirectly minimize the consequences of the quantity released away from the leak source. Consequently, there is no equivalent substitute for emergency isolation.
• Unavailable or inadequate emergency isolation dictates the need for enhanced complementary mitigation facilities and activities. However, it is generally more effective in human and financial terms to address the loss of containment issue by minimizing quantity rather than dealing with its effects outside of the process.
• Excess Flow Valves and Check Valves – excess flow valves and check valves are intended to be used in conjunction with, rather than in place of valving which is acceptable for use as emergency isolation.

• If proper selection and location of check valves are made, then these check valves can provide reasonable flow isolation. However, check valves cannot be relied upon to provide pressure isolation. Check valve selection and design is covered in EP 5-3-1 and EP 5-3-8. Gravity or spring-assisted check valves are required, and check valves shall not depend on flow reversal to close.
• Under fire conditions, however, some of these valves may be subject to large leakage conditions. For example, some check valves that are available contain soft-seat materials. In the event of the check valve located within a special fire risk area, the limitations of the check valve to prevent back-flow may occur due to destruction of the soft-seat.
• The designer should consider the design and application of check valves as well as excess flow valves in the same manner as that performed for emergency isolation valves. This includes the need for secondary metal seats in these valves, which have a TSO design. However, prevention and avoidance of placing critical TSO valves within special fire risk areas are again key to ensuring the integrity of the valve.
• EP 5-3-8 defines criteria where soft-seated check valves are required. Case-by-case evaluation as to the applicability of soft-seated check valves to specific situations shall occur.
• For fired heaters, check valves are especially advantageous where the downstream inventory is greater than the inventory in the fired heater tubes. The check valve can reduce backflow from the downstream inventory in the event of a heater tube rupture. However, where such check valves are incorporated at the fired heater outlet, they should be designed for the process conditions, which may include coking and severe fouling. These valves shall be examined during turnarounds to ensure that they remain functional.
• IPE will allow the conditional use of high-performance check valves in clean services for compressor discharge lines with a pressure rating Class 600 and less (EP 5-1-2, Table 3). A high performance check valve is defined as an "equivalent to" fire-safe valve which provides a tight shut-off design which can maintain seating capability in normal service and during process upsets. (Note: there are no "fire-safe" industry standards for check valves; hence, the "equivalent to" reference is made). However, such valves cannot be relied upon to provide TSO for fire conditions in excess of approximately 30 minutes. Consequently, the use of these high performance check valves in conjunction with further downstream isolation to prevent back flow plus manual or remote de-pressuring facilities needs to be provided in these instances.
• API Publication 2510A covers the use of excess flow valves for LPG loading and unloading service. API Publ 2510A is discussed in paragraph 7.5.
• The Importance of Detection Systems for Loss of Containment Situations – early detection of abnormal situations external to the process is key to directly mitigating the consequences of a loss of containment scenario. Consequently, fixed combustible and toxic gas detection are used to detect the presence of hydrocarbons as well as High Toxic Hazardous Materials (HTHM's). In the event of ignition of these materials, fire/heat/smoke detection systems can be used. Air -water environmental monitoring is often used for detection.
• Fire Protection/Design and Construction of Liquefied Petroleum Gas (LPG) Installations – API 2510 and 2510A cover both the preventive and mitigative aspects related to fire protection for LPG installations.

• API 2510 covers all minimum requirements associated with design, construction, and location of liquefied petroleum gas (LPG) installations at marine and pipeline terminals, natural gas processing plants, refineries, petrochemical plants, and tank farms. API 2510 is not intended to be retroactive, or take precedence over contractual agreements.
• API 2510A covers the fire protection associated with these facilities, complementing API 2510. It is considered a guideline document. However, API 2510 and API 2510A apply to storage, as well as loading and unloading systems. It does not apply to plant or production equipment preceding these facilities.
• API 2510 covers emergency isolation for these storage, loading, and unloading systems, and it shall be referred to specifically for emergency isolation requirements. EP 3-6-1 for LPG Pressure Storage Facilities must also be reviewed with regards to inherent safeguards as well as emergency isolation needs.
• API 2510A specifically covers excess flow valves as a distinct form of emergency isolation that is not covered by the Type 1 2, 3, or 4 emergency isolation systems. The purpose of this valve along with a check valve is that they will provide reliable, tight-shut off for such instances as when a rail-car or truck are moved during transfer operations.

ACCEPTABLE EMERGENCY BLOCK VALVE TYPES AND SYSTEMS

• The Use of Interlocks to Initiate and Enable Emergency Isolation Systems

Process interlocks are commonly used in safety systems to safely enable shutdown, isolation, and often de-pressurization systems for emergency situations including loss of containment. Usually, these interlocks are operator initiated using a push button arrangement. However, process interlocks can be used to initiate these same safety systems.

• Initiating Emergency Isolation Systems – fully-automatic versus operator-initiated situations may dictate the need for interlocks to activate the closure of actuator-controlled valves without operator intervention. However, the remote actuator push buttons are not replaced. These push buttons become additional options that the operator has to initiate to effect shutdown and isolation for the hazardous situations. As a result, for any emergency isolation system that contains process interlocks, these systems are considered Type 4 systems. In general, the owner does not use process interlocks involving external safety systems, such as fire, smoke, toxic gas, or combustible gas detection systems, to automatically shutdown and isolate a process. The owner prefers that emergency isolation be to be solely designed for operator initiation provided that appropriate PHA determines that this is a safe and practical approach. However, for those cases where process interlocks may be appropriate (for example, for remote unmanned facilities), PHA shall be performed. Given that a Type 4 valve is required, PHA criteria which are needed to evaluate whether automatic intervention as an additional precaution over simple push button activation includes the following.
• What are the frequencies and consequences of the loss of containment? Will the automatic shutdown reduce the societal, worker, physical damage, or business interruption consequences due to the use of automatic intervention?

• Will the operator hesitate in pushing the shutdown button? Human reliability may be the limiting factor of a push button safety system. Infrequent use of a push button actuator for fear of making a judgement error, distrust in the instrumentation, or wanting visual confirmation of an emergency prior to initiation can result in a loss of effectiveness in dealing with the emergency situation.
• Infrequent alarm conditions identified alarms are often the source of distrust in the instrumentation. Other causes of distrust can result from previous overt or covert failures of the emergency isolation and accompanying shutdown systems.
• The operator should have written authorization and support from management to initiate emergency isolation and shutdown in order to help eliminate the fear of making a judgement error, and any retribution that the operator perceives might occur.
• Will adequate maintenance and testing be provided for such detection systems to ensure reliability against overt failures (i.e. nuisance trips of the emergency isolation system)? If not, spurious trips or covert failures (i.e. a demand resulting in no response of the emergency isolation system) may result.

It should be noted that the above criteria assume that initiation of emergency shutdown and isolation by either push button or by automatic intervention through a detection system are equivalent.

Actuator buttons shall always be included in the design of shutdown systems, even if interlocks internal and external to the process exist. The covert or unrevealed malfunction of detection systems, or any component in the interlock system, may not result in a successful closure of the emergency isolation valve.

The use of actuator buttons also allows the operator to isolate the system for hazardous events that are not detected by the current internal or external safety system. For example, a compressor suction Type 4 valve that will close upon fire detection in a compressor house will not close due to an unignited pipe leak within the compressor house.

• PHA for Designing Process Interlocks Which Enable Safe Emergency Isolation – PHA is a necessary activity as part of the alarm-interlock design process. Such alarms-interlocks enable the safe isolation, as well as shutdown and possible de-pressurization of the process or sections of the process. PHA should address the following issues:
• magnitude and hazard of the loss of containment
• operator intervention response time
• time to close a valve (i.e. quarter turn valves versus gate valves)
• potential for water hammer conditions
• the number of streams present to be isolated, including streams such as hydrogen
• complexity of shutdown tasks, including valve actuation, and shutdown of upstream and downstream equipment, including pumps and compressors
• operator safety in button access/egress
• operator training/refresher training
• mitigation of consequences
• time to depressure downstream facilities
• design intent failure of one or more safety system components (i.e. relief, blowdown, etc.)

• consequences of EBV-closure on upstream and downstream equipment (i.e. shutdown of upstream vessel outlet valve, thus isolating a downstream pump or compressor); such closures should include overt, fail-safe trips which result in a valve closure in a non-emergency condition
• Potential long term business interruption due to long-term delivery of special metallurgical components
• These are the key PHA considerations, which must be addressed for the enabling portion of the safety system design, which includes the design of emergency isolation systems as well as alarms and interlocks.
• Type 3 and 4 EBV Conceptual Design Details
• For Type 4 systems, the valve control station shall be located outside special fire risk areas surrounding pumps and compressors. They should also be within sight of the pump, vessel, compressor, etc. The control station must not be accessible through such special fire risk areas.
• It is recommended that a Type 4 valve actuator button be located within the central control room, in addition to that located in the field.
• Inadvertent operation of all Type 3 and 4 push buttons using protective covers and appropriate warning signs and identification must be provided.
• The failure action of emergency isolation valves must be to the closed position. Consequently, pneumatic valves need to be pressure-to-open as well as spring loaded to close automatically in order to ensure that the valve will close when the pressure is lost.
• Cable-routing and pneumatic line routing should always take into consideration special fire risk areas. Designers need to understand the hazards which the emergency isolation valves are designed to mitigate against. Cable, pneumatic, and hydraulic control systems should be routed on the top level of all pipe racks, above utility piping systems. (Note: the utility systems should in turn be located above the hydrocarbon/HTHM piping systems.)
• Cable and actuator fireproofing is needed for all electrical, motor-operated valves. Unless such fire-proofing is provided, such valves may not fail closed in a fire situation, since they require electricity to move the valve actuator .
• Heat-activated, fusible links are recommended to activate the closure of valves in the event of a fire in the area of the valve. This consideration is especially important for electrically-operated valves to initiate immediate valve closure prior to a loss of power situation caused by a fire- damaged cable.
• Consideration must be made to prevent surge conditions from occurring that would be related to rapid closure of Type 3 and 4 valves.
• Damage to Emergency Isolation Systems Due to Explosion
• Identification of the potential leak sources is critical prior to locating emergency isolation valving. Therefore, it is not just a question of whether a Type 1 or 2, or a Type 3 or 4 valves are required.

• Explosions can render even Type 3 or 4 emergency isolation systems inoperable. Fragmentation can damage the actuators of these valves, regardless of whether or not the valve can fail-closed due to loss of pressure, or a heat-sensitive fusible-link is in place on the valve. Therefore, placement of a Type 3 or 4 valve within a special fire risk area should be avoided, especially if an explosion is a likely consequence. As an exception, however, such valves are required to be placed at vessel or tank nozzles in situations due to inventory considerations.
• For example, compressor emergency isolation valving should not be located adjacent to the machine being protected, or near an adjacent compressor. For the latter case, the explosion of one compressor may render the emergency isolation protecting the second machine ineffective.
• In choosing whether a pneumatically, hydraulically or electrically driven Type 3 or 4 valve is required, it should be noted that electrically driven valves which require power-to-close shall not be used in situations where the valve would be located within a special fire risk area. An explosion or fire which damages the electrical cables may render the valve inoperable. Although fire-protection can be provided for such cables, cable damage due to explosion cannot be easily prevented.
• Control Valves Can be Unsuitable for Emergency Isolation Service
• Control valves can be used to provide emergency isolation in a loss of containment situation in the event of only minor releases which may occur without a major fire and/or explosion. Typically, however, these control valves have to be assumed to be not equivalent to emergency isolation valves, as they do not in most cases meet the criteria provided in this document for large loss of containment situations. Such major deficiencies include, but are not limited to, the following:
• Unsuitable control valve failure action in the event of pneumatic or electric signal disruption
• Vulnerability of the pneumatic or electric lines to fire and/or explosion; the vulnerability stems from cable or instrument line routing, and line/cable fire protection
• Unsuitable control valve materials for a special fire risk area
• The process design for a continuous process control system takes into account the failure of a valve under process upset conditions, which may have, resulted from an instrument failure. The control valve failure options available to the process designer under these conditions include:
• fail open
• fail stationary (i.e. fail last position)
• fail closed
• fail stationary open (i.e. no immediate valve action, but the valve will eventually drift to the open position.)
• fail stationary closed (i.e. no immediate valve action, but the valve will eventually drift to the closed position)
• The designer chooses the appropriate failure action so as to minimize the upset of upstream and downstream conditions. However, the failure action of the valve is critical, as it may be contrary to the action required for emergency isolation, which is fail closed.
• For control valves which are also being relied upon by the designer to provide emergency isolation in a demand situation, several criteria must be met in order to consider a control valve for emergency isolation service:
• Only control valves which fail closed can be considered for emergency isolation purposes.

• The control valve must be located outside a special fire risk area.
• If anyone of these criteria is not met, the valve can only be considered as an alternate valve for emergency isolation, one that cannot be solely relied upon for emergency isolation. Therefore, given that an emergency isolation valve is required as determined by PHA and criteria provided in this document, then a primary , dedicated valve for emergency isolation must be provided.
• Should a control valve meet the above primary criteria, then the control valve and loop should be further evaluated by the criteria in this document so that the system meets the requirements of a Type 3 or 4 emergency isolation system.
• Acceptable Valves for Fire Conditions
• Definition of "Fire-Safe" Valves in Emergency Isolation Service
• There is no current industry testing and inspection standard for metal-metal seated valves which is equivalent to API Std 607 "Fire Test for Soft-Seated Quarter-Turn Valves". However, the owner considers all metal-metal seated valves to be "fire-safe", as the potential for failure of the seat material has been minimized by using metal rather than Teflon or a similar material.
• Only metal-metal seated valves are acceptable for emergency isolation in flammable service or within special fire risk areas.
• Soft-seated emergency isolation valves shall not be used for emergency isolation for flammable services or within special fire risk areas. This includes those soft-seated valves meeting the fire-test requirements of API Std 607 or some manufacturer's adaptation thereof.
• Although there are protection measures available for valves within special fire risk areas, protection such as fire-proofing, heat shields, and water-sprays are not considered safe enough to provide reliable protection prior to closure action in order to prevent valve plugging or seal destruction under fire conditions.
• Emergency Isolation Exception Allowing Soft-Seated Valves Meeting API Std 607 or Manufacturer's Equivalent Fire Test.
• The exception for the use of soft-seated valves for emergency isolation is as follows:
• the valve is confidently outside of the special fire risk area, and
• tight shut-off is essential during normal operations, and/or
• tight shut-off may be beneficial in isolating HTHM's which may also be flammable, or may be mixed with flammables.
• For such soft-seated applications, a technical deviation with supporting PHA documentation shall be required.
• The concern by industry is that soft-seated (i.e. non-metallic) materials used in valves that provide TSO under normal conditions might also quickly deteriorate under fire conditions. The consequences of this failure might include:
• an obstruction that would prevent valve closure under fire conditions
• significant leakage from a valve which is already closed, the cause of which might be a prolonged and/or larger fire

• Consequently, manufacturers have developed valves, which use two-piece seating construction. The primary seal, or "soft-seat", is often made of Teflon or an equivalent material. Should the soft material be destroyed, either back-pressure or a spring device would push the back-up metal seal into a position to maintain a seal under fire conditions. However, this type of design does not address the first failure mode listed above, namely the failure of the primary, resilient seal while the valve is in the open position resulting in an obstruction preventing valve closure.
• Requirements for Fire-Protection of Emergency Isolation Valve Bodies, Flanges, and Actuators
• Emergency isolation valve bodies, flanges, and actuators be clad with stainless steel jacketing with suitable insulation for fire conditions. Requirements for EBV body insulation requirements are shown below:
• non-removable insulation and cladding per EP 11-3-2
• removable insulation and cladding per EP 11-3-5
• The following four (4) fire protection system variations are also acceptable. However, the main drawbacks of each system are outlined to assist the conceptual designer in deciding which is the appropriate protective system:
• Stainless steel jacketing with removable, stainless steel bands – maintenance personnel must be relied upon to ensure that such components are properly re-installed after maintenance. Aluminum jacketing is not acceptable in place of stainless steel, and shall not be used in fire-protection service.
• Rigid "box" enclosures – space considerations along with the potential for maintenance doors to be left open are some of the problems, which could be experienced.
• Flexible shields – these systems are not "maintenance-friendly", as they are difficult to re- seal, and lacing is often left loose. Their insulation is hydro-scopic to moisture and chemicals. Under fire-conditions, hose streams could remove these systems.
• Intumescent coatings for valve actuators (i.e. coatings which "swell" under fire conditions) – these formed systems may not be applicable for complex, odd-shaped actuator systems. Therefore, box enclosures may be more suitable for this type of application. Good maintenance practices involving re-sealing of joints must be relied upon for this system to work effectively under fire conditions while also providing corrosion protection.
• The following items (a) and (b) are protective systems which are not recommended:
• Sprinkler systems – the drawbacks to this system are economics and their unreliability due to inactivity and corrosion. Freeze protection is another concern.
• Trowelled fireproofing – is not recommended for maintenance and integrity reasons. The integrity of trowelled or sprayed fireproofing can be compromised due to firewater stream forces coupled with fireproofing deterioration due to weathering. Fireproofing maintenance is often ignored, especially on small equipment.
• Use of Soft-Seated Valves In Services That Are Normally Closed – there may be situations where a required TSO, soft-seated valve may be relied upon under fire conditions to provide an effective seal in addition to primary emergency isolation already in place. Consequently, two- piece seating arrangements shall be used for such valves. Alternatively designers should avoid the use of soft-seated valves for these applications. Double-block, metal seated valves should be used.

9.0 TABLES

TABLE 1 EMERGENCY BLOCK VALVE TYPES DESCRIPTIONS, SIMILARITIES, DIFFERENCES

Notes:

• Type 1 acceptable if located at leak source of non-flammable materials only
• Type 4 valves preferably should be located outside the leak source area, especially for HTHM's (HF and Benzene) as well as areas which are special fire risk areas.
• Examples of Type 4 valve initiating interlocks include some fire, toxic gas and combustible gas detection systems. Examples of enablers include push buttons which also actuate shutdowns.

TABLE 2.1 FIRED HEATER EMERGENCY ISOLATION SELECTION CRITERIA

TABLE 2.2 PUMP EMERGENCY ISOLATION SELECTION CRITERIA

TABLE 2.3: COMPRESSOR EMERGENCY ISOLATION SELECTION CRITERIA

TABLE 2.4 PRODUCT STORAGE EMERGENCY ISOLATION SELECTION CRITERIA

TABLE 2.5 PRESSURE VESSEL EMERGENCY ISOLATION SELECTION CRITERIA

TABLE 2.6: BATTERY LIMITS EMERGENCY ISOLATION SELECTION CRITERIA

TABLE 2.7 LOADING AND UNLOADING EMERGENCY ISOLATION SELECTION CRITERIA

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