Section 3 — Process Safety & Loss Prevention

Use of Protective Instrumentation in

IPE Engineering Practice IPE-EP-3-7-4

Document number: IPE-EP-3-7-4 · Section: 3 — Process Safety & Loss Prevention

SCOPE

This Practice details the requirements for the use and categorization of protective instrumentation in pressure relieving systems.
Requirements for the design and testing of protective instrumentation systems shall be in accordance with EP 12–11-1.
Any deviation to this Practice shall be in accordance with the procedure given in EP 1–1–3.
An asterisk (*) indicates that a decision by the Owner of the Owner’s Engineer is required or that additional information is furnished by the Purchaser.

2.0 REFERENCES

The latest edition of the following standards and publications are referred to herein.

STANDARDS & PUBLICATIONS

IPE Engineering Practices
EP 1–1–3 Deviations to IPE Engineering Practices EP 3–7–1 Pressure Relieving Systems EP 3–7–2 Relief Disposal Systems EP 3–7–3 Register of Pressure Relieving Systems EP 12–11–1 Protective Systems
ASME Codes
Sec VIIIPressure Vessels, Division 1 Sec VIIIPressure Vessels, Alternative Rules, Division 2 B31.3 Chemical Plant and Petroleum Refinery Piping

DEFINITIONS

Owner – Inflection Point Engineering, LLC.
Owner’s Engineer – A Inflection Point Engineering, LLC appointed engineer.
Protective Instrumentation – Instrumentation provided to prevent losses of all kinds, particularly in process upsets or emergencies, as distinct from instrumentation provided for normal control.

CATEGORIZATION

All protective instrumentation used in pressure relieving systems shall be assigned one of the categories described in EP 12–11–1 and this Practice.

Protective instrumentation systems requiring a reliability greater than normal, where failure to act on demand could result in serious injury to personnel shall be categorized as a Category 1 system. Examples of Category 1 systems are:
Systems not requiring design to the ASME Code or systems per ASME Code Case 2211, where overpressure protection is provided solely by instrumentation. These systems are used in lieu of conventional pressure relief devices. Pressure vessels designed to the ASME Code require pressure relief devices and cannot be protected solely by instrumentation, unless Code Case 2211 is invoked.
Systems having pressure relief devices discharging to a closed system which has been sized by taking credit for operating automatic pressure limiting instrumentation.
Systems having pressure relief valves discharging to atmosphere where the protective instrument system is mandated by Statutory Authority requirements.
Systems which can release toxic gases in concentrations exceeding the Immediately Dangerous to Life or Health (IDLH) level, in areas normally accessible by workers.
Systems where the time for a potential liquid overfilling incident to occur is less than 30 minutes. Liquid relief capacity or Category 1 protective instrumentation is required.
Protective instrumentation systems where adequate self–actuating devices are available to prevent unacceptable equipment failure or serious injury to personnel if the protective instrumentation fails shall be categorized as Category 2 systems. Examples of Category 2 systems are:
Systems designed to protect against unacceptable damage to the environment or serious commercial consequences.
Systems having pressure relief valves discharging to atmosphere where the system is not mandated by Statutory Authority, but where there is a requirement to reduce demand on these devices for environmental reasons.
Systems providing protection against damage to unspared equipment essential for production.
Burner management systems of fired steam generators.
Protective instrumentation systems that are designed to prevent minimal financial loss or process interruption shall be categorized as Category 3 systems. Examples of Category 3 systems are:
Systems designed to limit the loss of products where a failure to operate could result in a release through the pressure relieving systems.
Low flow shutdowns and equipment trips, where failure to operate could result in damage to spared or non–essential equipment.
Systems where failure to operate could result in temporary loss of product quality.
Remote–actuated isolation valves where manual isolation valves are also available within a safe distance.
Interlock and sequencing systems not required or included in Category 1 or Category 2 systems.

USE IN PRESSURE RELIEVING SYSTEMS

Protective instrumentation systems shall not be used to decrease the size or number of conventional pressure relief valves unless the ASME Code Case 2211 has been invoked. Sizing criteria for pressure relief valves and closed relief systems shall meet the requirements of EP 3–7–1 and EP 3–7–2 .

(*) Protective instrumentation systems shall not be used, unless approved by the Owner.
Protective instrumentation systems may be used to minimize the frequency and magnitude of pressure relieving occurrences in order to:
Reduce any environmental incident from atmospheric relief or relief to flare to a level acceptable to statutory authorities.
Reduce possible hazards of atmospheric relief.
Minimize loss of material arising from pressure relief device operation.
Optimize the design of the closed pressure relieving system using a hazard quantification approach.
(*) Where Category 1 systems are identified, design modifications should be considered to avoid this requirement. Design measures for reducing relief loads are given in EP 3–7–1. The number of Category 1 systems should be minimized and shall be subject to approval by the Owner.
Where credit is taken for operating pressure limiting instrumentation in the sizing of closed relief systems this instrumentation shall be regarded as an integral part of the pressure relief system. Information requirements shall be included in the Register of Pressure Relieving Systems per EP 3–7–3. Complete documentation, strict control over bypassing or deactivation, regular maintenance, and proof testing at defined intervals is required.

6.0 DESIGN PROCEDURES

A systematic approach is required to implement protective instrumentation systems in a cost effective manner. Project Safety Reviews shall be carried out. Hazard and Operability Studies shall be carried out.

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