12 April 2007Senior Design Lecture 3 – SP07 Senior Design Guest Lecture 3 Process Safety Applications For Design Engineers CHEN 4470 Spring 2007.

Senior Design Lecture 3 – SP07 12 April 2007

Senior Design

Guest Lecture 3

Process Safety ApplicationsFor Design Engineers

CHEN 4470Spring 2007


Importance of Process Safety

•The safety record of the chemical process industry is the responsibility of all of us in the profession.

•Process safety is important for employees, the environment, the general public, and it’s the law.

•As process design engineers we are tasked with reducing the risk of operating a chemical manufacturing process to a level acceptable to employees, regulatory authorities, insurance underwriters and the community at large.

•Recent chemical plant disasters underscore the importance of this point in terms of both human and financial losses.


Importance of Process Safety

Sonatrach LNG Plant - Skikda, Algeria, January 2004

•Incident•A defective, high pressure, steam boiler ruptured.•The resultant explosion on rupture damaged nearby vessels containing flammables.•Flammable loss of containment resulted in further fires and explosions.

•Result•23 workers were killed.•Nine bodies never recovered.•74 were injured.•$800,000,000 (U.S.) estimated property damage.











Process Safety Terminology

Hazard vs. Risk

• HAZARD is a measure of the severity of the consequences of a catastrophic failure of a given process or system, regardless of the likelihood and without considering safeguards.

•RISK is the combination of both the severity of the worst case consequence and the likelihood of the initiating cause occurring.

•In short, for an EXISTING PROCESS, we have little influence on the HAZARD, but through the application of safeguards, we can reduce the RISK of operating the process.

How do we quantify the Hazards of a process????


Process Hazard Analysis

•Process Hazard Analysis (PHA) is a technique for determining the RISK of operating a process or unit operation.

•PHAs are required by law for process handling threshhold quantities for certain listed Highly Hazardous Chemicals (HHC) or flammables.

•Various techniques have been approved for conducting PHAs:–HAZOP

–What If?

–FMEA

•In general, a PHA is conducted as a series of facilitated, team brainstorming sessions to systematically analyze the process.


The operating risk is mitigated through the application of safeguards that reduce the risk to an acceptable level.

Mitigating Process Risk

Pro

cess

Ris

k

InherentRisk

OperatingSafeguards

Level of Acceptable Operating Risk


Layer of Protection Analysis

•LOPA is a quantitative technique for reducing the RISK of a process.

•The theory of LOPA is based on not “putting all your eggs in one basket”.

•The layers mitigate the process RISK as determined by the PHA.

•Each layer reduces the RISK of operating the process.

Core Process

1st Layer of Protection

2nd Layer of Protection

3rd Layer of Protection

Each layer must be: Independent; Effective; Reliable; Auditable.


LOPA Example

•Failure of Transfer Pump leading to overfill of Process Vessel.

•Potential release of material to the environment requiring reporting or remediation.

•Potential personnel injury due to exposure to material.

•Severity would be based on properties of the material released.

Process Vessel

Liquid In

Liquid Out

LTLAH

http://powerlink.powerstream.net/002/00174/051222bp/BPAnimations.asx


Inherently Safe Process Design

•Inherent safety is a concept based on eliminating the causes and/or reducing the consequences of potential process upsets.

•Inherently Safe Process Design is a technique applied during the conceptual phase of process design.

•Inherently Safe Process Design targets the HAZARD, rather than reducing the RISK after the fact.

•This technique is based on making inherently safer design choices at a point in the process development where the engineer has the most influence on the final design.


Inherently Safe Process Design

Inherently safe process design can be grouped into 5 categories:

1 Intensification Continuous reactor vs. batch reactor

2 Substitution Change of feedstock

3 Attenuation Alternate technology

4 Limitation of effects Minimization of storage volume

5 Simplification Gravity flow vs. pumping

Category Example


Inherently Safe Process Design – Example 1

Azeotropic Distillation vs. Pervaporation

AzeotropeColumn

EntrainerVessel

SolventColumn

HexaneMakeup

SolventFeed

RecoveredWater

RecoveredSolvent

AzeotropeColumn

Pervaporation Unit

SolventColumn

SolventFeed

RecoveredWater

RecoveredSolvent

Standard Process Inherently Safer Process


Conclusions

Questions & Comments

12 April 2007Senior Design Lecture 3 – SP07 Senior Design Guest Lecture 3 Process Safety Applications For Design Engineers CHEN 4470 Spring 2007.

Documents