ERT 312 SAFETY & LOSS PREVENTION IN BIOPROCESS ACCIDENT INVESTIGATIONS Prepared by: Pn. Hairul Nazirah Abdul Halim

Objective To discuss the method to investigate the accidents in the plant To analyze & evaluate in a case studies

Introduction The investigation of accidents and near misses provides opportunities to learn how to prevent similar events in the future. Accident investigation includes detailed descriptions and recommendations of the events.

Sub-topic Learning from accidents Layered investigations The investigation process Investigation Summary Aids for diagnosis Aids for recommendation

Learning from accidents Build an investigation team Every member learns about problems that precipitate accidents To avoid similar situations in the future Learn how to prevent future accidents.

Learning from accidents Fundamental step in accident investigation: 1.Developing a detail description of the accident 2.Accumulating relevant facts 3.Analyzing the facts and developing potential causes of the accident 4.Studying the system & operating method relevant to the potential causes of the accident 5.Developing the most likely causes 6.Developing recommendations to eliminate recurrence of this type of accident 7.fact-finding not fault-finding.

Layered Investigations First layer: immediate technical recommendations, Second layer: recommendations to avoid the hazards, Third layer: recommendations to improve the management system.

Example 12-1 Illustrate the layered investigation process to develop underlying causes of a municipal pool accident. A drowning accident occurred during an open swim period. Approximately 100 children, ranging between 5 and 16 years old, were in and around a pool (3 ft to 9 ft deep). An older child unknowingly pushed a 5-year-old into the deep water. The pool was relatively crowded, and the 5-year-old slipped under the water without being noticed by others, including the lifeguard.

Solution The facts uncovered by an investigation team are 1. the pool did not have deep and shallow markings, 2. the older child was engaged in horseplay, 3. the younger child did not know how to swim, 4. the lifeguard had many blind fields of vision, 5. the pool was overly crowded, 6. the pool did not have an orientation program, and 7. the pool did not offer swimming lessons.

First layer recommendations: Immediate technical recommendations 1. Paint pool depths at the pool edges. 2. Add more lifeguards. 3. Reduce the number of swimmers.

Second layer recommendations: Avoiding the hazard 1. Prohibit horseplay. 2. Zone pool to keep smaller children at shallow end of pool. 3. Add swimming lessons for all age groups. 4. Give all new swimmers (especially young children) a pool orientation. 5. Add a roving lifeguard to monitor and control pool behavior.

Third layer recommendations: Improving the management system 1. Train lifeguards to alert supervision of observed potential problems. 2. Assign the supervisor to make formal (documented) audits on a regular basis.

Investigation Process Steps (1) Investigation team – choose team (2) Brief survey – make overview survey to understand the type and information needed to derive causes of the accident. (3) Set objectives and delegate responsibilities – based on (1) and (2) (4)Preincident facts - gather & organize preincident facts. Use flowsheets, procedures, photograph

Investigation Process Steps (5)Accident facts - make detailed examinations with photos, inspections. - record extent of damage, hypothesize the sequences of event, cause of accident (6)Research and analyses – initiate research-type experiments & analyze facts (7)Discussion, conclusions and recommendations - study (2) to (6) to develop conclusion & layered recommendations. (8)Report - develop accident investigation report.

Accident Investigation Report format should be flexible and designed specifically to best explain the accident. The format may include the following sections: (1) introduction, (2) process description (equipment and chemistry), (3) incident description, (4) investigation results, (5) discussion, (6) conclusions, (7) layered recommendations.

Investigation Summary Summarizes the events and recommendations in a diagram

Aids for Diagnosis The data collected during accident are studied and analyzed: - to find the cause of accident - to develop recommendations to prevent a recurrence Sometimes, the evidence needs added analysis to uncover explanations. Require special techniques or aid to diagnosis to relate the evidence to specific cause.

Aids for Diagnosis a) Fire b) Explosions c) Sources of ignition in vessel d) Pressure Effects e) Medical Evidence

Aids for Diagnosis a) Fire - identification of the primary source of ignition is one of the major objectives of investigation. - For example; - the depth of wood charring is proportional to the duration of burning - most woods burn at a rate of 1.5 in/hr. - If the time of extinguishment is known; - If the depth of char at various locations is known; - the region of the origin can be approximated.

Aids for Diagnosis b) Explosions - The classification of the explosion as either deflagation or a detonation & magnitude of the explosion may be useful to develop causes and recommendations.

Aids for Diagnosis b) Explosions Deflagration -The pressure increases during deflagration: for hydrocarbon-air mixtures for hydrocarbon-oxygen mixtures P 1 and P 2 = upstream & downstream pressure, respectively

Aids for Diagnosis b) Explosions Detonations -In a single vessel detonations increase pressures significantly:

Aids for Diagnosis c) Pressure Effect -Investigation on ruptured pipe and vessel -important to know the pressures required to create the damage -Pressure necessary to produce a specific stress in a vessel depends on: 1. thickness of the vessel 2. vessel diameter 3. mechanical properties of the vessel wall

For cylindrical vessel (pressure p < 0.385S M ) For cylindrical vessel (pressure p > 0.385S M ) Where:p is the internal gauge pressure, S M is the strength of the material, t V is the wall thickness of the vessel, r is the inside radius of the vessel.

For spherical vessel (pressure p < 0.665S M ) For spherical vessel (pressure p > 0.665S M )

Example 12-3 Determine the pressure required to rupture a cylindrical vessel if the vessel is stainless 316, has a radius of 3 ft, and has a wall thickness of 0.5 in.

Solution Because the pressure is unknown, Equation 12-4 or 12-5 is used by trial and error until the correct equation is identified. Equation 12-4 is applicable for pressures below 0.385S M. S M for Stainless Steel 316 (from Table 12-3) = 85,000 psi, 0.385S M = 32,700 psi r = 3 ft = 36 in t v = 0.5 in. Therefore Equation 12-4 is applicable, and a pressure of 1170 psi is required to rupture this vessel.

Example 12-4 Determine the pressure required to rupture a spherical vessel if the vessel is stainless 304, has a radius of 5 ft, and has a wall thickness of 0.75 in.

Solution Equation 12-6 is applicable if the pressure is less than 0.665S M S M for Stainless 304 = 80,000 psi S M = 0.665(80,000) = 53,200 psi. Using Equation 12-6 for spherical vessels, The pressure criteria is met for this equation. The pressure required to rupture this vessel is 1990 psi.

(d) Medical Evidence Medical examinations of the accidents victims may be useful for identifying the source of accidents Type of medical data: 1. type & level of toxic in the blood 2. location & magnitude of injuries 3. type of poisoning (CO, toluene, etc.) 4. sign of heat exposure 5. sign of eye irritation Aids for Diagnosis

Aids for Recommendations To develop recommendations to prevent a recurrence To prevent similar accident within the company / industry

Aids for Recommendations Control Plant Modifications Often not given the same attention/concern as a new plant design Many accidents are result of plant modifications Recommendations to prevent this problem: a) All modification must be authorized. b) The modification design should have same quality of pipes/equipments as the original design c) Safety review – HAZOP must be conducted while the modification project is in the design phase. d) Training – operators & engineers: to understand the modified operation e)Audit – to ensure the modifications are made & maintain as designed.

User Friendly Design Not create hazardous conditions For example: 1. using nontoxic and nonflammable solvent 2. keep temperatures below the flash point & boiling point at atmospheric conditions 3. keep inventories low 4. design for safe shutdown during emergency situations

Preventive Maintenance - failure of emergency protection equipment such as cooling water pumps, instruments and deluge system can cause major accident. -Protective equipments failed due to no preventive maintenance -Preventive maintenance programs must be organized, managed & fully supported by management. -Must have maintenance schedule

ERT 312/4 – SAFETY & LOSS PREVENTION PBL PROJECT- INDUSTRIAL ACCIDENTS