© 2012 Delmar, Cengage Learning Chapter 15 Process System Hazards

© 2012 Delmar, Cengage Learning Operating Hazards Equipment and systems Weather Chemistry and chemicals

© 2012 Delmar, Cengage Learning Equipment and System Related Hazards Pumps: Cavitation Vapor lock Improper line-up Variation in suction head or NPSH Gasket leaks Seal flush tubing plugs up

© 2012 Delmar, Cengage Learning Figure 15-1 Pump Seal Leak

© 2012 Delmar, Cengage Learning Cavitation The formation and collapse of air pockets inside the pumping chamber. Boiling Cavitation can be prevented by increasing the NPSH or pinching down on the discharge valve.

© 2012 Delmar, Cengage Learning Pressure The force or weight per unit area. The higher the atmosphere, gas, or liquid the greater the pressure. Liquid pressure is exerted equally in all directions. Height of Liquid × × specific gravity = pressure

© 2012 Delmar, Cengage Learning Figure 15-2 Pump System

© 2012 Delmar, Cengage Learning Compressors Watching flammability limits is important when equipment containing air is purged using gas. If gas enters too slow a flammable mixture is formed. If it enters too fast it can produce a spark. When selecting a gas to purge with piping line-up is critical.

© 2012 Delmar, Cengage Learning Figure 15-3 Purging Procedure

© 2012 Delmar, Cengage Learning Figure 15-4 Reciprocating Compressor

© 2012 Delmar, Cengage Learning Common compressor safety issues: Noise hazards High-pressure hose blowing loose Hazards associated with compressed gas systems Hazards associated with rotating equipment Mixing air and hydrocarbons into flammable or explosive concentrations Avoiding high-pressure releases; eyes, nose Fires or explosions Incorrect line-up Loss of cooling water Lifted safety

© 2012 Delmar, Cengage Learning Figure 15-5 Compressed Air System

© 2012 Delmar, Cengage Learning Figure 15-6 Factor of 4 Safety Design

© 2012 Delmar, Cengage Learning Heat Exchangers The effects of absorbed heat: Increase in molecular activity Change of state Chemical change Energy movement from hot to cold Radiant heat transfer Conductive and convective heat transfer Electrical transfer – thermocouple Increase in volume Increase in temperature

© 2012 Delmar, Cengage Learning Figure 15-7 Heat Exchanger System

© 2012 Delmar, Cengage Learning Process technicians use a variety of temperature systems. The four most common are K, °C, °F, °R. Heat is a form of energy caused by increased molecular activity that cannot be created or destroyed, only transferred. The hotness or coldness of a substance determines the temperature. Heat is measured in BTUs. Temperature is measured in K, °C, °F, °R. Heat and temperature are not the same.

© 2012 Delmar, Cengage Learning Safety aspects associated with the operation of a heat exchanger system include: Chemical hazards associated with spills and leaks Hazards associated with burns Hazards associated with fires Hazards associated with explosions and boiling liquid expanding vapor explosion Confined space entry Equipment failure Gauge failure Sampling, purging, or venting the shell

© 2012 Delmar, Cengage Learning Cooling Tower Safety aspects of the cooling tower system include the following: Chemical additives Rotating equipment Hazards of hot water Equipment failure Working at heights Hazards of working with acids Confined space entry Hazardous energy

© 2012 Delmar, Cengage Learning Figure 15-8 Cooling Tower System

© 2012 Delmar, Cengage Learning Furnace or Fired Heater In the instance of a flame-out, the concentration of hazardous gases can build up in the furnace until it explodes. Another common problem is tube leaks. Tube failures are typically related to flame impingement, high heat loads, or erosion.

© 2012 Delmar, Cengage Learning Figure 15-9 Typical Fired Heater

© 2012 Delmar, Cengage Learning Steam Generation Accidental release of high-, medium-, and low-pressure steam. High-velocity steam can cut through solid objects. Steam can eat away the inner surfaces of industrial equipment used to contain it. Thermal warp, thermal shock, water hammer, and thermal expansion are all natural phenomenon process technicians should be aware.

© 2012 Delmar, Cengage Learning Figure Steam Generation – Uses and Applications

© 2012 Delmar, Cengage Learning Figure Power Generation System

© 2012 Delmar, Cengage Learning Electricity The hazards associated with electrical shock are severe and require specific training. Electrical equipment repair should be performed only by qualified plant electricians.

© 2012 Delmar, Cengage Learning Flare System When a flare is smoking badly, this is an indication that the plant is having serious problems. Black smoke from a flare shows unburned hydrocarbons and the loss of company profits.

© 2012 Delmar, Cengage Learning Figure Flare System

© 2012 Delmar, Cengage Learning The hazards associated with flare operation include: Flare pilot light goes out and heavy hydrocarbon vapors drop to the ground and seek ignition source Flare header overwhelms flare system and produces black smoke Fan motor catches fire Pump goes out on knock-out drum liquid seal and pressure increases on header Steam ring fails Support cable breaks during high winds and flare falls

© 2012 Delmar, Cengage Learning Weather-Related Hazards Lightning is a common occurrence that rarely finds an unprotected or ungrounded system in a plant. It is not safe to be on the tallest vessel or distillation column during a lightning storm. Heavy rain storms can quickly drop the temperature and cause wide variation swings in process variables.

© 2012 Delmar, Cengage Learning Freezing weather can also cause problems. Hurricanes present numerous hazards: high winds, flooding, power outage. The severity of the storm will determine the action plan the plant will use and how much of the facility will be shut down.

© 2012 Delmar, Cengage Learning Chemicals and Chemistry Related Hazards Chemistry related hazards are associated with the way two or more chemicals will respond to each other under specific operational conditions.

© 2012 Delmar, Cengage Learning Reactors Reactors are used to make new products by making or breaking chemical bonds. A reaction is either exothermic or endothermic.

© 2012 Delmar, Cengage Learning Figure Stirred Reactor

© 2012 Delmar, Cengage Learning Atoms are composed of positively charged particles called protons, an equal number of neutral particles called neutrons, and negatively charged particles called electrons. Valence electrons are important because they provide the link to almost every chemical reaction. Chemical bonding is classified as either ionic or covalent.

© 2012 Delmar, Cengage Learning Matter is anything that occupies space and has mass. The four physical states of matter are solid, liquid, gas, and plasma. A compound is defined as a substance formed by the chemical combination of the two or more substances in definite proportions by weight. A mixture is composed of two or more substances that are only mixed physically.

© 2012 Delmar, Cengage Learning In a chemical reaction, the raw materials or reactants are placed on the left side. As the reactants are mixed together, they yield predictable products. The products are placed on the right side of the equation. What goes into a chemical reaction must come out.

© 2012 Delmar, Cengage Learning

Safety hazards associated with the operation of a stirred reactor include: Runaway exothermic or endothermic reaction Feed composition changes cause rapid pressure changes Fee concentration increase – reaction becomes unstable Agitation problems will reduce reaction Loss of cooling water Loss of catalyst Temperature increase – doubles reaction rate for every 10°C increase

© 2012 Delmar, Cengage Learning Distillation System Operational hazards associated with distillation include the following: Fires and explosions Leaks – gasket, valve, instruments, piping, and pumps Pressure surges Loss of cooling water Steam valve stuck in open position Exothermic reaction occurs in the column Instrument failure

© 2012 Delmar, Cengage Learning Human Factors Human error has been identified as the most common cause of industrial accidents. A technician’s greatest nemesis is fatigue and mental stress. Most of the biggest industrial disasters have taken place between the hours of 1:00 A.M. and 4:00 A.M.