Refining and Petrochemical Company HAZOP Minute sheet

Project: Crude Distillation Unit

Node: 4

Draw No:2

Node Description: Pre flash column (10-C-07)

Guide Word

Cause

Consequence

Safeguards

Recommendation

1. High Pressure

1. Top temperature controller 10-TRC-1175 fails and top temperature rises

2. Flow regulator 10-FRC-1181 controlling reflux valve PV5 fails

3. Reflux valve PV5 closed

1. Reduces vapourisation of light ends

2. Increase atmospheric furnace load

3. Entrained water from desalter still passes on to atmospheric heater which may expand and rupture heater tubes

1. Install pressure controller

2. Pressure indicator should be installed

3. High pressure alarm should be installed

2. Low Pressure

1. Fall in preflash top temperature as temperature controller 10-TRC-1175 failed

2. Reflux valve PV5 fully opened

3. Flow regulator 10-FRC-1181 failed

1. Foaming in column, Producing black distillates as well as yield loss in atmospheric column

2. Flooding of column

1. Install pressure controller

2. Pressure indicator should be installed

3. Low pressure alarm should be installed

3. Low Temperature

1. Top temperature controller 10-TRC-1175 fails

2. Reflux flow controller 10-FRC-1181 faulty

3. Reflux flow control valve PV5 fully opened

4. Feed temperature controller 10-TRC-1137 faulty

5. Column middle temperature controller 10-TRC-1180 faulty

1. Reduces vapourisation of light ends hydrocarbons increasing atmospheric column vapour load

2. The high temperature in the atmospheric furnace causes the light ends and water still present in the crude to expand in the furnace tubes and rupture occurs

1. Maintain the column temperature controllers

2. Regular checking and maintenance of reflux flow lines and valves

3. Maintain heat exchanger tubes frequently

4. Low Level

1. Level controller 10-LRC-1188 failed

2. Discharge pump 10-P-02AB pumping capacity increased

3. Preflash furnace feed flow controller 10-FRC-1051faulty

4. Preflash furnace feed flow valve PV1 partly closed

1. Low vapourisation of light ends hydrocarbon increasing vapour loads of the atmospheric column

2. Cavitations of pumps

3. Off spec distillates

1. Check level controller

2. Maintain pumps

3. Check and maintain feed flow controllers, feed lines and valves

5. High Level

1. Level controller 10-LRC-1188 failed

2. Low head of discharge pump 10-P-02AB

3. Preflash feed flow controller 10-FRC-1051faulty.

4. Preflash feed flow valve PV1 fully opened

1. Entering feed throws liquid up the column and damage wash trays

Emergency valve 10-HS-1190 will open

1. Regular checking and maintenance of level controllers

2. Maintain pumps

3. Check and maintain feed flow controllers, feed lines and valves