Chapter 5 - Start Up & Shut Down of Process Equipment Flashcards
What are Process Equipment?
Arrangement of various mechanical equipment required for physical or chemical methods of mechanical and/or thermal treatment or processing of a raw material or product
What is process equipment used for in the refining and processing industries?
It is used in the refining and processing industries to turn raw materials into commercial products and materials for consumers.
What are some common classifications of process equipment and where are they generally found?
Designed for specific tasks mainly a single purpose that are generally classified as storage, reactors, controlling flow, steam production, heat exchanger etc. that are generally found in refineries, chemical plants, water and waste water treatments and many heavy industries.
Why is it important to review the safety of process equipment before operations?
Because it usually is subjected to high temperature, high pressure or may be handling hazardous chemicals.
When is a pre-startup safety review required for process equipment?
When it is newly procured or operating after certain modifications.
What are the Pre-Startup Safety Review (PSSR) activities?
• Fabrication of the equipment is complying with the design specification
• Design of equipment and the procurement of material is generally approved by a third party quality assurance agency
• Mountings on different equipment for safety are in place and is in good condition
• Standard operating procedures are set for safety, operation, maintenance and
emergency is adequate
• Process hazard analysis is performed before the startup of the equipment
What are some examples of general process equipment?
Boiler, pressure vessel, storage, heat exchanger etc.
What are the startup operations of general process equipment?
• Powering on the burners and pilots, preheaters, compressors, cooling towers etc. as it may apply for different equipment
• Check all the valves and its reseating – flow control valves, pressure control valves, direction control valves and other types
• Check the working of safety mountings
• Charge the system slowly to reach the rated operating
parameters of pressure, temperature or any other parameters
• Ensure the smooth functioning of all the automatic controls
Discuss the startup operations of a boiler.
• The burner switch is powered to prove the flames of standing, intermittent or interrupted pilots and the main flames
• Boiler vent and the drain between stop valve and non open to bleed air from the system
• Open the equalizing valve near the main stop valve
• Open the main steam stop valve
• Close the boiler vent when the pressure reaches up to 15 psi
• Secure the boiler feed and check whether power is cut-off at proper low level
• When steam reaches up to 85 % of system pressure open the non-return valve
• Manually test all the valves are operating and reseating
• The boiler pressure is slowly reached in low fire and allow the non-return automatically cut the boiler into live system
• Verify the drain between stop valves and non-return valve
• Check if all the automatic controls are operating and secured
Why is proper shutdown of process equipment highly important?
Because otherwise it may lead to damages and breakdowns by improper shutdown.
Why is the shutdown process important for process equipment operating at elevated temperatures and higher pressures? Give examples on such equipment.
If it is abruptly closed or drained, it may cause distortion of parts and affects its dimensional stability, and the residual heat may lead to crack formations on the equipment and many other damages.
This is true for process equipment like fractional distillation columns, boilers, furnaces, heat exchangers etc.
Why is there no singular shutdown process for all process equipment?
Because it varies in its function and design parameters.
What are the general steps in a sequential shutdown operation for process equipment?
• Reduce the temperature slowly to bring it down to normal ambient conditions.
• Close the fuel after its operating parameters are brought down to reduced levels.
• Close down all the accessories that is for the purpose of process efficiencies first.
• Shut down the feed systems.
What are the potential consequences of draining process equipment while it is hot?
When drained in hot conditions, internal parts like tubes, shells and non-structural elements may be subjected to warpage and distortions and cause leaks.
It could enhance the chance of scale formations inside the equipment.
What happens when the equipment is suddenly cooled or when cold water is used to cool it?
It leads to formation of crack or it will alter the mechanical properties of the material.
