PIPING & INSTRUMENTATION DIAGRAMS (P&IDs)
Piping & Instrumentation Diagrams (P&IDs) should:
Depict the connectivity of equipment and the instrumentation and piping used to connect and control the equipment.
Provides a visual reference to equipment configuration, valving, sensors, etc.
Provides useful information to assist in analyzing process hazards.
Supports development of operating procedures.
Communicates the configuration of equipment clearly and concisely to improve operator understanding of the process and reduce human errors.
Records the current (as-built) state of the process so that changes can be planned safely and effectively.
Unfortunately, many facilities have P&IDs that lack critical elements, or do not represent the current operating configuration and system components. These errors cause operating errors, delay efforts to minimize an ammonia release, and further increase the risks to emergency responders.
A typical set of P&IDs include:
Block Flow Diagram
Equipment and Valve List
Drawing of the equipment including valves, controls and piping.
Protexus engineers will come onsite and walk the facility to collect the information needed to provide new or updated P&IDs. Or you can provide red-lined P&IDs and our engineer will provide you with updated drawings.
The P&IDs will be provided to the facility electronically and in hard copy at the completion of the project.
OSHA and EPA require a facility to document the Maximum Intended Inventory of the hazardous chemical onsite. The meaning of maximum intended inventory is the maximum chemical inventory that a facility intends to utilize (have onsite) to operate the equipment. Many vessels within a refrigeration system are designed to operate partially filled with liquid or completely full of vapor (e.g. oil separators) during normal operation. The maximum intended inventory is not the inventory of ammonia that could be contained if all vessels, pipe, and equipment were filled to 100% capacity with liquid as this scenario would never be “intended”.
A facility also has to document the actual ammonia quantity that is maintained at your facility in the equipment.
Protexus engineers can provide the maximum intended inventory and actual inventory calculations for your facility. When we come onsite, our engineers will gather the equipment information and piping lengths used to provide the calculations. Or our engineers can work remotely with facility personnel to obtain the information.
PRESSURE SAFETY RELIEF DESIGN AND DESIGN BASIS
Relief valves are an important safety feature in industrial ammonia refrigeration systems. They protect the system from over pressurization and possible explosion. The discharge piping is an important part of the relief valve system, which must be sized properly so the relief valve capacity is not affected, and it must route the ammonia to a safe discharge location.
EPA defines the relief system as including, but are not limited to, relief valves, relief headers, relief drums, and rupture disks. Design basis means documenting how the loads and sizes of the relief system, as well as inlet and outlet sizes, were determined. This includes a description of overpressure scenarios considered, the scenario that creates the largest load to be relieved, the assumptions used, and if the device meets a certain code.
When our engineers come onsite, they will gather the information to assist them in creating a schematic of the RV system. The calculations will show if the piping branch and/or headers are properly sized for the relief valves in the system. The Relief valves will also be documented to indicate if they are properly sized for the vessel or piping. The finished report will include the schematic along with the results of the calculations of your relief system.
VENTILATION SYSTEM DESIGN AND DESIGN BASIS
Ventilation systems are provided to ensure that there is adequate air circulation in areas where refrigeration equipment has been installed.
Machine Room ventilation:
Purges ammonia vapor from the machine room in emergency situations
Prevents excessive temperature rise in machine room due to equipment generated heat
Provides fresh air for the operators
Maintains the machine room under negative pressure
Provides air movement to all for better ammonia detector response
Ventilation calculations are provided to ensure the fan ventilation rate (cfm) meets the temperature control ventilation, continuous ventilation and emergency ventilation requirements for the code or standard the system was designed.
Protexus engineers will work with facility personnel to gather the necessary fan and equipment information to evaluate the ventilation to ensure there is sufficient air flow in the Engine Room in the event of an ammonia release.