| P051 | PFD | Process Flow Diagram | Diagram showing the flow of materials and equipment in a process | Used in chemical plant design to visualize operations |
| P052 | PFMEA | Process Failure Mode and Effects Analysis | A tool for identifying and mitigating process risks | Used in automotive manufacturing quality control |
| P053 | PFM | Pulse Frequency Modulation | Modulation where information is carried in the frequency of pulses | Used in servo motor control systems |
| P054 | PFR | Plug Flow Reactor | Reactor where fluids move in a “plug” without mixing | Used in continuous chemical processes |
| P055 | PFRP | Pultruded Fiber Reinforced Polymer | Composite material made by pultrusion for structural strength | Used in corrosion-resistant beams |
| P056 | PG | Propylene Glycol | A synthetic liquid used for heat transfer and antifreeze | Used in HVAC chillers |
| P057 | PGA | Poly Glycolic Acid | Biodegradable polymer used in engineering and medicine | Used for medical sutures |
| P058 | PGB | Pressure Gauge Board | Panel displaying pressure readings | Found in boiler rooms |
| P059 | PGD | Power Generation Department | Section responsible for generating power | Found in power plants |
| P060 | PGR | Pressure Gradient Ratio | Ratio of pressure change per unit length | Used in fluid mechanics |
| P061 | PH | Potential of Hydrogen | Measure of acidity/alkalinity | Used in cooling water treatment |
| P062 | PHA | Preliminary Hazard Analysis | Early-stage hazard assessment method | Used before plant commissioning |
| P063 | PHC | Piston Hydraulic Cylinder | Actuator converting hydraulic energy to mechanical force | Used in presses |
| P064 | PHM | Prognostics and Health Management | Predictive maintenance strategy | Used in turbine monitoring |
| P065 | PHR | Process Hazard Review | Evaluation of process safety | Used in chemical plants |
| P066 | PI | Proportional-Integral | Control algorithm in automation | Used in temperature control loops |
| P067 | PID | Proportional-Integral-Derivative | Advanced control algorithm for process control | Used in speed control of motors |
| P068 | PIE | Plant Information Exchange | Digital sharing of plant operational data | Used in SCADA systems |
| P069 | PILC | Paper Insulated Lead Covered | Type of power cable | Used in underground installations |
| P070 | PIN | Product Identification Number | Unique code for identifying a part | Used in supply chain tracking |
| P071 | PIPE | Plastic Injection Process Equipment | Equipment for producing plastic parts | Used in injection molding |
| P072 | PIPESIM | Pipeline Simulation | Software for simulating pipeline operations | Used in oil & gas flow assurance |
| P073 | PIR | Passive Infrared | Sensor detecting infrared radiation from objects | Used in motion-activated lights |
| P074 | PIT | Pressure Indicator Transmitter | Device that measures and transmits pressure | Used in industrial process control |
| P075 | PJT | Project | A planned engineering work with objectives and timeline | Plant upgrade projects |
| P076 | PKM | Plant Knowledge Management | Managing plant technical documentation | Used in manufacturing |
| P077 | PLC | Programmable Logic Controller | Industrial computer for automation | Used in assembly lines |
| P078 | PLD | Programmable Logic Device | Integrated circuit for custom logic operations | Used in control panels |
| P079 | PLF | Plant Load Factor | Ratio of actual output to potential output | Used in power plant efficiency analysis |
| P080 | PLM | Product Lifecycle Management | Managing a product from design to disposal | Used in automotive manufacturing |
| P081 | PLS | Programmable Logic System | Control system using programmable logic | Used in factory automation |
| P082 | PLV | Pressure Limiting Valve | Valve to control max pressure | Used in hydraulic circuits |
| P083 | PM | Preventive Maintenance | Scheduled maintenance to avoid breakdowns | Used in machinery upkeep |
| P084 | PMB | Project Management Board | Governing body for engineering projects | Oversees major plant installations |
| P085 | PMC | Project Management Consultancy | Firm offering project management services | Used in large industrial projects |
| P086 | PMCS | Plant Monitoring and Control System | System for monitoring and controlling plant operations | Used in chemical plants |
| P087 | PMF | Probability Mass Function | Function giving probability distribution in discrete cases | Used in reliability analysis |
| P088 | PMIS | Project Management Information System | Digital system for managing projects | Used in EPC firms |
| P089 | PMO | Project Management Office | Department managing multiple projects | Used in construction companies |
| P090 | PMP | Project Management Professional | International certification for project managers | Used by senior engineers |
| P091 | PMR | Preventive Maintenance Report | Document summarizing maintenance actions | Used in asset management |
| P092 | PMS | Power Management System | System controlling electrical distribution | Used in ships and plants |
| P093 | PMT | Project Management Team | Group executing project management tasks | Used in industrial expansion projects |
| P094 | PN | Pressure Nominal | Nominal pressure rating for pipes and fittings | PN16 pipe flange |
| P095 | PNC | Pneumatic Control | Control using compressed air | Used in air-actuated valves |
| P096 | PNG | Piped Natural Gas | Natural gas supplied via pipelines | Used in industrial burners |
| P097 | PNL | Panel | Enclosure for housing controls | Electrical control panel |
| P098 | PNM | Project Network Model | Diagram showing project task dependencies | Used in CPM scheduling |
| P099 | PNP | Positive-Negative-Positive | Transistor type in electronics | Used in switching circuits |
| P100 | PO | Purchase Order | Commercial document for ordering goods | Used in procurement |
| P101 | POC | Proof of Concept | Demonstration to verify a concept’s feasibility | Prototype demonstration |
| P102 | POD | Point of Delivery | Location where goods are handed over | Used in supply chain |
| P103 | POE | Power Over Ethernet | Technology to transmit power and data over Ethernet cable | Used in IP cameras |
| P104 | POF | Probability of Failure | Likelihood of a component failing | Used in risk assessments |
| P105 | POL | Petroleum, Oil, and Lubricants | Common term for fuel and lubricants | Used in plant maintenance |
| P106 | POM | Project Operations Manual | Guideline for managing projects | Used in EPC projects |
| P107 | POP | Polypropylene | Thermoplastic polymer | Used in automotive bumpers |
| P108 | POR | Pressure Operated Regulator | Regulates pressure in a system | Used in gas distribution |
| P109 | POS | Point of Sale | System for retail transactions | Used in stores |
| P110 | POT | Potentiometer | Variable resistor for voltage control | Used in control circuits |
| P111 | POW | Power | Rate of doing work | Measured in watts |
| P112 | PP | Polypropylene | Common plastic polymer | Used in piping |
| P113 | PPA | Power Purchase Agreement | Contract for buying electricity | Used in renewable energy projects |
| P114 | PPD | Process and Product Development | Improving process and product design | Used in manufacturing plants |
| P115 | PPE | Personal Protective Equipment | Safety gear for workers | Helmets, gloves, goggles |
| P116 | PPF | Peak Particle Flux | Measurement of particle concentration | Used in cleanrooms |
| P117 | PPI | Producer Price Index | Economic indicator of price change | Used in project budgeting |
| P118 | PPL | Parts Per Liter | Measurement unit for concentration | Used in water analysis |
| P119 | PPM | Parts Per Million | Measurement of small concentration levels | Used in emissions control |
| P120 | PPS | Pulses Per Second | Frequency of pulse generation | Used in motor controls |
| P121 | PPT | Parts Per Trillion | Ultra-low concentration measurement | Used in chemical analysis |
| P122 | PPU | Price Per Unit | Cost per single unit | Used in cost estimation |
| P123 | PR | Pressure Relief | Method to release excess pressure | Safety valve operation |
| P124 | PRA | Preliminary Risk Assessment | Early evaluation of risks | Used before engineering design |
| P125 | PRB | Powder River Basin | Coal-producing region in the US | Used in energy discussions |
| P126 | PRC | Process Control | Managing process parameters | Used in manufacturing lines |
| P127 | PRD | Pressure Relief Device | Device to prevent overpressure | Found in boilers |
| P128 | PRE | Process Reliability Engineering | Improving process dependability | Used in oil refineries |
| P129 | PRF | Pulse Repetition Frequency | Frequency of radar pulses | Used in GPR equipment |
| P130 | PRH | Process Reaction Hazard | Hazard from chemical reactions | Used in safety reviews |
| P131 | PRI | Primary | First or main stage | Primary coil in transformers |
| P132 | PRM | Pressure Regulating Module | Controls output pressure | Used in gas systems |
| P133 | PRN | Pro Re Nata | As needed or required | Maintenance scheduling |
| P134 | PRO | Programmable Read-Only | Memory type | Used in embedded systems |
| P135 | PRP | Production Readiness Plan | Plan before manufacturing starts | Used in aerospace projects |
| P136 | PRS | Pressure Reducing Station | Reduces high-pressure flow | Used in steam systems |
| P137 | PRT | Platinum Resistance Thermometer | High-accuracy temperature sensor | Used in calibration labs |
| P138 | PRV | Pressure Relief Valve | Releases excess pressure | Used in pressure vessels |
| P139 | PSA | Pressure Swing Adsorption | Gas separation process | Used in oxygen generation |
| P140 | PSB | Process Simulation Block | Part of process modeling | Used in Aspen HYSYS |
| P141 | PSC | Process Safety Culture | Safety mindset in operations | Promoted in oil & gas industry |
| P142 | PSD | Process Shutdown | Safety measure to halt operations | Used during emergencies |
| P143 | PSE | Process Safety Event | Incident affecting safety | Used in safety reporting |
| P144 | PSF | Process Safety Factor | Safety margin in process design | Used in mechanical designs |
| P145 | PSI | Pounds per Square Inch | Pressure unit | Tire pressure measurement |
| P146 | PSIG | Pounds per Square Inch Gauge | Pressure relative to atmospheric | Boiler pressure |
| P147 | PSL | Pipeline Specification Level | Material specification for pipelines | Used in oil & gas |
| P148 | PSM | Process Safety Management | OSHA standard for managing hazardous processes | Used in chemical plants |
| P149 | PSO | Process Safety Officer | Person responsible for safety | Used in industrial plants |
| P150 | PSP | Power System Protection | Systems for protecting electrical grids | Used in substations |
| P151 | PST | Pacific Standard Time | Time zone reference | Used in scheduling |
| P152 | PSV | Pressure Safety Valve | Protects systems from overpressure | Used in LNG plants |
| P153 | PT | Pressure Transmitter | Converts pressure to electrical signal | Used in control systems |
| P154 | PTA | Purified Terephthalic Acid | Chemical raw material | Used in PET plastic production |
| P155 | PTB | Portable Test Bench | Equipment for testing instruments | Used in calibration shops |
| P156 | PTC | Positive Temperature Coefficient | Resistance increases with temperature | Used in thermistors |
| P157 | PTD | Product Technical Data | Document containing product specifications | Used in engineering design |
| P158 | PTE | Potential to Emit | Regulatory measure of emissions | Used in environmental permits |
| P159 | PTF | Pressure Test Fixture | Device for holding parts during pressure testing | Used in quality control |
| P160 | PTH | Plated Through-Hole | PCB hole with conductive plating | Used in electronics manufacturing |
| P161 | PTL | Part Tolerance Limit | Maximum allowable variation | Used in machining |
| P162 | PTM | Project Time Management | Planning and controlling project schedules | Used in EPC projects |
| P163 | PTO | Power Take-Off | Transfers engine power to auxiliary equipment | Used in tractors |
| P164 | PTP | Precision Time Protocol | Synchronizes clocks in networks | Used in industrial Ethernet |
| P165 | PTR | Pressure Test Report | Record of pressure test results | Used in QA/QC documentation |
| P166 | PTS | Performance Test Sheet | Records performance metrics | Used in plant commissioning |
| P167 | PTT | Push-To-Talk | Communication method | Used in radios |
| P168 | PTU | Power Transfer Unit | Transfers hydraulic power | Used in aircraft systems |
| P169 | PTV | Pressure Test Valve | Valve for conducting pressure tests | Used in piping systems |
| P170 | PU | Polyurethane | Polymer used in coatings and insulation | Used in machinery seals |
| P171 | PUA | Product Use Analysis | Study of product application | Used in market research |
| P172 | PUB | Public Utility Board | Governing body for public utilities | Used in infrastructure planning |
| P173 | PUE | Power Usage Effectiveness | Data center efficiency metric | Used in energy audits |
| P174 | PUF | Polyurethane Foam | Lightweight foam material | Used in insulation panels |
| P175 | PUI | Process User Interface | Interface for process operators | Used in SCADA systems |
| P176 | PUL | Pull | Mechanical force to draw something | Used in cable winches |
| P177 | PUM | Pump | Device to move fluids | Used in hydraulic systems |
| P178 | PUP | Pick-Up Point | Designated location for pickup | Used in logistics |
| P179 | PUR | Polyurethane Resin | Durable polymer | Used in coatings |
| P180 | PUT | Programmable Unijunction Transistor | Type of transistor | Used in triggering circuits |
| P181 | PV | Pressure Vessel | Container for pressurized fluids | Used in chemical plants |
| P182 | PVA | Polyvinyl Alcohol | Water-soluble polymer | Used in paper coatings |
| P183 | PVC | Polyvinyl Chloride | Common thermoplastic | Used in piping |
| P184 | PVD | Physical Vapor Deposition | Coating method | Used in cutting tools |
| P185 | PVDF | Polyvinylidene Fluoride | High-performance thermoplastic | Used in chemical piping |
| P186 | PVI | Pressure Vacuum Indicator | Measures pressure/vacuum | Used in tanks |
| P187 | PVL | Pressure Vacuum Relief Valve | Maintains safe pressure levels | Used in storage tanks |
| P188 | PVM | Permanent Virtual Machine | Software-based machine environment | Used in programming |
| P189 | PVP | Polyvinylpyrrolidone | Water-soluble polymer | Used in adhesives |
| P190 | PVR | Pressure Vacuum Relief | Combines pressure and vacuum relief | Used in petroleum storage |
| P191 | PVRS | Pressure Vessel Repair Specification | Guidelines for repairing vessels | Used in maintenance |
| P192 | PVS | Photovoltaic System | Solar power generation system | Used in renewable energy plants |
| P193 | PVSS | Process Visualization and Control System | Software for industrial control | Used in automation |
| P194 | PVT | Pressure Volume Temperature | Thermodynamic relationship | Used in gas law calculations |
| P195 | PVU | Pressure Vacuum Unit | Dual-function unit | Used in fuel systems |
| P196 | PVW | Process Value Weight | Weight given to process parameters | Used in optimization |
| P197 | PWA | Process Water Analysis | Testing process water quality | Used in cooling systems |
| P198 | PWB | Printed Wiring Board | Electrical board with printed wiring | Used in electronics |
| P199 | PWC | Plant Water Cooling | Cooling water for plant use | Used in thermal power stations |
| P200 | PWM | Pulse Width Modulation | Modulation method for controlling power | Used in motor speed control |