Design Criteria Formulation

📕How do we size common water & wastewater equipment — is it really difficult? 📌 For most conventional unit processes, it’s not as complicated as it looks. At concept design / tender / RFQ stage, we usually don’t start with simulation, detailed calculations or CFD. 📕We start with a proven workflow: correct criteria + the right equation + verified industry ranges. 📕You need to follow these simple steps but get familiar with verified practical and industial data to design most of the equipment: 📌1) Start with the water (before any math) Be clear on: • Water vs wastewater (municipal vs industrial) • Average / peak / minimum flows • Real drivers: TSS, BOD/COD, FOG, algae, colour/NOM, salinity, temperature • Variability and shock loads If you misclassify the water, you’ll pick the wrong criteria and your sizing will be off. 📌2) Identify what limits the process Most equipment is governed by one (or more) of: • Surface/area limits (clarification, separation, filtration) • Time/volume limits (contact tanks, reactions, biological conversion) • Mass loading limits (solids/organics/nutrients) • Hydraulics/headloss limits (distribution, short-circuiting) 📌3) Use the “workhorse” criteria (what we really size on) A small set of criteria covers most early-stage sizing: 📚Clarifiers / lamella / sedimentation • SOR: Q / A • SLR: (Q × TSS) / A • WOR: Q / Lw • HRT (check): V / Q 📚DAF • Hydraulic + solids loading, plus A/S (air-to-solids) 📚Rapid sand / multimedia filters • Filtration rate: Q / A + headloss and backwash capability 📚GAC adsorption contactors (or GAC filters/contactors) • EBCT: Vbed / Q (empty bed contact time) • Plus practical checks: target run time to breakthrough, headloss, media change-out strategy 📚Membranes (UF/MF/NF/RO) • Sized primarily by flux / specific throughput (think “flow per membrane area”): J = Q / Amembrane • Then confirmed by: feed water quality/fouling risk, recovery, TMP/headloss limits, CIP strategy, redundancy/trains 📌4) Add the practical checks (where projects win or lose) Even if sizing is empirical, the design must be operable: • Headloss / HGL allowance • Backwash capability (filters) • Mixing and chemical conditioning reality (DAF / floc) • Sludge/float removal and maintenance access • Redundancy (duty/standby), isolation, bypass logic 📕Bottom line: Know the water, select the governing criterion, apply the right equation, and validate against proven thresholds. For common equipment, this approach is often sufficient for a defensible concept design and pricing package.

As a formulation scientist, I’m always thinking about balance, how to design a product that delivers the right dose with the right excipient concentration to achieve both efficacy and stability, without compromising safety. Every formulation project teaches the same lesson: it’s not just about making a drug work; it’s about making it work safely and consistently. That’s where concepts like ED₅₀, LD₅₀, MEC, and MSC come into play. ED₅₀ (Effective Dose 50%) → the dose that produces the desired effect in half of the population. LD₅₀ (Lethal Dose 50%) → the dose that causes death in half of the test subjects (used in preclinical toxicity studies). MEC (Minimum Effective Concentration) → the lowest concentration at which the drug starts to show its effect. MSC (Maximum Safe Concentration) → the highest concentration that can be tolerated without toxic effects. The range between MEC and MSC defines the therapeutic window, the safe and effective zone where a drug performs its best. In formulation development, our job is to design within this window, adjusting excipients, release profiles, and dosage strength to keep plasma levels steady between MEC and MSC.

The ICH M13B guideline gives clear scientific criteria and procedures for obtaining biowaivers for additional strengths of orally administered IR solid oral dosage forms, provided that in vivo bioequivalence is established for at least one strength. It emphasizes consistency in formulation, dose proportionality in pharmacokinetics, and robustness of dissolution similarity testing to justify the extrapolation of BE conclusions to other strengths, thereby enabling efficient drug development and regulatory approval worldwide. #Key Points: 👉🏿Applies to orally administered immediate-release solid oral dosage forms designed for systemic delivery. 👉🏿Supports waivers of in vivo BE studies (biowaivers) for one or more additional strengths in drug development or post-approval, reducing the need for redundant clinical studies. Criteria for Biowaiver of Additional Strengths: 👉🏿Pharmacokinetic Dose Proportionality: The drug must exhibit proportional pharmacokinetics across strengths, as per criteria in ICH M13A. 👉🏿Qualitative and Quantitative Formulation Similarity: 1. Additional strengths must have the same qualitative composition as the bioequivalence-tested strength ("biobatch"). 2. Quantitative proportionality in drug substance and excipients is required, though justified deviations may be allowed (see Annex I). 3. Special provisions apply for high-potency drugs where drug substance is ≤5% of product core weight. 4. Manufacturing processes for additional strengths should be consistent with the biobatch strength. 👉🏿Similarity in Dissolution Profiles: 1. In vitro dissolution testing must demonstrate similarity between additional strengths and the biobatch. 2. Testing conditions include paddle (50 rpm) or basket (100 rpm) apparatus, media volume ≤900 mL, temperature 37±1 °C, multiple pH media (1.2, 4.5, 6.8), among others. 3. Dissolution profiles should be characterized with at least three suitable time points, with similarity evaluated via statistical methods including similarity factor (f2) and bootstrapping if needed. >4. Complete dissolution is not always required; allowance is made if differences are due to pH-dependent solubility, supported by appropriate comparisons. 👉🏿Specific Topics: 1. Addresses biowaivers for fixed-dose combination (FDC) products, considering proportionality individually or by layers. 2. Describes use of bracketing approaches if proportionality or dissolution similarity criteria are not met. 3. handling of drug substance instability and exceptions requiring additional justification. 👉🏿Documentation and Reporting: Applications should provide rationale for the biowaiver strategy, composition tables, dissolution protocol and data, and clear conclusions regarding similarity. 👉🏿Benefits: 1. Harmonizes regional approaches to additional strength biowaivers. 2. Reduces the need for repeated in vivo BE studies when justifiable. 3. Supports streamlined global drug development and regulatory submissions.

In mechanical design, especially in domains like BIW, structures, and product engineering, a strong grasp of core formulas is non-negotiable. These equations are not just academic—they directly influence durability, stiffness, weight optimization, and overall performance. 📌 1. Stress (σ = F / A) Stress defines how much internal force a material experiences per unit area. F = Applied force A = Cross-sectional area 👉 Design Insight: Higher stress means higher risk of yielding or failure. Reducing stress can be achieved by increasing area or redistributing load paths—critical in BIW load-bearing members. 📌 2. Strain (ε = ΔL / L₀) Strain measures deformation relative to original length. ΔL = Change in length L₀ = Original length 👉 Design Insight: Strain helps evaluate ductility and deformation limits. In crash scenarios, controlled strain is essential for energy absorption. 📌 3. Hooke’s Law (σ = E × ε) Defines linear elastic behavior of materials. E = Young’s Modulus (material stiffness) 👉 Design Insight: Higher E → stiffer material. This is why AHSS and UHSS steels are preferred in BIW for stiffness-critical zones. 📌 4. Shear Stress (τ = V / Aₛ) Occurs due to transverse forces. V = Shear force Aₛ = Shear area 👉 Design Insight: Important in weld design, joints, and fasteners. Improper shear design leads to joint failures. 📌 5. Torsional Shear Stress (τ = T·r / J) Stress induced due to twisting. T = Torque r = Radius J = Polar moment of inertia 👉 Design Insight: Critical for shafts, cross members, and BIW torsional rigidity. Increasing J (closed sections) significantly improves stiffness. 📌 6. Bending Stress (σ = M·y / I) Stress due to bending loads. M = Bending moment y = Distance from neutral axis I = Moment of inertia 👉 Design Insight: Section geometry plays a huge role. Increasing I (via ribs, embosses, closed sections) is more effective than just increasing thickness. 📌 7. Deflection (δ = FL³ / 3EI) Measures how much a structure deforms under load. 👉 Design Insight: Deflection control is key in NVH and perceived quality. Increase E → better material Increase I → better geometry Reduce L → better support strategy 📌 8. Power Transmission (P = 2πNT) Defines power in rotating systems. N = Rotational speed T = Torque 👉 Design Insight: Used in drivetrain and rotating components. Balancing torque and speed is crucial for efficiency. 🚀 Key Takeaways for Design Engineers ✔ Geometry (I, J) often impacts performance more than thickness ✔ Material selection (E, yield strength) is critical for stiffness vs durability trade-off ✔ Load path understanding is essential for stress reduction ✔ Optimization = Strength + Stiffness + Weight + Cost 💡 In real-world engineering, these formulas are interconnected. The best designs come from balancing them—not maximizing just one. #MechanicalDesign #BIW #EngineeringBasics #DesignEngineering #NVH #Durability #Crashworthiness #AutomotiveEngineering

One of the biggest challenges young engineers face when learning design is this: they jump straight into it. But that’s not how mastery works. Let’s step outside engineering for a moment and think about something familiar—writing. It’s nearly impossible to produce a flawless article on the first or even third draft. Before writing, you need to: 1. Clarify your core message -Identify supporting points, examples, and lessons 2. Understand your audience and how they’ll engage with your content - Do research where necessary 3. Create a logical flow and structure Then, you write the first draft… and revise it. And revise again. The same principle applies to engineering design—except it’s even more involving. You don’t start with software. You start with thinking and planning. Here’s what the typical process would look like: ➡️ Define the problem clearly. -Understand the goal of your design and its intended outcome. ➡️ Reframe when necessary. -Sometimes the real problem isn’t obvious at first glance. Ask deeper questions. Build hypotheses. ➡️ Think in systems. -Consider all affected components—users, environment, cost, safety, timelines, and more. ➡️ Apply scientific principles and standards. -Use first principles and relevant design codes to guide your decisions. ➡️ Draft your design criteria and controls. -These parameters will shape your preliminary design. ➡️ Document everything. -Track your assumptions, iterations, and decisions. This helps you improve and explain your thinking. ➡️ Iterate continuously. -Refine your design through reviews, feedback, and testing. Ask experienced engineers to challenge your ideas. Design is not a one-step act. It’s a layered process of learning, testing, and evolving. Take your time. Think deeply. Iterate intentionally.

Key Design Criteria for Water Treatment Plants – A Practical Perspective Designing a Water Treatment Plant (WTP) is far more than a hydraulic or structural exercise. It requires a balanced approach between technical performance, operability, and lifecycle sustainability. From my experience in large-scale water infrastructure projects, several design criteria must be clearly defined from the outset: 1. Raw Water Quality and Variability – The entire process design depends on seasonal fluctuations in turbidity, organic load, and microbiological content. A single misjudgment here can compromise the plant’s long-term efficiency. 2. Process Selection and Redundancy – The choice of treatment line (coagulation-flocculation, sedimentation, filtration, disinfection) should ensure flexibility. Redundancy in key units – particularly filters and pumping systems – is crucial for continuous supply during maintenance. 3. Hydraulic Balance and Head Losses – Proper alignment between hydraulic profile, pipe diameters, and energy consumption directly affects both OPEX and resilience against operational failures. 4. Automation and Control Philosophy – Modern plants must integrate SCADA systems, smart instrumentation, and predictive maintenance logic. Automation should simplify operations, not complicate them. 5. Chemical Handling and Safety – Chlorine, coagulants, and lime systems require secure storage, metering accuracy, and emergency ventilation measures aligned with international safety standards. 6. Constructability and Local Context – Design must consider available materials, local workforce capacity, and environmental constraints. A technically sound project can still fail if it’s not practical to build or maintain. Ultimately, a WTP’s success lies in integrating process engineering with operational reality. A well-designed plant is one that can be efficiently operated for decades — not just one that meets the initial technical specifications. #WaterTreatment #Infrastructure #ProjectManagement #Engineering #WTPDesign #Sustainability

If formulation desires are not guided by science, formulation surprises are unavoidable. Most times, huge attention is paid to achieve a parameter that is termed “most important” but less attention is paid to other parameters. This is the beginning of formulation struggles. Too much attention on sensory attributes could cost viscosity, too much attention on performance could cost “cost effectiveness”, too much attention on viscosity could cost pH, too much attention on naturality index percentage could cost viscosity. Of course, too much attention on a parameter could cost stability. In many cases, too much attention on one parameter could cost two or more parameters. Focusing energy on just maximizing one parameter creates many formulation challenges encountered in formulations. Just looking at a formula can easily tell the parameter that the designer wanted to maximize and the implications of trying to maximize the parameter on other parameters. The same is applicable to just looking at ingredients list. One time, I picked a popular product, read the ingredients list and started laughing as I saw the performance parameter that the designers maximized and the implication on viscosity parameter. I later came across another product of same format from same company and observed the reverse; the designers removed what maximized the performance of the previous product in order to maximize viscosity of the new product. It is important to state that no parameter balances itself when another parameter is maximized. A cosmetic product is a mixture and not a compound. This automatically makes Le Chatelier's Principle of Equilibrium not applicable - a cosmetic system does not adjust itself for equilibrium. The relationship between two parameters is not always a positive slope of a straight line graph but could also be a curve which has a maximum point. Heisenberg’s Uncertainty Principle is a Physics related principle which I find very helpful in formulation - it is impossible to simultaneously determine the accurate position and momentum of matter. It simply means that as a scientist is trying to achieve a parameter, another parameter is already deviating. Maximal achievement of one parameter leads to maximal deviation of another. This leaves scientist with no other choice than to compromise a parameter in order to maximize another. It is unscientific to expect no deviation of a parameter when another is maximized. Formulation desires should be guided by science which reveals implications before experiments in order to avoid surprises. Formulation surprises due to maximizing a parameter can be addressed by accepting the surprises or deploying science to design a formula that brings an intersecting point or balance point for all the active parameters of a product.

𝐌𝐚𝐬𝐭𝐞𝐫𝐢𝐧𝐠 𝐂𝐫𝐢𝐭𝐢𝐜𝐚𝐥 𝐐𝐮𝐚𝐥𝐢𝐭𝐲 𝐀𝐭𝐭𝐫𝐢𝐛𝐮𝐭𝐞𝐬 (𝐂𝐐𝐀𝐬) 𝐒𝐞𝐫𝐢𝐞𝐬: 𝐓𝐡𝐞 𝐊𝐞𝐲 𝐭𝐨 𝐄𝐱𝐜𝐞𝐩𝐭𝐢𝐨𝐧𝐚𝐥 𝐅𝐨𝐫𝐦𝐮𝐥𝐚𝐭𝐢𝐨𝐧 𝐃𝐞𝐯𝐞𝐥𝐨𝐩𝐦𝐞𝐧𝐭. (𝑷𝒂𝒓𝒕 04) 𝑫𝒐𝒄𝒖𝒎𝒆𝒏𝒕𝒂𝒕𝒊𝒐𝒏 𝒂𝒏𝒅 𝒈𝒖𝒊𝒅𝒆𝒍𝒊𝒏𝒆𝒔 𝒇𝒐𝒓 𝑪𝑸𝑨'𝑺 𝐚) 𝐈𝐂𝐇 𝐆𝐮𝐢𝐝𝐞𝐥𝐢𝐧𝐞𝐬 The International Council for Harmonisation (ICH) provides critical guidelines: 𝐈𝐂𝐇 𝐐8 (𝐑2): 𝐏𝐡𝐚𝐫𝐦𝐚𝐜𝐞𝐮𝐭𝐢𝐜𝐚𝐥 𝐃𝐞𝐯𝐞𝐥𝐨𝐩𝐦𝐞𝐧𝐭 Introduces Quality by Design (QbD) principles, defining CQAs as physical, chemical, biological, or microbiological properties that must be controlled to ensure final product quality. It links CQAs to the Target Product Profile (TPP), formulation strategies, and manufacturing processes, encouraging use of Design of Experiments (DOE) and risk assessments ▫️ Reference: ICH Q8(R2) 𝐈𝐂𝐇 𝐐9: 𝐐𝐮𝐚𝐥𝐢𝐭𝐲 𝐑𝐢𝐬𝐤 𝐌𝐚𝐧𝐚𝐠𝐞𝐦𝐞𝐧𝐭 Provides a structured approach for identifying, analyzing, controlling, and reviewing risks related to product quality. Tools like FMEA, fault tree analysis, and hazard analysis help prioritize CQAs based on criticality. ▫️ Reference: ICH Q9 𝐈𝐂𝐇 𝐐10: 𝐏𝐡𝐚𝐫𝐦𝐚𝐜𝐞𝐮𝐭𝐢𝐜𝐚𝐥 𝐐𝐮𝐚𝐥𝐢𝐭𝐲 𝐒𝐲𝐬𝐭𝐞𝐦 Introduces a lifecycle quality system integrating pharmaceutical development (Q8) and risk management (Q9). It emphasizes management responsibility, continuous improvement, and lifecycle monitoring of CQAs. ▫️ Reference: ICH Q10 𝐛) 𝐅𝐃𝐀 𝐆𝐮𝐢𝐝𝐚𝐧𝐜𝐞 The U.S. FDA provides specific guidance on managing CQAs, especially for generics: 𝐐𝐛𝐃 𝐟𝐨𝐫 𝐀𝐍𝐃𝐀𝐬 (𝐀𝐛𝐛𝐫𝐞𝐯𝐢𝐚𝐭𝐞𝐝 𝐍𝐞𝐰 𝐃𝐫𝐮𝐠 𝐀𝐩𝐩𝐥𝐢𝐜𝐚𝐭𝐢𝐨𝐧𝐬) FDA encourages applying QbD principles in ANDA submissions. Sponsors must identify CQAs, link them to process understanding, and show that formulation and process development consistently meet specifications. Key Document: "Quality Considerations for ANDAs: An Example for Immediate-Release Dosage Forms" ▫️ Reference: FDA Guidance 𝐅𝐃𝐀 𝐐𝐛𝐃 𝐏𝐢𝐥𝐨𝐭 𝐏𝐫𝐨𝐠𝐫𝐚𝐦 𝐑𝐞𝐩𝐨𝐫𝐭𝐬 Provide practical examples showing how companies identified and controlled CQAs under QbD frameworks, emphasizing scientific rationales and risk-based justifications for control strategies. 𝐜) 𝐔𝐒𝐏 𝐌𝐨𝐧𝐨𝐠𝐫𝐚𝐩𝐡𝐬 The United States Pharmacopeia (USP) establishes official public standards for pharmaceutical ingredients and products: 𝐒𝐩𝐞𝐜𝐢𝐟𝐢𝐜𝐚𝐭𝐢𝐨𝐧𝐬 𝐟𝐨𝐫 𝐂𝐐𝐀𝐬: ▪️ Assay: Defines potency and limits (e.g., USP <541>). ▪️ Dissolution: Methods and criteria for drug release (USP <711>). ▪️ Impurity Limits: Thresholds for degradation products. ▪️ Content Uniformity: Dosage consistency (USP <905>). ▪️ Microbial Limits: Microbiological testing (USP <61>, <62>). 𝐑𝐨𝐥𝐞 𝐢𝐧 𝐏𝐫𝐨𝐝𝐮𝐜𝐭 𝐃𝐞𝐯𝐞𝐥𝐨𝐩𝐦𝐞𝐧𝐭: Companies must align internal CQA specifications with USP standards unless scientifically justified otherwise, ensuring global harmonization. Reference: USP Official Compendia

🚀 Mastering Design Criteria for Chemical Process Engineering 🚀 Designing a chemical process plant is no small feat. It requires a deep understanding of design criteria to ensure safety, efficiency, and cost-effectiveness. Whether you're working on a Conceptual Design,Feasibility Study, getting the design criteria right is crucial for the success of your project. Here are some key insights from the Design Criteria for Chemical Process Engineering that every engineer should know: 1. Risk Management: - Risk = Probability x Impact Understanding risks is at the core of any design. From process safety to environmental protection,risk management ensures that your plant operates safely and efficiently. -Critical Services & Items: Identify operations and equipment that are vital to the process. 2. Operating Life & Time - Operating Life: Most process plants are designed to operate for 20 to 40 years. However, some plants, may have a shorter life. -Operating Time: Understanding the operating time helps in selecting the right equipment and designing for reliability. 3. Design Conditions: -Design Pressure & Temperature: These are critical for ensuring that equipment can withstand normal and abnormal operating conditions. -Pressure-Temperature Ratings: Pipe flanges and fittings have specific pressure-temperature ratings based on materials and applications. 4. Capacity & Quantity: - Capacity: Equipment is typically designed to handle 100% capacity, but sometimes partial capacity is sufficient. - Quantity: The number of equipment units depends on the capacity and operational needs. 5. Materials of Construction: Durability and Cost - Material Selection: The choice of materials depends on factors like corrosion resistance, temperature, and pressure. -Cost Considerations: Materials like titanium or Hastelloy are expensive but necessary for extreme conditions. 6. Utilities & Treatment Media: -Utilities: These include air, water, steam, and power, which are essential for the process. -Treatment Media: Materials like catalysts or absorbents are used to remove undesired components or speed up reactions. 7. Cost Estimation: -Economic Objectives: Every project is an investment. The design must balance cost-effectiveness with performance, and regulatory compliance. -Cost Estimation Models: Use models like the Rule of Six-Tenths or Cost Indices to estimate equipment costs. 📌Key Takeaway:  Design criteria are the backbone of any chemical process engineering project.Understanding these criteria is essential for delivering a successful project. 🔗 Download the full guide to dive deeper into the design criteria for chemical process engineering. 📢 Call to Action:  If you’ve worked on chemical process design, what’s the most challenging aspect of defining design criteria? Share your experiences in the comments below! Let’s learn from each other and grow as professionals. 💪 #ChemicalEngineering #ProcessDesign #DesignCriteria #EngineeringDesign #LinkedInCommunity

#process_design_basis #essential_data   Dear Chemical Engineer’s, For any project a process design basis document is the preliminary document that needs to be prepared, reviewed & approved before further engineering to generate a Basic Engineering Package or FEED package. What are the essential data that needs to be provided in this document 1. Line Sizing a. Max. allowable pipe velocities for a given process, utilities, m/s b. Criteria for Pressure drop ΔP/unit length (bar/m) in pipes which could include i) pump suction lines for sub-cooled liquids ii) pump suction lines for saturated liquids iii) pump discharge lines iv) Utility Lines c. Pipe Roughness Values, for pr. drop calculations, for example, for new CS pipe a roughness value of 0.046 mm is used. 2. Flow Rate a. Margin on flow rates for process & utility systems. For example, the sizing of lines may be done with a 10% margin on the flow rates arrived from material balance calcs. 3. Design Pressure/Vacuum a. Based on margin on max. operating pressure, for example, 120% on max. operating pr.. The max. operating pr. could also be estimated based on abnormal operating conditions which could be routinely encountered during plant operations. b. For piping the design pressure could be considered as pump shut-off pressure for pumped lines or it could be based on the pipe pound rating (for example #150/#300) corresponding to a design temp. as provided in the Temp.-Pressure Tables in ASME B16.5. c. Vacuum encountered during normal operations should be addressed by providing vacuum values either for normal operations or for conditions such as steam out. Since it's difficult to estimate the exact values of vacuum encountered, a frequent method is to specify “Full Vacuum” (FV) for the equipment. 4. Design Temperature/MDMT a. Based on margin on max. operating temp., for example, 25⁰C on max. operating temp.. The max. operating temp. could also be estimated based on abnormal operating conditions which could be routinely encountered during plant operations. b. Consideration for min. design metal temp. (MDMT) for either normal operations or for conditions such as equipment blowdown.  5. Pumps a. NPSHa guidelines, specifically for centrifugal pumps, for example mentioning NPSHa should be at least be 1m more than NPSHr.  6. Compressors a. Max. allowable pressure ratio/stage b. Max. allowable temp. rise/ stage c. Capacity control, for example, variable speed, inlet vanes, unloaders etc. 7. Heat Exchangers a. Provide fouling factors to be used. b. Provide margin on calculated surface area, for example 10%. This is the most recognized way instead of providing margin on heat duty. c. Max. allowable pressure drops for shell & tube side 8. Storage Tanks a. L/D ratios b. Freeboard 9. Relief Devices & Flare Systems Max. allowable backpressure There could be many more based on specific project requirement & engineers to consider them. Please feel free to share your views & comments. Regards, Ankur