What is Process Flow Diagram?

A Process Flow Diagram (PFD) demonstrates the relations between significant segments in a framework. PFD likewise arrange process configuration esteems for parts in various working modes, commonplace least, ordinary and greatest. A PFD does not demonstrate minor segments, funneling frameworks, channeling appraisals and assignments. They use a series of symbols and notations to depict a process. The symbols vary in different places, and the diagrams may range from simple, hand-drawn scrawls or sticky notes to professional-looking diagrams with expandable detail, produced with software.

A Process Flow Diagram has multiple purposes:

  • To document a process for better understanding, quality control and training of employees.
  • To standardize a process for optimal efficiency and repeatability.
  • To study a process for efficiency and improvement. It helps to show unnecessary steps, bottlenecks and other inefficiencies.
  • To model a better process or create a brand-new process.
  • To communicate and collaborate with diagrams that speak to various roles in the organization or outside of it.

A typical PFD for a single unit process will include these elements:

  • Major equipment: Including names and ID numbers. Examples include compressors, mixers, vessels, pumps, boilers and coolers.
  • Process piping: Moves the product, usually fluids, between equipment pieces.
  • Process flow direction
  • Control valves and process-critical valves
  • Major bypass and recirculation systems
  • Operational data: Such as pressure, temperature, density, mass flow rate and mass-energy balance. Values often will include minimum, normal and maximum.
  • Composition of fluids
  • Process stream names
  • Connections with other systems

What to exclude in a PFD:

  • Pipe classes and pipe line numbers
  • Process control instruments
  • Minor bypass values
  • Isolation and shutoff valves
  • Maintenance vents and drains
  • Relief valves and safety valves
  • Code class information

The process flow diagram is an essential part of chemical engineering. It conveys a process and the path of its individual components – therefore, it is essential to learn how to read and create one.

The information that a process flow diagram conveys can be categorized into one of the following three groups. The more detailed these three sections are, the easier it is for a user of the process flow diagram to follow along and understand.

  • Process Topology
  • Stream Information
  • Equipment Information

Process topology is characterized as the collaborations and areas of the distinctive hardware and streams. It incorporates the greater part of the associations between the hardware and how one stream is changed to another after it moves through a bit of gear.

Streams should be labeled so that they follow consecutively from left to right of the layout so that it is easier to follow along and locate numbers when you are trying to locate streams listed on the tables.

Notwithstanding the stream data, there ought to likewise be a table specifying gear data. This table can be useful for the practical investigation of the plant since it ought to give the data important to assess the cost of the gear. The gear data table ought to incorporate a rundown of the greater part of the hardware that is utilized as a part of that specific stream graph alongside a depiction of size, stature, number of plate, weight, temperature, materials of development, warm obligation, region and other basic data.

CIP System and Its Operations

The operation of the CIP system requires the control of several conditions, i.e., the fluid flow rates and velocities, temperatures, cleaning times and the concentrations of the cleaning chemicals (detergents, caustic soda). Systems in the pharmaceutical and bio-pharmaceutical industries use higher velocities for process piping. In the case of tanks, the rates of flow of either water or cleaning solution are largely determined by the size of the tank, as well as the number and the properties of the spray devices.

These gadgets arrive in an assortment of plans. The customary spray ball is generally used and gives directional streams of water or cleaning arrangement from little, static spouts. Rotational gadgets give round shower designs and direct impingement spray devices present high-weight streams at low streams, turning through 360˚ The impingement spray gadgets speak to a contrasting option to the expulsion of soils or stores by falling water or cleaning arrangement that course dmown the sidewalls of the tanks or vessels. The temperature of the CIP procedure may fluctuate from 135 to 175˚F and control is normally critical. The essential heat transfer requests are met either by joining heat exchangers into the CIP framework, or by direct infusion of steam. Chemicals might be added using peristaltic, pneumatic stomach and additionally more exact metering pumps. Groupings of the cleaning solutions are observed and controlled by the estimation of the pH or electrical conductivity of the solution.

The CIP procedure includes an arrangement of cycles that incorporates an underlying and last deplete step, a pre-flush, wash and post-flush. The span of the flush and wash cycles fluctuate from 5 minutes to 60 minutes. In the pharmaceutical, bio-pharmaceutical, dairy and food industries, the CIP procedure may incorporate a purify cycle to lessen the levels of bacterial contamination. This cycle essentially utilizes watery arrangements of solid oxidants, for example, hydrogen peroxide, ozone, chlorine dioxide and other chlorine-containing compounds.

At the point when a sanitize cycle is incorporated, thorough last flush cycles are required to maintain a strategic distance from erosion of the stainless steel tanks, vessels and process funneling, because of the nearness of hints of the solid oxidant, especially the chlorine containing mixes or chloride ions.
To efficiently drain process equipment and process piping, the system design must allow the fluids to flow out. Avoid sections of the piping and equipment in which fluid flow is restricted. Split flow designs also adversely affect the flow of solution through a piping system. Any problem areas should be identified and the piping modified or an appropriate cleaning method developed. The pre-rinse uses recycled water to flush out loosely adhering particulates and soil. This water is often flows directly to the drains as it leaves the CIP system. Depending on the nature of fouling and deposits, the number of chemicals for the wash cycle is used. The post-rinse cycle provides the final flush for the system. The effluent from this cycle is then discharged to the drains and directed to a tank. The effluent may flow to the drain or recovery points under gravity, but some CIP systems include return pumps or eductor devices.

Clean in Place Systems

To improve product quality in manufacturing systems, Clean-in-place (CIP) technology offers significant advantages. Right from efficient and reliable cleaning of process equipment and piping to lower costs, they have much to offer. The controls provide variety of cycle times, temperatures, composition and concentration of cleaning solutions.  In order to reduce costs and control waste disposal these systems include current recycling and regeneration technologies.

The automatic, reproducible and reliable delivery of cleaning solutions improves both product quality and plant hygiene. The ability to clean a processing system, incorporating tanks, pumps, valves, filters, heat exchange units and process piping, significantly reduces cleaning costs. It also helps minimize the handling of chemicals to provide a safer environment for plant personnel. CIP systems must be included in the design of any new process system.

CIP systems have several designs. The “single-pass” and the “recirculating” configurations are often utilized in the processing industries, since both require minimal capital investment. They usually have a small footprint and are flexible, in that the unit can readily adjust to a range of cleaning protocols. However, the cost for the chemicals, water and steam and for disposal of the wastewater are higher than for other designs.

The food industry usually favors a ‘re-use design’ that provides recycling of the water and regeneration of the cleaning chemicals. These systems have a larger footprint and are at greater risk of cross-contamination.  It also lacks flexibility i.e. a single temperature and single concentration of cleaning solution is used for the whole process system.

The pharmaceutical and bio-pharmaceutical industries prefer to use a multi-tank configuration. They have independent, stainless steel tanks that hold water of different quality, e.g., deionized water (DI), hot or cold water for injection (WFI) and water from reverse osmosis units (RO). These multi-tank systems are operated as if they were single-use systems, the tanks being drained between subsequent programs to minimize cross-contamination. This system is capable of circulating small volumes of water at relatively high rates.

A single use unit developed for the use in dairy and food processing industries has recently found application in selected pharmaceutical industries. These systems reduce the consumption of water and chemicals.