INTRODUCTION TO PART - II OF ROTOCONE VACUUM DRYER/ ROTARY CONE VACUUM DRYER/ DOUBLE CONE VACUUM DRYER (RCVD/ RVD/ DVD)
In Part -I, we discussed about RCVD and its components in details. In this post i.e. Part - II, we will discuss about the need based considerations while designing and planning an RCVD.
(Pic Ref: www dot promasengineers dot com)
THE FACTORT THAT MAKES RCVD or RCVD or DVD SO POPULAR AND A PREFFERED CHOICE ARE AS UNDER:
1. Vacuum Drying under Moderate or Low Temperature:
RCVD bowl is provided with a metal jacket (usually SS304 grade in Pharma API) which allows the Hot Water or Low Pressure Steam (at usually 3 to 3.5 bar, Non IBR) to heat the surface and inturn heat the mass to be dried by conduction and convection. Because of the application of the vacuum inside the closed bowl, the vapor pressure inside the bowl drops and hence the boiling point of the liquid to be evaporated (viz. Water or Solvent) too drops and hence boiling takes place at lower temperature and vapor generation (and subsequently extraction of vapors) happens faster as compared to any other traditional drying method.
2. Material Shuffling for achieving Uniform Heat Transfer:
RCVD is provided with a rotary mechanism, wherein, the bowl rotates along a horizontal axis (it is supported over A or C shaped strong metal structures with bearings) at a low rpm (rotations per minute). Here the layer by layer shuffling of the mass inside the RCVD bowl takes place, resulting into uniform heat transfer amongst the wet powder particles. Most importantly, the powder mass shuffling takes place with minimum contact with any mechanical moving parts inside the RCVD bowl. All other vacuumized dryers works on either a complete static bed Or wet powder being shuffled by some mechanical agitator type structure. However, such structures needs to be cleaned thoroughly as per pharmaceutical standards and hence RCVD is preferred over other vacuumized dryers.
3. Vacuum Application, Inert Gas Purging and Temperature sensing through a smallest possible protrusion:
RCVD has a unique design in which a horizontal hollow pipe (which acts as a vacuum Or suction pipe) protrudes inside the RCVD bowl through a central smallest possible opening. The same pipe acts as a inert gas (usually nitrogen) purging nozzle (used to push the vapors). Further, a temperature sensing element is passed through this horizontal pipe, which, further tries to sense the temperature of the inside mass And/ Or vapors. In any other type of a vacuum dryer, managing all these things is too difficult as there is a risk of vacuum leakage.
4. Possibility of fully automatic loading and unloading of the mass:
It is one of the biggest concern of the Pharma, as well as, other industries today, to handle hazardous and polluting drugs Or chemicals, while ensuring Or following the safety standards. RCVD comes with a charging manhole, discharge butterfly valve and optional sampling valve, as well as, spray ball for cleaning in place (CIP/ WIP). The Charging and Discharging operation can be made completely automated.
CARE TO BE TAKEN WHILE DESIGNING AN RCVD:
1. Material of Construction: As mentioned above, the right MOC will decide the adherence to the quality and process parameters, as well as, longevity of the RCVD.
2. Level of Automation: Depending on the needs of the Production Department, as well as, budget allocation, the level of automation can be decided. Example, if product charging Or discharging is the prime need, the external Powder Transfer System can be integrated along with the RCVD and the bottom discharge valve can be pneumatically actuated.
3. Statutory and Safety compliance: Sometimes, due to company policy and FDA mandate, special features are incorporated such as Touch Screen HMI (Human Machine Interface) with PLC (Programmable Logic Control). In some cases, there can be further sophistication by adopting special Data Security measures such as 21 CFR Chapter 11 compliance, which allows password protected individualistic logins and maintains record of each activity by each user. Overall, Safety, GMP guidelines along with respective FDA mandates has to be followed while designing an RCVD.
4. Batch Size Calculations: A basic Process Calculations must be done followed by Thermodynamics Or Heat Load calculations. This helps in deciding the optimum batch size, as well as, the time cycle, hence monthly Or timely production throughput.
5. Available Floor Space, Availability of the Utilities and Floor Layout/ Elevation: Many a times, project team overlooks the area and space available and later have to regret the decision as RCVD doesn't fit in that size. Similarly, the utility equipments such as Hot Water Tank, Vacuum Pump, Chilled Or Cooling Water, Steam, Nitrogen and Electrical Panel etc if not planned favorably can cause a lot of trouble such as financial loss due to structural rearrangement work, major construction work and sometimes production time loss too. As a usual practice all these things are planned simultaneously and in sync with each other. Also, RCVD GAD (General Arrangement Drawing) is superimposed on Autocad Layout Drawing to see the feasibility of installation during design stage.
6. Thorough attention to the minute design aspects: Designing aspects such as Positioning of the Mechanical Seal, Spur-Pinion Geared Drive versus Direct Gearbox Drive system, Usual Vacuum Bulb with PP cloth bag versus Sintered Mesh Filterbag, CIP system (cleaning in place) by Spray Ball, In-Process Sampling, Nitrogen Purging, External Choppers/ Lump Breakers, Cantilevers Shaft versus Both side Supported Structure etc has to be given extremely detailed attention.
7. Product Specific Operational Challenges (based on the previous experience Or Studies): Since it is a capital purchase, the careful attention must be given to the specific needs of the Production Team, concerns and apprehensions of the Engineering and Maintenance, as well as, the Safety and Statutory department, which helps ensure the production goes smooth.
8. Mechanical and Process Design, as well as, Sizing of the Equipments: Stress analysis/ calculations must be done under varying parameters such as temperature, vacuum and pressure. Similarly, the thickness calculations must be done keeping in mind the static and dynamic loads. The important bought out items such as Motor, Gearbox, Seal, Valves etc should be designed as per the Industry Standards.
CASES OF RCVD FAILURE WITH ILLUSTRATIONS:
This topic is really vast and hence I will cover it through a separate blog.
Please do visit Part - I of the same post for understanding RCVD details.
Please feel free to contact me regarding any questions, queries Or additional assistance needed on Design, Sales, Qualification or other aspects at shg.techo@gmail.com
Post a Comment