A batch reactor is widely used in the chemical and process industry to perform several operations such as providing an environment of chemical reactions, crystallization, product mixing, dissolution of solids, polymerization, liquid to liquid extraction as well as batch distillation. The equipment comprises of tank that has an integrated heating and cooling system as well as an agitator. The main advantages of using a batch unit is it ability to perform various function without the need to change or break containment. Toxic and highly potent compounds can be processed in the batch unit.
Part one
Question 1
a) Explain why you would regard this batch chemical reactor as a plant unit.
According to the definition of a chemical plant, a plant is comprised of several units that are interconnected by piping. Materials move in and out of these units. These materials or raw materials are converted into different products. In this example, the batch reactor is a separate unit of the plant which processes the raw materials introduced before feeding them to the centrifuge system. This batch reactor is also the principle chemical converter in this plant.
b) Explain your reasons for concluding that this unit is critical for production
This unit is critical for the production in this process because
- It prepares and processes the raw materials by heating them to the prescribed temperature and also providing the required pressure for the process.
- It ensures full utilization of the centrifuge unit; this is because it produces more than the centrifuge can process. the batch unit produces 18 (te) of product
- The batch unit is the principle raw material processor in this process, it receives raw materials, process them to complete products, thereafter, these materials are sorted out by the centrifuge. There is no other unit for processing materials in this plant unit.
- The batch unit temporary stores the materials before they are feed to the centrifuge system.
b) Extract any user requirements for this designated unit from the plant description. Are there any production ‘windows’?
The main user information is;
- The vessel consist of a jacketed agitated glass lined vessel, heated to a certain temperature and pressure and consist of a thermocouple, a temperature alarm and has a safety relief valve
- The equipment list is also provided to the plant engineer with information about the different components installed on the plant.
- The drawing of the batch unit also shows the plant engineer the layout of the different components in the reactor. Jacket safety valve, temperature pocket, temperature controller, steam trap, agitator and the pipe work.
- The batch reactor process is also described so that the user or the operator can clearly understand how the processes are carried out, for example “the batch unit starts when 18 (te) of raw materials are introduced to the reactor”, the content are heated through to a preset temperature/ time profile that takes 10 hours” the products are then feed to the centrifuge system. This explanation helps the user or the plant operator understand its operation.
d) Extract any corporate requirements for this unit from the plant description
Some of the corporate requirements for this unit obtained from the text are:
- The equipment is shutdown for 16 hours during the 40th week of each year.
- The production of the batch reactor is also indicated, that is “the manufacturing unit makes 13,000 te of bulk pharmaceutical product within a given year”
- The information provided for the batch reactor jacket is also vital to the corporate use. This information is “the jacket is a registered steam receiver and also has a safety relief valve”
- The company guidelines state that reactors should be maintained to archive 25 years and gear boxes should be maintained to give 15 years life.
e) Extract any legislative requirements for this unit from the plant description.
The legal requirements include;
- The procedure for controlling maintenance activities must conform to the environment standard ISO14000.
- The manufacturing process must be licensed by FDA and the British pharmaceutical product.
- The manufacturing activities must comply with GMP (good manufacturing practice) and the process must be to the quality standard ISO 9002.
f) Table 1 shows the existing life plan for this unit. Comment on whether you think that some of the tasks designated for the scheduled shutdown could be completed during production windows or when the plant is on-line. Could any of the tasks designated for completion during production windows be completed on-line?
From the company maintenance guidelines, it can be seen that the company stipulates a 16 hour shutdown for the batch reactor during it 40th week of operation each year. Various test and maintenance activities are carried out to ensure that the batch reactor archives 25 years life and the gear boxes give a 15 year working life. In addition to the maintenance activities, the industry should be kept clean and painted to ensure that it passes the pharmaceutical inspectors test and prevent unnecessary shutdown.
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The maintenance activities should however be scheduled in such a manner that they don’t interfere or affect the operation of the plant thereby maximizing the profits obtained from the production line. This calls for the scheduling of light maintenance operation to be done when the plant is still operating. Based on this classification, three maintenance operation are carried out for this batch reactor these are
On line:
these are maintenance activities that run concurrent with the production line. The maintenance activities are performed when the machine is still in use. Proper scheduling must be done to ensure that these activities are well planned for. The online and offline maintenance windows should also not coincide.
Offline maintenance:
These are maintenance activities that are performed when batch reactor is switched off or some interruption has to occur the machine is shut off and a part in the system is removed or repaired. Back up systems are used.
Maintenance window:
this is a user defined period of time in which automatic maintenance activities are carried out. During the maintenance window, the need for maintenance activity is first evaluated, and if the system does not meet the required parameters a maintenance activity is carried out. If the required conditions are met the maintenance activity is not carried out (IBM, 2009).
The activity for this batch reactor can be scheduled as follows
Activity |
Comments |
|
CV1, replacing trim |
Currently the machine is shutdown before this maintenance activity is performed, based on the time taken to perform this activity and the frequency, it is best that it is done during the production window. |
|
|
|
Agitator coupling |
Can be done when the production is progressing (online) as the process takes a short time and is performed often. |
|
SV1, pressure test and inspection |
This is a rigorous activity and can only be performed when the reactor is shutoff. |
|
Agitator visual check |
Does not require to be performed during shut off, it can be done as the machine operates (online) and can also be scheduled during the production window. It can also be performed when the agitator coupling is being checked |
|
Internal inspection Pressure test |
Should be done when the equipment is shutoff as it is a rigorous activity and takes a long time |
|
Pressure test and inspection |
It can be done during the production window. |
|
Visual checks for leaks Leak test Vibration monitoring of the motor and pump bearing |
Should be done on daily basis. The pump motor should also be checked as the leak tests are done. This will help monitor the pump. The checks are done by the plant operator. |
g) Analyze the recorded jobs from the computer maintenance management system
(CMMS) for this unit. (These jobs are shown in a Microsoft Excel spreadsheet called Worklist.xls.) Is there any evidence which confirms that the life plan is being carried out? Is there any evidence to say if the life plan is effective or not?
To check and analyze the data recorded on the computer maintenance management systems for this unit. The different maintenance activity was evaluated and the frequency of these activities, as well as the time taken to complete this activity was evaluated. The excel data was first sorted into the various groups of maintenance activities. The obtained data was as follows
For the agitator coupling the Visual check – annual ticket for weekly task were as follows
|
8/8/1996 |
4.33 |
5.2 |
Planned |
|
8/8/1997 |
4.33 |
5.2 |
Planned |
|
8/8/1998 |
4.33 |
5.2 |
Planned |
|
8/8/1999 |
4.33 |
5.2 |
Planned |
|
8/8/2000 |
4.33 |
5.2 |
Planned |
|
8/8/2001 |
4.33 |
5.2 |
Planned |
|
8/8/2002 |
4.33 |
5.2 |
Planned |
|
8/8/2003 |
4.33 |
5.2 |
Planned |
From the table the maintenance activities were carried out as per the schedule and the activities took a longer time than was actually planned for. were as planned for.
For the agitator visual check, the table is as shown in the figure below
|
3/3/1996 |
2 |
4 |
Planned |
|
3/4/2002 |
2 |
4 |
Planned |
The activity interval time was 6 years between subsequent maintenance activities and this was carried out as per the life plan specifications. They however took more time than was specified.
For the oil seals, the maintenance information was as shown in the table below;
|
Check oil seals and for leaks – annual ticket for weekly task |
7/7/1996 |
8.67 |
10.4 |
Planned |
|
Check oil seals and for leaks – annual ticket for weekly task |
7/7/1997 |
8.67 |
10.4 |
Planned |
|
Check oil seals and for leaks – annual ticket for weekly task |
7/7/1998 |
8.67 |
10.4 |
Planned |
|
Check oil seals and for leaks – annual ticket for weekly task |
7/7/1999 |
8.67 |
10.4 |
Planned |
|
Check oil seals and for leaks – annual ticket for weekly task |
7/7/2000 |
8.67 |
10.4 |
Planned |
|
Check oil seals and for leaks – annual ticket for weekly task |
7/7/2001 |
8.67 |
10.4 |
Planned |
|
Check oil seals and for leaks – annual ticket for weekly task |
7/7/2002 |
8.67 |
10.4 |
Planned |
Again the time taken was longer, however the maintenance was according to the life plan.
For the vibration monitor gearbox and checking of the motor bearing, the data for year 1996 and 2002 is as shown in the table below;
|
Vibration monitor gearbox & motor bearings |
2/10/1996 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
3/10/1996 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
4/10/1996 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
5/10/1996 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
6/10/1996 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
7/10/1996 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
8/10/1996 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
9/10/1996 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
10/10/1996 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
11/10/1996 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
12/10/1996 |
1 |
2 |
Planned |
For the 2002 data
|
Vibration monitor gearbox & motor bearings |
1/10/2002 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
2/10/2002 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
3/10/2002 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
4/10/2002 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
5/10/2002 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
6/10/2002 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
7/10/2002 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
8/10/2002 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
9/10/2002 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
10/10/2002 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
11/10/2002 |
1 |
2 |
Planned |
|
Vibration monitor gearbox & motor bearings |
12/10/2002 |
1 |
2 |
Planned |
Again the life plan was strictly followed and all maintenance activities planned were carried out every month.
For the pressure test (SV2), again the maintenance activities followed the life plan
|
Pressure test and inspect |
9/6/1996 |
2 |
3 |
Planned |
|
Pressure test and inspect |
9/6/1997 |
2 |
3 |
Planned |
|
Pressure test and inspect |
9/6/1998 |
2 |
3 |
Planned |
|
Pressure test and inspect |
9/6/1999 |
2 |
3 |
Planned |
|
Pressure test and inspect |
9/6/2000 |
2 |
3 |
Planned |
|
Pressure test and inspect |
9/6/2001 |
2 |
3 |
Planned |
|
Pressure test and inspect |
9/6/2002 |
2 |
3 |
Planned |
For the pressure test and inspection to determine if reconditioning was required, the maintenance was as scheduled and took place after 6 years as shown in the table below; however the time for the activity was longer than it was expected.
|
Pressure test and inspect |
3/3/1996 |
2 |
3 |
Planned |
|
Pressure test and inspect |
3/4/2002 |
2 |
3 |
Planned |
For the steam jacket, the life plan was followed but again the allocated time was short.
Despite the carefully planned maintenance activities, there were some reactive maintenance activities these resulted from detection of anomalies in the system. Some of these activities are shown in the table below.
Component |
Item |
Activity |
Date |
Standard time |
Actual time |
Type of job |
|
Reactor |
P1 |
Replace leaking mechanical seal |
7/2/1996 |
4 |
4 |
Reactive |
|
Centrifuge |
P2 |
Replace mechanical seal |
1/18/1997 |
2 |
3 |
Reactive |
|
Reactor |
T1 |
Re-calibrate temperature sensor |
9/1/1998 |
2 |
3 |
Reactive |
|
Raw Material Storage |
P3 |
Replace seal |
11/16/1998 |
5 |
5 |
Reactive |
|
Centrifuge |
P2 |
Replace mechanical seal |
3/29/1999 |
2 |
4 |
Reactive |
|
Centrifuge |
P2 |
Replace mechanical seal |
5/18/1999 |
2 |
2 |
Reactive |
|
Raw Material Storage |
P3 |
Repair plinth – impact damage |
10/1/1999 |
4 |
4 |
Reactive |
|
Raw Material Storage |
P3 |
Repair seized pump |
10/3/2000 |
12 |
12 |
Reactive |
|
Reactor |
T1 |
Re-calibrate temperature sensor |
4/17/2001 |
2 |
2 |
Reactive |
|
Centrifuge |
T3 |
Replace temperature sensor |
6/25/2002 |
2 |
2 |
Reactive |
From this analysis it can be seen that maintenance operations were done as scheduled and planned. However, most of the activities took a longer time than was scheduled. The planned maintenance operations were not wholly effective as reactive maintenance operation were performed.
h) Use your experience in conjunction with Figures 1 & 2, the plant description and the data from the CMMS to analyze the unit into its maintenance causing items
From the diagrams 1 and 2, the main areas that are likely to fail include
The major maintenance causing units are;
(i)The steam unit
The unit comprises of the safety valves, the steam jacket, the steam jacket safety valve, the
Globe control valve etc. these units are bound to fail and cause critical damage to the equipment as well as the manpower manning the plant. Their maintenance is critical.
(ii)The agitator unit:
Comprises of the agitator, the agitator motor, the motor gearbox and coupling. The gearbox and the drive mechanism are bound to fail due continuous use as well as the forces acting on the agitator. Bearing wear are also likely to cause vibration on the shaft.
(iii)The reactor unit
The reactor unit, the reactor safety valve SV2, the safety valve discharge pipe work is also likely to cause plant failure and should be checked regularly.
(iv)The centrifuge
The centrifuge system is also critical in the operation of this plant and is likely to cause major maintenance problems. Some of the maintenance checks include; testing the motor bearing, checking the vibration on the machine, checking the wear on the seals of the centrifuge, physical check of the centrifuge as well as checking its drive motor and the valves leading to the pump and out of the pump.
The minor units likely to cause maintenance problems are:
(v)Temperature sensor calibration
The failure of the temperature alarm to detect increase in temperature beyond 125 degrees. This is due to a faulty temperature sensor. This calls for regular temperature sensor control, calibration and testing if the system works according to the set parameters.
(vi)Checking the pipes
Checking of the pipe work for any leakage should also be done. Checks should be done regularly.
(vii)Checking the pump for proper workability
Pump delivering materials to the centrifugal unit should be checked. Some checks include the driving motor vibration tests, the motor starter tests as well as the functioning of the motor tests. Tests should be performed every month through physical checking of the motor. The agitator motor should also be checked to determine if it’s working at its rated torque and speed.
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(viii)Checking the steam trap
The steam trap and the heat exchanger should also be regularly checked, this is because it cools the steam efficiently. The condenser should be checked for any leakages, blockages, wear, temperature and heat dissipation as well as its performance and efficiency. Tests involve both the physical checks as well as specialized tests using thermometers and thermocouple sensors to detect if the heat loss in the steam trap is sufficient enough.
Checking the raw materials storage
The warehouse used to store the raw materials should be regularly inspected to ensure that the materials are not contaminated. Presence of excess water, humidity, temperature and pests may damage the raw materials resulting to inferior products.
Checking the raw materials feed mechanism
The raw material feed mechanism should be checked to ensure delivery of materials to the batch reactor with ease. The motor used to run the feedstock should be checked, the physical leakages should also be checked and other component of the feed mechanism. The test should be done every month.
Checking the paint coating
Involves the Physical inspection of the plant to ensure that all the parts are not rusted or the paint has not been scourged. These tests are obligatory to ensure conformity with the pharmaceutical inspector’s rules and regulation. The inspection can be done every year.
i) Develop your own life plan for these maintenance causing items using the task selection logic for Reliability Centered Maintenance
For the implementation of RCM the following main tasks are carried out;
- Selection of the equipment to perform analysis
- Identification of potential failures
- Identification and evaluation of the effects of the started failures
- Identification of the causes of failure
- Selecting the maintenance tasks
- Maintenance packaging
1) Selection of equipment to perform analysis on;
The main equipments to perform analysis on are;
· The batch reactor
· The centrifuge
· The steam jacket
· The centrifuge motor
· The raw materials handling equipment
The identification of potential failures and the causes of failure
The potential problems that are likely to occur are
BATCH REACTOR
The agitator
· The agitator motor failure
· The agitator gearbox failure
· The agitator coupling failure
The centrifuge
· Centrifuge discharge pipe failure
· The centrifuge pump may fail
· The pump motor failure
· The piping system may fail
The steam jacket
· Failure of the reactor safety valve
· Failure of the safety valve
· The temperature alarm system failure
· The failure of the pressurized steam pipe network.
Sensors and alarms
· Failure of the temperature controller
· The globe control valve failure
· The steam trap
Raw materials feed system
· Failure of the inlet pipe work
· Failure of the motors conveying the raw materials
The table below shows the maintenance strategy developed after conducting a RCM analysis.
Table 1: RCM analysis
|
Item |
Causes of failure |
Maintenance activity |
Frequency of maintenance |
Time for maintenance |
|
|
The agitator |
The motor |
(1)Brush wear (2)Winding may overheat (3)The motor starters may fail |
Checking the motor |
3 months |
2 hours |
|
The gearbox (oil gearbox ) |
(1)The viscosity of oil may reduce lubricity |
Testing the oil viscosity |
3 months
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