55 - 7947 Equipment Engineering and Design
Factory Maintenance problem (7947 PBL)
Part of a factory that manufactures extruded building products is shown bellow.
Dust that is processed in another factory is loaded by a wheeled shovel into a hopper and is raised via an inclined conveyor and bucket elevator to the top of the system. The dust is then distributed to storage hoppers by a large scraper chain conveyor.
Each hopper is equipped with an extract conveyor which load dust onto a
collection conveyor & then onto the machine feed conveyor.
The machine hopper acts as a surge hopper, allowing an even controllable feed of dust to be added to the mixer of the main extrusion machine. Much ancillary equipment has been excluded for clarity.
The large making machine consists of a single shaft mixer where water and dust are combined and then fed through a de-airing chamber into the extruder. None of the forming or handling equipment is shown.
Product from the extrusion machine is loaded onto refractory lined bogies and processed through a dryer and kiln, which is a continuous process. If the firing process is slowed or stopped, large scrap rates and a kiln fall could follow.
The main extrusion process has to run 16 hours per day but this can fluctuate with demand. Because this is only part of a larger factory, if staff are not working on this system, they are employed elsewhere.
Two fitters and an electrician are always on duty within the factory as a whole.
The immediate task is to suggest a maintenance strategy for the equipment. The strategy should contribute to a factory wide Reliability Centred Maintenance strategy. This includes mobile and electrical equipment. Full explanations must be given and related to this equipment.
Please note any suitable condition monitoring techniques that may be appropriate, which pieces of equipment they relate to and why.
FMEA would not be appropriate as it is not expected students have a full understanding of the equipment. Suggest and justify any modifications which would increase reliability of the plant. This may include changes to layout or maintenance policies.
It is essential that any answers are very specific to this problem. Descriptions of general / generic design issues, management techniques etc. are not acceptable and will lose marks; all discussions must be related to the problem and describe how the proposed changes would improve the current solution.
Plant Name Description Function Complexity Maintenance
Large wheeled loading shovel Bucket loader Loads processed dust into the system High V Easy..
Incline conveyor Belt conveyor with toughing idlers. Driven by shaft mounted gear box Raises dust from below ground hopper Low V Easy..
Bucket elevator Rotating belt with pressed steel buckets. Driven by shaft mounted gear box Raises dust to top of hoppers Low Reasonable..
Scraper chain conveyor 300mm centre roller chain conveyor with scrapers attached to chain by K brackets. Driven by a large worm and wheel gearbox, direct coupled Drags dust to each hopper. Gate valves can isolate hopper from scraper chain. Low to Medium Difficult, on top of hoppers. Poor
accessibility to large drive
Dust hoppers Hopper Stores dust
(100 T in each) Only ever requires cleaning internally V Low N/A..
Extract conveyor Belt conveyor with toughing idlers. Driven by shaft mounted gear box Removes dust from hopper Low Easy..
Collection conveyor & Machine feed conveyor Belt conveyor with toughing idlers driven by shaft mounted gearbox Low Easy..
Machine feed hopper & conveyor Hopper, reduces surges,
giving even feed to the machine
(1 tonne capacity) Has simple extract conveyor to feed mixer Low V Easy..
Making machine mixer Single shaft mixer with high chrome steel blades Mix dust water and lime V High V Difficult..
Making machine extruder High chrome worms and
liners Extrude product. V High VV Difficult..
This is a report, so only a short introduction is required Do not restate the problem. Do not pad your report out with words that do not answer the specific requirements of the case study.
Word count must be shown on cover sheet and is absolute
Do not explain what PM, CBM and breakdown maintenance is. It will be assumed that they are terms known to all readers of the report.
Do not describe specific maintenance tasks, although appropriate CM tasks would be appropriate. Remember this is about strategy
Do not attempt to do a Failure mode analysis; you do not have sufficient information. Do not try to add costs and hourly rates; you do not have sufficient information.
The term management, in this context relates to RMC. (Process management, spares inventory, information, some redesign at a system level etc.)
Please use maintenance books, not web or book sources on conveyor maintenance. This is about maintenance strategy, the mix of different maintenance types and the justification.
Work without discussion/justification is not acceptable
Please check your work, unintelligible grammar and English will not be accepted. Occasional typos and small errors are not a problem.
Assessment criteria –PBL reports, module 7947 equipment engineering & design
See Marking Criteria sheet on Black Board.