### Recent Question/Assignment

Department of
Engineering and
Mathematics Assignment
Specification 27/09/21
Session: 2021-22
Module: 55-701475 Equipment Engineering and Design
Maximum word count : 2500 Words Maximum equally split between problems A and B.
Percentage contribution to overall module mark: 50%
Method and Location for Submission: Blackboard Submission
Deadline for return of feedback: 02/12/2020
Module learning outcomes to be assessed:

• Analyse the performance and reliability of machines.
• Design systems for maintenance, reliability and good performance.
• Propose and justify measurement and monitoring systems for plant.
• Predict the behaviour of mechanical engineering systems.
• Criticise the design and implementation of machine systems from cost and efficiency standpoints.
See Blackboard site - Support Resources for information and Reading Lists
Please ensure that all sources of information used are referenced. For guidance see http://libguides.shu.ac.uk/referencing
All assessments are subject to SHU's collusion and plaigiarism regulations. Please refer to:
https://students.shu.ac.uk/shuspacecontent/assessment/plagiarism
Task 1 - (A) Factory Maintenance Problem (D. Tipper)
Problem background
Part of a factory that manufactures extruded building products is shown in Fig. 2. 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 loads dust onto a collection conveyor and then onto the machine feed conveyor.
The machine hopper acts as a surge hopper, allowing an even and controllable feed of dust to be added to the mixer of the main extrusion machine.
Much ancillary equipment has been excluded for clarity.

Fig. 1
The large making machine (Fig. 1) 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 that 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.

Fig. 2

Plant name Description Function Complexity Maintenance difficulty
Incline conveyor. Belt conveyor with troughing idlers. Driven by shaft mounted gearbox. Raises dust from below ground to hopper. Low Very easy
Bucket elevator. Rotating belt with pressed steel buckets. Driven by shaft mounted gearbox. 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 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 (100t in each). Only requires cleaning internally. Very low N/A
Extract conveyor. Belt conveyor with troughing idlers. Driven by shaft mounted gearbox. Removes dust from hopper. Low Easy
Collection conveyor and machine feed conveyor. Belt conveyor with troughing idlers. Driven by shaft mounted gearbox. Low Easy
Machine feed hopper and conveyor. Hopper. Reduces surges giving feed to the machine (1t capacity) Has simple extract conveyor to feed mixer. Low Very easy
Making machine mixer. Single shaft mixer with high chrome steel blades. Mixes dust, water and lime. Very high Very difficult
Making machine extruder. High chrome steel worms and liners. Extrudes product. Very high Extremely difficult
Table 1: Illustration of likely reliability and accessibility Check List
• 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 the 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 as 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 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.
Background (Refer to figure 3)
You are the factory engineer working in a highly automated modern earthmoving equipment factory that has been in operation for some years. You are in charge of the equipment described below. The circuit shows a hydraulic system. The hydraulic cylinder (item 2) is one of several fully automatic clamping stations that hold large pieces of steel together while they are welded together.
The cylinder operates and holds a nominal pressure of 175 bar for approximately 15 minutes, then is off for approximately 2 minutes while the welded component is removed and recharged with unwelded components. The relief valve (item 7) is set to 200 bar. Materials for the production process are rigorously checked and are very consistent.
When pressure is required for the welding process, the Programmable Logic controller (PLC) energises the 2 position, 2 port spring return solenoid valve (item 6).
When the correct clamping pressure has been achieved, the pressure switch detects system pressure as being correct and the resulting signal is used by the PLC to signal valve 6 via its solenoid to unload the pump. An accumulator is fitted to accommodate any equipment internal leakage.
During the welding process; if the pressure switch (item 1) sees a drop in pressure below the pressure switch differential setting; valve 6 is re–energised, until correct clamping pressure is regained.
The machine is capable of operating continuously as production requirements demand. The Hydraulic power-pack is outside the main machine guard and can be adjusted and visually inspected safely while the machine operates (and is away from the welding process). In general the plant is so well automated, personnel may manage a number of different machines at any time.
BS 2917-1:1993 ISO 1219-1 should prove useful.
Remember circuits are always drawn in an 'at rest position'.

Figure 3
A fixed speed AC motor is used to power the system.
Item Description
11 Strainer (In tank Suction)
10 Fixed displacement gear pump approx. 5 l/ min capable of achieving 210 bar
9 Fixed speed Motor (AC)
8 Pressure filter with bypass (opens at 2bar)
7 2 stage Pressure Relief Valve cracks at 200 bar
6 2 Position Directional Control valve
5 Non Return Valve
4 Accumulator: Nitrogen filled bag type
3 3 Position Directional Control Valve
2 Hydraulic Cylinder
1 Pressure switch activated 175 bar, differential 5 bar
Figure 3. Legend
The problem
When you arrive in the morning the oil reservoir is so hot you cannot hold your hand on it. This is not the normal state; the tank is usually at ambient temperature.
The oil level is correct and the regular oil sample checks show there to be no issue with contamination.
The system seems to be losing its capability to operate correctly.
What are the possible causes of the problem? These must be precisely defined.
Suggest any improvements to the circuit that might protect against this occurrence in the future. You are not expected to suggest major hydraulic changes as the circuit is a standard unloading circuit that works well and has worked well for many years.
Full explanations are required as to how you arrive at your conclusion, with any theory being applied to the problem at hand. You must tell me how the issues/faults you identify have resulted in the symptoms being experienced.
Please be brief, succinct and to the point. I see this as a technical report. Use your experiences gained from the seminars as well as reading on the subject to inform your answer.
All theory and discussions must be directed and related to this problem. Lists of general/generic ideas, issues, theories etc. are not acceptable and will lose marks; all discussions must be related to the problem at hand.
You must use the correct terminology, such as relieving, unloading etc. and when referring to equipment in the case study, ensure the correct names and identification numbers are always used.
I think this hydraulic section of the case study can easily be completed in approximately 1000 words – there is a maximum word count of 1200 words. There is no minimum word count, nut you will be heavily penalised if you do not convey the information required to answer the problem.
Report requirements
Reports must be handed as electronic versions on Blackboard. Any work in excess of word count will not be marked.
Please check your work; unintelligible grammar and English will will be heavily penalised.