Timed Preventative Maintenance (TPM) in Parts Cleaning

Considerations when investigating what parts cleaning method to use for your components.

With twenty years of parts cleaning, in machine sales, service and sub-contract cleaning, I have noticed a common oversight by potential purchasers. In both cases mentioned below, the user is experienced with cleaning but is unaware of the TPM differences between solvent and aqueous parts cleaning. The typical scenarios I’ve experienced and provided consultancy for are: –

  • They have used aqueous systems for years and shy away from solvents
  • They are moving away from solvent degreasing for perceived eco-reasons.

The critical point is that every application has its ideal cleaning method and media, Ultimately, the bottom line is what manufacturing is about, and customers should be aware of potential financial and time constraints when selecting a cleaning process.

OestConsider an example application where a customer processes five hundred brass components an hour. Geometry is simple, yet, the parts remain covered in a thin film of neat cutting oil, and the swarf is minimal.

Typical oil content is 1ml per part, and the customer wants components to come out cleaned and dry.

Because the solvent degreaser can process eight baskets/hr, we need at least 63 parts per load. Whereas, with its longer washing and drying cycle, our aqueous unit requires a basket that handles 125 components per load, processing four loads/hr.

In both cases, oil removal is approx.. 500ml/hr

Since the components are susceptible to damage, we use the TechRack system from FRIES to maintain zero metal to metal contact. In both cases, this system also improves cleaning and drainage.

Our machines run on a single eight-hour shift for five days a week and forty-eight weeks per year.

So it’s Day One – we have two cleaning processes, both working fine and delivering perfectly clean and dry components. From this day on, TPM maintenance occurs, and for this example, we will use the recommendation from Safechem to exchange the solvent after two years. I have used this as the measured TPM period.

The calculations are as follows: – Hours required every two years = task duration x frequency x 2 years.

Typical TPM for a SOLVENT system over two years

TPM Function Time (Hr) Action required, Frequency ad Time taken for each task
Test media for stability. 24 Carry out solvent stability tests once per week.  Each test takes 15mins
Add stabiliser 2 Once every 6-8 weeks, add the stabiliser. 10 mins per top-up.
Bath exchange 6 Replace solvent after two years*
Distillation 0 An automated process removes the waste and transfers it to a waste container, such as a Safechem system. Distil at the end of the previous shift, so the vapour generator cools and is empty for cleaning out first thing in the morning.
Clean vapour generator 12 The vapour generator is opened and cleaned every six months to maintain heating efficiency. 3 hours/ TPM.
Solvent top-up 2 **Replace solvent lost through distillation. 30mins/top-up twice per year.
Vacuum pump service 1.5 Replace oil and oil filter after 1000 hours (45 mins each)
Seals 1.5 Check and replace filter housing and door seals once a year. (45 mins each).
Machine lubrication system 12 Following the manufacturer’s recommendations, service vapour generator, process chamber, tanks 1 and 2 (if fitted) water separation and vacuum pumps. Check for leaks and electrical loads. 6hr/ea.
Annual Service 1.5 Rotation unit – Replace the grease cartridge or refill the reservoir quarterly. (11 mins each).
TOTAL 62.5 hours Total TPM functions over two years, Or 31.25hr/yr

 

Two years of TPM equates to 2.6hr/mth or 1.6% of the working month.

*Bath exchange recommendations versus reality – Cleaning media that remain stable and do not show an increasing demand for stabilisers can stay in use for considerably longer than two years. An annual analysis by the solvent manufacturer will confirm that no co-boilers are present and that the solvent meets accepted norms for the application. Again, these results will demonstrate the need to replace the solvent or continue with the existing fill.

**Solvent systems will lose some solvent through the distillation process, and this loss ranges between 1-15% depending on the application and contamination. Because we are using a single neat cutting oil contaminant which typically has excellent distillation properties, we can use 3% for this example. Therefore: –  500ml/hr @ 8/hr = 4litres/day with 3% 120ml of solvent lost per day in the waste.  One year or one hundred twenty working days equals 14.4 litres/year. In a machine containing 400 litres of solvent, this amounts to 3.6%/yr. Therefore, topping up once every six months with 6-8 litres of solvent will suffice.

Typical TPM – AQUEOUS AND DETERGENT-BASED cleaning system over two years

TPM Function Time (hr) Action required, Frequency and Time taken for each task
Test media concentration. 48 ♦Use Titration to establish detergent concentration test twice per week. (15 mins each test).
Add Detergent 32 ♦♦Add detergent twice per week to maintain 4-5% concentration—10 mins per top-up.
Bath exchange 96 ♦♦♦Bath exchange and tank clean once per month at 4hrs per exchange.
Oil Removal 40 ♦♦♦♦An oil skimmer removes the waste oil and detergent into a 20l container. Emptying the container – 10mins every other day.
Drying System 1.5 Hot air blower – check filter if fitted, check the electrical load on heating elements and fan—20 mins 6 monthly.
Machine lubrication 1.5 Rotation unit – Replace the grease cartridge or refill the reservoir quarterly. (11 mins each).
Annual Service 12 Following the manufacturer’s recommendations, thoroughly clean tanks and pipework and check and clean spray nozzles. Check all level sensors for contamination and function. Check for leaks and electrical loads. Annually 6hrs.
TOTAL 231 hours Total TPM functions over two years  Or 115.5hr/yr

 

Two years TPM equates to 9.6hr/mth or 6% of the working month.

♦Titration is a slow and subjective testing process. Customers have replaced Titration with a mobile Teqwave-T unit from Endress & Hauser, which reduces testing time from 15mins down to 2-3 minutes. The results are precise, and the data gets logged for future reference. This single step removes 10% of the annual TPM load.

♦♦Assuming our wash tank is 750 litres running a 5% detergent concentration, 37.5 litres of detergent are required. With 500ml detergent losses/hr, 8 litres of detergent get removed every two days. After two days, the concentration level is 3.8%

Further reductions in TPM loading are possible by installing the Teqwave-I static unit. This variant enables the continuous monitoring of detergent levels and, when connected to a dosing system, automatically maintains detergent levels without human intervention. The outcome of this investment is to remove 40hr/yr or 35% of the TPM loading.

♦♦♦♦500l of oil entering the cleaning system will be taken up by the detergent and skimmed off into the 20l container. As a typical rule, 1 litre of oil requires 1 litre of detergent. Therefore 1 litre/hour enters the waste container leading to its emptying every other day. The addition of a pump, timer and level sensor would enable almost maintenance-free management of the waste into an IBC or 205l drum, reducing TPM load by 20hr per annum or 2%.

Summary

Aqueous systems generally have a significantly lower CAPEX when compared to solvent systems, but this doesn’t always make them the lower-cost option in the long-term when we consider: –

  • If we assume the overhead for a maintenance engineer is £35/hr, solvent TPM equates to about £1,100/yr. In contrast, the aqueous system equates to £4,000/yr.
  • Many factories have multiple aqueous cleaning systems, and TPM combined with cleaning issues and breakdowns can quickly leave a valuable maintenance engineer dedicated to the cleaning systems.
  • Factor in the energy load needed for an aqueous system, and the total system life costs (CAPEX, TPM, Media and Energy) can switch to favouring a solvent machine in less than three years.

The first impression is that solvent systems require far less TPM work when compared to aqueous systems. The many conversations I’ve had with maintenance staff support these observations.     ♦♦♦ However, customers who have a clear picture of an aqueous machine’s TPM hours also consider using automated systems like Teqwave to monitor and control concentration levels and automatic waste transfer to reduce the overall TPM hours.

Deploying such strategies can remove 60hrs/yr or more than 50% from the TPM workload. In addition, the increased control can extend the bath life. For example, consider the monthly bath exchange becoming every six weeks instead of monthly. The annual TPM hours reduce from 48hr to 32hr/annum offering the user a further 14% reduction in TPM hours.

Fully optimised, an aqueous system processing these components can have TPM hours of 46 hr/yr or 3.8hr/mth, reducing potential maintenance hours for this machine from £4,000/yr down to £1,610.00/yr, a saving of £2400/yr, which would more than cover the cost of optimisation over five years.

Of course, it’s still 46% more TPM than a solvent system, but optimisation has vastly improved the maintenance load for the engineer and costs for the business.

For those looking to use solvent degreasing, one of the most critical steps a company can take is the OCT analysis (Oil Compatibility Test). A test ideally carried out before receiving proposals can provide valuable information to the end-user and supplier by: –

  • Knowing which is the best solvent chemically for the task
  • How well the oils distil, and an understanding of potential solvent residues left in the waste
  • A sense of potential by-products produced during distillation
  • Being aware of potential co-distillation issues
  • Offering a potential understanding of the stabilisation requirements
  • OCT also confirms if potential corrosion problems lay ahead for components and machines.

In terms of TPM, understanding the OCT results will potentially reduce: –

  • the solvent top-up because there is the opportunity to optimise the distillation to leave less than 3% solvent in the waste.
  • Stabilisation
  • Bath exchanges can safely get pushed out from two years to four or even six years without detriment.

Other considerations – solvent systems have very few variables compared to an aqueous cleaning system, and as such further optimisation results in relatively small TPM gains. However, optimising a standard aqueous degreasing system to include valuable automation can reduce TPM hours by more than half, significantly contributing to the business or piece price of work passing through the system.

Final Observation,

I know I’m only discussing one aspect of manufacturing, and in the big scheme, these points may not make a huge difference. However, optimising all systems can make the difference between profit and loss in any business, smooth running or fraught, and a happy or stressed company. Optimising systems to ensure minimal TPM requirements can have surprising outcomes: –

  • Maintenance Engineers will be thankful for the automation of the mundane, time-consuming tasks, and the resulting reduction in TPM hours
  • Inspection and Quality control will appreciate the more consistent results
  • Management will be relieved “that degreasing plant” is no longer on the weekly production meeting agenda.
  • Financial Department will see an improved bottom line.
  • Salespeople will have that bit more scope for negotiation
  • Production Managers/Directors will reduce the need for oversight and potential overwhelm.
  • Apprentices will experience a monitor and control atmosphere rather than mend and make do culture.

Contact Kumi Solutions for unbiased advice from a production engineer via our website contact us page