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Pharmaceutical Manufacturing and Packing Sourcer

Fired Up

The UK Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) and the Explosive Atmosphere Directive (ATEX 137) set the minimum requirements for protection against risks from fire, explosions and similar events arising from dangerous substances used or present in the workplace. Introduced in 2002, the DSEAR legislation ensures more rigorous testing for operators, including regular and representative analysis of thermal fluids used in heat transfer systems.

Meeting DSEAR guidelines helps companies to identify early warnings relating to process problems, maintain a safe and efficient working environment, and save costs. Preventative maintenance and frequent testing can also help extend the life of thermal fluid. More importantly, a timely reaction to early warnings can help avoid the need to replace costly equipment and even save lives, should the worst-case scenario arise.

In high-risk environments such as those found in pharma manufacturing, no expense should be spared to ensure legislation is complied with and effective steps are taken to keep employees and premises safe.

Thermal Cracking

The dangers caused by the lack of preventative maintenance are rooted in the degradation of thermal fluid. Over time, heat transfer fluid breaks down through a process called 'thermal cracking'. The fluid’s molecules are broken down into smaller particles, and several types of fractions are released from this chemical reaction.

When thermal cracking occurs, the first side-products are light ends that have a low boiling point and are very volatile. The second are heavy ends, which recombine to form heavy polyaromatic molecules that usually cause fouling of the heat transfer system. Carbon molecules will stick to the system internals and reduce process efficiency, unless cleaned and flushed in time.

Degradation Curve

It is important to note that thermal fluid does not go from being fit for use to needing replacement overnight. There is a grey area where fluids can be managed against what specialists call 'the degradation curve'. Degradation is steady if a system is operated properly. It is only as the fluid approaches the end of its practical working life that there is a gradual curve, which eventually drops off very sharply. This sudden change in the quality of thermal fluids is one of the reasons why regular and preventative maintenance is so vital.

Diluting the thermal fluid by topping up is a cost-effective and durable option, but only while the fluid is in the early part of the degradation curve. After the condition of the fluid has significantly deteriorated, dilution is no longer a viable alternative. It would have the same effect as putting a new battery into a two-battery torch, alongside a battery that has already been used for some time – it would not be a long-term solution and would result in the system not operating at optimum capacity.

The best thing to do when thermal fluid reaches the end of its lifespan is to flush and clean the system, prior to refilling it with a fresh charge of heat transfer fluid.

Correct Sampling

Despite the clarity of existing legislation and the dangers of neglecting thermal fluid analysis, companies often fail to perform the sampling required by DSEAR. In addition, some companies carry out irrelevant tests, including lube oil tests, which are sometimes non-applicable and do not always provide the necessary information.

Sample methodology is crucial – incorrect sampling gives inaccurate flash point results, which can have very dangerous consequences. Unless the fluid samples are collected when the oil is hot and circulating, they will reveal artificially high flash point values. This incorrect sampling will lead to the conclusion that the system is safe, when in reality it might not be. Inaccurate samples can have negative consequences, including decreased energy efficiency, unmanageable flash points, and a dangerous working environment with risks of explosions.

Furthermore, the sample needs to be 'closed' so that no potential atmospheric particles can contaminate it or distort the results, which might happen if it was 'open'. An open sample would also allow light ends to flash off to the atmosphere, instead of remaining in the sample – producing unreliable readings.

Frequent sampling is vital too. DSEAR requires manufacturers to show they are taking appropriate measures to mitigate health and safety. In our view, an 11-point test should be performed at least twice a year, every three months ideally, and even more frequently in some applications.

Finally, testing in an accredited laboratory in the correct conditions is key to getting accurate results. As with general maintenance, identifying a problem early helps avoid complications without excessive cost or efforts.

Best Practice Testing

After the samples have been taken correctly, the interpretation of data is essential – and this is where the 11-point test helps ensure best practice. This looks in detail at key data to ensure the results completely reflect reality.

The 11-point test includes three specific tests focusing on: carbon level and the amount of insoluble particles; closed flash point; and the acidity level.

Carbon Residue
The Ramsbottom carbon residue test is a method of calculating the carbon residue in a fluid. If the carbon level (heavy ends) is too high, build-ups can occur which will reduce the efficiency of the system, make pumps work harder, and result in higher running costs for the company.

Flash Point Measurement
Both types of flash point measurement are taken, for open and closed cups. The Pensky-Martens closed flash test involves the heating of test specimens within a covered brass cup at regular intervals until a flash point that spreads throughout the inside of the cup is identified. The temperature at which this spread takes place is the sample’s flash point. Because closed cup tests give lower flash point values (between 5°C and 10°C difference), they are a better approximation to the temperature at which the vapour pressure reaches the lower flammable limit. To ensure final result accuracy, a Seta open cup flash test is also performed on the fluid sample.

Acidity Level
An acidity level test identifies the amount of additive depletion, oxidation or acidic contamination in a thermal fluid sample. The acid number is determined by the amount of potassium hydroxide base required to neutralise the acid in 1g of an oil sample.

These three main areas of testing are complemented by additional checks, including appearance, viscosity, water and ferrous content, particulate quantities and fire point testing. The data from the entire 11-point test forms the basis of a holistic analysis based on trend data, to provide an accurate thermal fluid evaluation. Parameters for action, caution and satisfactory levels are the key factors when conducting the result analysis.

The complexity of thermal fluid testing might seem intimidating, but the importance of the process cannot be stressed enough.

Complying with regulations, performing preventative maintenance and frequent testing are the best ways to ensure your company is not taking any unnecessary risks.

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About the author

Andy Burns is Technical Business Manager at thermal fluid specialist, Global Heat Transfer. He has worked in the heat transfer and thermal fluid industry for over 18 years, contributing to the success of several of the UK’s largest manufacturing companies. Andy is a central part of Global Heat Transfer’s specialist support team, which deals with thermal fluid management and proactive maintenance to ensure employers comply with health and safety regulations.
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