Filtration

Many companies, including those in the food and beverage, pharmaceutical, cosmetics, manufacturing and electronics industries, recognize the negative effects on quality created by oil contact with their product during production. Product rejections and consumer safety concerns associated with oil contamination can have broad negative financial and commercial impacts on a company. However, an often overlooked source of oil in compressed air — ambient air — is frequently misunderstood, underestimated or ignored.

In this blog, we’ll examine the effect that ambient oil vapour levels can have on downstream compressed air quality and what to consider when looking for technically oil-free compressed air to ISO8573-1 Class 0 or Class 1 for total oil.

For details on oil vapour testing levels in ambient air, test methods, compliance and other gaseous contaminants of concern, download the full white paper “Oil Vapour in Ambient Air”.

Ambient air is the air we breathe and it’s all around us. It’s also the air that is drawn in by air compressors. Ambient air is made up of approximately 78% nitrogen and 21% oxygen. The remaining 1% contains a mix of argon, carbon, helium and hydrogen as well as a variety of contaminants — oil vapour being one of them. Ambient air is an often overlooked source of contamination that can have a big impact on a compressed air system.

Ambient air quality is directly impacted by air pollution caused by industrial processes such as burning fossil fuels and emissions from vehicle exhaust, oil and gas fields, paints, and solvents.

Oil vapour in ambient air is made up of a combination of hydrocarbons and volatile organic compounds (VOC). Ambient air typically contains between 0.05mg/m3 and 0.5mg/m3 of oil vapor, however, levels can be higher in dense, urban or industrial environments or next to car parks and busy roadways.

These levels may seem negligible, but when it comes to compressed air contamination, we must consider the effect that compressing the air has on the ambient contamination, the amount flowing into the compressed air system, and the time the compressor is operating.

The process of compression, as well as flow rate and time, build the level of oil in the compressed air that travels through a production system — air that eventually finds its way to production equipment, instrumentation, products and packaging materials.

Compression, or pressurizing the compressed air, can significantly increase the volume of oil. The greater the operating pressure, the higher the potential level of oil in the compressed air. This is compounded by the flow rate and time of operation. Compressors are often designed to operate continuously. This means that the concentration of oil continues to multiply in the confined space of the compressed air system. In turn, it will only exit the system at points where the air is released. These exit points are often in areas where the contaminated air comes in contact with product, production equipment or instrumentation. So, what may seem like negligible levels of hydrocarbons and VOC in ambient air, can become a great concern when the same is drawn in and compressed for use in manufacturing.

Once inside the compressed air system, oil vapour will cool and condense, mixing with water in the air. This contamination causes numerous problems to the compressed air storage and distribution system, production equipment and final product leading to:

• Inefficient production processes.
• Spoiled, damaged or reworked products.
• Reduced production efficiency. 
• Increased manufacturing costs.

Due to the financial and commercial impact of contaminated product, many companies specify the use of an oil-free compressor, in the mistaken belief that this will deliver oil-free compressed air to critical applications. 

Oil-free compressed air systems are typically installed without downstream purification equipment intended to remove oil, as they are deemed unnecessary accompaniments. While it is true that oil-free compressed air systems will not contribute contamination in the manner that oil lubricated systems will, oil vapour from ambient air remains untreated.  

Technically oil-free air, in accordance with ISO8573-1 (international standard for compressed air purity) Class 0 or Class 1 for Total Oil, can only be guaranteed through the proper application of downstream purification equipment. This equipment may include water separators and coalescing filters to remove liquid water and oil, aerosols of water and oil, and solid particulate as well as adsorption filters to treat oil vapour. Compressed air users seeking an oil-free source of air would be wise to consider these precautionary purification steps, whether they are used with oil-lubricated or oil-free compressed air systems. 

In order to establish compliance with ISO8573-1 Class 0 or Class 1, the international standards categorizing oil level in compressed air, users must perform tests to assess both oil aerosol and oil vapor presence in their systems. The levels of each phase will combine to establish total oil in the compressed air system. 

To conduct the tests, samples of each phase must be drawn through a solvent extraction process and analyzed using gas chromatography (GC) or Fourier transform infrared (FT-IR) technology. The combination of the two methods will provide an accurate reading down to 0.003mg/m3. 

While there are other methods for testing oil levels, like Photo Ionisation Detector (PID), these will leave certain compounds undetected. To this end, they should be used for estimation purposes only. GC and FT-IR will provide results that can be related to ISO standards with reliable and complete accuracy.  

Parker has recently introduced a new compressed air purification system. The OFAS Oil Free Air System is a fully integrated heatless compressed air dryer and filtration package suitable for use with any compressor type and can be installed in the compressor room or at the point of use. Fitted with a third adsorbent column for oil vapour removal, the OFAS has been third-party validated by Lloyds register to provide ISO 8573-1 Class 0, with respect to total oil from both oil-lubricated and oil free compressors, ensuring the highest quality air at the point of use for critical applications.

Compressed air is vital to any production process. Whether it comes into direct contact with the product or is used to automate a process, a clean, dry reliable compressed air supply is essential. If the compressed air contains oil, the consequences can be high both financially and in terms of brand damage. 

For details on oil vapour testing levels in ambient air, test methods, compliance and other gaseous contaminants of concern, download the full white paper "Oil Vapour in Ambient Air". 

This blog was contributed by Mark White, compressed air treatment applications manager, Parker Gas Separation and Filtration Division, EMEA.

10 Contaminants Affecting Your Compressed Air System - Part One

10 Contaminants Affecting Your Compressed Air System – Part Two

Seven Myths About Oil-Free Compressors

Why Are Coalescing Filters Installed in Pairs?

One of the challenges faced in any biopharmaceutical process is bioburden control and containment — or how do you keep what is out, "out" and what is in, ‘"n".

For a stainless steel-based manufacturing system, the process is well understood. The lines are set up, the CIP and SIP cycles are run, the appropriate valves are closed and the system is pressurized and then left for a period of time, perhaps overnight, while it is monitored for pressure decay. If the pressure decay is minimal, you have an integral system.  

If you tried this method with a single-use system, assuming the bag could take the pressure, at a minimum you would see losses from the tubing as it is a porous material which has a diffusion rate. Identifying a fail in a single-use system based on pressure decay, therefore, becomes difficult. The question is, is the decay due to a leak and therefore a faulty assembly or is it diffusion across the tubing material on an assembly that is intact and fit for use? Commercially available systems are now available which will provide the answers.

A key point for discussion is: should the biopharma industry be talking about integrity testers or should we be talking about leak detection systems? This is an important difference due to the weight this industry places on the word integrity, especially if we talk about integrity tests.

If we use the language of integrity testing, it implies a level of security backed up by validation and a clear binary result. The meaning in this context is well defined and if a system fails an integrity test, a batch ultimately could be rejected, pending any rework or investigation.

At the post integrity testing stage, you can report that a sterilizing grade filter is integral or is not by using recognized and validated methods. However, it may be more difficult to make the same statement for a single-use assembly.

As an industry, we should be sure what integrity means in this context and how it should be described.

Leak detection on a system requires and allows for the interpretation of the results. Of course, if the interpretation is backed up by the manufacturer’s validation package then so much the better. The questions that are open are:

• What size of leak/hole in the system, can be detected and is there a critical limit?
• Can a collection of small holes be equal to one large hole, possibly giving a false negative?
• What is the impact of tubing on the result?
   

There is no need, however, to revert to stainless steel in bioprocessing operations. Stainless steel is not without its own challenges and potential points of weakness. The connections on a system, many of which are not used in a process — for example blanking ports on a vessel — all need to be assembled and tested. The stresses and strains, when going from ambient temperature to 121oC and back again, which are put on stainless steel systems, are avoided in single-use.

But we should be very clear about what we are testing and what those test results mean, so as not to create a false sense of security. The impact of simply assuming a single-use assembly is integral when there is no knowledge of how testing has been carried out can have serious consequences for a biopharmaceutical manufacturer.

We should also be challenging the vendors of single-use systems to ensure that the facilities and processes used to build and ship assemblies minimize any risk and that those processes are validated.

The old adage "you cannot test in quality, you must build it in", certainly rings true in this case.

Find out about Parker's SciLog SELECT GO single-use assemblies

Modified atmosphere packaging is now a prerequisite for many food products, extending shelf life, appearance and taste by preventing or retarding spoilage mechanisms. Quite simply, modified atmosphere packaging uses the main constituent gases that make up the Earth’s atmosphere – nitrogen, oxygen and carbon dioxide then alters the mix and or ratios to obtain beneficial qualities enabling extended food preservation.

Food grade nitrogen within Europe is given an additive number, E941, as it is classed as a food additive when used for modified atmosphere packaging applications. Many other legislative authorities globally also adopt the European standard or have a very similar specification.

• Nitrogen* ≥ 99% v
• Oxygen ≤ 1% v
• Water ≤ 0.05% v (500ppmV)

*99% including other inert gases such as noble gases (mainly argon)

• Carbon monoxide ≤10 ppmV
• Methane and other hydrocarbons (as methane) ≤100 ppmV
• Nitrogen monoxide and nitrogen dioxide ≤ 10 ppmV
   

The main contaminant to consider within the specification is oxygen @ ≤1%, however, this is for the nitrogen gas itself whether produced from on-site generation or supplied via traditional methods such as high-pressure cylinders or bulk liquid. One important factor for gas generation is that the higher the acceptable level of maximum remaining oxygen content, (MROC), in the output N2 stream, the less compressed air is required to produce the gas and hence the lower the overall unit gas cost. Typically, to produce nitrogen from a gas generator at 10 ppm MROC is 3 times higher cost than at 0.5%.

Often the oxygen content within the finished gas flushed food pack is higher than 1% and the actual acceptable level is specified based on the type of food, designated shelf life, storage conditions and possible spoilage mechanisms.

Many food producers employ the services of expert independent food research establishments such as Campden BRI based in the UK for example. In these facilities, packing and storage conditions along with microbial assessment can be evaluated pertaining to the specific food product to establish the optimum modified atmosphere specification — including maximum remaining oxygen content within the finished pack.

A specific range of foods that have a long history of benefiting from modified atmosphere packaging are dried, powdered products such as coffee, infant formula and spices. These are routinely packaged using Vertical Form Fill and Seal, (VFFS), machinery, fitted with a dedicated nitrogen gas flushing system.

Parker has many nitrogen gas generators operating globally, employed for modified atmosphere packaging of dried powdered foods with VFFS machines. Establishing initial suitability can often be challenging if simple logic is not taken into consideration.

Food producers that use MAP are rapidly realising the benefits of on-site generation as a safe, convenient, sustainable and low-cost alternative to traditional methods of supply. The change from purchased gas to self-produced might seem a little daunting to some and there is often insistence that the new generated supply must match the existing specification with regards to oxygen content. 

Sometimes an impasse is reached where a food producer wants to change to a Parker gas generator but insists on 99.999% (10ppm maximum remaining oxygen content) purity unless it can be proven that a slightly higher oxygen content gas will achieve exactly the same results, even though the acceptable oxygen level within the finished pack would typically be in the region of 2%.

Parker appreciates this stance and fully understands that for food producers there is a lot at stake in getting it right. However, considering using purchased gas at typically 10-20 ppm purity, does switching to generated gas at say 0.5% change the 2% MROC achievable in the finished pack?

In reality, it doesn’t and the reason for this is that it is almost impossible to flush all of the air out of the packs as they are rapidly and continuously formed within the packing machine, so some oxygen content from the residual ambient air always remains. Secondly, as the product is dropped into the pack from the multi-head weigher through the filling funnel, it pulls in ambient air, thus introducing a little more oxygen into the pack.

One possible way of confirming the suitability of an on-site supply of food grade nitrogen at various purities to establish the most suitable would be to install a small nitrogen generator system to run on a trial basis. This however in most instances is not logistically or physically viable.

Recently Parker UK was faced with the dilemma where a high-quality coffee producer desperately wanted to convert from an expensive and problematic long-standing bulk liquid supply to a NITROSource PSA on-site solution. The producer fully understood the huge cost savings that could be enjoyed by specifying 0.5% purity as opposed to 10ppm but wanted absolute proof that their reputation and produce would not be jeopardised by the change in purity.

To overcome the problems associated with the installation of a full-scale trial unit, Parker's nitrogen generation manufacturing GSFE Division UK and the Local UK Parker sales company devised a solution to introduce a small, fully variable quantity of food grade compressed air into the existing high purity nitrogen supply, thus enabling the ability to increase the MROC to any desired level. A calibrated independent oxygen analyser was installed at the device outlet to constantly monitor O2 levels.

A series of tests were carried out on one packing line where the device was installed and the producer’s quality assurance department was on hand to oversee the trial and sample the finished packs using a calibrated bench top pack analyser for MROC.

The machine was run at its standard 36 bags/min first with only the 10ppm liquid supply and then 2 levels of raised oxygen gas at 0.1% and 0.5% achieved through a small bleed in of food grade compressed air.
 

As can be seen from the table of results, there was virtually zero difference between the gas purities with regards to MROC in the pack and the target O2 level was maintained well below the limit.

The test was evaluated by the producer's decision-making team and a twin bank NITROSource PSA system was duly ordered and installed to fulfill the demand of the entire factory.

Interesting to note that on the day of change over from the existing liquid supply to Parker generated gas, the operatives and QA department were not informed so as to execute a blind test. We are happy to report that the system actually ran for 3 weeks without any detected difference before the parties concerned were eventually informed!

Considering the total cost of ownership including energy, maintenance and capital expenditure, the entire system is expected to realise pay-back within 2 years and reduce cost by up to 75% thereafter.

Now, watch this video to learn more about NITROSource:

For additional information on Parker NITROSource gas generators, download the product brochure. You can also contact Phil Green, the author, directly: phil.r.green@parker.com

This post was contributed by Phil Green, industrial gas application and training manager, Parker Gas Separation and Filtration Division EMEA. 

The Importance of a Food Grade Compliant Nitrogen Gas Supply

Nitrogen: A Cost Effective Way to Extend Food Shelf Life

Modified Atmosphere Packaging with a Nitrogen Generator

Nine Reasons To Consider On-Site Nitrogen Generation

Simple Safety Steps to Follow When Installing a Nitrogen Generator

Top Frequently Asked Questions About Nitrogen Generators

There are numerous manufacturers in the water cooler market. Water coolers are also called chillers but it is important to draw a clear distinction between process water coolers and chillers for industrial or non-industrial cooling applications.

Many people think that all chillers for the industrial manufacturing sector are the same but there is a risk of making a huge error of judgment which could have an impact on the final choice for the application.

When referring to cooling and climate control systems, we mean systems that can control both the temperature and the humidity level of a space. They are usually used for cooling rooms, electrical cabinets or other places where the water cooling temperature does not have to be precise and constant.

Chillers for cooling process water, on the other hand, are compression water cooling units that can be sub-divided, depending on the fluid used for the cooling of the condenser, into air-cooled and water-cooled. The most common cooling power range for installed systems is between 2 and 750 kW.

Process coolers for industry provide a high and constant degree of precision of the output water temperature (in all atmospheric conditions) and keep the fluid clean to prevent damage to the end user. In fact, process chillers are used to cool industrial machinery that requires the cooling fluid to be uncontaminated and at a precise and constant temperature. For example, in all of the hydraulic circuits of machines, if the oil temperature exceeds a certain limit, the machine shuts down with a resulting loss of productivity. Therefore, precise and constant cooling is both necessary and crucial for speeding up and improving production processes. When there is a need for accuracy and a water temperature lower than the ambient temperature, precision process coolers offer the only solution. A precision cooling chiller is a machine designed to cool water using a cooling circuit. It is a closed circuit which must ensure:

• No waste of the cooling fluid.
• No control of outlets.
• Control of the water quality.
• Modularity: possibility for expansion.
• Complete flexibility.
• Water temperature can be set.
• Independence from ambient conditions.

Parker's Hyperchill Plus industrial water chiller is compact, easy to use, safe and reliable in all operating conditions — guaranteeing precise and accurate control of the water temperature. Cooling capacities range from 1.7kW to 23.6kW. The availability of a wide range of accessories and options makes Hyperchill Plus an extremely flexible solution which can satisfy demands in all industrial applications. Thanks to the non-ferrous hydraulic circuit, Hyperchill Plus ensures stable operating conditions, maintaining the highest possible quality and cleanliness, which has an ensuing positive impact on the efficiency and productivity of the process, reducing maintenance costs and system downtime. Each individual Hyperchill Plus is extensively tested in the factory to guarantee the highest possible levels of efficiency and reliability in all operating conditions.

Parker's Hyperchill range of water chillers is designed specifically for industrial applications. Advanced solutions, the utmost attention to detail and a highly sophisticated production process have resulted in a compact, reliable and easy-to-use product that offers flexibility in a variety of conditions as well as precise control of the water temperature. The high level of efficiency and low operating costs make Hyperchill the perfect solution for the modern industry.

Parker is the leading supplier of water coolers for production processes which offer complete ease of use and a high degree of operational reliability thanks to the use of the latest technologies and the availability of a vast array of versions and accessories. The Parker liquid coolers range represents a simple but effective solution to most common problems arising from the use of water. The chart below contains general technical specifications.

To learn more about Hyperchill Plus download the brochure. 

For information on Parker's complete compressed air and gas treatment solutions including the Hyperchill range of water chillers, download the brochure.

This article was contributed by Fabio Bruno, compressed air purification, gas generation & process cooling application engineer, Parker Gas Separation and Filtration Division EMEA.

Sizing a Chiller for Your Application - What You Need to Know 

Why You Need a Maintenance Plan for Manufacturing Equipment

Protect Your Process from Mycoplasma Contamination

Filtration Technologies and Key Markets

In an industrial manufacturing plant, coalescing filters are probably the most important piece of purification equipment found in a compressed air system. They treat six of the ten main contaminants found in compressed air (atmospheric particulate, rust, pipe scale, micro-organisms and aerosols of oil and water). But more importantly, they are also used to protect refrigeration and adsorption (desiccant) air dryers from contamination.

This blog compares the benefits of installing a pair of coalescing filters in series versus a 2 in 1 filter in terms of differential pressure, dirt holding capacity, and total cost of ownership.

Typically, coalescing compressed air filters are installed close to where the compressor is located (either in the compressor room on larger installation or on the compressor itself for smaller fixed or portable compressors). 

In order to effectively reduce the aerosols of oil and water, micro-organisms and particles to a level that will protect the compressed air dryer requires the use of a fine filter (treating contaminants down to 0.01 micron).  

The particulate found in a compressed air system is of varying sizes and as this filter is very fine, it will block rapidly with large particles (especially rust and pipe scale).

As the filter blocks, the differential pressure across the filter increases. This not only reduces the available pressure downstream, it also requires the compressor to generate the compressed air at a higher pressure, resulting in higher operating costs.

On average, it is found that for every 1 bar additional generation pressure there is a loss of 7% in specific energy, therefore keeping pressure losses low helps reduce operating costs.

Running a compressed air filter with high differential pressure is therefore very costly and keeping pressure losses as low as possible is imperative. One way to keep the pressure losses low is to change the filter element on a frequent basis (every 3-6 months). Another way is to oversize the filter; however, making a filter too large has its own issues in terms of filtration performance, purchase cost and installation. Neither way is a cost-effective compressed air treatment solution. 

If the fine filter could be protected, the pressure losses could be reduced, therefore the most cost-effective solution is to install a pair of coalescing filters in series. 

Each filter will reduce the same 6 contaminants but to differing levels of purity. The first filter, a general purpose filter protects the second, a high-efficiency filter from bulk contamination. This not only improves filtration performance but more importantly, reduces pressure losses and operational costs. Additionally, it also extends the service life of the element from 3-6 months to 12 months.

Yes, there are single filter alternatives, but care has to be taken with this type of filter as they do not always provide the perceived benefits. 

In an attempt to reduce the pressure losses associated with compressed air filters, a number of manufacturers are now offering 2 in 1 filters. These are claimed to reduce the pressure losses associated with having two filter housings (and therefore energy consumption) whilst providing the same level of purification (i.e. particulate retention & oil carryover down to 0.01 micron / 0.01 mg/m3 or lower). In theory, the thought process is a sound one, however, these types of filter do not always deliver in practice.

In a compressed air filter, pressure losses are a combination of fixed pressure loss and incremental pressure loss. Fixed pressure losses are designed into the filter from the beginning and come from the filter housing and element endcap designs whereas incremental pressure losses come from the filter element as it starts operating. Pressure losses for compressed air purification equipment are stated as dP or differential Pressure.

Literature dP is often used to select one filter brand over another, however many users are unaware that this data is only indicative of a filter in a clean, “as new” condition and does not indicate how a filter blocks as it operates.

When selecting a filter, its blockage characteristics must also be considered as this is an indication as to the filters dirt holding capacity (and true operational cost). 

Therefore, to show the real performance of the 2 in 1 type of filter and the true benefits of their new OIL-X filter range, a comparative test between a pair of Parker domnick hunter OIL-X coalescing filters (Grades AO + AA) and a single 2 in 1 filter was undertaken.

As the filters on test are coalescing filters, they were wetted out with oil aerosol (in accordance with ISO12500-1, the international standard for coalescing filter testing) to give an initial saturated dP representative of a new filter as it enters the first days of service. Oil carryover performance was also recorded.  

Results of the initial ISO12500-1 testing showed that whilst the OIL-X AO + AA combination achieved the claimed literature performance for oil carryover and initial wet dP, the 2 in 1 filter oil carryover performance was 87% higher than literature claims and initial saturated dP 5% higher. 

The second test determines the dirt loading characteristics of the two offerings by injecting and diffusing equal amounts of test particulate into the air stream and measuring the dP (this is done 12 times to simulate monthly particulate loading).

So whilst the initial performance of the two filters may look similar in literature, actual dirt load testing indicates otherwise as can be seen in the graph. Testing confirms that a pair of Parker domnick hunter OIL-X filters have a much higher dirt holding capacity than the 2 in 1 filter and will, therefore, have significantly lower operational costs. 

From the test data, true operational costs can now be calculated and the table below shows the financial savings available by installing a pair of Parker OIL-X filters over a 2 in 1 filter.

Based upon 37kW compressor / Cost of electricity £0.10. Parker OIL-X savings will be greater with larger filter/compressor combinations.

The table highlights operational costs, however, when selecting compressed air purification equipment, the total cost of ownership (TCO) should always be considered (purchase price / operational costs/maintenance costs). The initial purchase price for the two Parker OIL-X filters is only 26% higher than the 2 in 1 filter whilst a pair of Parker OIL-X filter elements is 42% lower than a single element for the 2 in 1. As the 2 in 1 filter has a lower operating lifetime than OIL-X, it may require 2 element changes per year in which case the pair of OIL-X elements is 183% lower cost than a pair of 2 in 1 elements. What seems like a low-cost alternative may turn out to be a costly investment. 

The new OIL-X filter range is the latest addition to Parker's comprehensive line of compressed air and gas treatment product solutions. The new OIL-X technology has been designed to carefully balance the need for precise compressed air quality with the need for low dP, low energy consumption and low lifetime cost.

Parker domnick hunter OIL-X filters incorporate unique flow management devices to significantly reduce the pressure losses associated with poor housing designs whilst their filter elements use airflow management technology, specially selected filtration media, energy efficient coatings and unique deep pleated element construction. This not only ensures air quality, it also provides a high dirt holding capacity, culminating in a filter element dP that starts low and remains low for the 12-month lifetime of the filter element.

All Parker domnick hunter OIL-X filtration grades have performance 3rd party validated by Lloyds register in accordance with international standards and are backed up by an air quality guarantee.

For more information on Parker's compressed air treatment solutions, download the brochure.

This blog was contributed by Mark White, compressed air treatment applications manager, Parker Gas Separation and Filtration Division, EMEA.

10 Contaminants Affecting Your Compressed Air System - Part One

10 Contaminants Affecting Your Compressed Air System – Part Two

Compressed Air Treatment Solutions for Today's Manufacturing Plants

Seven Myths About Oil-Free Compressors
 

A question that is frequently asked when considering the installation of a nitrogen gas generator is "will the system create an oxygen rich or oxygen deficient atmosphere that could be potentially hazardous?"

• The exhaust or permeate contains oxygen that is vented to atmosphere as part of the normal process to produce nitrogen, possibly increasing the ambient oxygen level.
• Nitrogen could leak from buffer or process vessels and pipe-work within the installation area, possibly reducing the ambient oxygen levels.
• Automatic or manual venting of "off-specification" nitrogen during commissioning or purity control, possibly reducing the ambient oxygen levels.
• Safety pressure relief valves on pressure vessels could vent nitrogen on over-pressure situations, possibly reducing the ambient oxygen levels. 
• At point of use, nitrogen could be vented into the workplace as a normal part of the application or process, possibly reducing the ambient oxygen levels.
• Depressurisation by venting nitrogen vessels during servicing or inspection, possibly reducing the ambient oxygen levels.

Ensure adequate ventilation and set vessel vent flow to ensure no oxygen depletion occurs. Alternatively, fit a suitable flexible hose of the correct pressure rating to the vessel drain connection and vent to a safe location.

Warning labels must be installed in prominent locations on plant rooms, equipment, vessels and pipe-work to inform personnel of the possible presence of nitrogen gas. This labeling should also be positioned and spaced on all equipment, vessels and pipe-work so that it is visible, readable and clear from all directions that nitrogen gas is present, preventing wrongful connection resulting in possible contamination or potentially harmful/fatal usage of the gas; for example, connection to breathing air systems.

If there is any doubt whatsoever as to the oxygen content of a specific location, especially in confined areas or where ventilation criteria is unknown, then a simple but effective solution is to install an ambient room analyser. These work by having a sensor or multiple sensors installed within the area where oxygen depletion or enrichment may occur, connected to an audible/visible alarm indication unit. Generally, there is alarm indication both inside and outside of the area in question so as to prevent entry to the location in the first place or to warn should an out of specification oxygen situation arise while working within the location. There are many suppliers of these type of alarm units and obviously, the manufacturer's instructions should be fully adhered to when installing, operating and maintaining them as they are a critical safety device.