Process Control

When designing a leak-free instrumentation system, one of the first steps to ensuring safety and reliability is to select the right tubing for the intended application. No system integrity is complete without this critical link and its compatibility with the rest of the components. In this post we list four key parameters to consider when selecting quality instrument tube for use with Parker A-LOK® and CPITM tube fittings.

Parker’s instrument tube fittings have been designed to work in a wide variety of applications that demand the utmost in product performance. Their compatibility with selected tubing is critical for providing consistently high-level of reliability.

The most important consideration in the selection of suitable tubing for any application is the compatibility of the tubing material with the media to be contained. Table 1 lists common materials and their associated general applications. It also lists the minimum and maximum operating temperatures for the various tubing materials.

In addition, Parker instrument fittings are designed to work on like materials. Stainless steel fittings should be used only with stainless steel tubing, 6MO fittings with 6MO tubing, etc. The practice of mixing materials is strongly discouraged.

Read about Parker’s stance on using 316 stainless steel tube fittings on 6MO tube.

Table 1. Common tubing materials with their applications and operating temperatures.

The key is to select tube material which is softer than the tube fitting material. For example, Stainless Steel tubing should be specified as Rb 80 or less hardness value. Parker A-LOK® / CPI™ Tube Fittings have, however, been tested on tubing up to Rb 90 hardness level with excellent performance.

Proper wall thickness is necessary to accommodate accepted safety factors relative to desired working pressures. Tube tables published in Parker’s literature, list the tube Outside Diameter (OD) sizes and Wall Thickness combinations per material for safe use with Parker A-LOK® and CPITM tube fittings. Do not use tube with wall thickness values which fall outside of the table ranges.

All working pressures are calculated following the recommendations contained within the ASME B31.3 Chemical Plant and Petroleum Refinery Piping Code and ASME B31.1, Power Piping. All calculations are confirmed via rigorous and extensive testing procedures at our Parker R&D Laboratories. Each calculation utilises an allowable stress figure that incorporates a 4:1 factor of safety.

All testing is carried out to replicate actual working conditions where possible. Parker does not ‘support’ tube to facilitate failure at certain points as this does not truly represent the forces that our products would see in ‘real-time’ applications.

Not all manufacturers support their assemblies’ pressure rating claims with extensive testing. In these cases it is important to understand the implications associated with using unverified recommendations.

Special care must be taken when selecting tubing for gas service. In order to achieve a gas-tight seal, ferrules in instrument fittings must seal any surface imperfections. This is accomplished by the ferrules penetrating the surface of the tubing.

Penetration can only be achieved if the tubing provides radial resistance and if the tubing material is softer than the ferrules. Thick walled tubing helps to provide resistance and the table below provides a range of wall thickness options available for safe use with Parker tube fittings. The ratings in blue indicate the combinations of diameter and wall thickness which are not suitable for gas service.

Table 2. Maximum working pressures (in psig) for imperial tube in 316/316L Stainless Steel material based on tube O.D. size and wall thickness combinations.

At elevated temperatures, a de-rating factor should be applied to the working pressure listed in the Parker tube tables. Please see the table below for the de-rating factors for the common materials Parker offers in our A-LOK® tube fittings range.

In all cases, tube fitting assemblies should never be pressurised beyond the recommended working pressure.

Table 3. This table lists the de-rating factors which should be applied to the working pressures for elevated temperature conditions. Simply locate the correct factor in this table and multiply this by the appropriate value in the pressure tables e.g. Table 2 (above) for 316/316L SS.

* Dual-certified grades such as 316/316L, meet the minimum chemistry and the mechanical properties of both alloy grades.

Register today for our industry-leading SBEx (Small Bore Expert) training and learn how to specify and install efficient, safe and leak-free small bore tubing systems.

Remember,

The Right Tubing + The Right Fitting + SBEx Training = High Integrity Solution.

Article contributed by Dave Edwards, product manager - tube fittings, Instrumentation Products Division Europe.

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Mixing high- and medium-pressure fittings or incompatible parts makes systems unstable, inefficient and potentially dangerous. At worst, it can cause a potentially fatal explosion.

At Parker, we’re all about making our products safe as possible and helping customers to minimise risk. Safety doesn’t happen by accident, so you need to know how to avoid the risk and what to do if you come across a mixed-pressure connection that could be hazardous.

Our engineers have recently come across situations where customers have created system connections using components with different pressure ratings. These instances are rare, but they can and do happen; creating unnecessary risks for everyone using the system.

If a Medium pressure tube is machined with High pressure tooling, this reduces the wall thickness below safe limits, and can lead to catastrophic failure. Similarly, combining a High pressure fitting with a Medium pressure tube means the male and female connections will not fit correctly. It may seem like the threads match, but the gland nuts will not engage to the required depth for the system to remain safe. The mechanical properties of the metals used in High and Medium pressure fittings are very different, meaning medium pressure units cannot withstand the application of high pressure.

Different pressure-rated fittings just don’t mix, and there’s no safe way to combine Medium and High pressure elements. Mixing different types of connections, product lines or parts from different manufacturers is also dangerous and removes any warranties.

Remember, just because something "can be done", doesn't mean that it "should be done"!

The diagram below shows how the positions of collars and glands are different, depending on the pressure of the connection.

Fig. 1. The difference in positions of collars and glands in medium and high pressure connections.

We recommend that you never mix together:

• High pressure and Medium pressure Parker Autoclave Engineers parts
• Parker parts with those from other manufacturers.

All Parker Autoclave Engineers fittings carry our manufacturer’s name, part number, material, heat code and maximum pressure rating. We also make it easy to distinguish between different pressure ranges by clear notch markings on High pressure nuts.

Parker Instrumentation Products Division provides specialist SBEx (Small Bore Expert) safety training on correct and safe assembly of instrument connections to improve safety and skills across the engineering sector. For further support you can contact your local Parker Instrumentation Products distributor or visit our website.

Fig. 2. Notch marking on Parker Autoclave Engineer's High pressure fitting nuts provides differentiation from Parker's other pressure fittings.

If you need to assemble Medium pressure with High pressure in one system, we recommend the use of Parker adapters. For safety reasons, the Maximum Allowable Working Pressure (MAWP) rating is based on the lowest rating of any component (Maximum 20,000 psi).

Fig 3. Male-to-male medium-pressure to high-pressure adapter.

The second adapter (Fig. 4) overcomes the problem of the final rotational position not being predictable, making it safe and practical to use when positioning elbow/tee fittings and valves.

Fig. 4. Male-to-male adapter.

Download Parker Autoclave Engineers adapters technical catalogue.

If you come across a mixed-pressure arrangement, you should immediately isolate, remove and replace it with a proper connection using matching and compatible Parker parts. Otherwise, there is a real risk of failure or burst that could lead to catastrophic failure, resulting in injury or death.

Learn more about Parker Autoclave Engineers range of fittings and tubing suitable for low, medium and high pressure applications:

Parker Autoclave Engineers cone and thread fittings - up to 150,000 psi

Parker Autoclave Engineers Tubing - from 15,000 psi to 150,000 psi

Article contributed by Franck Grignola, product manager EMEA - high pressure, Instrumentation Products Division Europe.

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NORSOK M650 Compliance – An Essential Prerequisite for the Offshore Industry

Securing leak-free connection of impulse lines to manifolds for applications that use differential pressure flowmeters is a subject that has taxed instrumentation engineers for more than a century. Back in 1910, when the very first orifice plate installations made an appearance, they involved 33 connections and 16 lengths of tubing! Thanks to the development of highly integrated manifolds, today’s installations often only require just two tube connections. However, ensuring the long-term integrity of these connections remains a contentious issue.

The first manifolds on the market used NPT taper threads for their tube connections. Despite being the bane of installers’ lives, this type of technology continues to enjoy widespread use today, with most manifold manufacturers still offering it as an option. But much better tube connector technologies are now available.

Unlike compression type tube fittings with one or more ferrules, taper thread fittings rely on the threads themselves to provide the seal. During make-up, progressively larger diameter threads on the fitting are compressed into progressively small diameter threads on the manifold, until eventually there is no clearance left between the crests and roots of the threads and they effectively form a metal-to-metal seal.

NPT taper thread fittings are popular because they are relatively inexpensive, but they also have distinct disadvantages. The fittings cannot easily be installed with a specific torque, which makes it all too easy to crack or distort the female part by applying too much torque, or to apply too little, resulting in potential leak paths due to incorrect thread cling. There is also always some thread clearance due to manufacturing tolerances, which means that if the fitting is not tightened to the point where thread deformation creates a metal-to-metal seal, there is a spiral leak path. Furthermore, the upper and lower machining limits of NPT taper threads mean that there might only be two turns of thread engagement in an assembled connection; the most reliable means of preventing this is to use, if possible, a matched pair of male and female parts produced by the same manufacturer.

Another major disadvantage of NPT fittings is that their radial orientation cannot easily be adjusted without compromising connection integrity.

Most installers of NPT fittings elect to use some form of thread sealant to help prevent leaks. This usually comprises a fluid carrier which transfers a filler compound into the threads and then cures. Unfortunately, not all sealants act as lubricants and they are also very easy to misapply. Too much sealant can cause system contamination, which can result in unseated valves or blocked lines, while too little can allow the threads to gall (cold weld) during installation, requiring replacement of the entire manifold and tubing system. A further problem is that the fitting cannot be adjusted once the sealant has cured.

A popular alternative approach is to use PTFE tape as a sealant. This additionally acts as a lubricant during assembly and facilitates tighter connection of taper thread fittings – although it can lead to over-torquing. Another issue with PTFE tape is that it has a tendency to shred and cause system contamination. For this reason, its use is often prohibited in sensitive instrumentation systems.

Parker now offers two manifold connection solutions – PTFree connect and inverted A-LOK – which completely eliminate the need for taper threads, PTFE tape and thread sealant.

Our PTFree connect system provides a simple means of connecting impulse lines to manifolds without involving the use of taper threads, PTFE tape or thread sealant. Available as an option for every type of manifold valve block that Parker produces, PTFree connect offers different versions that accommodate metric tube sizes from 6 to 12 mm and imperial sizes from 1/4 to 1/2 inch.

Manifolds fitted with the PTFree connect system are exactly the same as their standard counterparts, except that their inlet/outlet and drain/test ports can be factory fitted with male adapters, supplied complete with a preassembled nut and ferrule(s). The (parallel) thread on the male adaptor is screwed into the manifold and uses the same type of stainless steel sealing washer as the valve heads, to provide a high-pressure leakproof and bubble-tight connection. The adaptor is securely locked by a cam or locking plate mechanism. We have used this connection principle well over a million times, so you can be confident that it’s a tried and trusted system.

Installation of PTFree connect manifolds is simple. A variety of connection bodies can be used – including straights, elbows and tees – and all angled components can be freely swivelled to facilitate secure positioning. And if anything does go wrong during installation, the sacrificial element is the male adapter – not the manifold – so the cost of remedial action is considerably less than with any other type of connection.

More recently, we developed inverted A-LOK fittings, designed specifically for connecting impulse lines directly to manifolds. Like our PTFree connect system, these also eliminate taper threads and the need for PTFE tape or thread sealant, but they do not involve the use of adapters – the tube is fitted directly to the manifold. Each of the two manifold ports forms the female half of a connector and is machined with a cone-shaped orifice and a standard parallel (non-tapered) thread. Each male part comprises a tube and an inverted nut, with threads on its outside surface, which drives two ferrules forward during assembly; the pressure seal is provided by the front ferrule – not the threads of the connector.

Inverted A-LOK fittings facilitate direct-to-manifold connections

A key advantage of our inverted A-LOK fittings is that the tube is not twisted during installation – all make and remake motion is transmitted axially to the tubing. Since there is no radial movement of the tubing, it is not stressed and its mechanical integrity is not compromised. These fittings are suitable for both thin wall and thick wall tubing, can be used with a wide variety of tubing materials and accommodate repeated disassembly and remake. However, they still require careful installation. If the internal cone becomes damaged, the manifold block will need to be replaced. And due to cross-hole drilling in the block, the technology is not available on all types of manifolds.

Spencer Nicholson, product manager, instrument manifolds, Instrumentation Products Division Europe.

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Industrial settings with strenuous applications, such as thermal cycling and vibration, are recognised as some of the toughest environments for tube fittings. In all cases such applications demand highly precise, leak-free technology to ensure protection from vibration and thermal cycling. For example, in power generation, nuclear and chemical plants, worker and atmospheric safety is business-critical.

Engineers face numerous options when choosing tube fittings for instrumentation, process and control systems and equipment. In most cases, buyers need a solution that will minimise risk, prevent leakage and provide robust value for money.

In instrumentation installations such as impulse pipework, typically a three piece (single ferrule) or four piece (double ferrule) design is preferred. While both types of fittings have their own merits, the four piece fittings are slightly better known in the market. But in some cases, there are definite advantages for choosing a three piece, single ferrule design.

Single ferrule designs, such as Parker’s CPI™ compressed tube fittings, are ideal where leak-free connections are needed for process, power and instrumentation applications.

With just three pieces required - a nut, body and single ferrule - this type of fitting is easy to install. The ferrule design also provides a strong anti-vibration hold on the tube.

Single ferrule fittings typically offer six core benefits:

1. Fewer leak paths

Many engineers constructing fluid or gas handling systems aim to eliminate potential leak paths. This approach also applies to the design of tube fittings.

With single ferrule fittings such as CPI™, only two potential leak paths need sealing. But double ferrule fittings have three or more paths to seal, depending on the fitting design and composition.

2. Sealing mechanism

With double ferrule designs, the front ferrule contacts the body seat over the entire surface. This causes the end load to be distributed over a wide area.

With Parker’s CPI™ design, there is less body seat contact; the end load is concentrated over a smaller area. Higher contact pressure enhances the ability of the single ferrule solution to seal low density gases, which means it can out-perform its double ferrule counterpart in some applications.

The CPI™ fitting also has the benefit of the one-piece ferrule, utilising Parker’s unique Suparcase™ system. This offers better corrosion resistance and is less likely to be damaged in service; but it’s not available on the front ferrule in twin ferrule tube fitting designs.

3. Dampening vibration

Tubing vibration can affect the ferrule seal. However, with single ferrule designs, a light compression grip at the rear of the ferrule isolates seal points from system vibration. This creates a cushioning effect, providing excellent vibration resistance – again, a potential advantage over double ferrule designs.

4. Better performance in temperature cycling

During temperature cycling, metals naturally expand and contract; this causes dimensional changes in fitting connections. With single ferrule fittings, the ferrule features a ‘spring loaded’ effect; this creates a constant tension between the fitting body and nut.

The spring action compensates for cycling changes. By storing excessive force in the bowing action of the ferrule, it maintains effective sealing points. There is no corresponding spring action with double ferrule designs.

5. Ease of installation

The CPI™ single ferrule tube fitting uses a Molybdenum Disulfide coated nut, which reduces the torque required to make up the assembly by as much as 40%. This coating also gives the added advantage of precise and consistent re-makes. As a result, the fitting can last longer in service - reducing potentially costly maintenance work.

6. Precision assembly

Both single and twin ferrule designs can potentially seal all leak paths, as long as they are assembled precisely. With double ferrule fittings, there’s scope for incorrect alignment, lining fittings up backwards, or leaving a ferrule out completely.

Ultimately, with fewer components, there is less that can go wrong; single ferrule solutions are quicker and easier to assemble, so the scope for error is reduced. With Parker’s CPI™, fittings are sold completely assembled and ready for immediate use.

Offering superior corrosion resistance, the CPI™ product series is manufactured to the highest quality standards and available in a range of sizes, materials and configurations. There is documented heat code traceability on stainless steel fittings for nuclear and other critical applications.

Article contributed by Dave Edwards, fittings product manager, Instrumentation Products Division Europe.

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Certified Natural Gas Vehicle and Fueling System Products

The Ash Probe is a portable instrument for measuring the ash content of coal, providing the user with highly accurate readings within seconds. Instantaneous readings can be made of coal quality on stockpiles, trains or trucks, allowing customers to check the quality of incoming coal supplies and specifications against their suppliers’ claims.

Widely used in the mining industry, it allows suppliers to verify the quality of their product and therefore have confidence that the delivery will be accepted by the client ensuring the agreed price per tonne is paid.

Ash Probe was the first portable product to be developed by Bretby Gammatech (now a part of Parker's Instrumentation Products Division) with the first one sold to a mine in South Wales. Since then, hundreds of Ash Probes have been delivered all around the world, with many of these customers also purchasing Ash Eye or Lab Ash equipment.

Like all Parker Bretby Gammatech’s products, the Ash Probe uses natural gamma radiation, with no radioactive sources.

The Ash Probe has been developed to withstand harsh environments and is therefore renowned for being extremely robust. It is currently being used in temperatures down to -50oC in Mongolia, China, as well as in temperatures over 40oC in many African countries.

• Simple to use, easy to calibrate
• Much quicker than conventional sampling and analysis
• More information on ash and ash variability
• Facilitates dispatch more quickly - reducing train standing time
• Enables increase of saleable tonnage - leading to increased revenue
• Reduces discard - leading to reduced disposal costs
• Reduces sampling effort - leading to reduced costs
• High resolution colour touch-screen display
• Multi language user interface with more languages being added all the time.

Pic. 1. Parker's Ash Probe with a display unit.

The Ash Probe comprises two main parts: a probe and a display unit. To obtain an ash reading, the probe is pushed into the coal pile or truck to be tested. After a few seconds an ash result shows on the display unit.

In order to obtain an accurate assessment of the ash content of the whole pile (or wagon load) the probe is inserted at several locations. This is repeated until the desired precision level has been reached.

In Pile Mode up to 99 probings per pile can be made and data from up to 99 piles can be stored. In Truck Mode up to 12 probings per truck can be made and data from up to 600 trucks can be stored.

Calibration is readily achieved by the customer using the supplied calibration sample gathering equipment.

Tests on a wide range of coals from over twenty countries on five continents have shown that the Ash Probe can measure the ash content to closer than 1% (1σ) ash. In some cases better than 0.5% (1σ) accuracy has been achieved with high-grade anthracite.

The Ash Probe is currently being used by customers around the world to provide quick testing for the ash content of: 

• Run-of Mine (ROM) coal
• Washed product (smalls, peas, beans, singles, doubles etc.)
• Screened coal (dry fines, PSF etc.)
• Slurry
• Blended products
• Final product (e.g. composite ash pile)
• Discard
• Unknown coals prior to blending
• Rail or truck deliveries to blending plants, power stations, coking plants and cement works

Download the Ash Probe product bulletin.

Article contributed by Gary Wain, piping products, product manager, Instrumentation Products Division Europe of Parker Hannifin.

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The quest to find and retain skilled machinists and engineers is harder than ever with Eurozone countries experiencing their lowest ever levels of unemployment.

Instrumentation Products Division Europe (IPDE) and Parker globally recognizes that providing competitive benefits is just one factor in achieving this. To develop a high performing and stable workforce we must engender the right values and behaviours coupled with a shared vision, supported by solid strategies and delivered through engaging leadership. But what about beyond this?

In 2017, IPDE introduced its apprenticeship scheme aimed at attracting and developing the finest mechanical engineering apprentices in our regions, who will define and deliver our future for many years to come.

A mechanical apprenticeship within IPDE affords talented people the opportunity to ‘earn, learn and qualify’ and also prepares the foundations for a fantastic career in one of the world’s most successful organizations.

“Having worked with various apprenticeship schemes in my previous roles, I was keen to introduce this scheme into IPDE so that we can develop and grow our own talent from within. It also enables us to protect our business for the future as our most skilled professionals move into retirement.”

Andrew Spivey, General Manager of Parker Instrumentation Products Division Europe.

IPDE has a strong track record of developing people through previous apprenticeship schemes. Former apprentices have made impressive progress in the organization and currently hold roles such as Division Supply Chain Manager; Production Manager; Lean Manager; Deputy Production Manager; Value Stream Champion; Senior Quality Engineer and Design Engineer.

Neil Shapland, Materials, Planning and Production Manager at IPDE, who began his career with Parker as a manufacturing apprentice 24 years ago, worked within several key areas including value stream manager roles and planning and production manager. He believes that his apprenticeship and the skills he learnt stood him in ideal ground to progress within the organization. He said:

"I am passionate about the manufacturing apprenticeship programme and the positive impact it will have on the business as a whole. I believe it provides the ideal opportunity to nurture and develop first class engineers, our next top manufacturing leaders and committed team members of the future."

Neil Shapland, Materials, Planning and Production Manager at Parker Instrumentation Products Division Europe.

Learn more about career programs at Parker and contact us to discuss your career path.

Article contributed by Michelle Liney, Group HR Manager, Instrumentation Products Division Europe of Parker Hannifin. 

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