Increasing pressure to improve the performance of critical pumping equipment and reduce costly down time is creating opportunities for a novel method for making one of a pump’s key components.

Impellers play a crucial part in a pump’s overall efficiency, but ensuring their blades are perfectly balanced and of a suitable surface quality, thickness and geometry to ensure a long service life, delivering maximum flow rates, is difficult to achieve using traditional casting processes.

It is not unusual for blade thicknesses to vary, when impellers are made using sand moulds and, although they can be dynamically balanced in air, that does not mean they will remain balanced during operation, when pumping a fluid.

Improving the surface quality of the impeller’s blades is also difficult and expensive because protective shrouds severely restrict access.

Castings Technology International, based on the Advanced Manufacturing Park at Catcliffe, near Sheffield, realised its Replicast process could offer an alternative solution.

The organisation, which specialises in helping castings companies to solve problems and improve production, has now further developed the process so that it can produce impellers which have inherently challenging narrow passageways.

As a result, Replicast can now be used to produce correctly balanced impellers up to a metre in diameter with high dimensional accuracy and superior surface finish.

At first, it seemed that the lower cost of impellers made using traditional processes limited demand for Replicast impellers. However, that is changing following optimisation of the Replicast process, which has reduced the cost of impellers by around 30%, and a shift of focus among pump users and manufacturers towards the total cost of pump ownership and ‘up time’.

At least one manufacturer has moved from focusing on a casting’s ticket price to how much it costs them to buy the raw casting, process it and install it in a pump. The switch makes Cti’s impellers far more attractive since they have significantly lower, to zero, non-conformance costs, require little or no ‘detailing’" and far less finish machining, thanks to the company’s near-net-shape process.

Replicast uses ceramic shells formed around sacrificial replica patterns, made directly from CAD designs using additive manufacturing technologies or machined from polystyrene.

Tests have shown that pumps using Replicast impellers are 10 per cent more efficient than impellers made by traditional methods, which means pumps can be smaller, further reducing material and manufacturing costs.

New designs can be produced in half the time it would take if a conventional wooden pattern had to be made, modifications can be made just as rapidly and it is far easier to reverse engineer a product, using a Coordinate Measuring Machine to collect the data to produce a CAD design from which the sacrificial pattern can be made.

“The oil and gas, chemical process, power and water purification industries are all beginning to focus on total cost and realising how financially damaging it can be to suffer any down time because of pump failures,” says Cti’s Richard Gould.

Weir Minerals Europe has launched a new addition to its Warman range of centrifugal pumps - a vortex pump featuring an open, recessed impeller designed to minimise abrasion, clogging and damage to delicate materials.

Unlike standard centrifugal pumps, the Warman WRR pump uses a vortex to move slurry through the unit, created by an impeller which sits outside of the main flow path. This provides an unobstructed passage between suction and discharge, even for particles as big as the suction inlet.

The Warman WRR pump is designed for applications across the wastewater, food and drink manufacturing, mining, minerals and chemical processing industries.

The WRR pump is available in a large range of sizes and configurations including standard horizontal, close coupled, submersible and vertical bearingless designs. Flow rates range from 1 to 1250 m3/h and free spherical passages from 40 to 250mm.

The Warman range of pumps from Weir Minerals is widely considered a benchmark in pumping technology and offers the widest range of slurry pumps in the industry.

Originally developed for estimating leakage rates through valves to flare in oil refineries and offshore platforms, acoustic emission technology is also finding use in other process industries such as power generation, nuclear, chemicals and pharmaceuticals, says Tim Bradshaw

The detection of leaks by acoustic methods was used well before the technology of acoustic emission (AE) was applied elsewhere. However, the equipment that was available was susceptible to noise from sources other than leaks, such as that from normal plant operation and the surrounding environment. As the AE industry grew in other areas, technology became available which meant that the problems of environmental noise could be largely overcome.

A trials programme carried out by BP between 1982 and 1984 selected the AE method as most promising for development as a method of quantifying leakage through valves. The field development programme lasted six years and involved removing more than 800 valves from service that had been identified as leaking, and retesting these in the laboratory to build up a correlation between physical loss and acoustic signal level.

Following this, a 'best fit' correlation was developed so that the technology could be easily applied. Factors having a significant effect on the acoustic signal level include valve type, size, and differential pressure. This development was followed by the commissioning of a new instrument able to make accurate field measurements to make practical use of the database. The new instrument, the VPAC II from Mistras Group, is intrinsically safe, portable and simple to use by virtue of all the measurement functions being automatic. This instrument together with the 'VPAC' Valve Leak Technology Package, as the quantification method is known, has become widely used in the oil and gas industry for the identification and estimation of through-valve gas losses, thus enabling cost effective operational and maintenance decisions to be made quickly and easily without plant disruption, and by personnel with just one hour of training.

Detection principle

The source of the acoustic emissions should be considered initially. These are generated by a fluctuating pressure field that is associated with turbulent flow of the fluid at the leak site. The conditions for turbulent flow are met when the inertial effects of the fluid flow overcome the viscous drag; the ratio of the former to the latter is defined as the Reynolds number. Turbulence has been found to commence when the value for the Reynolds number is between 103 and 104. Acoustic Emission, therefore, is an effective method for detection of through valve leaks where the velocity across the leak is sufficiently high with respect to the size of the leak orifice to produce a Reynolds number in this region.

Quantification

The calculation to deduce the flow rate in a cylindrical orifice would be simple. However, this is far from the real world situation where a leak is likely to be anything but a cylindrical orifice and is also likely to be made up from a number of smaller leaks around the entire valve seat. As a result, an alternative method of correlating the AE received and the flow rate through the leak was required. This was achieved empirically by testing 800 valves in the field and repeating the tests with the valves removed to a flow rig. Valves in the size range 1 - 18-in and of a range of types were used in this exercise and a database of results was compiled from which a predictive equation was derived. It is this predictive equation that allows the quantification of through valve leaks in the field.

Test method

The operation of the instrument is simple. The sensor is held in contact with a flat surface, using a suitable acoustic couplant such as grease, on the valve to be tested.

The current value of the signal level (dB) is noted. This may also be stored with a single key-press in one of the 300 memory locations. If a leak is indicated by a reading greater than normal background (12 -16dB) then readings are taken on the pipework upstream and downstream of the valve.

As the signal level will be highest close to the leak and attenuate as the distance from the leak increases, these upstream and downstream figures will be lower if the valve is truly the source of the acoustic emission. The noted reading is then inserted into a PC spreadsheet along with the other relevant information:

* Valve inlet size

* Differential pressure across the valve

* Valve type

This information is used in the spreadsheet by the predictive equation to calculate the loss rates. The spreadsheet is often modified to present the loss rate in convenient units such as tonnes/year, m3/day or even product value/period.

Current experience

The VPAC II system has now been licensed for use on more than 200 sites and has proved capable of quickly surveying large numbers of valves and estimating losses from the leaking valves. In one offshore survey, 20 valves were tested and the results recorded in just over an hour. In this one small survey, leaks totalling approximately 5,100 litres/min were identified, equating to 4,500 tonnes/year. Other spectacular successes have been commonplace with the largest leak found to date being over 3,800 litres/minute from a single 24-in valve. In one refinery, a 4-inch PRV with a signal level of 85db was found, equating to 1,100 tonnes/year.

In one petrochemical plant, four 24-inch control valves were tested using VPAC. Two of these were shown to be leaking more than 2,500 tonnes/year. One oil company identified losses of $14 million from four refineries.

Not all large scale losses are due to damaged valves; leaking control valves are a common problem and these often require only a minor adjustment. One particular one-inch valve, shown to be losing £20,000/year, was fixed on the spot by simply adjusting the stop. An offshore PCV was found to be losing 500,000 mscf/day, equating to $300,000 per annum.

Troubleshooting and maintenance

The system is also being widely used for operations troubleshooting and maintenance where the value of the losses may not be the most significant feature. This is particularly true for offshore projects where the value of the gas is not high. The use of the VPAC system is now written into several maintenance procedures in the North Sea.

Initial surveys will quickly highlight the large-scale losses, which may then be dealt with. It is here that the sensitivity of the VPAC system becomes a significant advantage. Losses of as little as 1 litre/min are detectable in the field. A refinery suffering virtually no background losses is using the VPAC system to quickly track down leaks as they occur. They can achieve in a couple of hours what used to take two to three days.

Even in apparently noisy environments it is possible to detect very small leaks. This is due to the sensor design, which is very effective at rejecting vibrational noise, and advanced signal processing in the instrument. A leak of only 1.5 litres/min was detected in a relief valve in an offshore gas production platform compressor module. The background signal level on the 5131 sensor was no higher than normal even in this 'high noise' environment.

Losses also have secondary effects. One refinery user reported that hydrogen was its production bottleneck. Each tonne of hydrogen was used to make 30 tonnes of product. A control valve was identified by VPAC as losing 770 tonnes of hydrogen a year to flare. This equates to a loss of production of 23,100 tonnes per annum. These valves are now checked on a regular basis.

Of great concern to many governments is the issue of environmental damage caused by the excessive release of hydrocarbons into the atmosphere. Operators working in countries, which do not yet have strict environmental policies, will know that it is only a matter of time before they also will have to comply with the strictest emission regulations. VPAC offers a quick and simple solution to monitoring plants and effectively keeping emissions from through valve losses under control. Some company operating procedures which had required that relief valves that had lifted should be replaced (in case they had not properly re-seated) now specify VPAC to check for reseating, thus saving the cost of replacing valves after the majority of releases.

Further developments

The detection of through valve leakage using VPAC is not confined to gas systems. Where there is sufficient differential pressure to satisfy the conditions for turbulent flow, then liquid leakage can also be readily detected. The database of results on liquids has now been built up allowing quantification of through valve liquid losses. At present, work is ongoing to expand this database, which will further improve the liquid leak correlation to larger valve sizes.

A programme run offshore and in the workshop extended the procedure and correlation to very large offshore Emergency Shutdown Valves, up to 48-in diameter, in both gas and liquid service, with soft and hard seats. The purpose was to replace the statutory SI1029 test requirement, which required long period platform shutdown, with a test that could be applied rapidly during any temporary production stop, saving $400,000 per annum in the Forties field.

In addition to the detection of liquid through valve leaks, the system is also being used to detect the leaks that lead to sand erosion of valve bodies. This can also be extended to detect sand erosion at vulnerable areas in pipework.

Leak detection using AE techniques is also being used successfully on boilers, where steam leak detection systems provide early warnings of steam leaks, which allows plant operators to manage the problem cost effectively, often running the plant for weeks following initial detection. These systems use sensors mounted on waveguides welded to the outside of the boiler, making installation straightforward.

Handheld AE leak detection systems are also identifying and quantifying through-valve losses of normally closed steam valves for power generation. Identifying the valves that are allowing the greatest loss is a critical tool in the financial management of these plants.

Leak detection is also being carried out in nuclear applications, where AE systems are installed on various types of nuclear reactor pipework and pressure vessels.

Conclusions

The quantification of through valve losses allows the identification of significant cost savings through loss control; prioritising of maintenance based on quantitative information; speedy and effective operations and maintenance troubleshooting; and the effective control of emissions to the environment.

Tim Bradshaw, General Manager, MISTRAS Group, UK operations. 

In order to better protect industrial control systems from cyber attacks, companies should take heed from the wise words of successful military tacticians and the lessons learned from some of the greatest failures in military defence, says Tim Ricketts

In 2016, NATO officially recognised cyberspace as a warfare domain – an important change that has led many cyber security companies to liken their strategies for preparation and defence to Sun Tzu’s philosophies shared in The Art of War.

While it is important to take heed from the wise words of a successful military tactician and philosopher, it is paramount that we look to history for some of the greatest failures in defence so that you may learn from these too.

This article looks at a historical defence failure that mirrors that of many security breaches in the cyber realm, where a persistent threat will take full advantage of an opportunistic weakness in the defender’s wall.

This historical event took place in Istanbul (then known as Constantinople) in the year 1453, fought by the defending Roman Byzantine rulers and the advancing Ottoman Empire.

The Roman rulers erected a series of defence structures that featured large, high walls and secured entrances, spanning the city and protecting it from conquest.

The legend has it that one of the main gates to the city had been left open by an outbound raiding force. This open gate was quickly discovered by a small group of Ottoman forces, who realised that they could get inside and raise their banner.

The raising of the banner caused panic among the defending forces, who retreated and lost vital ground within the City walls. The ensuing Ottoman forces eventually overwhelmed the city’s internal defences and, as history tells, for the Byzantine and the Roman Empire in the East – the battle was lost.

With the history lecture now out of the way, it is important to pick out the key points presented in this story and take these as golden nuggets:

* Your organisation’s defences may be strong, but will always need entry points.

* Ensure that access to entry points is well reviewed, logged and audited.

* Plan for the worst; be as proactive in your internal defences as your external ones.

* “These lessons learnt are great,” you may be thinking, “But how do they apply to my Industrial Control System?”

Let’s start with the first one: you may not have a wall – but you do have a moat, in the form of an air gap. This keeps your operational network seemingly safe from the outside world, with the ‘jump’ being too great for your conventional attack.

No network, however, is truly isolated from the outside world, just as no city is ever truly isolated by a moat; there needs to be a way in to allow for updates and to access equipment remotely, and this will always leave the possibility for mistakes to be made.

Regular maintenance tasks, such as removing outdated pieces of equipment, could also be likened to our story.

Think of it like this: you have your very own Wall of Constantinople in the form of your firewall, and you have gates through that wall in the form of ports. When an engineer removes that piece of equipment, but doesn’t close the port, then you now have an open gate – one that has turned into an exploitable attack vector.

Products such as Cyber-X can detect these open ports, quickly allowing engineers to close these gates to your operational network.

You will almost certainly understand where your entry points are, but you should also be aware of the times, manner and reasons in which people access them.

An early warning sign to a breach on your network is sporadic and unauthorised access to systems.

Detection of these breaches could help to close gaps or even prevent major incidents, but if you notice that there is an entry point that is infrequently used or is now surplus to requirements, then you should consider its removal.

Products such as Cyber-X learn about your usual network traffic, making it easy to spot traffic that is unusual for your network, such as traffic that occurs during off-peak hours, unusually large packets or unexpected protocols.

Planning for the worst is not the same as admitting defeat, but rather being prepared to recuperate from the worst possible outcome, often meaning that your disaster recovery will be mature and developed enough to restore services as quickly as possible.

Frequently monitoring the state of your network devices allows you to develop customised, efficient and profoundly effective plans that evolve along with your organisation’s scale.

Tim Ricketts is Director of MAC Solutions. 

In an increasingly competitive marketplace, operators of applications such as food and beverage, chemical and pharmaceutical processing are under pressure meet the highest standards of hygiene - and the repercussions of falling below these levels are unthinkable.

Failure to maintain cleanliness standards of electric motors and other equipment can result in product contamination, not to mention reduced efficiency and premature failure.

The problem is that washdowns with high-pressure water jets not only risk damage to motors and drives, they also spray debris onto equipment, which finds its way beneath rating plates and cooling fins. This provides a perfect place for bacteria to thrive, while the ingress of water can permanently damage components.

Solutions exist in the form of waterproof electric motors and variable-speed drives, such as those offered by Gibbons Engineering Group. The company recently launched its stainless steel motor and ABB ACS355 drive package – offering dust-tight equipment that’s fully resistant to high-pressure water jets.

Gibbons’ stainless steel motors have a completely smooth surface free of cooling fins or rating plates – with information laser engraved. There’s no paint to peel, chip or flake off, and the IP69K totally enclosed non-ventilated (TENV) casing means they can withstand powerful water jets.

For optimal speed control and energy efficiency, Gibbons can couple the motors with ABB ACS355 variable-speed drives, which are rated at IP66/67 ingress protection – meaning they’re dust-tight and impervious to water. Plus, a keypad membrane cover means the unit can be operated normally in all conditions.

AW-Lake Company introduces the MicroTRICOR TCM-100 Coriolis Mass Flow Meter– the smallest TRICOR Coriolis meter designed for the accurate measurement of very low flow rates.

This new mass flow meter is suitable for dosing, blending and batching in applications such as chemical injection, precision painting and coating applications, and batch processing associated with liquid or gas handling and dispensing.

The new multivariable instrument reports mass flow, density, concentration, temperature, and volumetric flow in one device.

Without any moving parts such as gears that require maintenance or can corrode and fail, the TCM-100 Coriolis Mass Flow Meter uses smooth tubes through which material flows at rates as low as 5cc/min (300 grams/hr, .001 gallons/min).

Unlike volumetric flow meters, the MicroTRICOR Low Flow Meter measures mass instead of volume, providing for greater accuracy as the mass of a fluid or gas remains constant and is unaffected by changing process conditions such as temperature, pressure and viscosity.

As a result, process engineers get truer readings in all conditions from the MicroTRICOR Mass Meter.

In addition, the unique compact dual tube design provides for a more balanced system with greater resistance to external vibration and pulsating flow.

Offering fast response times, the MicroTRICOR meter deliver high repeatability with long-term operations. With no filter requirements, the low flow mass meter requires little or no maintenance. Units are flushable and simple to clean.

Having all wetted components made of 316L stainless steel, this meter is compatible with most fluids. Multiple connection types are available including NPT, AutoClave, and tubing.

The TCM-100 Mass Flow Meter is suitable for high pressures up to 5,000 psi, and is EX certified with ATEX, IECEx, EAC certifications and a pending CSA rating.

The MicroTRICOR Meter is sold with TCE transmitters that are available with analog, frequency pulse and status outputs.  Transmitters can be ordered as panel mount or remote field mount versions.

Solids handling specialist, Ajax Equipment, has supplied leading speciality chemicals producer, Vertellus, with an agitated screw feeder and screw conveyor for its Teesside, UK plant.

The site supplies monomers and performance enhancers for the plastics and polymers market, as well as, manufacturing advanced intermediates for pharmaceutical, agricultural chemicals and photographic applications.

Capable of holding 3.5T of damp centrifuge cake, the agitated screw feeder is the largest produced by Ajax to date.

The stainless steel unit has a large capacity hopper with multi-bladed agitator to provide gentle agitation to maintain ‘live’ product condition, disturb any potential consolidation and deliver positive infeed to the integral screw feeder.

Once discharged, the cake is transferred to two dryers via a long screw conveyor.

Special care was taken in outlet and screw design to ensure output goes to the appropriate dryers.

The screw feeder and conveyor both feature LynFlow ribbon flights which inhibit adhesive materials from clogging up the screw.

The Type 8652 was designed by Burkert for applications in the pharmaceutical and water treatment industries. It offers users adjustable monitoring and diagnostic functions that improve system availability and process reliability, while at the same time enabling preventive maintenance. An integrated display for this purpose shows detailed on-site information such as the current switching statuses of the pilot and process valves, issues a message if pre-set pressure limit values are exceeded or displays errors such as cable breaks in plain text. During development, particular attention was also devoted to the compact design. The valve island 8652 is significantly smaller than its predecessor and therefore fits perfectly into compact control cabinets that can be placed close to the process valves.

The valve island communicates via common industrial Ethernet protocols or PROFIBUS DP. In sealed ring topologies and PROFINET IO communication, the Media Redundancy Protocol (MRP) for highly available networks ensures that even switch or cable break can be compensated for. This increases system availability and makes processes more reliable.

Every single valve is hot-swap capable, which means it can be replaced during live operation without shutting down the system. As an additional safety function, check valves are used in the exhaust channel. These prevent the unwanted activation of valves by pressure peaks and the resulting mixing of media. Consequently, a reliable process is also guaranteed on the pneumatic side.

Manchester University’s School of Chemical Engineering and Analytical Sciences is leading world class developments in energy efficiency in the process industries. Researchers have incorporated TorqSense transducers into a test rig that is analysing losses in in-line mixers.

Efficient production is fundamentally important to success in the process industries, many of which serve global markets. While there are multiple elements of cost in the production processes, optimising energy consumption is seen as essential because improvements will repay dividends over many years.

The energy consumption involved in in-tank mixing processes is well researched and understood. But with in-line rotor-stator mixers the flow is often controlled independently of the rotor speed and collecting sufficient data to accurately model the process has to date required a large number of experiments.

Now researchers Dr Mike Cooke and T. L. Rogers at Manchester University have developed two simplified methods for obtaining the necessary information for particular stator-rotor mixers: one uses torque measurements, the other heat balance.

Dr Cooke explains that high shear rotor-stator mixers are widely used in process industries, including the manufacture of many food, cosmetic, healthcare products, fine chemicals and pharmaceuticals. Rotor-stator devices provide a focussed delivery of energy, power and shear to accelerate physical processes such as mixing, dissolution, emulsification and deagglomeration.

“To reliably scale-up these devices from laboratory size to industrial scale we need to understand the relationship between rotor speed, flow rate and the energy dissipated,” he says. “The first step is to link the energy dissipation rate to desired process results.”

The scientists created two mixing experiments and set about measuring the torque profile and heat balance. In the first experiment torque was measured by a Sensor Technology’s TorqSense in-line torque meter fitted to the drive shaft.

There are two main sources of potential error when measuring the torque on the rotor shaft: time-based zero-drift and bending moments on the shaft, both of which are easily counteracted with the TorqSense. Other corrections also have to be made for bearing losses, temperature fluctuations etc.

TorqSense proved a good choice for this work because its non-contact operation meant extra drag forces were not added to the system and also allowed rapid assembly and disassembly during the experiments. It uses two piezo-electric combs which are simply glued to the drive shaft at right angles to one another. As the shaft turns it naturally twists along its length very slightly and in proportion to the torque, which deforms the combs changing their piezo-signature. This change is measured wirelessly by a radio frequency pick up and used to monitor the torque.

Its data is output to a very user-friendly computer screen which uses graphics to aid instant interpretations and also automatically logs all data for later analysis.

In fact the School of Chemical Engineering and Analytical Sciences at Manchester University is a major user of TorqSense, having many installed on permanent teaching aids and various research rigs.
“The students like the readout displays, which look no more complicated that a car’s dashboard,” says Dr Cooke. “For us researchers, the ease with which they can be mounted and removed is a God-send in experiments where you are constantly reconfiguring the rig. Also their lack of slip rings means one less set of calculations to account for – and one less fiddly fixing task.”

The conclusion from Dr Cooke’s experiments is that the performance characteristics of in-line mixers can be easily modelled. This lets industrial users calculate their optimum energy consumption and tune their mixer drives accordingly. Power and cost savings will accrue during the whole production period, and make a valuable contribution to the company’s bottom line and green credentials.

To analyse the long term performance and reliability of hard working valves and pumps, serial innovators Manchester-based Bifold Group has adopted radio frequency based torque transducers from Sensor Technology Ltd for two of its specialist test rigs.

By using the power of computer aided design many of Bifold’s products are built to custom designs, yet they are produced to very short lead times thanks to the efficiency of internet communications. To maintain this standard, sample products and components are comprehensively tested so that their reliability and capabilities are never in doubt.
   
So when Bifold wanted to assess the effects of wear on its long-life valves they set about designing a special test rig. Engineer Andrew Laverick recalls: “We wanted to measure the power required to operate the valve to see how it changed over time and with long term use. It was clear that the best way to do this was to measure the torque input over an extended period.”

“We were open to any design concept for the test rig, but soon found ourselves gravitating towards a TorqSense solution because the Sensor Technology engineers were so helpful and really knowledgeable about test rigs.”

TorqSense transducers lend themselves to test rig uses because they are non-contact measuring devices. Attached to the surface of the transducer shaft are two Surface Acoustic Wave (SAW) devices, when torque is applied to the shaft the SAWs react to the applied strain and change their output. The SAW devices are interrogated wirlessly using an RF couple, which passes the SAW data to and from the electronics inside the body of the transducer.

Sensor Technology’s Mark Ingham explains: “All you have to do is set up a TorqSense transducer in the test rig and fire it up. The SAW frequencies reflected back are distorted in proportion to the twist in the test piece, which in turn is proportional to the level of torque. We have some clever electronics to analyse the returning wave and feed out torque values to a computer screen.

“TorqSense has been used on many test rigs over the years and I was delighted to hear the Bifold engineers say how easy it is to use and how robust the software is.”

Laverick again: “As a test engineer you are almost resigned to long set up procedures and software that falls over at the drop of a hat. But Sensor Technology has designed these problems out of their TorqSense equipment, with the result that we were able to complete our long term test procedures with the minimum amount of fuss and heartache and well within the allotted time schedule.”

In fact Bifold has since bought a second TorqSense which is being fitted to a new test rig used to assess the performance of mission critical chemical injection pumps, as used at oil and gas wellheads and on process pipelines.

“This project is proceeding well,” says Laverick, “and is allowing us to further develop our abilities to quickly provide bespoke equipment for ultra demanding applications, safe in the knowledge that it will perform faultlessly over a long working life.”

Increasing pressure to improve the performance of critical pumping equipment and reduce costly down time is creating opportunities for a novel method for making one of a pump’s key components.

Impellers play a crucial part in a pump’s overall efficiency, but ensuring their blades are perfectly balanced and of a suitable surface quality, thickness and geometry to ensure a long service life, delivering maximum flow rates, is difficult to achieve using traditional casting processes.

It is not unusual for blade thicknesses to vary, when impellers are made using sand moulds and, although they can be dynamically balanced in air, that does not mean they will remain balanced during operation, when pumping a fluid.

Improving the surface quality of the impeller’s blades is also difficult and expensive because protective shrouds severely restrict access.

Castings Technology International, based on the Advanced Manufacturing Park at Catcliffe, near Sheffield, realised its Replicast process could offer an alternative solution.

The organisation, which specialises in helping castings companies to solve problems and improve production, has now further developed the process so that it can produce impellers which have inherently challenging narrow passageways.

As a result, Replicast can now be used to produce correctly balanced impellers up to a metre in diameter with high dimensional accuracy and superior surface finish.

At first, it seemed that the lower cost of impellers made using traditional processes limited demand for Replicast impellers. However, that is changing following optimisation of the Replicast process, which has reduced the cost of impellers by around 30%, and a shift of focus among pump users and manufacturers towards the total cost of pump ownership and ‘up time’.

At least one manufacturer has moved from focusing on a casting’s ticket price to how much it costs them to buy the raw casting, process it and install it in a pump. The switch makes Cti’s impellers far more attractive since they have significantly lower, to zero, non-conformance costs, require little or no ‘detailing’" and far less finish machining, thanks to the company’s near-net-shape process.

Replicast uses ceramic shells formed around sacrificial replica patterns, made directly from CAD designs using additive manufacturing technologies or machined from polystyrene.

Tests have shown that pumps using Replicast impellers are 10 per cent more efficient than impellers made by traditional methods, which means pumps can be smaller, further reducing material and manufacturing costs.

New designs can be produced in half the time it would take if a conventional wooden pattern had to be made, modifications can be made just as rapidly and it is far easier to reverse engineer a product, using a Coordinate Measuring Machine to collect the data to produce a CAD design from which the sacrificial pattern can be made.

“The oil and gas, chemical process, power and water purification industries are all beginning to focus on total cost and realising how financially damaging it can be to suffer any down time because of pump failures,” says Cti’s Richard Gould.

Weir Minerals Europe has launched a new addition to its Warman range of centrifugal pumps - a vortex pump featuring an open, recessed impeller designed to minimise abrasion, clogging and damage to delicate materials.

Unlike standard centrifugal pumps, the Warman WRR pump uses a vortex to move slurry through the unit, created by an impeller which sits outside of the main flow path. This provides an unobstructed passage between suction and discharge, even for particles as big as the suction inlet.

The Warman WRR pump is designed for applications across the wastewater, food and drink manufacturing, mining, minerals and chemical processing industries.

The WRR pump is available in a large range of sizes and configurations including standard horizontal, close coupled, submersible and vertical bearingless designs. Flow rates range from 1 to 1250 m3/h and free spherical passages from 40 to 250mm.

The Warman range of pumps from Weir Minerals is widely considered a benchmark in pumping technology and offers the widest range of slurry pumps in the industry.

Originally developed for estimating leakage rates through valves to flare in oil refineries and offshore platforms, acoustic emission technology is also finding use in other process industries such as power generation, nuclear, chemicals and pharmaceuticals, says Tim Bradshaw

The detection of leaks by acoustic methods was used well before the technology of acoustic emission (AE) was applied elsewhere. However, the equipment that was available was susceptible to noise from sources other than leaks, such as that from normal plant operation and the surrounding environment. As the AE industry grew in other areas, technology became available which meant that the problems of environmental noise could be largely overcome.

A trials programme carried out by BP between 1982 and 1984 selected the AE method as most promising for development as a method of quantifying leakage through valves. The field development programme lasted six years and involved removing more than 800 valves from service that had been identified as leaking, and retesting these in the laboratory to build up a correlation between physical loss and acoustic signal level.

Following this, a 'best fit' correlation was developed so that the technology could be easily applied. Factors having a significant effect on the acoustic signal level include valve type, size, and differential pressure. This development was followed by the commissioning of a new instrument able to make accurate field measurements to make practical use of the database. The new instrument, the VPAC II from Mistras Group, is intrinsically safe, portable and simple to use by virtue of all the measurement functions being automatic. This instrument together with the 'VPAC' Valve Leak Technology Package, as the quantification method is known, has become widely used in the oil and gas industry for the identification and estimation of through-valve gas losses, thus enabling cost effective operational and maintenance decisions to be made quickly and easily without plant disruption, and by personnel with just one hour of training.

Detection principle

The source of the acoustic emissions should be considered initially. These are generated by a fluctuating pressure field that is associated with turbulent flow of the fluid at the leak site. The conditions for turbulent flow are met when the inertial effects of the fluid flow overcome the viscous drag; the ratio of the former to the latter is defined as the Reynolds number. Turbulence has been found to commence when the value for the Reynolds number is between 103 and 104. Acoustic Emission, therefore, is an effective method for detection of through valve leaks where the velocity across the leak is sufficiently high with respect to the size of the leak orifice to produce a Reynolds number in this region.

Quantification

The calculation to deduce the flow rate in a cylindrical orifice would be simple. However, this is far from the real world situation where a leak is likely to be anything but a cylindrical orifice and is also likely to be made up from a number of smaller leaks around the entire valve seat. As a result, an alternative method of correlating the AE received and the flow rate through the leak was required. This was achieved empirically by testing 800 valves in the field and repeating the tests with the valves removed to a flow rig. Valves in the size range 1 - 18-in and of a range of types were used in this exercise and a database of results was compiled from which a predictive equation was derived. It is this predictive equation that allows the quantification of through valve leaks in the field.

Test method

The operation of the instrument is simple. The sensor is held in contact with a flat surface, using a suitable acoustic couplant such as grease, on the valve to be tested.

The current value of the signal level (dB) is noted. This may also be stored with a single key-press in one of the 300 memory locations. If a leak is indicated by a reading greater than normal background (12 -16dB) then readings are taken on the pipework upstream and downstream of the valve.

As the signal level will be highest close to the leak and attenuate as the distance from the leak increases, these upstream and downstream figures will be lower if the valve is truly the source of the acoustic emission. The noted reading is then inserted into a PC spreadsheet along with the other relevant information:

* Valve inlet size

* Differential pressure across the valve

* Valve type

This information is used in the spreadsheet by the predictive equation to calculate the loss rates. The spreadsheet is often modified to present the loss rate in convenient units such as tonnes/year, m3/day or even product value/period.

Current experience

The VPAC II system has now been licensed for use on more than 200 sites and has proved capable of quickly surveying large numbers of valves and estimating losses from the leaking valves. In one offshore survey, 20 valves were tested and the results recorded in just over an hour. In this one small survey, leaks totalling approximately 5,100 litres/min were identified, equating to 4,500 tonnes/year. Other spectacular successes have been commonplace with the largest leak found to date being over 3,800 litres/minute from a single 24-in valve. In one refinery, a 4-inch PRV with a signal level of 85db was found, equating to 1,100 tonnes/year.

In one petrochemical plant, four 24-inch control valves were tested using VPAC. Two of these were shown to be leaking more than 2,500 tonnes/year. One oil company identified losses of $14 million from four refineries.

Not all large scale losses are due to damaged valves; leaking control valves are a common problem and these often require only a minor adjustment. One particular one-inch valve, shown to be losing £20,000/year, was fixed on the spot by simply adjusting the stop. An offshore PCV was found to be losing 500,000 mscf/day, equating to $300,000 per annum.

Troubleshooting and maintenance

The system is also being widely used for operations troubleshooting and maintenance where the value of the losses may not be the most significant feature. This is particularly true for offshore projects where the value of the gas is not high. The use of the VPAC system is now written into several maintenance procedures in the North Sea.

Initial surveys will quickly highlight the large-scale losses, which may then be dealt with. It is here that the sensitivity of the VPAC system becomes a significant advantage. Losses of as little as 1 litre/min are detectable in the field. A refinery suffering virtually no background losses is using the VPAC system to quickly track down leaks as they occur. They can achieve in a couple of hours what used to take two to three days.

Even in apparently noisy environments it is possible to detect very small leaks. This is due to the sensor design, which is very effective at rejecting vibrational noise, and advanced signal processing in the instrument. A leak of only 1.5 litres/min was detected in a relief valve in an offshore gas production platform compressor module. The background signal level on the 5131 sensor was no higher than normal even in this 'high noise' environment.

Losses also have secondary effects. One refinery user reported that hydrogen was its production bottleneck. Each tonne of hydrogen was used to make 30 tonnes of product. A control valve was identified by VPAC as losing 770 tonnes of hydrogen a year to flare. This equates to a loss of production of 23,100 tonnes per annum. These valves are now checked on a regular basis.

Of great concern to many governments is the issue of environmental damage caused by the excessive release of hydrocarbons into the atmosphere. Operators working in countries, which do not yet have strict environmental policies, will know that it is only a matter of time before they also will have to comply with the strictest emission regulations. VPAC offers a quick and simple solution to monitoring plants and effectively keeping emissions from through valve losses under control. Some company operating procedures which had required that relief valves that had lifted should be replaced (in case they had not properly re-seated) now specify VPAC to check for reseating, thus saving the cost of replacing valves after the majority of releases.

Further developments

The detection of through valve leakage using VPAC is not confined to gas systems. Where there is sufficient differential pressure to satisfy the conditions for turbulent flow, then liquid leakage can also be readily detected. The database of results on liquids has now been built up allowing quantification of through valve liquid losses. At present, work is ongoing to expand this database, which will further improve the liquid leak correlation to larger valve sizes.

A programme run offshore and in the workshop extended the procedure and correlation to very large offshore Emergency Shutdown Valves, up to 48-in diameter, in both gas and liquid service, with soft and hard seats. The purpose was to replace the statutory SI1029 test requirement, which required long period platform shutdown, with a test that could be applied rapidly during any temporary production stop, saving $400,000 per annum in the Forties field.

In addition to the detection of liquid through valve leaks, the system is also being used to detect the leaks that lead to sand erosion of valve bodies. This can also be extended to detect sand erosion at vulnerable areas in pipework.

Leak detection using AE techniques is also being used successfully on boilers, where steam leak detection systems provide early warnings of steam leaks, which allows plant operators to manage the problem cost effectively, often running the plant for weeks following initial detection. These systems use sensors mounted on waveguides welded to the outside of the boiler, making installation straightforward.

Handheld AE leak detection systems are also identifying and quantifying through-valve losses of normally closed steam valves for power generation. Identifying the valves that are allowing the greatest loss is a critical tool in the financial management of these plants.

Leak detection is also being carried out in nuclear applications, where AE systems are installed on various types of nuclear reactor pipework and pressure vessels.

Conclusions

The quantification of through valve losses allows the identification of significant cost savings through loss control; prioritising of maintenance based on quantitative information; speedy and effective operations and maintenance troubleshooting; and the effective control of emissions to the environment.

Tim Bradshaw, General Manager, MISTRAS Group, UK operations. 

In order to better protect industrial control systems from cyber attacks, companies should take heed from the wise words of successful military tacticians and the lessons learned from some of the greatest failures in military defence, says Tim Ricketts

In 2016, NATO officially recognised cyberspace as a warfare domain – an important change that has led many cyber security companies to liken their strategies for preparation and defence to Sun Tzu’s philosophies shared in The Art of War.

While it is important to take heed from the wise words of a successful military tactician and philosopher, it is paramount that we look to history for some of the greatest failures in defence so that you may learn from these too.

This article looks at a historical defence failure that mirrors that of many security breaches in the cyber realm, where a persistent threat will take full advantage of an opportunistic weakness in the defender’s wall.

This historical event took place in Istanbul (then known as Constantinople) in the year 1453, fought by the defending Roman Byzantine rulers and the advancing Ottoman Empire.

The Roman rulers erected a series of defence structures that featured large, high walls and secured entrances, spanning the city and protecting it from conquest.

The legend has it that one of the main gates to the city had been left open by an outbound raiding force. This open gate was quickly discovered by a small group of Ottoman forces, who realised that they could get inside and raise their banner.

The raising of the banner caused panic among the defending forces, who retreated and lost vital ground within the City walls. The ensuing Ottoman forces eventually overwhelmed the city’s internal defences and, as history tells, for the Byzantine and the Roman Empire in the East – the battle was lost.

With the history lecture now out of the way, it is important to pick out the key points presented in this story and take these as golden nuggets:

* Your organisation’s defences may be strong, but will always need entry points.

* Ensure that access to entry points is well reviewed, logged and audited.

* Plan for the worst; be as proactive in your internal defences as your external ones.

* “These lessons learnt are great,” you may be thinking, “But how do they apply to my Industrial Control System?”

Let’s start with the first one: you may not have a wall – but you do have a moat, in the form of an air gap. This keeps your operational network seemingly safe from the outside world, with the ‘jump’ being too great for your conventional attack.

No network, however, is truly isolated from the outside world, just as no city is ever truly isolated by a moat; there needs to be a way in to allow for updates and to access equipment remotely, and this will always leave the possibility for mistakes to be made.

Regular maintenance tasks, such as removing outdated pieces of equipment, could also be likened to our story.

Think of it like this: you have your very own Wall of Constantinople in the form of your firewall, and you have gates through that wall in the form of ports. When an engineer removes that piece of equipment, but doesn’t close the port, then you now have an open gate – one that has turned into an exploitable attack vector.

Products such as Cyber-X can detect these open ports, quickly allowing engineers to close these gates to your operational network.

You will almost certainly understand where your entry points are, but you should also be aware of the times, manner and reasons in which people access them.

An early warning sign to a breach on your network is sporadic and unauthorised access to systems.

Detection of these breaches could help to close gaps or even prevent major incidents, but if you notice that there is an entry point that is infrequently used or is now surplus to requirements, then you should consider its removal.

Products such as Cyber-X learn about your usual network traffic, making it easy to spot traffic that is unusual for your network, such as traffic that occurs during off-peak hours, unusually large packets or unexpected protocols.

Planning for the worst is not the same as admitting defeat, but rather being prepared to recuperate from the worst possible outcome, often meaning that your disaster recovery will be mature and developed enough to restore services as quickly as possible.

Frequently monitoring the state of your network devices allows you to develop customised, efficient and profoundly effective plans that evolve along with your organisation’s scale.

Tim Ricketts is Director of MAC Solutions. 

In an increasingly competitive marketplace, operators of applications such as food and beverage, chemical and pharmaceutical processing are under pressure meet the highest standards of hygiene - and the repercussions of falling below these levels are unthinkable.

Failure to maintain cleanliness standards of electric motors and other equipment can result in product contamination, not to mention reduced efficiency and premature failure.

The problem is that washdowns with high-pressure water jets not only risk damage to motors and drives, they also spray debris onto equipment, which finds its way beneath rating plates and cooling fins. This provides a perfect place for bacteria to thrive, while the ingress of water can permanently damage components.

Solutions exist in the form of waterproof electric motors and variable-speed drives, such as those offered by Gibbons Engineering Group. The company recently launched its stainless steel motor and ABB ACS355 drive package – offering dust-tight equipment that’s fully resistant to high-pressure water jets.

Gibbons’ stainless steel motors have a completely smooth surface free of cooling fins or rating plates – with information laser engraved. There’s no paint to peel, chip or flake off, and the IP69K totally enclosed non-ventilated (TENV) casing means they can withstand powerful water jets.

For optimal speed control and energy efficiency, Gibbons can couple the motors with ABB ACS355 variable-speed drives, which are rated at IP66/67 ingress protection – meaning they’re dust-tight and impervious to water. Plus, a keypad membrane cover means the unit can be operated normally in all conditions.

AW-Lake Company introduces the MicroTRICOR TCM-100 Coriolis Mass Flow Meter– the smallest TRICOR Coriolis meter designed for the accurate measurement of very low flow rates.

This new mass flow meter is suitable for dosing, blending and batching in applications such as chemical injection, precision painting and coating applications, and batch processing associated with liquid or gas handling and dispensing.

The new multivariable instrument reports mass flow, density, concentration, temperature, and volumetric flow in one device.

Without any moving parts such as gears that require maintenance or can corrode and fail, the TCM-100 Coriolis Mass Flow Meter uses smooth tubes through which material flows at rates as low as 5cc/min (300 grams/hr, .001 gallons/min).

Unlike volumetric flow meters, the MicroTRICOR Low Flow Meter measures mass instead of volume, providing for greater accuracy as the mass of a fluid or gas remains constant and is unaffected by changing process conditions such as temperature, pressure and viscosity.

As a result, process engineers get truer readings in all conditions from the MicroTRICOR Mass Meter.

In addition, the unique compact dual tube design provides for a more balanced system with greater resistance to external vibration and pulsating flow.

Offering fast response times, the MicroTRICOR meter deliver high repeatability with long-term operations. With no filter requirements, the low flow mass meter requires little or no maintenance. Units are flushable and simple to clean.

Having all wetted components made of 316L stainless steel, this meter is compatible with most fluids. Multiple connection types are available including NPT, AutoClave, and tubing.

The TCM-100 Mass Flow Meter is suitable for high pressures up to 5,000 psi, and is EX certified with ATEX, IECEx, EAC certifications and a pending CSA rating.

The MicroTRICOR Meter is sold with TCE transmitters that are available with analog, frequency pulse and status outputs.  Transmitters can be ordered as panel mount or remote field mount versions.

Solids handling specialist, Ajax Equipment, has supplied leading speciality chemicals producer, Vertellus, with an agitated screw feeder and screw conveyor for its Teesside, UK plant.

The site supplies monomers and performance enhancers for the plastics and polymers market, as well as, manufacturing advanced intermediates for pharmaceutical, agricultural chemicals and photographic applications.

Capable of holding 3.5T of damp centrifuge cake, the agitated screw feeder is the largest produced by Ajax to date.

The stainless steel unit has a large capacity hopper with multi-bladed agitator to provide gentle agitation to maintain ‘live’ product condition, disturb any potential consolidation and deliver positive infeed to the integral screw feeder.

Once discharged, the cake is transferred to two dryers via a long screw conveyor.

Special care was taken in outlet and screw design to ensure output goes to the appropriate dryers.

The screw feeder and conveyor both feature LynFlow ribbon flights which inhibit adhesive materials from clogging up the screw.

The Type 8652 was designed by Burkert for applications in the pharmaceutical and water treatment industries. It offers users adjustable monitoring and diagnostic functions that improve system availability and process reliability, while at the same time enabling preventive maintenance. An integrated display for this purpose shows detailed on-site information such as the current switching statuses of the pilot and process valves, issues a message if pre-set pressure limit values are exceeded or displays errors such as cable breaks in plain text. During development, particular attention was also devoted to the compact design. The valve island 8652 is significantly smaller than its predecessor and therefore fits perfectly into compact control cabinets that can be placed close to the process valves.

The valve island communicates via common industrial Ethernet protocols or PROFIBUS DP. In sealed ring topologies and PROFINET IO communication, the Media Redundancy Protocol (MRP) for highly available networks ensures that even switch or cable break can be compensated for. This increases system availability and makes processes more reliable.

Every single valve is hot-swap capable, which means it can be replaced during live operation without shutting down the system. As an additional safety function, check valves are used in the exhaust channel. These prevent the unwanted activation of valves by pressure peaks and the resulting mixing of media. Consequently, a reliable process is also guaranteed on the pneumatic side.

Manchester University’s School of Chemical Engineering and Analytical Sciences is leading world class developments in energy efficiency in the process industries. Researchers have incorporated TorqSense transducers into a test rig that is analysing losses in in-line mixers.

Efficient production is fundamentally important to success in the process industries, many of which serve global markets. While there are multiple elements of cost in the production processes, optimising energy consumption is seen as essential because improvements will repay dividends over many years.

The energy consumption involved in in-tank mixing processes is well researched and understood. But with in-line rotor-stator mixers the flow is often controlled independently of the rotor speed and collecting sufficient data to accurately model the process has to date required a large number of experiments.

Now researchers Dr Mike Cooke and T. L. Rogers at Manchester University have developed two simplified methods for obtaining the necessary information for particular stator-rotor mixers: one uses torque measurements, the other heat balance.

Dr Cooke explains that high shear rotor-stator mixers are widely used in process industries, including the manufacture of many food, cosmetic, healthcare products, fine chemicals and pharmaceuticals. Rotor-stator devices provide a focussed delivery of energy, power and shear to accelerate physical processes such as mixing, dissolution, emulsification and deagglomeration.

“To reliably scale-up these devices from laboratory size to industrial scale we need to understand the relationship between rotor speed, flow rate and the energy dissipated,” he says. “The first step is to link the energy dissipation rate to desired process results.”

The scientists created two mixing experiments and set about measuring the torque profile and heat balance. In the first experiment torque was measured by a Sensor Technology’s TorqSense in-line torque meter fitted to the drive shaft.

There are two main sources of potential error when measuring the torque on the rotor shaft: time-based zero-drift and bending moments on the shaft, both of which are easily counteracted with the TorqSense. Other corrections also have to be made for bearing losses, temperature fluctuations etc.

TorqSense proved a good choice for this work because its non-contact operation meant extra drag forces were not added to the system and also allowed rapid assembly and disassembly during the experiments. It uses two piezo-electric combs which are simply glued to the drive shaft at right angles to one another. As the shaft turns it naturally twists along its length very slightly and in proportion to the torque, which deforms the combs changing their piezo-signature. This change is measured wirelessly by a radio frequency pick up and used to monitor the torque.

Its data is output to a very user-friendly computer screen which uses graphics to aid instant interpretations and also automatically logs all data for later analysis.

In fact the School of Chemical Engineering and Analytical Sciences at Manchester University is a major user of TorqSense, having many installed on permanent teaching aids and various research rigs.
“The students like the readout displays, which look no more complicated that a car’s dashboard,” says Dr Cooke. “For us researchers, the ease with which they can be mounted and removed is a God-send in experiments where you are constantly reconfiguring the rig. Also their lack of slip rings means one less set of calculations to account for – and one less fiddly fixing task.”

The conclusion from Dr Cooke’s experiments is that the performance characteristics of in-line mixers can be easily modelled. This lets industrial users calculate their optimum energy consumption and tune their mixer drives accordingly. Power and cost savings will accrue during the whole production period, and make a valuable contribution to the company’s bottom line and green credentials.

To analyse the long term performance and reliability of hard working valves and pumps, serial innovators Manchester-based Bifold Group has adopted radio frequency based torque transducers from Sensor Technology Ltd for two of its specialist test rigs.

By using the power of computer aided design many of Bifold’s products are built to custom designs, yet they are produced to very short lead times thanks to the efficiency of internet communications. To maintain this standard, sample products and components are comprehensively tested so that their reliability and capabilities are never in doubt.
   
So when Bifold wanted to assess the effects of wear on its long-life valves they set about designing a special test rig. Engineer Andrew Laverick recalls: “We wanted to measure the power required to operate the valve to see how it changed over time and with long term use. It was clear that the best way to do this was to measure the torque input over an extended period.”

“We were open to any design concept for the test rig, but soon found ourselves gravitating towards a TorqSense solution because the Sensor Technology engineers were so helpful and really knowledgeable about test rigs.”

TorqSense transducers lend themselves to test rig uses because they are non-contact measuring devices. Attached to the surface of the transducer shaft are two Surface Acoustic Wave (SAW) devices, when torque is applied to the shaft the SAWs react to the applied strain and change their output. The SAW devices are interrogated wirlessly using an RF couple, which passes the SAW data to and from the electronics inside the body of the transducer.

Sensor Technology’s Mark Ingham explains: “All you have to do is set up a TorqSense transducer in the test rig and fire it up. The SAW frequencies reflected back are distorted in proportion to the twist in the test piece, which in turn is proportional to the level of torque. We have some clever electronics to analyse the returning wave and feed out torque values to a computer screen.

“TorqSense has been used on many test rigs over the years and I was delighted to hear the Bifold engineers say how easy it is to use and how robust the software is.”

Laverick again: “As a test engineer you are almost resigned to long set up procedures and software that falls over at the drop of a hat. But Sensor Technology has designed these problems out of their TorqSense equipment, with the result that we were able to complete our long term test procedures with the minimum amount of fuss and heartache and well within the allotted time schedule.”

In fact Bifold has since bought a second TorqSense which is being fitted to a new test rig used to assess the performance of mission critical chemical injection pumps, as used at oil and gas wellheads and on process pipelines.

“This project is proceeding well,” says Laverick, “and is allowing us to further develop our abilities to quickly provide bespoke equipment for ultra demanding applications, safe in the knowledge that it will perform faultlessly over a long working life.”