Month: June 2016

Twelve tips for better cylinder selection

Guest contributor: Marty Hegyi Product Manager, Cylinders, Bosch Rexroth Corp.

Here’s how to design hydraulic cylinders that improve performance, last longer and cost less.

Hydraulic cylinders harness fluid pressure and flow to generate linear motion and force, and they work well in both industrial machines, like presses and plastic-molding machines, and in mobile equipment, like excavators and mining trucks. And when compared with pneumatic, mechanical or electric linear-motion systems, hydraulics can be simpler, more durable and offer significantly greater power density.

Rexroth-photo-1_large-hydraulic-cylinders

Bosch Rexroth builds large hydraulic cylinders with bores to 1.5m and strokes to 24 m

Hydraulic cylinders are available in an impressive array of types and sizes to meet a wide range of application needs. Choosing the right cylinder is critical for maximum performance and reliability. Here are 12 practical tips for selecting, sizing and operating the best one for a job.

Selection considerations

1. Choose the right cylinder type. Two basic hydraulic cylinder designs for industrial applications are tie-rod and welded cylinders.

Tie-rod cylinders use high-strength threaded steel tie rods on the outside of the cylinder housing for additional strength and stability. In the U.S., this is the most common cylinder type. They’re used on most general industrial applications, such as plastics machinery and machine tools, although they tend to be limited to 3,000 psi maximum operating pressure. The cylinders are built to NFPA standards, which makes their dimensions and pressure ratings interchangeable with any other cylinder built to that standard.

Welded or mill-type cylinders have a heavy-duty housing with a barrel welded or bolted directly to the end caps and require no tie rods. Designed for higher pressures, to 5,000 psi

Rexroth-photo-3_mill-type-cylinder

Mill-type cylinders have a heavy-duty housing with a barrel welded or bolted directly to the end caps

Mill -type cylinders have a heavy-duty housing with a barrel welded or bolted directly to the end caps and require no tie-rods

or greater, they are generally preferred in more-rugged applications such as presses, steel mills and offshore settings with harsh environments and wide temperature swings.

Unlike U.S. OEMs, European manufacturers typically use mill-type cylinders in almost all general industrial applications. (They also use tie-rod cylinders, but generally for lower-pressure tasks up to 160 bar (2,350 psi).) However, due to the design, tie-rod cylinders are less expensive than mill-type cylinders—another reason for widespread use in the U.S.

Also keep in mind that cylinders are often customized. NFPA cylinder standards dictate dimensions, pressure ratings, type of mountings, and so on—they’re standard catalog products. However, engineers designing custom machinery often need to deviate from the standards with special mountings, port sizes or configurations to suit a particular application. About 60% of the cylinders sold in the U.S. are catalog items, while 40% are modified products with unique requirements.

2. Select the proper mountings. Mounting methods also play an important role in cylinder performance. The cylinder mounting method first depends on whether the cylinder body is stationary or pivots.

For stationary cylinders, fixed mounts on the centerline of the cylinder are usually best for straight-line force transfer and minimal wear. Among the different variations, flange mounts are generally preferred. Loads are centered on the cylinder and opposing forces are equally balanced on rectangular or round flanges. They’re strong and rigid, but have little tolerance for misalignment. Experts recommend cap-end mounts for thrust loads and rod-end mounts for pull loads.

Centerline lug mounts also absorb force on the centerline, but require dowel pins to secure the lugs to prevent movement at higher pressures or under shock conditions.

Side-mounted or foot-mounted cylinders are relatively easy to install and service, but

Rexroth-BR_Tie-Rod-Cylinders

Tie-rod cylinders have high-strength threaded steel tie rods on the outside of the cylinder  housing for added strength and stability

they generate offset loads. The mounts experience a bending moment as the cylinder applies force to a load, potentially increasing wear and tear. Heavy loading tends to make long-stroke, small-bore cylinders unstable.

Side and foot mounts need to be well aligned and on the same plane, and the load supported and guided. Otherwise, induced side loads due to misalignment lead to cylinder wear and seal leaks. Engineers also must be concerned with shear forces on the bolts. Add a dowel or shear pin and keyway behind the feet to prevent the forces from potentially shearing the mounting bolts. If necessary for extra support, add another set of foot mounts in the cylinder midsection in addition to those on the head and cap ends.

3. Select the right pivot mountings when the cylinder body moves. Pivot mounts absorb force on the cylinder centerline and let a cylinder change alignment in one plane. Common types include clevis, trunnion and spherical-bearing mounts.

Clevis mounts can be used in any orientation and are generally recommended for short strokes and small to medium-bore cylinders. Cylinder engineers prefer clevis mounts with spherical bearings over those with plain bearings because they allow for a bit more misalignment and are, thus, a bit more forgiving. However, if using a spherical bearing on a rear clevis, they also recommend a rod-end attachment that pivots—such as a spherical rod eye. The combination helps compensate for any side loading or potential misalignment.

Trunnion mounts come in head, mid and rear-mount versions. The mid-trunnion design is likely most common, as it offers designers a bit more flexibility. They can be specified exactly in the cylinder mid-section or most anywhere toward the front or rear as the application demands. Once specified, however, the mount is not adjustable.

Sizing considerations

For all types of cylinders, important parameters include stroke, bore diameter, rod diameter and pressure rating.

4. Piston-rod diameter is critical. Perhaps the most common error in hydraulic design is underspecifying the piston rod, making a cylinder more prone to stress, wear and failure. Piston-rod diameters can range from 0.5 to more than 20 in., but they must be sized for the available loads. In a push application, it is extremely important to size the rod diameter properly, based on Euler calculations, to avoid rod buckling or bending.

When designing a cylinder to generate a required force, sizing the rod is always the first consideration. From there, work backward and determine bore size for the available pressure, and so on.

5. Prevent rod bending. In cylinders with long strokes, a fully extended rod can bend under its own weight. Excessive bending leads to wear and damage to seals and bearings. It could even cock the piston inside the bore, which can score and damage the inner surface of the cylinder. Rod deflection should never exceed 1 to 2 mm.

Cylinder rods that are at risk for bending or misalignment require additional support. Depending on the stroke length, a stop tube—which increases the bearing area of the cylinder—may be required to prevent excessive wear and jack-knifing. Engineers might also consider a larger diameter rod, which increases strength. But that also increases weight and may be self-defeating, so do the math carefully. In extreme cases, users may also need to add external mechanical support for the rod, such as a saddle-type bearing.

6. Watch out for impact loads. Stroke length, the distance needed to push or pull a load, can vary from less than an inch to several feet or more. But when the cylinder extends or retracts, ensure that the piston doesn’t bottom out and generate impact loads at the end of stroke. Engineers have several options: Add internal cushions to decelerate the load near the end of stroke; add an external mechanical stop that prevents the cylinder from bottoming out; or use proportional-valve technology to precisely meter flow and safely decelerate the load.

7. Weigh bore diameter versus operating pressure. To produce a given amount of force, engineers can specify large-bore cylinders that operate at low pressures, or vice versa. Generally, systems that operate at higher pressures but with smaller cylinders are more cost effective. Also the benefits cascade. Smaller cylinders require less flow and, in turn, smaller pumps, lines, valves and so on. Many installations see an overall cost reduction by moving to higher pressures.

That said, cylinders are rated for both nominal (standard) pressure and test pressure to account for variations. Systems should never exceed the nominal rated design pressure of a cylinder.

8. Add a factor of safety. While design calculations are essential, real-world operations differ from theoretical results. Always assume peak loads will require additional force. The rule of thumb is to choose a cylinder with a tonnage rating of 20% more than required for the load. That compensates for losses like friction from the load, efficiency losses in the hydraulics, actual pressure below the rated system pressure, slip-stick on cylinder seals and bearings, and so on.

Operating considerations

Cylinder parameters like stroke and force must match machine requirements, but that is only half the challenge. Environmental and operating demands also play a major part in determining a cylinder’s ultimate success.

9. Match the seals to the job.Seals are probably the most vulnerable aspect of a hydraulic system. Proper seals can reduce friction and wear and increase service life, while the wrong seal leads to downtime and maintenance headaches. It probably goes without saying, but ensure the seal material is compatible with the fluid. Most hydraulics use a form of mineral oil, and standard Buna-N seals tend to work well. But applications involving synthetic fluids, such as phosphate esters, require Viton seals. Polyurethane is also incompatible with high water-based fluid such as water glycol.

Regardless of the fluid, keep it clean. Contamination and dirt in the fluid will damage Rexroth-BR_CylinderApplicationseals. It can also score the inside of the barrel and eventually ruin the cylinder.

If operating temperatures exceed 300° F, standard Buna-N nitrile rubber seals may fail. Viton synthetic rubber seals generally handle temperatures to 400° F and fluorocarbon seals even higher. When in doubt, assume conditions will be worse than they first appear.

10. Add a gland drain. Probably 90% of cylinder failures are due to the seals. That holds even if engineers specify the proper seals for the fluid, pressure, environment and application as they wear out over time and need replacement. Most experts recommend that seals should be maintained periodically, rather than waiting for failure at a usually inopportune time.

If cylinders are in hard-to-access locations that makes maintenance difficult, or if leaks will damage products or lead to costly downtime, order cylinders with a “gland drain.” This is a special port machined into the cylinder head between primary and secondary seals; or between primary and rod wiper. Then, if the primary rod seal begins to fail and leak, oil bypasses the seal and flows out the gland-drain port—generally through tubing to a collection bottle. If oil collects in the normally empty bottle, it gives a visual indication that seals are wearing out and will soon need replacement.

Cylinders usually have a secondary rod seal or a double-lip rod wiper that temporarily prevents oil from leaking out the rod end, giving maintenance personnel time to schedule repairs.

11. Watch the materials. The type of metal used for the cylinder head, base and bearing can make a significant difference. Most cylinders use SAE 660 bronze for rod bearings and medium-grade carbon steel for heads and bases, which is adequate for many applications. But stronger material, such as 65-45-12 ductile iron for rod bearings, can provide a sizable performance advantage for tough industrial tasks.

Also consider extreme temperatures. Typical carbon steels used in cylinder components are generally suited for around –5 to 200° F. In arctic conditions well below 0° F, for example, standard steel can become brittle and may require alternative materials.

12. Protect the rod. Because the piston rod meets the outside environment, it must resist attack from water, salt air, corrosives, and other harmful substances. In general industrial applications, carbon steel with chrome plating is the norm. But in wet or high humidity environments, such as marine hydraulics, 17-4PH stainless steel with chrome plating is used for most piston rods. Some cylinder manufacturers offer special protective coatings. Bosch Rexroth, for example, offers Enduroq, which is a proprietary thermal-spray coating or plasma-welded overlay that’s applied to rods for extreme corrosion protection and high wear resistance. It’s used in harsh environments, typically for specialty large-bore, long-stroke cylinders.

For dirty, abrasive conditions, engineers have a love/hate relationship with protective rod boots. Installing a boot over the rod keeps out dirt, metal shavings and other external contamination that would otherwise damage the rod and eventually the seals. However, if the boot punctures or rips, dirt gets drawn in and may not get out, which is worse than no boot at all. Maintenance personnel must routinely check for worn or torn boots that could accelerate damage to the cylinder.

Don’t overlook sizing software

Sizing software for cylinders is a great tool, but more engineers need to take advantage of the benefits it offers. These programs address most, if not all, of the pertinent questions designers need to answer to spec the right cylinder.

One such program developed by Bosch Rexroth is the Interactive Catalog System Rexroth-BR_Catalog2 (1)(www.boschrexroth.com/ics). It lets users enter parameters like force, pressure, load, angle of installation and mounting type, and the software sizes the cylinder, lists variations that meet the criteria and offers possible alternatives. It also lets engineers select and test cylinders on-screen before specifying the actual components. In addition, ICS generates dimensional drawings and 2D or 3D models for direct import into AutoCAD or other CAD software.

CMAFH Resources

Shop online for Rexroth hydraulic products here

Considerations for Industrial Enclosure Cooling

Guest contributor, Eric Corzine, Product Manager – Climate Control, Rittal

Data Centers and server racks run hot. Protecting the technology backbone of your company means managing air flow, temperature, energy consumption and cooling technology.

Rittal, the world’s largest enclosure manufacturer and a leader in thermal management of electrical, electronic and IT equipment, offers some important guidelines to ensure your equipment stays in optimum condition. The following tips are based on decades of practical experience in the use of enclosures climate control solution in industrial environments. By ensuring sufficient planning and maintenance guidelines are in place, control cabinets and electronic enclosures can be last longer and be more energy-efficient.

7 Considerations for More Efficient Enclosures

1. Devices and electrical components must be installed in the enclosure in accordance with the manufacturer instructions. Storage space for necessary documents and circuit diagrams should also be taken into account during the planning phase.

2. When arranging the components in the enclosure, verify that the cooling air flows from top to bottom. You can ensure this in the planning stages by properly routing the air flow away from the electronic components. When roof-mounted units are used, particular attention needs to be paid to the air flow from blowers built into electrical components. The use of air duct systems is advisable in the case of roof-mounted cooling units

Proper Enclosure Heat Dissipation

3. There should be sufficient space for air to flow between the parts and electrical components.

4. Air intake openings of climate control components must not be obstructed by electrical devices equipment or cable ducts. With all climate control solutions, the cold air should always be routed close to drive units. This is where the greatest heat losses occur. This arrangement ensures that the cold supply air from the climate control solution optimally cools the drive units without losses.

Air intake design for cooling enclosures

5. Internal temperatures of the enclosure should always be set to +35◦C. There is no technical justification for setting the temperature any lower. If the temperature inside the enclosure is any lower, condensation will be significantly increased.

6. Institute a systematic cleaning cycle. As most climate control components are used in industrial environments external filters of the climate control must be maintained to ensure long-lasting operation.

7. Ensure the correct filters are used for the industry application.

PU Filter for Industrial Enclosure Cooling

In heavily dust-laden atmospheres, PU filters should be used and replaced on a regular basis. Cooling units with Ri Nano coating typically do not need a dust filter.

Metal Filter for Enclosures

If the air is oil-contaminated, use metal filters. These separate the oil condensate from the air and can be cleaned with appropriate detergents

Textile Enclosure Lint Filter

In the textile industry, the use of lint filters is recommended.

Fiber Mat Filter

Chopped fibre mat filters are not suitable for cooling units.

CMAFH Rittal Resources:

Rittal Wallmount Program

Rittal Enclosure and Process Cooling handbook

Rittal Innovations 2016

How do I see PLC data from my smartphone?

Guest contributor, Pat Millot, Balluff

From my smartphone, I can do anything from making coffee to adjusting my home thermostat. This wave of appliances and other physical devices connecting and communicating through a network is known as the Internet of Things and it’s playing a crucial role in industry. With the Industrial Internet of Things (IIoT) we can now monitor PLC data without ever intruding on the PLC. Let’s take a look at how I implemented PLC tags on a web application.

IIoT_computer The first step is to download OPC UA historian software. OPC UA stands for Open Platform Communications Unified Architecture. OPC is a client/server communication standard that was made as a gateway between the PLC and a Windows PC. The UA was added as an upgrade that allowed communication across other operating systems such as Linux and iOS along with other added functionality improvements. Once this software is running and the PLC and PC are communicating, we can work on hosting that data.

IIoT_StructureHosting the controller data can seem like a daunting task at first due to the many different options in software and programming languages to use. For example: Ruby, PHP, ASP, ASP.NET and much more are available for back-end development. For my web app, I used SQL to host the data from the OPC UA software. As for the back-end, I went with node.js because it has great packages for working with SQL; in addition to the fact that node.js uses JavaScript syntax which I’m familiar with. The front end of the app was written with HTML and CSS with JavaScript for interactivity. With all these elements in place, I was ready to host the server on the PC to host PLC data.

With smart IO-Link sensors on our conveyor I was able to look at diagnostic and functional data in the PLC and setup an interactive screen at the conveyor for viewing production and maintenance information.

And now I can even check my sensor outputs with the same smartphone that just made my coffee and adjusted my office’s temperature.

IIoT_warehouse

You can learn more about the Industrial Internet of Things at www.balluff.us.

Shop Balluff products online at www.cmafh.com

Hydraulic Training you can get excited about!

Roxann Machac,  CMA/Flodyne/Hydradyne
Think for a moment on the subject of hydraulic training.   Does it conjure up images of stale textbooks or content so dull it could make an insomniac sleep peacefully?  Do you believe that only inexperienced workers need hydraulic training? Do you expect hydraulic training to be expensive, and can you even spare an employee –  or yourself – to be away from the job for four days?

Let’s go over these training notions and myths starting with some background info about our training program. CMAFH has offered hydraulic training to our customers  in Illinois, Wisconsin, Northern Indiana and Iowa for many years, but we have had the greatest success during the past ten years with our dedicated Bosch Rexroth training specialists, and we can’t say enough good things about them.  Neither can our customers.

  • “Jim makes difficult content easy to understand.” Chris F.
  • “I can take what I have learned this week and apply it immediately to my job. I can already see that I am going to save my company a lot of money if we make these changes.” John S.
  • “Jim taught me a different way to look at circuits. He helped me to better understand some components and cleaned up questions that I have had for awhile.” Mike D.
  • Steve showed me what I was actually doing when I adjusted components. This instructor is very knowledgeable!!”

Our instructors have worked hands on with the equipment our customers use: hydraulic systems for stamping presses, machine tools, mobile hydraulic equipment, oil drilling equipment, plastic injection machines and more. Their experience allows them to  present hydraulic concepts in a way that students relate to, bringing hydraulic theory to life using real world examples.  The only “textbook” used is a notebook of Bosch Rexroth component diagrams, and the students also get daily lab exercise sheets that they work on at the test stands.  Our hydraulic classes have never a dull moment – they are dynamic, hands-on, interesting and challenging!

Who needs hydraulic training?

Training & Repair dept 034.jpg

People who are just starting out in hydraulics will benefit from hydraulic training, but you may be surprised to learn that even seasoned hydraulic veterans appreciate our Basic and Advanced Hydraulic classes!  Those who manage hydraulic system improvement, system modification and/or system design tell us that there is always something new to learn or something that they have missed.

Better basic hydraulic knowledge helps you to improve machine efficiency and prevent machine breakdowns.  Training is the key to understanding what your machines are doing and why. When a student goes back to work and his/her manager can see the improvements, they often cycle all of their hydraulic area employees through our classes!  It is not unusual to see repeat customers attend the same class every few years as a refresher!

Is hydraulic training expensive?  

“If you think education is expensive, try ignorance.” We believe that Hydraulic training is
worth the cost if it is a good quality curriculum and class – and we believe that every one of our customers with hydraulic equipment would benefit from hydraulic training.  Cost of training becomes less relevant when you consider this;  many of our customers tell us that our training classes pay for themselves!

CMAFH training provides exceptional value for two reasons: we offer great quality training at a reduced cost.  CMAFH classes fill quickly because we offer low cost training to our customers as a value-added benefit.  We don’t open the classes up to the public, rather we keep the classes small and invite our industrial manufacturing customer base.

Many customers inquire about hosting a custom or private training at their facility or ours, and this is great way to get a lot of people trained at once on your own equipment.  There isn’t a better way to train your group!   One thing to be aware of, however,  is that custom classes bear the full cost of a standard training event.  To get a ballpark idea of that cost, take the tuition for a single attendee at a standard class and multiply that by 16. It may be more or less depending on travel expenses, length of training, test stand freight, custom curriculum planning etc.

The biggest problem with Hydraulic Training

The single biggest problem customers have with hydraulic training is not the cost, it’s finding the time to schedule employees or themselves to come to training!   The following scenario is all too common:

Mike has heard a lot of good things about our program, and he is excited about taking training. In January, he gets approval and a PO and signs up for an upcoming Hydraulic training class that will be held in May.  The Friday before the class, Mike suddenly realizes he is “too busy” to attend and calls regretfully to reschedule.  We have had a few people repeatedly reschedule themselves right into the following year!

No one should bear the burden of being the only one who can keep a plant running! Everyone deserves time to invest in themselves.  If you want to enable quality improvements at your facility and make yourself a more valuable employee, you will need to make the time for training.

Tactics that have worked:  Try staggering attendees so that individuals attend different sessions and can cover for one another at work.  Or you can wait until a traditionally slow time to schedule most of your training.  No matter how you do it, training is an important part of the job and will contribute greatly to your success.

What NOT to look for in a training program

There are many sources of hydraulic training available from online courses, longer duration vocational courses to a myriad of short term classes provided by companies that you may have never heard of.  A few red flags: A person who reads mainly from a book or a power point is not a reality-based instructor.  An instructor who has never actually worked in hydraulics will not understand the problems that you may be experiencing.  And an instructor who does not sincerely love what he or she does can not be counted on to give you the best possible training.  Some of this you will not discover until you get into the class, so it’s always a good idea to ask for referrals.

The best thing about our training program

The best thing about CMAFH’s training program is that our students really do walk away with concrete knowledge that they can apply immediately.  We see the sparkle in their eyes and hear the excitement in their voices – they can’t wait to get back and use what they have learned. In addition to the other products and services CMAFH provides to help our customers excel; our training program is also empowering people to be their best, and that’s something we are proud of.

DSCN4827.JPG

CMAFH Training Resources

Basic Hydraulic Outline and 20 ideas you will take back to work and use after attending our hydraulic training 

Basic Hydraulic Training 

Advanced Hydraulic Training 

Understanding Proportional Valves Training 

 

Which cable is best for your application?

Guest contributor, Janet Czubek, Balluff

There are many different types of cable jackets and each jacket works well in a specific application.  The three main sensor cable jackets are PVC (Polyvinyl Chloride), PUR (polyurethane) and TPE (thermoplastic elastomer). Each jacket type has different benefits like washdown, abrasion resistant or high flexing applications.  Finding the correct jacket type for your application can extend the life of the cable.PVC

PVC is a general purpose cable and is widely available.  It is a common cable, and typically has the best price point.  PVC has a high moisture resistance, which makes it a good choice for wash-down applications.

PURPUR is found mostly in Asia and Europe.  This cable jacket type has good resistance against abrasion, oil and ozone.  PUR is known for being Halogen free, not containing: chlorine, iodine, fluorine, bromine or astatine.  This jacket type does have limited temperature range compared to the other jacket types, -40…80⁰C.

TPETPE is flexible, recyclable and has excellent cold temperature characteristics, -50…125⁰C.  This cable is resistant against aging in the sunlight, UV and ozone.  TPE has a high-flex rating, typically 10 million.

The table below details the resistance to different conditions. Note that these relative ratings are based on average performance. Special selective compounding of the jacket can improve performance.

resistanceto2

Choosing the right jacket type can help reduce failures in the field, reducing downtime and costs.  Please visit www.balluff.us to see Balluff’s offering of sensor cables in PVC, PUR and TPE.

Nine steps to the proper drive

Guest contributor, Bosch Rexroth

A fully structured approach, well-founded knowledge of the formulae and a fundamental understanding of the technology are essential to designing drives. These are the prerequisites for perfect matching of the machine and the drive.18089-x734_w734

Drive engineering is undertaken when the machine is initially designed, and also when the requirements for the machine have changed or a retrofit is due. Leaving excess tolerances – either upward or downward – is counterproductive for the design. If the drive is under-dimensioned, then the machine will not achieve the desired performance level and, in the worst case, the drive will have to be changed out for a more powerful one. That involves major outlays. The procurement costs will rise and because of poor efficiency, the life-cycle costs will increase. But what does designing a drive mean? It means laying out the motor’s torque curve so that it ideally matches the needs of the machine being served.

Technical understanding is a prerequisite

Software can provide assistance when calculating and planning the drive. It can save time, for example, when several versions have to be analyzed. With the help of the IndraSize engineering tool made by Rexroth, users can select IndraDyn motors and IndraDrive drives simply by entering parameters. But in spite of this support, the technician or engineer has to bring with him or her a fundamental understanding of the technology involved. Technical understanding will allow critical magnitudes to be taken into account so that  we will recognize how the drive might be optimized. Whether with software support or without – the calculations for the proper drive can be carried out in nine clear steps.

ProperDrive_complete_w486

Electric Drives & Controls Product Catalog: http://www.boschrexroth.com/dcc/Vornavigation/VorNavi.cfm?PageID=g97568

Rexroth IndraSize – Turbo for Drive Sizing:  https://www.boschrexroth.com/en/xc/products/product-support/econfigurators-and-tools/indrasize/indrasize-2

Acids Can Put Your Sensors in a Pickle

Guest contributor,  Henry Menke, Balluff

In many types of metals production, pickling is a process that is essential to removing impurities and contaminants from the surface of the material prior to further processing, such as the application of anti-corrosion coatings.

In steel production, two common pickling solutions or pickle liquors are hydrochloric acid (HCl) and sulfuric acid (H2SO4). Both of these acids are very effective at removing rust and iron oxide scale from the steel prior to additional processing, for example galvanizing or rolling. The choice of acid depends on the processing temperature, the type of steel being processed, and environmental containment and recovery considerations. Hydrochloric acid creates corrosive fumes when heated, so it typically must be used at lower temperatures where processing times are longer. It is also more expensive to recover when spent. Sulfuric acid can be used at higher temperatures for faster processing, but it can attack the base metal more aggressively and create embrittlement due to hydrogen diffusion into the metal.

Acids can be just as tough on all of the equipment involved in the pickling lines, including sensors. When selecting sensors for use in areas involving liquid acid solutions and gaseous fumes and vapors, care must be given to the types of acids involved and to the materials used in the construction of the sensor, particularly the materials that may be in direct contact with the media.

PressureSensor

A pressure sensor specifically designed for use with acidic media, at temperatures up to 125 degrees C.

A manufacturer of silicon steel was having issues with frequent failure of mechanical pressure sensors on the pickling line, due to the effects of severe corrosion from hydrochloric acid at 25% concentration. After determination of the root cause of these failures and evaluation of alternatives, the maintenance team selected an electronic pressure sensor with a process connection custom-made from PVDF (polyvinylidene fluoride), a VitonTM O-ring, and a ceramic (rather than standard stainless steel) pressure diaphragm. This changeover eliminated the corroded mechanical pressure sensors as an ongoing maintenance problem, increasing equipment availability and freeing up maintenance personnel to address other issues on the line.