Improving Process Quality and Reducing Downtime with SSi Gas Analysers

As an industry, heat treatment is probably fairly conservative when it comes to technological progress, but I’m pleased to work for a manufacturer that is constantly expanding, innovating, and developing its product range. In 2001, SSi produced the first PGA3000 to verify and troubleshoot the a gas carburising furnace’s carbon potential. Today, SSi produces (what I think is) the heat treatment industry’s most comprehensive range of gas analysers, comprising:

  • SGA (new) single gas analysers available in OEM or wall mounted versions.
  • PGA portable multi gas analysers.
  • MGA multi gas analysers available in OEM, wall mounted, or rack mounted (new) versions.
  • MZA multi gas, multi zone gas analysers available in wall mounted or Rittal cabinet versions.
The MZA has proven to be an incredibly successful system because it cost-effectively provides valuable process and troubleshooting data for up to 8 zones from a single sensor. Installation and commissioning of a 4-zone system is typically completed in 2-3 days.

Pictured is a recently completed MGA and MZA installation at a UK aerospace manufacturer. The system measures and automatically corrects the Carbon Potential on three pit furnaces and three endothermic gas generators.

Below are some recently installed systems that demonstrate the versatility of the current range of gas analysers:

4 Zone MZA Rittal Cabinet for a global bearing manufacturer

Pictured is the second MZA cabinet designed and built for installation at a bearing manufacturer in Poland. 9205 controllers were installed alongside the MZA to provide automatic correction of COF and highly precise, stable temperature and carbon potential control.

Rack mounted MGA to replace a Siemens Ultramat 23

SSi developed a 19″ rack mounted MGA due, partly, to multiple requests to replace old Siemens Ultramat (and others) gas analysers. As SSi manufactures the complete analyser, including the 3-gas IR sensor, we can provide rapid, cost effective calibration and repair services meaning that lifetime costs are significantly lower than our competitors.

4 Zone standard MZA for a global fastener manufacturer

An MZA system was recently installed and commissioned in Holland. The CQI-9 compliant system automatically monitors continuous furnaces and endothermic gas generators. It saves process engineers many hours (and many miles) per week versus manual checks.

Please contact us to discuss any of the standard or custom systems mentioned in this blog post!

WE HAVE MOVED!

We are very pleased to announce that we have moved to a larger premises on the Tyburn Trading Estate in Birmingham. We have some exciting plans for the new premises which we will reveal in upcoming blog posts.

We are moving stock on the 15th September so please accept our apologies for any compromise in service. We will resume normal service on the 18th September.

Our new address is:

Super Systems Europe
Unit E
Tyburn Trading Estate
Ashold Farm Road
Birmingham
B24 9QG

Our new telephone number is: +44 (0) 121 306 5180

The previous telephone extensions are now invalid. Please ask whoever answers the phone for the new extension and direct dial details.

See a map showing the new location here: www.supersystemseurope.com/contact/head-office

Upgrading A Vacuum Furnace Control System

There is often a tough decision when a vacuum furnace reaches a certain age. Do you scrap it and replace it with a state-of-the-art new furnace? Or do you commit time and resources to upgrade the existing furnace’s control system? Sometimes the driver for this decision may dictate that a furnace is replaced, but there is often a false assumption that an ‘old furnace can not be taught new tricks’. In reality, mechanically, the furnace may be in reasonable condition. The real source of the issue is unsupported, unreliable, out-of -date, non-compliant, and in the worst case, unsafe control technology. Increasingly demanding customers, combined with standards that require more traceability, force heat treaters to ask the question: do we buy a new vacuum furnace or upgrade our existing vacuum furnace control system?

A seemingly complex vacuum furnace actually consists of relatively few components: the shell, hot zone, heating systems, cooling systems, diffusion pump, vacuum pumping system, pipework and valves. Degrading hot zones, cooling jackets, failing diffusion/vacuum pumps can be cleaned, repaired, rebuilt or replaced.

Vacuum Furnace Uniformity

Many vacuum furnaces struggle with passing temperature uniformity survey (TUS), especially where uniformity requirements are tight and strictly enforced in the aerospace sector. Even with routine hot-zone maintenance, this may be inevitable. TUS failures are commonly cited as a reason to discard a furnace. However, even minor modifications to the existing control and heating system can result in drastic improvements.

Heat chambers traditionally have three to five distinct zones with the same number of variable reactance transformers (VRTs). Each VRT’s output is proportional to a command signal and generates from a single silicone-controlled rectifier (SCR), split into three to five distinct signals. Each is manually trimmed via adjustable rheostats. Optimal rheostat settings often vary between temperature ranges which limits the overall uniformity capabilities of the furnace. Huge improvements are achieved by installing an independent SCR per VRT and trimming, through an SSi 9220 for example, the outputs from the controller to the SCR during tuning.

Example of electric heating modification which resulted in a spread reduction at 1050 deg from 10 deg C to 3 deg C. Click to enlarge.

SSi controllers can scale each output at specified temperatures, which improves uniformity at the required set points. It also means we can center the load TC delta around the set point which is a simple but effective way to quickly improve uniformity, since it is deviation from set point that determines total uniformity, not simply the spread between hot and cold TCs.

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Portable Three Gas Analyser: Top 3 Uses

The PGA 3510 portable three/four gas furnace analyser for the carburising/nitriding process is one of SSi’s most popular products. This is largely because it displays and records data that is critical for verifying process quality and maintaining equipment. Below are top three ways SSi Europe engineers use the PGA:

1. Verifying carbon potential (carburising) and dissociation (nitriding).

The large majority of carburising processes are controlled with an in-situ oxygen probe (e.g. the SSi Gold Probe!), a carbon potential PID control loop that adjusts air and/or gas additions using a proportional valves you can see in the image. See a simplified diagram above. Theoretically, with stable carbon monoxide and carbon dioxide values, the carbon potential value on the controller/regulator is the carbon potential of the furnace atmosphere. In practice there are many potential reasons that a controller/regulator’s actual carbon potential value could be false or inaccurate. These include unstable or rich/lean carrier gas being produced by an endogas generator or nitrogen/methanol supply, furnace leaks, oxygen  probe damage or degradation, contaminated reference air, improper installation, calibration status of the controller and many more. A verification is critical to ensuring that the carbon potential on the controller is the carbon potential of the atmosphere in the heat treatment furnace, and is a requirement of heat treatment standard CQI-9.

The same principle applies to gas nitriding where often the only method of atmosphere control is a periodic burette inspection which indicates the % of NH3 which has dissociated. The PGA can be used to verify the burette reading and also provides a Kn value. Where a diluent gas is used (e.g pre-cracked NH3 or nitrogen), burette readings are less useful but the PGA automatically calculates the Kn if the user enters gas flows. With a nitrocarburising atmosphere, the PGA can calculate both Kn and Kc.

2. Identifying furnace air ingress or radiant tube cracks.

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Preventive and Predictive Oxygen Probe Maintenance

Note that, if not burned off, soot will gather around the probe tip and eventually cause sensor failure.

Since starting SSi Europe in 2003, I have always tried to help our customers extend the lifetime of their furnace’s oxygen probes. The most important factor, in my experience, is staff training.

This morning, we (myself and Karina Frampton, Project Administrator) visited a commercial heat treatment supplier to follow up on a staff training session we performed around 1 year ago. The Maintenance Manager asked us if we had noticed that their probe consumption had dropped since the training. He is responsible for 6 Ipsen sealed quench furnaces with SSi Redundant Probe Systems fitted, i.e. 12 oxygen probes in total on site. The furnaces tend to run at pretty high carbon potentials (near to the soot limit), so probes were regularly filling with soot and being returned to us for cleaning, testing and re-certification.  Dani, in the workshop, had been advising during his test reports that the burn-off did not seem to be effective, so during the training we advised that burn-off air pumps were inspected. Some of them were replaced in order to get higher flow during burn-off.

We also advised that regular burn-off checks are performed. During the burn-off, it is important to measure the response of the zirconia element and the probe’s temperature rise or fall. Air should pass the tip in significant volumes (typically between 3-6 l/min), so the mV should drop to around 200 mV (remember, as air/oxygen % goes up, mV goes down). If this is not happening, there will not be enough oxygen present to burn-off the soot. The temperature of the tip (only measurable from an internal TC) is a good indication that burn-off is occurring, and that the flame tip is beyond the probe sheath. You will see a rise of between 5 and 25 deg C if soot is being burned correctly. If the temperature rise is higher than this, the flame tip is too close to zirconia element. Over time this will affect the probe readings and in the worst case scenario, cause a material failure, so burn-off airflow should be adjusted.

Extreme example of damage to the tip of an oxygen probe sheath due to overheating during burn-off.

By training operators, replacing a few burn-off pumps, and regularly checking the burn-off performance, the heat treater has significantly reduced the furnace running costs (by thousands of £s), but more importantly, reduced reworks and unplanned furnace downtime.

Those are a couple of simple items. By combining those with quarterly impedance and recovery time tests (which are performed automatically in SSi controllers but can also be performed manually), we can start to analyse the level of deterioration/degradation of the sensor. Those values (see image below) can be recorded and charted in a SCADA system. When the trend begins to accelerate, or the values exceeds pre-defined tolerances, we know that the probe is beginning to deteriorate so know when to return it for inspection.

Probe data, recorded and charted in a SCADA system as part of predictive maintenance plan.

Many furnaces have inadequate reference and burn-off air supplies, which may be reducing the life of the oxygen probes. It is definitely worth checking them to ensure that they are not the cause of furnace problems or quality issues. Let us know if we can help with training or advice!

 

Heat Treat Forum in Poland, April 2017

SSi will be attending the 4th Central Eastern European Heat Treatment Forum & Exhibition on April 26-27, 2017 in Wroclaw, Poland alongside our distributor Avion. This annual international conference and exhibition of the heat treatment industry in Poland and Central Eastern Europe was held for the first time in 2014.

As a founding exhibitor, we’ve been pleased to see its progression and we’re looking forward to a interesting conference and busy exhibition.

We will be delivering a presentation on CQI-9 compliance with specific regard to oxygen probes and furnace maintenance. Please see the official website for more information: www.heat-treatment-forum.pl/homepage 

CQI-9 Technical Seminar in Turkey

James Cross speaks to an audience in Pendik, Istanbul about applying core automotive tools.

James Cross speaks to an audience in Pendik, Istanbul about applying core automotive tools.

CQI-9 appears to have gained serious traction in Turkey in the past year so Damian Bratcher and myself presented a technical seminar in in Istanbul last week (December 22nd). The main topic was CQI-9, but we also covered NADCAP and AMS2750E. Turkey has a well established automotive industry but we are getting more requests for AMS 2750E compliance every year.

We had great feedback (especially regarding the specific details we provided about CQI-9 compliance and failure mode effect analysis (FMEA) best practice in the heat treatment industry) so thanks to all those that attended for taking the time out of their schedules for joining the session!

We see technical seminars as a great way of imparting our ideas and expertise to our customers so please let us know if you would like us to visit your factory, company, territory, country in 2017!

Advanced technical training for SSi Europe and Partners

SSi Europe and our technical partners visited SSi headquarters in Cincinatti, Ohio in December for an intensive 4 day training course. As attendees all already had a good understanding of heat treatment and SSi products, the aim of the training was to get into the detail of new products and systems as well as to spend time with the excellent new nitriding test furnace. It is also a great chance to talk to SSi design, production, and R&D engineers about the main challenges that European heat treaters face. That feedback loop is partly why SSi is one of the few truly global suppliers to the heat treatment industry with a significant presence in every region.

The training’s main topics were:

  • Nitriding and nitrocarburising metallurgy.
  • DataCenter (new SSi SCADA system).
  • Vacuum furnace control technology.
  • Endothermic gas generator turndown system commissioning.

There is no subsitute for practice: we designed programmes, phsycially loaded, ran, unloaded and analysed nitriding and nitrocarburising processes supervised by SSi’s nitriding expert Chuck Thomas.

We also spent time on the new AutoGen endothermic gas generator turndown system using SSi’s new e-Valve control valve.

New Website Live

We have just pushed the button on the new website. It will be a constantly evolving site, with new blog posts, products and features, and resources available on a weekly basis.

Our focus in developing the site was on ease of support (both sales and technical support), ease of navigation (products have been categorised by type and process), and we have uploaded a huge number of new products and technical documentation.

The new site is also completely responsive so should be extremely easy to use on phones/tablets/laptops.

Press ctrl+D to bookmark the site!

Let us know if you have any feedback or questions about the new site.

 

Refurbished Stock

We have added a clearance section which will be updated to include products that have been refurbished, repaired, and/or re-certified in our UK workshop.

Product performance and quality is guaranteed for 12 months (unless otherwise stated) but there may be cosmetic damage to the product or its packaging.

You can visit the clearance page here: www.supersystemseurope.com/clearance-items.

Please contact me at workshop@supersystemseurope.com to discuss any of the items listed!