The hot zone is a critical component of a vacuum furnace, responsible for generating and maintaining the precise temperatures required for heat treatment.
“To me, the hot zone is the most important part of the furnace. It’s the key ingredient that makes heat treating possible.” – Brett Bird, Ipsen Production Supervisor
Bird is proud of the work that his team in Pecatonica, Illinois does assembling hot zones. “Our guys could assemble a TITAN H6 hot zone blindfolded,” Bird explained. “We’re able to make sure that every part of the assembly will meet quality standards before the plenum even moves onto the production floor.”
Before the Pecatonica assembly team starts their work on a hot zone, it’s worth taking a step back to look at the whole process of building a hot zone from start to finish.
Getting the Call
A hot zone can take one of two paths: it’s either installed in a new Ipsen furnace or delivered as a replacement for an existing furnace that’s been in operation for years.
New equipment orders are straightforward: each Ipsen furnace model has a standard hot zone that can be modified based on the customer’s requirements. Once a new furnace order has been placed, engineering reviews the plans and requested modifications. Then the order is submitted with all the engineering drawings to Ipsen’s Souderton, Pennsylvania plant to start manufacturing parts for the kit and gathering the relevant sub-assemblies.
Hot zone replacements or retrofits follow a different process—one that can range from routine to highly complex, according to Aaron Bolhous, Ipsen’s Hot Zone Product Leader.
“When a customer reaches out to us in need of a new hot zone for their furnace, that’s when I get involved,” Bolhous began. “These furnaces are already installed, working in a facility with well-established routines. Some may have had aftermarket modifications. A typical hot zone’s lifespan is between five and seven years, depending on the processes it runs. On occasion, we will encounter furnaces that have been operating for twenty years or so that may have had two or three replacements already.”
Each case is unique. Some customers might approach Ipsen knowing that they’ll have a need for a hot zone in a year’s time and want to have the replacement ready to go, while others may wait to make the call at a time of an imminent breakdown.
“About 90% of my hot zone inquiries come from Ipsen’s representatives – field service or sales teams. Quite often, the calls come when a customer experiences a hot zone malfunction, has missing or damaged pieces, or is showing signs of deterioration in the insulation.” – Aaron Bolhous, Ipsen Hot Zone Product Leader
At this point Bolhous can review the circumstances of the order with the technician, recommend temporary solutions, and start the process of ordering either a new hot zone, a hot zone rebuild kit, or scheduling a full hot zone rebuild.
Hot zone rebuild kits can reuse a functioning plenum, removing the old insulation, elements, and other end-of-life parts, replacing them all with entirely new parts custom designed for that specific furnace. Bolhous explained that “the customer could opt to have us ship the rebuild kit directly to them. This would include all the components needed for an on-site rebuild. Either Ipsen’s field service team or the customer’s maintenance team would do the tear-down and rebuild in place.”
While some customers may want to rebuild their own hot zone, others have opted to send their hot zone to Ipsen for a rebuild. “For us to rebuild the hot zone, the customer would strip out the old insulation and elements and send the plenum to our Souderton plant. There we would test the plenum’s integrity, and once we can confirm the plenum meets quality standards, we can rebuild it as we would a new hot zone.”
Sometimes a rebuild isn’t the best solution – particularly if there has been any damage to the plenum from years of operation. Quite often, customers are looking for a little more assurance for a long-term solution. Factors like these often make requesting a quote for a new hot zone the most practical solution.
“If the existing hot zone in question is older than ten years, and a replacement hot zone is the correct plan, we typically will have an engineering visit built into the quote as a part of a proposal to make sure that any aftermarket modifications made to the furnace are properly recorded. We want to ensure that the new hot zone is either an exact match to the one it’s replacing, or appropriate for the vessel it’s going to live in,” Bolhous explained.
Wear and tear isn’t the only reason a customer might want to replace their hot zone. “We had a customer recently that wanted to replace an all-metal hot zone with a graphite hot zone that uses molybdenum elements. Aftermarket modifications can be tricky situations, but we are able to take what the customer wants and bring their request to our engineering team to see if it’s feasible.” Bolhous noted, “By doing that, we could find out that the solution may be simple because we’ve done it before, or it may be complex enough to require some amount of additional engineering. We’ll make new drawings, track the updated costs, and go from there.”
From Order to Production
Once an order for a new hot zone has been placed, Bolhous hands off the design documents to production, checks the current lead time, responds to the customer with a schedule and due dates, and triggers the go-ahead for ordering parts to send to assembly. That’s when the team in Souderton gets involved.
Ipsen’s Souderton, Pennsylvania plant is the home of production and assembly for Ipsen hot zones for both new equipment and after-market sales. Every component of a hot zone that goes into a customer’s furnace is plotted out, tracked, inspected and assembled. Schedules are reviewed, milestones are set, and customer ship dates are estimated.
“Turnaround time is often dependent on the lead times for the components of a furnace,” Christopher Enwright, Ipsen’s Manufacturing Manager at Souderton, explained. “Once we have sourced and reviewed each component, the job order generates all of the work orders needed for use on our shop floor.”
This process starts with the sales order. “Once we get the sales order, our project manager and I put the order into our hot zone schedule. The schedule keeps track of milestones, customer shipping dates, and essential information about the components,” Enwright explained. “Engineering will then provide us with their preliminary or final release documentation. Preliminary releases are for projects that are known to have a long lead time.”
Lead times can be affected by several factors. Customers may request a longer lead time to ensure their facility and maintenance teams are ready to receive a new furnace or hot zone. Certain larger furnaces or hot zones may have a longer lead time as their components are ordered less often, making them a little scarcer. And some customizations just take a bit longer to assemble and test than others.
“We use an ERP (Enterprise Resource Planning software) for the release to help us track parts on order through the purchasing department, assign fabrication work, and build sub-assemblies based on the Bill of Materials (BOM) in the system,” Enwright said. “The ERP will then be able to generate the work orders needed for the shop floor. Our machinists will have one central location for the prints and drawings for each part they’re fabricating.”
As each part is manufactured and assembled, checklists are marked done and the parts and sub-assemblies are tagged, checked for quality, and stored together until the BOM for the order is complete.
“Hot zones are complex things, with so many parts and assemblies that go into them. It takes a lot of craftsmanship to manufacture and assemble these by hand. There may be 500 or more parts to one hot zone, and every piece needs to fit perfectly so that the hot zone works as soon as it is on site,” Enwright explained.
“Every part, large and small, matters.” – Chris Enwright, Ipsen Manufacturing Manager at Souderton, PA
Once the assemblies and kits have been completed, Souderton can ship them to different locations. Customer replacement hot zones and kits can be delivered directly to the customer or a field service team.
Complete hot zones for new customized equipment can be shipped directly to Cherry Valley, while kits for TITAN furnaces and other specific orders can be sent to Pecatonica, Illinois, taking advantage of their proximity to regional plenum manufacturers, while adding production bandwidth.
That’s when Brett Bird gets involved.
“Part of our job is to relieve Ipsen’s backlog by being a local resource for assembly,” Bird explained. “About 90% of our hot zones are going into new equipment. Since plenums can be large, having a manufacturer local to northern Illinois supply the TITAN plenum saves long haul shipping costs and time.”
When Souderton sends the parts kit to Pecatonica, Bird’s team can assemble, store, and ship the hot zone for one of Ipsen’s most frequently ordered lines all within 30 miles of the Cherry Valley assembly plant.
“With the kit from Souderton and the new plenum, we’ll install the felt hangers, the layers of graphite felt, then add the gas nozzles and carbon fiber composite (CFC) shields with the molybdenum washers, pin everything in once the washers are on, and check to make sure we have the perfect thickness. We’ll build the door pack and the end pack, and at that point have it ready to ship,” Bird outlined. “For all-metal furnaces, the process is a bit more detailed. Felt has some give if the hangers aren’t exact, but pins for the all-metal hot zone must be precise. The stamped metal shields require everything to line up with the mounting holes, and we can spot almost immediately if our pins are off.”
“If it’s not precise, we’re not afraid to remove everything and do it again.” – Brett Bird, Ipsen Production Supervisor
Ensuring accuracy and quality before shipment is a key priority for Bird’s team.
“We don’t have hot zones come back to us because they had failures during quality control testing. Our guys go through and nail every detail. Once we’ve put it together, we know it’s good.”