How to Order a Custom Heating Element or Temperature Sensor
The short answer: You do not need a part number, a drawing or technical knowledge. Send Thermocouple Products the failed component — or a photograph with a tape measure beside it — and we will measure it, work out why it failed and build a replacement. There is no minimum order quantity, and custom dimensions cost no more than standard ones.
At Thermocouple Products, “custom” is not a special order. It is the normal one. Almost everything manufactured at our Edenvale facility is built to a specific customer’s dimensions.
What we can work from
In order of usefulness:
- The failed part itself. By far the best option. We measure it directly, identify the construction, and — importantly — examine how it failed.
- A photograph with a scale reference. A tape measure or steel rule laid alongside the part. Take several angles, including the terminals and any cutouts.
- A sketch with dimensions. A hand drawing on the back of a worksheet is entirely adequate. It does not need to be to scale.
- An old invoice or part number. If you have bought it before — from us or anyone else — the paperwork often carries enough detail.
- The machine details. Make, model and which zone. For common machinery we can frequently identify the component from that alone.
- A description. “The third barrel zone on the green extruder, about 150 mm across.” More than you would think can be worked out from this.
You do not need all six. One is usually enough to start.
How to measure a band heater
This is where most measurement errors happen.
Internal diameter — measure the barrel, not the heater
A band heater is manufactured slightly larger than its nominal internal diameter so it can be clamped down tight. If you measure a used heater in its relaxed, opened state you will get a figure larger than the true size.
Measure the barrel the heater fits onto. That is the dimension we need.
If you can only measure the old heater, close it up fully first, or measure the circumference with a tape and tell us that instead — we can calculate from it.
Width
Straightforward: the dimension along the barrel axis.
Wattage and voltage
Usually on the terminal label or the original documentation. If both are missing:
Measure the resistance across the terminals with a multimeter.
Then: Watts = Volts² ÷ Ohms
A heater reading 48 ohms on a 230 V supply is 230² ÷ 48 ≈ 1 100 W.
This only works if the element has not failed open circuit. An open circuit reads infinite resistance — in that case send us the part and we will work it out from the construction.
Terminals
Photograph them. There are many variants — flying leads, screw terminals, post terminals, plug receptacles, and leads exiting at different angles or positions.
Cutouts and holes
Note the position and size of any cutout for a nozzle, thermocouple, bolt or clamp. Measure from a fixed reference point — usually the gap in the band.
How to measure a cartridge heater
- Diameter — measure the element itself, and if possible the bore it fits into
- Length — the heated section, plus overall length if different
- Wattage and voltage — from the label, or calculated from resistance as above
- Lead length and type — flying leads, armoured, braided, right-angle exit
- Fittings — any thread, flange or bracket
Also measure the bore. If cartridge heaters keep failing in the same hole, the bore is the likely cause — an oversized or oval hole leaves an air gap, and the element overheats internally. We would rather solve that than sell you another element that will fail the same way.
How to specify a thermocouple or RTD
Six pieces of information:
- Type — J, K, T, E, R, S or B for a thermocouple; Pt100 for an RTD. Not sure? Tell us the temperature range and we will advise.
- Insertion length — in millimetres, from the mounting point to the tip
- Sheath diameter and material — 1,5 mm to 32 mm; stainless, Inconel or ceramic
- Process connection — NPT thread size, flange, compression fitting, or none
- Termination — connection head, plug, transition cable or bare tails
- Configuration — single, duplex or triplex; and for RTDs, 2-, 3- or 4-wire
If you are replacing an existing sensor, the old one answers all six.
The most valuable question we ask
“How did the last one fail?”
This matters more than any dimension, because a component that failed early failed for a reason — and a like-for-like replacement will usually fail the same way again.
What the failure tells us:
What you see | What it usually means | What we change |
Burned through on one edge | Air gap, worn or out-of-round surface | Ceramic instead of mica — it radiates as well as conducts |
Failed at the lead exit | Flexing or mechanical stress | Armoured leads, or a different exit position |
Cooked internally, looks fine outside | Bore or surface fit — heat could not escape | Check the bore; adjust watt density |
Sheath corroded or pitted | Wrong material for the process | Different sheath alloy |
Sensor drifted, not physically damaged | Normal ageing, or wrong type for the atmosphere | Heavier sheath, different calibration, or a Pt100 |
Repeated failures in one position only | Something about that location | Investigate before replacing again |
We would rather build you something that lasts than sell you the same failure twice. A customer replacing a heater once every four years is worth considerably more than one replacing it three times a year and quietly getting annoyed about it.
When a better specification costs the same
Frequently, the improved version is not more expensive:
- Mica to ceramic band heater — a genuine price difference, but usually repaid within a year through lower power consumption and fewer replacements
- Different sheath material on a sensor — often a marginal cost, sometimes none
- Repositioned thermocouple hole — free. It is made to order either way
- Longer or armoured leads — small cost, frequently eliminates the actual failure mode
- Different terminal type — usually no difference in price
Custom dimensions carry no premium. We are not modifying a stock item; we are building from raw materials to your figures. A non-standard diameter costs the same as a standard one.
Obsolete parts and discontinued machines
A significant share of our work involves machinery whose manufacturer no longer exists, no longer supports the model, or quotes a lead time measured in months.
We have manufactured replacements for:
- Equipment from manufacturers long since closed
- Plant installed decades ago with no surviving documentation
- Imported machinery where the original supplier will not quote a single unit
- Components with no markings whatsoever
If you have been told a part is unobtainable, ask us before giving up on it. 34 years in Edenvale means we have seen most constructions before, and anything we can measure, we can usually reproduce.
No minimum order quantity
One unit is a normal order.
You do not need a bulk purchase order, an annual commitment, or to buy a pack of ten because that is how it is boxed. If you need one band heater for one machine, we will make one.
This is the practical difference between a manufacturer and a distributor. A distributor breaks into stock that arrived in a container and sells what the pack size dictates. We build from raw material to your specification — so the quantity is entirely up to you.
It also means no import lead time. When a zone fails on a Tuesday afternoon, being 20 minutes away in Edenvale is a materially different proposition.
What happens after you enquire
- You send us the part, a photo, a sketch or a description
- We measure and identify it — and check how it failed
- We quote — including any recommended improvement, with the reasoning
- You approve — like-for-like, or the improved version, your call
- We manufacture — to your dimensions, in Edenvale
- You collect, or we deliver
If anything is ambiguous we will phone you rather than guess. A five-minute call is cheaper for both of us than a wrong part.
Send it to us
Drop it off: 10 Edendale Road, Eastleigh, Edenvale, Gauteng Email photos: tcprod@mweb.co.za Call and describe it: (011) 452-6617
Office hours Monday to Thursday and Friday mornings.
If you are unsure whether we can help, phone and describe it. If it heats something, or measures the temperature of something, the answer is usually yes.
CTA: Request a Quote → /contact · Call (011) 452-6617
Related reading:
- The Complete Guide to Heating and Measuring an Injection Moulding Machine
- Band Heaters, Cartridge Heaters and Supercoils: Which One Does Your Machine Need?
- How to Choose a Thermocouple Sheath Material for Corrosive Service
Related products: Mica Band Heaters · Ceramic Band Heaters · Cartridge Heating Elements · Supercoil Heating Elements · Thermocouples · Pt100 RTDs
FAQ schema for this page
Can you make a replacement heating element without a part number? Yes. Thermocouple Products can manufacture a replacement from the failed component itself, a photograph with a scale reference, a dimensioned sketch, an old invoice, or a description of the machine and zone. We measure the original, identify the construction and build a replacement at our Edenvale facility.
How do I measure a band heater for a replacement? Measure the internal diameter of the barrel the heater clamps onto, not the used heater in its relaxed state, as band heaters are manufactured slightly oversized for clamping. Also record the width, wattage, voltage, terminal type and the position of any cutouts. If wattage is unknown, measure the resistance across the terminals and calculate watts as volts squared divided by ohms.
Is there a minimum order quantity for custom heating elements? No. Thermocouple Products has no minimum order quantity. A single unit is a normal order. Because elements are manufactured to order from raw materials in Edenvale rather than supplied from imported stock, quantity is determined entirely by the customer.
Do custom dimensions cost more than standard sizes? No. Because every element is built to order from raw materials, a non-standard diameter or length costs the same as a standard one. Some specification upgrades — such as ceramic instead of mica construction — carry a price difference, but these are usually repaid through longer service life and lower running costs.
Can you replace heating elements for obsolete or discontinued machinery? Yes. A significant proportion of our work involves machinery whose manufacturer no longer exists or no longer supports the model. If the component can be measured, it can usually be reproduced. Thermocouple Products has manufactured replacements for equipment with no documentation and no markings at all.