Replacing a kiln sitter often refers to replacing its critical internal components, particularly the kiln sitter tube, which is essential for accurate firing. This guide focuses on the common task of replacing the tube and offers insights into maintaining the overall mechanism.
Understanding Your Kiln Sitter
A kiln sitter is a mechanical safety device in many electric kilns that automatically shuts off the kiln when a pyrometric cone bends to a specific degree, indicating the desired temperature-time equivalent has been reached. This ensures consistent firing results and prevents over-firing. Over time, components like the kiln sitter tube, timing rod, or cone supports can wear out or become damaged, necessitating replacement.
Tools and Materials Needed
Before you begin, gather the following:
- New Kiln Sitter Tube: Ensure it's compatible with your kiln model.
- Screwdriver or Wrench Set: To loosen and tighten components.
- Needle-Nose Pliers (optional): For manipulating small parts.
- Gloves: For safety and to keep parts clean.
- Kiln Manual: For specific diagrams or instructions for your model.
- Flashlight: To illuminate the internal components.
Step-by-Step Guide to Replacing the Kiln Sitter Tube
Replacing the kiln sitter tube is a common maintenance task that can restore your kiln sitter's accuracy.
Safety First
Always disconnect your kiln from its power source before attempting any repairs or maintenance. This is crucial to prevent electrical shock. Unplug the kiln or turn off its dedicated circuit breaker.
Accessing the Sitter
- Locate the Kiln Sitter: It's usually a small box-like mechanism on the side or front of your kiln, with a rod protruding into the firing chamber where the pyrometric cone is placed.
- Open the Kiln Lid and Sitter Housing: Depending on your model, you might need to open the kiln's lid and/or remove a small cover plate over the sitter mechanism itself to access its internal workings.
Removing the Old Kiln Sitter Tube
The kiln sitter tube holds the small witness cone that triggers the shut-off.
- Loosen the Sitter Mechanism: Use the appropriate wrench or screwdriver to carefully loosen the retaining nut or screws holding the sitter mechanism in place. This allows you to manipulate it more easily.
- Remove Components: Once the sitter is loosened, carefully remove it along with its accompanying washer.
- Slide Off Rod Components: Then, slide the nut and washer off the actuated rod.
- Extract the Tube: Finally, gently slide the old kiln sitter tube out of the kiln sitter assembly. Note its orientation and how it was seated.
Inspecting Other Components
While the sitter is open, take a moment to inspect other related parts:
- Timing Rod: Check for any bends, corrosion, or wear.
- Cone Supports: Ensure they are clean and not warped or broken.
- Electrical Contacts: Look for any signs of arcing or excessive wear on the switch contacts.
Installing the New Kiln Sitter Tube
- Insert the New Tube: Carefully slide the new kiln sitter tube into the assembly, ensuring it's oriented correctly, usually with the opening facing the inside of the kiln chamber.
- Reassemble Components: Slide the washer and nut back onto the actuated rod.
- Secure the Sitter: Reattach the sitter mechanism and its accompanying washer. Ensure all components are snugly fitted but avoid over-tightening, which could damage the mechanism.
- Replace Cover Plate: If you removed a cover plate, put it back in place.
Testing and Calibration
- Power On: Once everything is securely reassembled, reconnect your kiln to its power source.
- Dry Run (Optional): Many users perform a test run with a small cone (or even just an empty tube if safe for your model) to ensure the mechanism engages correctly.
- Check for Proper Operation: Observe if the rod moves freely and the mechanism trips when the cone bends, indicating proper function.
For a visual guide and more detailed information on specific models, consider exploring resources like Paragon Industries' maintenance series.
When to Replace the Entire Kiln Sitter Mechanism
While individual components like the tube are commonly replaced, sometimes the entire kiln sitter mechanism might need replacement. This is typically necessary if:
- Major Structural Damage: The housing is cracked, bent, or severely corroded.
- Electrical Failure: The internal switch or wiring is faulty and cannot be repaired.
- Irreparable Wear: Multiple critical parts (e.g., timing rod, tube, and internal switch) are simultaneously worn beyond simple component replacement.
- Obsolete Parts: If replacement parts for your specific model are no longer available.
Replacing the entire mechanism is a more complex task and might require electrical wiring knowledge. If you're unsure, it's advisable to consult a qualified kiln technician.
Maintenance Tips for Kiln Sitters
Regular maintenance can extend the life of your kiln sitter:
- Keep it Clean: Regularly clean dust and ceramic debris from the sitter mechanism, especially around the rod and cone supports.
- Inspect Regularly: Before each firing, quickly inspect the tube and rod for any signs of wear or damage.
- Use Correct Cones: Always use the correct size and type of pyrometric cones specified for your kiln sitter.
- Avoid Over-Tightening: When reassembling, tighten components securely but avoid excessive force that could warp parts.
By following these steps and performing regular maintenance, you can ensure your kiln sitter operates reliably for many firings.
