Okay, this is a common, and frustrating, problem. Exothermic welding (Cadweld, etc.) in wet trenches is a challenge, but definitely solvable. Here's a breakdown of the likely causes and what you can do about it

Root Causes (Based on your description and common issues):

1. Moisture, Moisture, Moisture

This is the #1 enemy. Even a tiny bit of moisture can ruin the weld.2.

Mold Degradation

Repeated heating/cooling cycles, combined with moisture, will degrade the graphite molds. They have a limited lifespan, and wet conditions shorten it significantly.3.

Improper Mold Sealing

Poor sealing (or seal degradation) allows molten metal to leak, exacerbating the problem.4.

Uneven Ground/Mold Movement

If the mold isn't perfectly stable and level, the molten metal pressure can force it apart.5.

Overfilling/Improper Powder Charge

Using the incorrect charge, or overfilling the crucible, can increase the pressure on the mold.6.

Material Contamination

Dirt/Mud, or other contaminates can cause the mold to wear down at an accelerated rate.

Solutions and Best Practices (in order of likely impact)


Intensify Moisture Control



Temporary Mini-Dewatering

Even if the GC can't do more large-scale dewatering, can you create localized, temporary dry zones for each weld? This could involve:

Small Sump Pump

Continuously pumping water away from the immediate welding area. A small, submersible pump is perfect.

Sand Bags/Berms

Create a small dam around the weld location to block water flow. Line the area with plastic sheeting to create a dry pocket.

Absorbent Materials

Kitty litter, absorbent pads, or even old towels can soak up residual moisture in the bottom of the trench. Replace them frequently.

Heat the Cable Ends (AGGRESSIVELY)

Your torching is a good start, but:

Prolonged Heating

Heat each cable end for longer than you think is necessary. You want to be sure you're driving out ALL moisture from the copper.

Focus on the Contact Area

Pay special attention to the area that will be within the mold.

Immediate Welding

Once heated, weld immediately. Don't let the cable cool and re-absorb moisture.

Mold Preheating is KEY



Thorough and Consistent Heating

Heat the ENTIRE mold, not just the crucible area. Get it hot enough that any remaining moisture steams off visibly.

Inside and Out

Heat both the inside and outside surfaces of the mold.

Protect from Re-wetting

Once preheated, try to keep the mold protected from any splashing or ground moisture while it's waiting to be used.

Consider a Moisture Meter

A simple moisture meter can help you determine how dry the cable and mold are.2.

Mold Sealing and Maintenance



Mold Sealer

Use a high-quality mold sealant specifically designed for exothermic welding. Apply it liberally to all joints and seams before each weld. Pay attention to the manufacturer's instructions for application and drying time. If you can't get the proper compound, something like the "Rutland 82B High Temp Silicone" may do.

Tighten Clamps

Ensure that the mold clamps are tight and in good condition. If they're worn or loose, replace them. Tighten them securely (but not excessively) after applying the sealant.

Clean Thoroughly

After each weld, clean the mold thoroughly with a wire brush and scraper to remove any residual slag or debris. This prevents buildup that can compromise the seal.

Inspect for Damage

Before each weld, carefully inspect the mold for cracks, chips, or other damage. Discard any damaged molds immediately.

Mold Life

Accept that molds have a limited life in these conditions. Consider them a consumable item and be prepared to replace them more frequently than usual.3.

Stabilize the Mold



Level Ground

Create a level and stable base for the mold. Use a shovel and level to ensure the ground is even.

Supports

Use bricks, rocks, or other stable supports to further stabilize the mold. Make sure these supports are themselves on a firm, level surface.

Sandbags/Chocks

Place sandbags or wooden chocks around the mold to prevent it from shifting during the weld.4.

Powder Charge and Technique



Correct Charge

ALWAYS use the correct powder charge size specified for the cable size and mold type. Overcharging is a major cause of mold failure.

Proper Pouring

Pour the powder carefully and evenly into the crucible, following the manufacturer's instructions. Avoid spilling powder onto the mold surface.

Ignition Technique

Use the recommended ignition method and ensure that the powder ignites completely and evenly.5.

Material Compatibility



Cleanliness

Ensure that both the cables and the mold are free from dirt, grease, or other contaminants. These can interfere with the weld and shorten the mold's lifespan.

Cable Type

Verify that the cable type you're using is compatible with the exothermic welding process and the mold you're using.

Troubleshooting Steps



Observe the Failure

When a weld fails, carefully examine the mold to determine where the molten metal is leaking. This will help you identify the root cause of the problem (e.g., cracked mold, poor seal, uneven ground).

Document Each Weld

Keep a log of each weld, including the date, time, weather conditions, mold number, powder charge, and any problems encountered. This will help you identify trends and patterns.

Important Considerations



Manufacturer's Instructions

ALWAYS follow the manufacturer's instructions for the exothermic welding system you're using. These instructions will provide specific guidance on mold preparation, powder charges, and safety precautions.

Safety

Exothermic welding involves molten metal and high temperatures. Wear appropriate personal protective equipment (PPE), including safety glasses, gloves, and a fire-resistant jacket.*

Training

Ensure that all personnel involved in exothermic welding are properly trained and certified.

Example Workflow (Combining Best Practices)


Dewater

Use a small pump and sandbags to create a dry area in the trench.2.

Prepare Cable

Thoroughly clean and torch the cable ends until completely dry.3.

Prepare Mold

Clean the mold, inspect for damage, and preheat it thoroughly with a torch.4.

Seal the Mold

Apply mold sealant liberally to all joints and seams.5.

Stabilize Mold

Place the mold on a level surface and use supports/sandbags to prevent movement.6.

Charge and Weld

Carefully pour the correct powder charge into the crucible and ignite the mixture.7.

Inspect and Clean: After the weld has cooled, inspect it for quality. Clean the mold thoroughly for the next use.By systematically addressing these potential issues, you should be able to significantly improve your success rate with exothermic welding in wet trench conditions. Good luck! Flag for review