Securing screws

When installing end caps and sensor heads, care should be taken when tightening the screws. The following guidelines, incorporating best practices and specific torque recommendations, will assist you in achieving optimal results.

Preparation

Cleanliness: Ensure that all screws, threads, O-rings, and sealing surfaces are clean and free from contaminants. Even minor debris can compromise the seal and lead to leaks.
Make sure to not squeeze the harness when reattaching the endbell.
Spring Washers: Always use new spring washers during reassembly, as reused washers may not provide the necessary tension.

Thread Engagement

Proper Alignment: When reinserting screws, ensure they align correctly with the threads. A recommended technique is to turn the screw slowly counterclockwise until you feel it "drop" into the first thread winding, then proceed to tighten clockwise. This method helps prevent cross-threading and ensures proper engagement.

Tightening Sequence

Cross-Pattern Approach: Adopt a cross-pattern (or star-pattern) tightening sequence to ensure even compression of the O-ring and to minimize mechanical stress:​

• Slightly tighten one screw.​
• Move to the screw directly opposite and tighten it slightly.​
• Continue this pattern with the remaining pairs of opposing screws.​
• Repeat the sequence, gradually increasing torque, until all screws are appropriately tightened.​

This method promotes uniform O-ring compression and reduces the risk of leaks or damage.

Torque Specifications

• Torque Values: Applying the correct torque is essential to avoid over-compression of the O-ring and potential damage to the threads or housing. Refer to the following torque specifications for different screw sizes:

• Manual Tightening: If a torque wrench is unavailable, tighten the screws until the spring washer is compressed, then apply the additional turn as specified above
• Caution Against Over-Tightening: Excessive torque can strip threads or damage the surrounding material. Tighten screws slowly and evenly, allowing the plastic to deform appropriately. A turning rate of approximately 5 degrees per second is recommended.

Post-tightening checks

• Visual Inspection: After tightening, inspect the assembly to ensure the end cap is seated correctly against its flange and that there is uniform compression of the O-ring.
• Functional Test: If possible, perform a pressure test to confirm the integrity of the seal before deploying the equipment.​

Please refer to this video created by our support department for visual guidelines on how to open a close an ADCPs endbell.

Over-torquing has no positive effect and may damage the threads and/or area around the screw holes on the head and end cap. Keep in mind that ocean pressure holds the end cap tightly; all the screws have to do is to secure the end cap from falling out when the system is above water. Most water leak damage can be traced back to O-rings in poor condition, damaged sealing surfaces or contaminants on O-rings and/or sealing surfaces.