Sealing design – Why minor details matter
Minor details can make a major difference. This statement recently rang true for the contractor on an SBE-designed project. The bottom seal of a rolling gate didn’t function properly at some point in the middle of the gate and hence leakage occurred. This blog post reveals the solution SBE has proposed.
Diving inspection revealed a gap between the gate and the sill. This gap had a width of 1-2 cm and measured 1-1.5 m in length. The gap was large enough to cause a waterjet inside the lock, negatively affecting the filling & emptying times of the lock. On paper the problem had a very simple solution; simply replace the bad UHMWPE-block (the seal) with a good one and problem solved.
Fixing the problem underwater, however, is simpler said than done. It was not realistic to do it and it would have been very expensive without any guarantee of success. Only working in dry condition would result in a proper solution of the malfunctioning seal.
Fortunately, SBE and the contractor had selected a double rolling gate system at both lock heads during the design phase. Taking a gate out of operation for maintenance, didn’t result in a closed lock and it didn’t result in any penalties for being in a non-scheduled out of operation situation.
Moreover, SBE and the contractor designed a well-conceived lifting system to close and empty the lock recess easily and to lift the gate in its maintenance position. Solving the problem was doable, although not without cost implications.
On further inspection it was discovered that this issue could have easily been avoided if that minor detail (from the above saying) was properly highlighted from the outset. The following details were discovered after some research:
- The gate was positioned on a quay for more than a month, in dry conditions, easily reachable, before it was placed in position;
- On the quay, it was obvious that one of the UHMWPE-sealing blocks wasn’t in line with the seals adjacent to it (photos taken on the quay of the gate and the bottom seal revealed this); and
- When dry and on the quay, the block could have been effortlessly replaced.
In conclusion, if a responsible contractor had tackled this very minor detail on the quay, this issue and the resulting additional cost would have been avoided. Or; minor details can make a major difference.