The sealing gasket for the UV intensity sensor assembly on Trojan UV Swift SCD reactors, Trojan part 820693-007. It seals the port where the sensor enters the irradiated chamber, keeping the chamber pressure-tight and the sensor’s optical face dry. Renew it every time the sensor is withdrawn: a gasket that has been compressed, aged or nicked on refit is the usual cause of weeping at the sensor boss, and of moisture reaching the sensor window — which does not read as a leak but as a UV intensity signal that drifts low, and so gets misdiagnosed as a failing lamp or a failing sensor. Item number 15174-0118. Supplied by cBallast on quote-to-invoice terms; lead time and freight are quoted per RFQ against the destination Incoterm.