The AltairNeptune range of filter elements consists of the cleanable HV1000 and HV1500 coalescer/filter bags, which offer superior coalescence performance and salt removal capabilities. Features & Benefits HV1000 The HV1000 is a high-efficiency bag filter consisting of synthetic laminated media layers formed into multiple pockets. The HV1000 is particularly suited to vessels operating in high dust environments. HV1500 Designed to protect gas turbines operating in the most severe marine environments, the HV1500 is particularly suited to naval applications, and is approved and specified by numerous navies around the world.