Which filter is more expensive because it must withstand system pressure?

• A. Suction line (Mesh)
• B. Off-line filtration
• C. Return line filter (low pass)
• D. Pressure line filter (high pass)

Answer: (D)

The key idea is that filtration components must be rated for the pressure they will encounter in service. The filter placed in the pressure line is directly exposed to the full system pressure from the pump to the actuators, including any spikes. Because it must resist that high pressure and maintain a seal under load, its housing, seals, and filter element are built to higher pressure ratings, which raises cost. Suction-line filters sit at the pump intake where the pressure is near ambient or slightly below, so they don’t have to withstand high pressure and can be made with less robust, cheaper components. Return-line filters operate on the path back to the reservoir and typically face lower pressures than the discharge line, so they don’t require the same high-pressure rating. Off-line filtration is in a bypass loop and generally configured for moderate pressures. In short, the filter in the pressure line must handle the system’s pressure, making it the most expensive option.