On an operating boiler, the superheater safety valve shown in the illustration is set to lift at 670 psi and reseat at 630 psi. To increase the lifting pressure to 700 psi, but maintain the previous reseat pressure, you would turn the compression screw __________. See illustration SG-0018.
• Relationship between spring compression and set (lifting) pressure in a safety valve • Function of the adjusting (blowdown) ring in controlling the reseat pressure / blowdown • How turning the compression screw clockwise vs counterclockwise changes the spring force shown in the illustration (SG-0018)
• If you want the valve to open at a higher pressure but close at the same pressure, which part of the valve actually controls each of those pressures? • Looking at the spring in the illustration, what happens to its force on the disc when the compression screw is driven downward vs upward? • What valve component is specifically designed to adjust blowdown (difference between lift and reseat) rather than the initial lift point?
• Identify in the illustration which part is the compression screw and which part is the adjusting ring near the seat and disc area • Confirm which direction of turning the compression screw will increase spring compression, and therefore increase lift pressure • Verify which way to move the adjusting ring to keep the reseat pressure at 630 psi when the lift pressure is increased to 700 psi
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