Baker Hughes Safety Relief Valves 1900/1900 DM Series

The Thermodisc must be replaced if: - Seat defects and damage cannot be lapped out without reducing the A dimension below those listed in Table 6 (see Figure 33).

- The standard 1900 Series disc can be machined until the N dimension is reduced to its minimum size (see Table 5).

- The T dimension is provided to ensure the disc has not been machined beyond its limits.

- If re-machining reduces the thickness of the disc (T min.), the entire disc holder assembly drops with respect to the seating plane of the nozzle.

- This creates a significant change in the huddle chamber configuration and results in significantly more simmer before opening.;

- Using a measuring magnifying glass (see Lapped Nozzle Seat Widths), determine whether the seating surface must be machined before lapping.

- If the seat can be lapped flat without exceeding the required seat width (see Tables 1a, 1b or 1c), it does not require machining.

- To reduce the seat width, the 5º angle surface must be machined and all seat dimensions need to be verified, and reestablished if necessary.

- The nozzle must be replaced if the D dimension is reduced below the minimum (see Tables 3).

- ATTENTION! Flange thickness changes the center-to-face dimension. Ensure the minimum dimension for orifice D through P is .656" (16.67 mm), and for Q through W is .797" (20.24 mm).;

Replace the spring (18) if: - Pitting and corrosion of the coils reduce coil diameter

- Spring ends are not parallel in the free height condition

- Obvious uneven coil spacing or spring distortion is present.

- The maximum clearance between A and A1 and between B and B1 (see Figure 37) is more than: .031" (.79 mm) for springs with an inner diameter (ID) of less than 4" (100 mm)

.047" (1.19 mm) for springs with an ID of 4" (100 mm) or greater.

- If there is constant backpressure in a conventional 1900 Series SRV (without balancing bellows), check that the cold differential set pressure of the replacement spring (18) is within the recommended range.

- If the relieving temperature causes the cold differential set pressure, then select a spring based on the valve’s actual set pressure, not on the cold differential set pressure (See Set Pressure Compensation).

- ATTENTION! If a spring must be replaced, order a spring assembly, as it includes custom fit spring washers.;

Replace the guide (9) if: - Visible galling is present on the inside guiding surface

Gasket seating areas are pitted and cause the valve to leak between the bonnet (11) and base (1).

- The guide (9) type varies depending on the valve type: O-ring valve, bellows valve, or standard valve.

- Inspect the guide as follows: Find the correct valve orifice size and disc holder (8) measurements (see Table 9)

- Measure the barrel portion of the disc holder and compare it to the nominal measurement on Table 6 to determine the maximum allowable clearance between the disc holder and the guide

- Replace the guide and disc holder if the clearance between the inner diameter (I.D) and the guide and/or the outer diameter (O.D) of the disc holder is not within the clearance dimensions.;