Example

Approximate the size of a suction and a discharge volume bottle for a single-stage, single-acting, lubricated, reciprocating compressor. The gas being compressed is natural gas at the following conditions:

Cylinder bore: Cylinder stroke: Rod diameter: Suction temperature: Discharge temperature: Suction pressure: Discharge pressure: Isentropic exponent: Specific gravity: Percent clearance:

9 in. 5 in. 2.25 in. 80°F 141 °F 514 psia 831 psia 1.28 .60

Step 1. Find the suction and discharge volumetric efficiencies using Equations 3.5 and 3.21 with rp = 831/514 — 1.617. The natural gas compressibility values can be obtained by using the gravity/compressibility charts (see Appendix B-29 through B-35) for a specific gravity of .60. Both Zj and Z2 values are .93. Applying Equation 3.6, the value of f may be obtained as follows:

Using the equation for the suction volumetric efficiency,

Ev - .823 suction volumetric efficiency

For the discharge volumetric efficiency, use Equation 3.21.

Evd = .565 discharge volumetric efficiency

Step 2. Find the total volume displaced per revolution using Equation 3.1 for a single-acting compressor.

Step 3. Using the volumetric efficiencies found in Step 1, find the size multiplier from the volume bottle sizing chart, Figure 3-27.

Suction multiplier =13.5 Discharge multiplier = 10.4

Step 4. Find the required bottle volume from the displacement and the multiplier.

Vol = 4,294.2 in.3 suction bottle volume

Vold= 10.4x318.1

Vold = 3,308.1 in.3 discharge bottle volume

Step 5. Find the bottle dimensions from Equations 3.22 and 3.23 for vessels with 2:1 elliptical heads. Use Equation 3.22 to calculate the diameter.

16.3 in. diameter of suction bottle .86 (3308.1)1/3 dbd = 14.9 in. diameter of discharge bottle Use Equation 3.23 to calculate the length. Lhs - 2 x 16.3

LK = 32.6 in. length of suction bottle

Lbd = 29.8 in. length of the discharge bottle

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