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ASME PTC 17-1973 (2012) scan — Reciprocating Compressors for Chemical Plant
🛠️ ASME PTC 17-1973 (2012) is the ASME performance test code for reciprocating compressors in chemical plant service, published in 1973 and reaffirmed in 2012. The Code establishes test rules for determining the thermodynamic performance of reciprocating compressors under chemical-plant operating conditions, including the measurement and computation of capacity (gas delivery), indicated and shaft power, and discharge temperature, together with unified rules for correcting test results to specified conditions. For the medium- and high-pressure reciprocating compressors widely used in refining, petrochemical, fertilizer, and gas-processing plants, PTC 17 is the key basis for shop acceptance and field performance verification.
💡 Unlike PTC 10 for centrifugal/axial compressors, PTC 17 addresses “positive-displacement” compression: performance is governed directly by cylinder geometry, clearance volume, speed, and suction/discharge conditions. The core of the test is accurately measuring the actual cycle’s indicated work and valve process losses.
1. Object and Scope 📌
The Code applies to reciprocating compressors driven by electric motors, internal-combustion engines, or turbines in chemical plant service, including single- and multi-stage, single- and double-acting, and single- and multi-cylinder arrangements. The performance parameters determined include:
- Capacity: the actual volume of gas delivered at specified suction conditions;
- Indicated power: power computed from the area enclosed by the cylinder indicator diagram;
- Shaft power: input power at the shaft determined by dynamometer, torque meter, or electrical measurement;
- Discharge temperature: gas temperature at each stage discharge, reflecting the compression process and cooling effectiveness;
- Pressure ratio and flow characteristics: stage inlet/outlet pressures and the corresponding performance relationships.
⚠️ The “capacity” definition in PTC 17 follows compressor-industry practice: the actual volume of gas drawn in at specified suction temperature and pressure. Reports must state the state basis used for the capacity correction; otherwise results from different reports cannot be compared.
2. Measurement Requirements 🎛️
The Code defines measurement requirements for each quantity; the principal measurements are summarized below:
| Measured Quantity | Typical Instrument/Method | Measurement Notes |
|---|---|---|
| Capacity | Critical-flow nozzles, orifice meters, wet gas meters | Measure on a stable run; arrange straight runs per PTC 19.5 |
| Indicated power | Mechanical indicator or electronic pressure-vs-crank-angle system | Keep indicator passages short and clean; synchronize crank-angle signal |
| Shaft power | Torque meter, dynamometer, electrical power meter with efficiency correction | Record speed simultaneously; deduct transmission losses |
| Speed | Electronic tachometer, stroboscope | Record speed fluctuation continuously during the test |
| Suction/discharge pressure | Precision gauges, pressure transmitters | Tap near the cylinder valves; avoid misattributing line losses |
| Suction/discharge temperature | Thermocouples, RTDs | Sufficient insertion depth for true gas temperature |
🚨 The accuracy of the indicator diagram directly determines indicated-power accuracy: long or fouled indicator passages introduce time lag and distort the diagram area. With electronic indicating systems, synchronize the crank-angle signal rigorously and verify calibration before and after the test.
3. Computation and Corrections 📊
Section 5 defines the computation methods:
- Capacity: from measured flow, or from cylinder geometry (bore, stroke, speed) as theoretical displacement minus clearance re-expansion and leakage effects;
- Volumetric efficiency: ratio of actual drawn-in volume to theoretical displacement, affected by clearance, pressure ratio, and suction temperature rise;
- Indicated power: converted from the indicator-diagram area using scale factors;
- Correction to specified conditions: correct test results to the contract suction temperature, pressure, speed, and gas composition using gas properties (compressibility, specific heat ratio);
- Shaft power correction: shaft power includes mechanical losses; record lubrication and cooling states and their influence on losses.
💡 Clearance volume is a key geometric parameter for reciprocating compressors: the larger the clearance, the lower the volumetric efficiency and the stronger the effect of pressure ratio. Confirm clearance matches the manufacturer’s design file before the test, otherwise capacity deviations may be misinterpreted as nonconformance.
4. Test Preparation and Execution 🛠️
- 🔍 Pre-test checks: verify valve condition, piston-ring sealing, cooling-water and lubrication systems, and record cylinder dimensions and clearances;
- 🔧 Stable operation: run at the test load until stage pressures, temperatures, and speed stabilize before recording data;
- 📊 Multi-point measurement: to build a performance curve, measure at different loads (different clearance settings or bypass ratios);
- 📋 Data records: record speed, stage pressures and temperatures, flow, power, and barometric pressure synchronously to form a complete test log.
5. Frequently Asked Questions ❓
❓ Q: How do PTC 17 and PTC 10 differ in scope?
A: PTC 17 covers reciprocating (piston) compressors for chemical plants — positive-displacement machines. PTC 10 covers axial and centrifugal compressors and exhausters — dynamic turbomachines. The test and conversion rules differ, so choose the code by machine type.
A: PTC 17 covers reciprocating (piston) compressors for chemical plants — positive-displacement machines. PTC 10 covers axial and centrifugal compressors and exhausters — dynamic turbomachines. The test and conversion rules differ, so choose the code by machine type.
❓ Q: Why do valve conditions strongly affect test results?
A: Valve timing and sealing determine the suction/discharge losses of the actual cycle: sticking plates, fatigued springs, or poor sealing reduce capacity and raise power. Inspect and record valve condition before the test and repair if necessary.
A: Valve timing and sealing determine the suction/discharge losses of the actual cycle: sticking plates, fatigued springs, or poor sealing reduce capacity and raise power. Inspect and record valve condition before the test and repair if necessary.
❓ Q: What is the relationship between indicated power and shaft power?
A: Shaft power = indicated power + mechanical losses (friction, oil pump, cooling fan). The difference reflects mechanical efficiency; acceptance is usually based on shaft power, so a machine with normal indicated power but high mechanical losses may still exceed the shaft-power guarantee.
A: Shaft power = indicated power + mechanical losses (friction, oil pump, cooling fan). The difference reflects mechanical efficiency; acceptance is usually based on shaft power, so a machine with normal indicated power but high mechanical losses may still exceed the shaft-power guarantee.
🔍 Q: How are test results corrected to specified conditions?
A: Correct the pressure-volume relationship for gas compressibility and specific heat ratio, and correct suction state, speed, and gas composition item by item to the contract values. The correction method should be agreed in writing by both parties before the test to avoid disputes.
A: Correct the pressure-volume relationship for gas compressibility and specific heat ratio, and correct suction state, speed, and gas composition item by item to the contract values. The correction method should be agreed in writing by both parties before the test to avoid disputes.
