Compression Technology and Equipment Flashcards
7 cards from real CNG practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Compression Technology and Equipment flashcards as text
Before performing maintenance on a CNG compressor, what is the FIRST required safety step?
Answer: Isolate and de-energize the compressor using lockout/tagout, then vent and verify zero pressure in the system
Lockout/tagout procedures and complete pressure relief with pressure verification are mandatory first steps before any CNG compressor maintenance to prevent electrocution and high-pressure gas release injuries.
What is the correct method for detecting gas leaks on CNG compressor fittings and connections?
Answer: Apply an approved leak detection solution or use a calibrated combustible gas detector
Approved combustible gas detectors and leak detection solutions (soap-based formulas) are the safe, accepted methods for locating CNG leaks without creating an ignition hazard.
What is the purpose of a pressure relief valve (PRV) on a CNG compressor discharge line?
Answer: Prevent downstream components and storage vessels from overpressurization if the system exceeds safe pressure limits
PRVs are safety devices that automatically vent gas to a safe location when discharge pressure exceeds set limits, protecting downstream piping, cylinders, and equipment from dangerous over-pressurization.
What lubricant is recommended for oil-lubricated CNG reciprocating compressors?
Answer: Manufacturer-approved synthetic oil specifically formulated for natural gas compressor service
CNG compressors require manufacturer-approved synthetic lubricants formulated for natural gas service; incorrect oils can contaminate the fuel gas and degrade compressor seals and components.
What operational condition results when CNG compressor piston rings become excessively worn?
Answer: Gas blow-by past the piston, reducing efficiency and contaminating crankcase oil with compressed gas
Worn piston rings allow compressed gas to bypass the piston (blow-by), reducing compression efficiency, contaminating crankcase oil, and potentially causing elevated crankcase pressure.
What is the primary value of continuous vibration monitoring on a CNG compressor?
Answer: Excessive vibration can indicate bearing failure, shaft misalignment, or valve issues before catastrophic mechanical failure occurs
Abnormal vibration signatures are early indicators of mechanical problems such as bearing wear, shaft misalignment, or unbalanced components that can lead to catastrophic failures if left unaddressed.
Under NFPA 52, what ventilation requirement applies to enclosed CNG compressor buildings?
Answer: Ventilation must prevent natural gas concentrations from exceeding 25% of the lower flammable limit (LFL)
NFPA 52 requires adequate ventilation in CNG compressor enclosures to keep natural gas concentrations below 25% of the LFL, providing a safety margin well below the explosive range.