API standards for oil and gas engineers define the minimum technical requirements for safe, reliable, and efficient operation of equipment, piping, and systems in oil and gas plants.

Introduction

API standards for oil and gas engineers define the minimum technical requirements for safe, reliable, and efficient operation of equipment, piping, and systems in oil and gas plants. For oil and gas engineers, API standards define the minimum technical requirements for safe, reliable, and globally accepted plant operation. In the oil & gas industry, rotating equipment is not just machinery — it is the heartbeat of production.

From LNG terminals and refineries to gas processing plants, equipment such as pumps, compressors, and turbines operates continuously under extreme conditions:

• High pressures
• Elevated temperatures
• Corrosive and hazardous fluids

A single failure can trigger plant shutdowns, safety incidents, and massive financial losses.

This is exactly why API standards exist.

They are not optional documents or “reference material for later”. They are the engineering rulebook of oil & gas.

What Are API Standards?

API standards are published by the American Petroleum Institute and define how rotating equipment must be designed, manufactured, tested, installed, operated, and maintained.

In real-world oil & gas projects:

• OEMs design equipment to API

• EPCs specify equipment as per API

• Operators audit failures against API

• Maintenance teams repair equipment following API

If you don’t understand API standards, you’re technically blind in this industry.

Why API Standards Matter So Much

API standards help engineers to:

• Ensure equipment reliability & availability
•  Reduce unplanned shutdowns
•  Improve process and personnel safety
• Standardise best practices globally
•  Protect people, assets, and the environment

In short:
Most rotating equipment failures happen when API principles are ignored. API standards play a critical role in ensuring safe and reliable operations at LNG terminals in India, where rotating equipment and piping systems operate under extreme cryogenic conditions.

Core API Standards Every Rotating Equipment Engineer Must Know

🟦 API Standards for Pumps

API 610 – Centrifugal Pumps

The most important pump standard in oil & gas.

Used extensively in:

• Refineries
• Petrochemical plants
• LNG & gas processing facilities

Covers:

• Hydraulic design
• Materials of construction
• Bearings & lubrication
• Mechanical seals
• Testing & reliability criteria

If you work with process pumps, API 610 is non-negotiable.

API 674 / API 675 / API 676 – Positive Displacement Pumps

Essential for:

• Chemical injection systems
• Metering & dosing
• High-pressure services

Includes:

• API 674 – Reciprocating pumps
• API 675 – Controlled-volume pumps
• API 676 – Rotary PD pumps

API 682 – Mechanical Seals

One of the most critical standards for pump reliability.

Defines:

• Seal categories & arrangements
• Flush plans
• Leakage control philosophy

Wrong seal selection = leaks, fires, frequent shutdowns.

API RP 691 – Risk-Based Machinery Management

Introduces risk-based maintenance, replacing blind time-based schedules.

Helps identify:

• Critical equipment
• Failure consequences
• Maintenance priorities

To know more about units used in oil and gas and natural gas measurement, refer to our detailed guide.

🟦 API Standards for Compressors

API 617 – Axial & Centrifugal Compressors

Widely used in:

• LNG plants
• Gas processing units
• Refining operations

Covers:

• Aerodynamic design
• Performance testing
• Reliability requirements

API 618 – Reciprocating Compressors

Vital for high-pressure gas services.

Focus areas:

• Pulsation control
• Vibration limits
• Valve & cylinder reliability

Long compressor life depends heavily on API 618 compliance.

API 619 – Rotary-Type Positive Displacement Compressors

Used for screw and rotary compressors in gas applications.

API 672 – Packaged Integrally Geared Compressors

Common in:

• Refineries
• Air separation units
• Process industries

API 692 – Dry Gas Sealing Systems

A mission-critical standard for modern compressors.

Ensures:

• Seal integrity
• Reduced gas leakage
• Emissions control

🟦 Installation, Reliability & Maintenance (Where Failures Begin)

API RP 686 – Machinery Installation & Installation Design

One of the most underrated yet powerful standards.

Reality check:
❌ Poor installation = guaranteed failure, no matter how good the equipment is.

Covers:

• Foundations & grouting
• Shaft alignment
• Piping strain control

To know more about CNG vs LNG vs PNG. Check our detailed comparison.

API RP 687 – Repair of Rotating Equipment

Ensures repairs:

• Restore original design intent
• Or improve reliability beyond OEM condition

Essential for overhaul engineers.

API 684 – Rotor Dynamics & Balancing

Critical for high-speed rotating equipment:

• Vibration analysis
• Critical speed evaluation
• Dynamic balancing

API 688 – Pulsation & Vibration Control

Important for:

• Reciprocating compressors
• PD pumps
• Complex piping systems

API RP 697 – Pump Repair

Defines best practices to ensure repaired pumps don’t become repeat failure cases.

For mechanical engineers in oil & gas, LNG, and LCNG, API standards are not optional skills — they are career survival tools.

Mastering API standards means:

• Fewer failures
• Higher technical credibility
• Better global job opportunities
• Stronger safety culture

Equipment doesn’t fail suddenly — it fails when standards are ignored. API knowledge helps you see failures before they happen.

API Standards for Piping, Pipes, Valves & Fittings (Often Overlooked)

In LNG and LCNG plants, piping systems are as critical as pumps and compressors.
A failure in piping can lead to gas leaks, fire hazards, pressure loss, and shutdowns.

This is where API + ASME piping standards come into play.

API 5L – Line Pipe

One of the most widely used standards for oil & gas pipelines.

Covers:

• Carbon steel line pipes
• Seamless & welded pipes
• Pressure-containing capability
• Material grades & testing

Used in:

• Gas transmission lines
• Process piping headers
• Utility gas pipelines

API 570 – Piping Inspection Code

A must-know standard for operations & maintenance engineers.

Defines:

• Inspection intervals
• Corrosion monitoring
• Remaining life assessment
• Fitness-for-service decisions

Critical for ageing LNG/LCNG plants.

API 6D – Pipeline Valves

Applies to:

• Ball valves
• Gate valves
• Plug valves
• Check valves

Used in:

• Isolation of gas lines
• Emergency shutdown systems
• High-pressure gas services

Ensures:

• Leak-tight shutoff
• Fire-safe design
• Operational reliability

🟦 ASME Standards (Used Alongside API)

While API defines industry requirements, piping design is often governed by ASME codes.

ASME B31.3 – Process Piping

This is the core piping code for LNG, LCNG, refineries, and gas processing plants.

Covers:

• Pipe thickness calculation
• Allowable stresses
• Material selection
• Design pressure & temperature
• Fabrication & testing

Why SS 304L Is Used in LNG/LCNG Plants

SS 304L (low carbon stainless steel) is commonly used for:

• Gas lines
• Instrument tubing
• Low-temperature & corrosive services

Advantages:

• Excellent corrosion resistance
• Better weldability (low carbon)
• Reduced risk of carbide precipitation
• Suitable for cryogenic and gas services

Material selection is verified against ASME B31.3 + API inspection standards.

 Key Takeaway for Mechanical Engineers

API standards do not stop at pumps and compressors.

A complete oil & gas mechanical engineer must understand:

• API for rotating equipment
• API for piping & valves
• ASME for piping design
• API for inspection & integrity

Many real-life failures happen not because of bad equipment,but due to wrong material selection, poor piping design, or ignored inspection codes

To know more about how LNG invoicing works, including billing and measurement, refer to this article.