Sample Probe Assemblies for Oil and Gas Applications

Oil and Gas Pipeline Sampling

The oil and gas industry is the largest single market for sample probe assemblies, with installations spanning upstream production facilities, midstream gathering and transmission pipelines, gas processing plants, and downstream distribution networks. In every segment, accurate compositional analysis of the process stream is essential for custody transfer metering, regulatory compliance, process control, and safety monitoring.

Our sample probe assemblies are engineered specifically for the demanding requirements of oil and gas service — high pressures (up to 1,480 psig and beyond for ANSI 600 systems), corrosive process fluids containing H2S and CO2, remote locations with minimal maintenance access, and strict compliance requirements under NACE MR0175 / ISO 15156.

Key Applications

Custody Transfer Sampling

When natural gas changes ownership at a metering station — between producers and gatherers, gatherers and processors, or transporters and distribution companies — the gas composition must be measured accurately because it determines the heating value (BTU content) and the contract price. Even small measurement errors can represent thousands of dollars per day on high-volume pipelines.

Custody transfer sampling requires:

• Probe tip positioned in the center third of the pipe per API MPMS Chapter 14.1
• SilcoNert 2000 coated probe tubes and sample transport lines for trace H2S and sulfur accuracy
• Full wake frequency analysis per ASME PTC 19.3 TW-2016
• NACE MR0175 compliant materials throughout (316 SS NACE as minimum)
• Complete documentation package including MTRs, wake frequency report, and dimensional drawings

H2S Monitoring

Hydrogen sulfide (H2S) is a toxic, corrosive gas present in many natural gas and crude oil streams. Pipeline quality specifications typically limit H2S to 4 ppm (1/4 grain per 100 SCF), and even lower limits may apply for specific pipeline tariffs. Accurate H2S measurement at these low levels requires:

• SilcoNert 2000 coated probe tubes to prevent H2S adsorption on bare metal surfaces
• Short, swept sample transport paths with minimal dead volume
• Materials resistant to sulfide stress cracking (SSC) per NACE MR0175

Our probe assemblies for H2S service are designed to deliver greater than 95% H2S recovery at 100 ppb concentrations, ensuring that your analyzer sees the true process concentration without adsorption losses.

Sour Gas Service

Sour gas — natural gas containing H2S above the threshold levels defined in NACE MR0175 / ISO 15156 — presents unique material challenges. In sour environments, carbon steel and improperly specified stainless steels are susceptible to:

• Sulfide stress cracking (SSC): Hydrogen-assisted cracking under tensile stress in the presence of H2S
• Hydrogen-induced cracking (HIC): Blistering and stepwise cracking caused by hydrogen diffusion
• Stress-oriented hydrogen-induced cracking (SOHIC): A combination of SSC and HIC mechanisms

All wetted components of our sour-service probe assemblies — probe tube, packing gland body, valve body and trim, fittings — are specified to meet NACE MR0175 / ISO 15156 requirements. Standard sour-service materials include:

For extremely aggressive sour environments (high H2S partial pressure combined with chlorides, low pH, or elevated temperatures), Hastelloy C-276 or C-22 may be required for the probe tube and wetted components.

Natural Gas Liquids (NGL) and Crude Oil

Liquid sampling probes in NGL pipelines and crude oil lines face challenges including:

• Multiphase flow and phase separation in horizontal pipe runs
• Wax deposition and asphaltene precipitation on probe surfaces
• High viscosity at low temperatures
• Entrained water and solids

Probe assemblies for liquid service are designed with larger bore tubes (1/2" or 3/4" OD) to prevent plugging, beveled or notched tips for phase-representative extraction, and materials selected for the specific corrosion environment (sweet vs. sour, chloride content, temperature).

Produced Water and Injection Water

Sampling produced water and injection water streams is critical for monitoring:

• Residual H2S content for disposal or reinjection compliance
• Total dissolved solids (TDS) for formation compatibility
• Oil-in-water content for discharge permits
• Scale-forming ions (calcium, barium, strontium) for production chemistry

Probe materials for produced water service must resist chloride pitting and crevice corrosion. 316 SS is adequate for low-chloride produced water; Monel 400 or Hastelloy C-276 may be required for high-salinity brines.

Design Considerations for Oil and Gas

Pressure Classes

All probe assembly components — tube, packing gland, valve, fittings — must be rated for the ANSI class of the pipeline. Pressure ratings are verified using Barlow's formula with appropriate safety factors and temperature derating.

Environmental Conditions

Oil and gas installations span extreme environments — Arctic tundra, desert heat, offshore platforms, and tropical humidity. Probe assemblies must be specified for the ambient conditions as well as the process conditions:

• Cold service: Low-temperature carbon steel or stainless steel per impact test requirements; heat tracing of sample lines to prevent freezing
• Offshore: Marine-grade materials (316 SS minimum), corrosion-resistant fasteners, chain and hardware rated for salt spray exposure
• Remote locations: Robust designs requiring minimal maintenance; extended sealant life; redundant safety features

Standards and Compliance

Our oil and gas probe assemblies are designed and documented to comply with:

• NACE MR0175 / ISO 15156: Material requirements for sour service
• API MPMS Chapter 14.1: Natural gas sampling for custody transfer
• GPA 2166 / GPA 2261: Natural gas sampling and analysis methods
• ASME PTC 19.3 TW-2016: Wake frequency analysis
• ASME B31.3 / B31.8: Pressure piping and gas transmission codes
• Client-specific specifications: We comply with major operator engineering standards (ExxonMobil, Chevron, Shell, BP, ConocoPhillips, etc.)

Contact our engineering team to discuss your oil and gas sampling requirements. We provide complete application engineering support from initial specification through wake frequency analysis, material selection, and final documentation.