Why Use a Swagelok Sample Probe Module?

The oil, gas, and chemical industries use process analyzers to measure the concentration of key components in their gas and liquid streams. These analytical measurements must be reliable to maintain precise process control, which helps reduce costs and improves quality and safety. To ensure a useful analytical measurement, it is critical for extracted samples to be representative of what is in the process pipe and to reach the analyzer in a timely manner. Using sample probes in conjunction with sample probe valves can improve safety, sample purity, and timeliness.

Swagelok Sample Probe Module (SPM) Basics

• SPW welded sample probes are best suited for use with double block-and-bleed SPVs (SPV61 and SPV62). SPV61 contains a primary block valve, a secondary block valve, and a bleed valve. SPV62 contains the same valve configuration, but adds a mechanical interlock between the primary block valve and the bleed valve.
• SPR retractable sample probes are best suited for use with single block-and-bleed SPVs(SPV63 and SPV64), which include safety features that do not allow the valve to actuate while the probe is in service. SPV63 contains a primary block valve, a bleed valve, and a probe spool lock. SPV64 adds a mechanical interlock between the primary block valve and the bleed valve.

Probe Design A probe provides a faster analyzer response by reducing the volume of the sample system. The nozzle volume can be significant, increasing the required purge volume of the entire sample system. Also, the probe allows the sample to be extracted from the center of the process pipe, which eliminates the extraction of sludge along the pipe walls. Further, the 45° angle cut of the Swagelok probe greatly reduces the amount of particulate extracted into the sample system. Both features help ensure the probe extracts a representative sample from the process. For these reasons, we recommend using a probe in pipes larger than 2 in. (50 mm); this is especially critical for pipes larger than 4 in. (100 mm). Probe designs can vary in length, diameter, wall thickness, and materials of construction.These parameters will affect the probe’s strength, filtering ability, and internal flow velocity. Thicker, larger welded probes will withstand more impact from high process flows, but offer slower flow speeds through the larger internal diameter. However, this slower flow speed allows more particles to fall out of the probe instead of continuing into the analytical sample system. Smaller retractable probes are not as strong as welded probes, but their smaller internal volume provides faster flow speeds to the analyzer.