Detecting gas compressor fugitive methane leaks to comply with international safety and environmental regulations

Fluid Components International’s (FCI) ST75 Series Thermal Mass Flow Meter provides technicians monitoring natural gas compressors for dry seal leaks with precision methane (CH4) gas monitoring to detect hazardous and costly gas leaks. It provides accurate and repeatable measurements to enable operators to comply with local, national and international regulations. This precision instrument detects the slightest of changes in flow, making it ideal for leak detection.

 The ST75 is direct mass flow measuring and produces flow rate and totalised flow output signals and readouts in lbs, kgs or tonnes of gas emissions to provide the legally requisite monitoring data – it, therefore, offers the ideal solution for carrying out critical monitoring tasks in busy and crowded industrial locations.

Dry gas seals, often the cause of fugitive methane emissions, are ubiquitous in gas compressor stations. Flow meters, when deployed to monitor the primary and secondary vent gas on dry seals, alert operators of increases in vent gas, which is a sign of possible seal quality degradation, which would require costly and inconvenient maintenance work. Additionally, the ST75 will also indicate the quantity of methane leaked into the environment, or sent to the flare, thereby providing crucial data for greenhouse gas emission reports.

The ST75 features built-in temperature compensation and provides an accuracy of ±2% of reading with ±0.5% repeatability over the differing process temperatures and pressures in line sizes ranging from 0.25 to 2 inches/6 to 51 mm. In situations where there is a limited straight-run, as well as for operating in the Reynolds Number transitional flow range FCI’s Models ST75V and ST75AV, featuring a Vortab flow controller, perform with an accuracy of ± 1% reading, ± 0.5% full scale.

FM/FMC approved, the ST75 is housed in highly robust, industrial grade, all-metal, dust and water resistant NEMA Type 4X (IP66) rated package designed for operation in Class 1, Div 1/Div 2 hazardous area installations. It features a tough, all-welded sensing element made with 316 stainless steel and Hastelloy-C tips. The ATEX/IEC approvals include Zone 1, II 2 G Ex d IIC T6  -  T3; II 2 D Ex tD A21, IP67 T90º  - T300º.

The instrument’s flow sensor has been designed to avoid the use of moving parts, opting instead for precision-matched, platinum RTD sensors that are embedded in equal mass thermowells. The ST75, calibrated to NIST laboratory standards to guarantee a high standard of performance. is far less prone to fouling than other flow measurement technologies used in particulate-laden gas streams. Moreover, there is hardly any of the permanent pressure loss one would expect with a compact sensor design, so it is ideal for use in low-pressure, low-flow applications; it can measure mixed or single-process gases in many applications.

This versatile device is also an excellent choice for use in processing, transportation and storage stages of the oil/gas industry when used for small line, low flow measurement applications. The flow meter includes remote mounting for monitoring where the measurement point has poor accessibility, or for deployment in busy and hazardous areas. The remote transmitter can be mounted as far as 50 feet or 15 meters away from the flow sensor located within the process piping. As an option, FCI offers a version that provides a local display of flow, totalised flow and temperature.

Choosing FCI’s ST75 or ST75A meters means that the is no need for extra temperature or pressure sensors or other additional items necessary with other options; these instruments offer superb performance, at an economical price.