Instrumentation valves and manifolds: it’s the material is that counts

Paul Boughton

Instrumentation valves and manifolds come into contact with many different types of media, each with unique characteristics. Leak free service is important for both the operator and environment. Linda MacDonald reports.

Soft seated valves and manifolds have proven to be safe and reliable solutions in countless applications, including, chemical plants, oil refineries and natural gas pipelines.

In contrast to metal seated valves, their stem needle or seat pocket incorporates a synthetic seat. When the valve closes, the elastic seat material is compressed, creating a leak free, bubble-tight closure. This provides the highest possible safety and ensures accurate instrument calibration and measurement results.

AS-Schneider’s Soft Seated Instrumentation Valves and Manifolds are used in applications such as extraction and transportation of natural gas. Leak free valves and manifolds are critical for accurate measurement.

Emissions monitoring of gas is required and gas is not allowed to escape into the environment for reasons of safety and environmental protection.

Additionally leaking measurement installations can lead to incorrect measurements of pressure or flow. Incorrect measurement or ‘lost and unaccounted for’ natural gas adds to higher operating costs. As a result it is critical for valves to be absolutely tight and operate consistently.

Raw natural gas comes from three types of wells: oil wells, gas wells and condensate wells. Depending on the type of well, it can be accompanied by a variety of other components, including crude oil, ethane, propane, butane, pentane, water vapour, carbon dioxide, helium and nitrogen.

Sand, grit, dirt and hydrogen sulphide can also contaminate raw natural gas. In addition, producers add chemicals such as mercaptan, which gives natural gas its characteristic odour, as well as corrosion inhibitors and glycol to protect pipelines against moisture and freezing. These substances make raw natural gas into a highly aggressive and complex process medium that can corrode equipment, eventually causing damage.

Selection of the right seat material is therefore very important. Not every material is resistant to all the components and additives in natural gas. Moreover, the materials have different limits in regard to operating temperatures and pressure. These factors must be considered to achieve long term reliable valve performance. AS-Schneider therefore offers a range of different soft seat materials, ensuring that its valves provide excellent long term performance.

Soft Seated Instrumentation Valves and Manifolds have a number of other advantages: they are safe and reliable, and the resilient synthetic material compensates for debris on the sealing surfaces.

Also the seats are easy to replace, which prolongs the life of the valves in the case of aggressive or dirty process media. Users can replace the valve seat instead of the entire valve or manifold. This cuts repair costs and increases reliability: by performing regular maintenance, system operators can reduce the risk of leaks to a minimum.

Linda MacDonald is US Sales Manager at AS-Schneider America, Inc, Houston, Texas. AS-Schneider is based in Nordheim, Germany.