Dry gas seals are usually utilized as shaft seals in turbo machinery, mainly turbo compressors, and work with pressurized sealing gas to maintain a higher pressure than that of the process medium inside the machine. This effectively seals the housing and shaft from the process gases to prevent leaking into the atmosphere.
While the shaft is rotating, a very tiny gap is formed at the seal ring, through which the seal gas flows. To protect these dry gas seals in turbo machines, which are very complex and extremely sensitive to contamination, the seal gas is carefully filtered by GCF gas filters.
Hydac gas filters are high performance duplex coalescing filters which specially have been developed for the use in dry seal gas systems in order to protect the mechanical dry gas seal in turbo compressors.
All the filter components, including the filter housing, are made of stainless steel machined parts without weld connections and comply fully with API 614-5 requirements. All seals within the filter are double sealed for safety reasons, either pressure wise or due to the type of gas (dangerous).
Hydac offers two different standard versions of the GCF gas filters: a one stage coalescer version, preferably used for dry gases, and two stage patented coalescer version with integrated cyclone pre-separator, for those applications using wet gases which could contain aerosols, oil mists, or condensates.
This modular design allows also to retrofit a cyclone pre-separator to an existing standard filter, by just replacing individual filter housing parts.
For special high pressure applications and those using hazardous gases, filters are also available in a Double Block & Bleed version. The materials of the seals and housing can be adapted individually to suit the process conditions.
The filtration is either via the left or the right hand filter housing, there is no interruption of filtration during change-over of the duplex filter. To achieve this, the adjacent filter housing is first pressurized via a pressure equalization valve. Once the pressure has equalized, the filter can be switched over using the duplex change-over valve.
This is a new ball change-over valve, especially developed by Hydac Accessories GmbH, due to this design there is almost no pressure drop during the manual change-over operation even at high-flow rates achieved by the maximum negative overlap.
The GCF gas filters operates by filtering with a flow direction through the elements from in to out. Contamination particles are removed and retained in the filter element, the liquid is coalesced on the outside of the filter element and drained through the drain layer by gravity.
For those applications where the proportion of liquid phase in the gas is too high, a pre-separator or pre-conditioning (heating) must be used. In this case Hydac suggests the GCF with integrated cyclone, as sudden sludge and larger quantities of aerosols and coarse particles can easily be pre-separated by the integrated cyclone. Depending on operation conditions, the cyclone separates aerosols and particles of up to 5 µm. The separated liquids are collected inside the filter housing in collection chambers (both stages with it’s own chamber) after it can be drained via appropriate valves. The capacity of these collection chambers are generous in order to cope with the possible liquid available.
Extensive filed testing has been done in order to develop these filters also computer-aided design and modern research and test laboratories are utilized to get to the maximum result. Tensiometers, Karl Fischer titration equipment, rinsing cabinets to determine the cleanliness of components and test rigs for multi-pass tests and water removal efficiency are used on a daily basis.
Hydac developed a unique sizing program using all types of gases and operating conditions to select the optimum filter for each application.
This program indicates the possibility of aerosols in your gas but also indicates the pressure loses over the filter element and complete filter assembly which are confirmed by the extensive field test which have been done.