The end fitting of a filter is the only seal between the filter and the housing into which it is installed. A poor seal means that the filter will be totally ineffective and if you purchase certain end fittings you will restrict yourself to buying from that supplier and that supplier only. A trick is often to give a set of filters free with a housing meaning they then have a customer for life and can dictate the prices charged.
To start with, here are a few basic rules. There are two main styles of filter end fitting, the Double Open Ended style and the Plug In / On style.
The Double open ended style relies on a flat gasket or crush fit and the seal is maintained by the pressure exerted between the filter and the housing knife end seal. The slightest damage to the housing "knife edge" will mean that liquid can pass via the damaged area and this is particularly prevalent in plastic housings. The general rule must be:
1 For Sub Micronic FIltration always use a plug in or plug on style.
2 If high differential pressures are expected never use a plastic housing or knife end seal. By pass is proven at 1.8 bar and similar differentials as the pressure of the knife edge relies on the strength of the operator who installed it.
The Double Open Ended end fitting is used for general filtration and should only be used for filtration larger than 1 micron ideally. This style can be used in metallic housings or plastic housings but care should be taken not to damage the knife edge seal in any way. Plastic housings can become damaged with time and should be replaced. The pressure exerted on the seal and the security of that seal is 100% reliant on the pressure exerted by the operator or the length of the filter housing in the case of a plastic unit. Seals contain a much larger quantity of elastopolymer so for a PTFE seal the cost of the seal alone can be very high but with silicon seals it can be a cost effective way of filtering.
The Code 2, as it is best known, is a single open ended filter with two BS 226 seals at one end, but with a and a "Flat" end fitting at the other end. This end fitting is universally available from all filter manufactures and has become the industry standard for Pharmaceutical and critical applications mainly for gas filtration where single filters are used. It has two locking lugs which once the filter is installed can be rotated to securely hold the filter. There are filter manufacturers out there who even with this universal filter have tried to ensure only their filter fit their housings but with CFS you can be assured our filters will fit all known housings of this style. Seals are availabe of all types and the two seals give the most secure fitting possible.
The Code 3 consists of two BS 222 seals at one end of the filter and a Flat top the other making this a single open ended filter. The filter is pressed into the base plate or cup and retained by a top plate with springs or the plate alone. The Code 3 is generally used for industrial applications where a secure twin seal is required without the complexity of the code 7. The code 3 is universally available from all known filter suppliers with no worries at all.
The GR fitting is used in applications where a 10 or 20 inch filter may be fitted. The housing is plastic and we believe the housings themselves are no longer made. Originally manufactured by a company who was taken over some years back, the GR fit has no seals at all in the actual filter. Instead there are two seals on the spigot of the housing onto which the filter is pushed. The bowl of the housing retains the filter. Although there are no new housings made there are a large number of these filters still used and CFS can supply these to fit.
The Code 7, as it is best known, is a single open ended filter with two BS 226 seals one and a "Fin" at the other. This end fitting is universally available from all filter manufactures and has become the industry standard for Pharmaceutical and critical applications from small to large scale. It has two locking lugs which once the filter is installed can be rotated to securely hold the filter. In a single housing the fin does very little, however, in a multi cartridge housing the fin normally sits inside a top retaining plate. There are filter manufacturers out there who even with this universal filter have tried to ensure only their filter fit their housings but with CFS you can be assured our filters will fit all known housings of this style. Seals are available of all types and the two seals give the most secure fitting possible.
The Code 8 end fitting is in effect a code 3 but with a "Fin" end rather than a Flat Top. This filter has two BS 222 seals which push into the base plate of the housing or cap. The top end of the filter has a "Fin" which sits in a retaining plate in multi cartridge housings and is normally screwed down. This style is used for industrial semi critical applications but gives a secure seal.
The "A" end fitting is only believed to be made by one company in the UK. It has two secure seals but they are a "non industry standard" BS 224 size meaning that this filter will only fit the housings supplied by the same company. I cannot emphasise this enough, if you are considering a new filter system DO NOT consider a housing taking a non industry standard filter end fitting as in this style. Always go for Code 3, Code 8 or Code 7. Consider this... You buy housing for filters and they give you the first set free as an incentive to buy. You validate your application and the supplier is burned down. You have nowhere else to go for filters to fit your equipment. They also have 100% control over the price charged for filters as there are no other suppliers.
CFS has started making this end fitting to help customers in this situation, so can supply filters of this style, but if you have a choice go for a filter fitting that anyone can supply and remember competition is good for the customer's prices.
The BS 213 internal seal is designed to fit Amatek filter housings although this will also fit housings from other manufacturers. The single "O" ring seal pushes up onto the spigot in the head of the plastic filter housing making a more secure seal than the designed DOE fitting. The bowl then retains the filter.
For better security the AM Fit is preferred for 10 inch and 20 inch plastic housings.