Veloci Stainless 3/8" Female Locking QC Coupler
Locking QC Couplers were manufactured with safety and speed in mind. These specialized couplers have a small pin installed below the collar that inhibits the collar from disengaging unless you intended on removing an accessory. Stainless locking couplers are excellent for OSHA regulated facilities and food production where chemicals and hot water are traditionally used to clean. Note in the image, the collar can be spun and offset from the pin so that disconnecting an accessory intentionally is the only way it will disengage.
All stainless couplers are National Pipe Thread (NPT) which means they have a tapered Male or Female thread (depending upon the model). NPT is mainly used in the Western Hemisphere and was developed on the concept of interference by the third thread. When installing NPT fittings to another NPT thread we recommend that you use 4-5 wraps of teflon tape wound clockwise, or 2-3 drops of Loctite thread sealant.
British Standard Pipe Thread (BSP) is found in the European market and has a different thread pitch than NPT. BSP is also considered a 'straight thread' which means it has no taper at the end. When installing NPT on BSP or vice versa, use 6-7 wraps of Teflon or 2-3 drops of Loctite and tighten accordingly. When tightening opposing thread styles (BSP and NPT) you will experience more interference sooner and you will not be able to tighten the fitting as far as like-threads. You will still have a tight seal, just make sure to use the recommended amount of Teflon Tape or Loctite.