Abstract: Various embodiments of the teachings herein include a nipple. Some example nipples include: a fluid passage; a housing; a valve for the fluid passage; and a relief valve for the valve. The relief valve may include: a first sleeve axially movable for sealing against a first seal of the housing; a second sleeve for sealing against a second seal of the housing; and a third seal for sealing between the first sleeve and the second sleeve. Relative axial movement between the first sleeve and the second sleeve opens or closes, respectively by the direction of the axial movement. The relief valve, the first seal, and the third seal are arranged at a set radial distance from a central axis of the fluid passage.

Abstract: Various embodiments of the teachings herein include a pulse counter for fluid pressure changes. The pulse counter may include: a first and a second housing part with a fluid passage; a circuit board at least partially enclosed within the housing, the circuit board comprising a light pulse transmitter and a light pulse receiver; a battery at least partially within the housing, the battery supplying electric power to the light pulse transmitter and the light pulse receiver; a rod slidably arranged within the housing, with one end of the rod within the fluid passage, and a second end arranged at least partly breaking a light pulse between the light pulse transmitter and the light pulse receiver; and a spring forcing the rod away from the light pulse and towards the fluid passage.

Abstract: Various embodiments of the teachings herein include a pulse counter for fluid pressure changes. The pulse counter may include: a first and a second housing part with a fluid passage; a circuit board at least partially enclosed within the housing, the circuit board comprising a light pulse transmitter and a light pulse receiver; a battery at least partially within the housing, the battery supplying electric power to the light pulse transmitter and the light pulse receiver; a rod slidably arranged within the housing, with one end of the rod within the fluid passage, and a second end arranged at least partly breaking a light pulse between the light pulse transmitter and the light pulse receiver; and a spring forcing the rod away from the light pulse and towards the fluid passage.

Abstract: A nipple for a coaxial coupling is disclosed. The nipple comprises a housing (40), and a nipple tube (30) arranged in the housing (40). The nipple comprises a first passage (42) between the housing (40) and the nipple tube (30), and the nipple tube (30) comprising a second passage (32) within the nipple tube (30). A relief valve (20) is slideably arranged in the nipple tube (30). The nipple comprises sealing means (24, 26) for sealing between the nipple tube (30) and the relief valve (20). The nipple tube (30) further comprises a relief passage (34), the relief passage (34) forming a fluid passage between the first passage (42) and the second passage (32). The relief passage (34) being arranged so that the sealing means (24, 26) seals the relief passage (34) when the nipple is fully coupled.