Abstract: According to at least one aspect, a fluid flow tube can define a first cavity for receiving a first ultrasonic sensor. The first cavity can have a first longitudinal axis intersecting a longitudinal axis of the fluid flow tube. The fluid flow tube can define a second cavity for receiving a second ultrasonic sensor. The second cavity can have a second longitudinal axis aligned with the first longitudinal axis. The fluid flow tube can define a third cavity having a first transverse cross sectional area larger than a second transverse cross sectional area of the fluid flow tube and sized to receive a shut-off valve.

Abstract: According to at least one aspect, a monolithic sensor mount can include a first cylindrical portion and a second cylindrical portion. The first cylindrical portion can have a first diameter and the second cylindrical portion can have a second diameter larger than the first diameter. The second cylindrical portion defining a recess region to host an ultrasonic transducer. The second cylindrical portion can have an outer surface that defines a male thread to mechanically engage a female thread of a cavity within a fluid flow tube configured to host the sensor mount.

Abstract: According to at least one aspect, a fluid flow tube can define a first cavity for receiving a first ultrasonic sensor. The first cavity can have a first longitudinal axis intersecting a longitudinal axis of the fluid flow tube. The fluid flow tube can define a second cavity for receiving a second ultrasonic sensor. The second cavity can have a second longitudinal axis aligned with the first longitudinal axis. The fluid flow tube can define a third cavity having a first transverse cross sectional area larger than a second transverse cross sectional area of the fluid flow tube and sized to receive a shut-off valve.

Abstract: According to at least one aspect, a monolithic sensor mount can include a first cylindrical portion and a second cylindrical portion. The first cylindrical portion can have a first diameter and the second cylindrical portion can have a second diameter larger than the first diameter. The second cylindrical portion defining a recess region to host an ultrasonic transducer. The second cylindrical portion can have an outer surface that defines a male thread to mechanically engage a female thread of a cavity within a fluid flow tube configured to host the sensor mount.

Abstract: A self latching latch mechanism is disclosed which includes a latch mounted to a first wing and a strike mounted to a second wing or a fixed member. The latch has a latch tongue which can move between a latching position in which the latch tongue can engage the strike to secure the first wing relative to the second wing or fixed member, and a free position which allows relative movement between the first wing and the second wing or fixed member. Latch tongue biasing means are provided to bias the latch tongue towards the latching position. Operating means are also provided to move the latch tongue from the latching position to the free position, and there is a hold back member which can move between a first position in which the latch tongue is prevented from moving to the latching position, and a second position in which the latch tongue can move to the latching position. The hold back member is biased to the first position.