Concerns about the vertical installation of butterfly valves

As a key control element in the fluid path, the choice of the installation direction of the butterfly valve is by no means a simple matter of space layout. At the construction site of petrochemical pipelines, experienced engineers will repeatedly emphasize that butterfly valves must be installed horizontally.

Butterfly valve structure design

The butterfly plate and stem of the centerline butterfly valve are coaxial, and when the valve is fully open, the plane of the butterfly plate is parallel to the direction of the fluid. When this structure is installed horizontally, the fluid impact force on the stem is symmetrically distributed, and the sealing ring is evenly in contact with the seat. However, in the vertical installation state, the direction of gravity and the direction of fluid movement form a 90-degree angle, resulting in the additional torque generated by the self-weight of the butterfly plate continuously acting on the stem bearing.

The metal seal structure of the triple eccentric butterfly valve is more precise, and the axis of the valve stem forms a specific eccentric angle with the sealing surface. This design allows for frictionless opening and closing when installed horizontally, but the weight of the disc when installed vertically can unbalance the contact pressure distribution of the dynamic sealing surface. An oil refinery once caused unilateral wear on the sealing surface due to the vertical installation of a triple eccentric butterfly valve, resulting in an unplanned shutdown of a catalytic cracking unit worth tens of millions of dollars.

The impact of vertical installation

In vertical lines, the butterfly valve actuator needs to additionally overcome the torque generated by the disc's own weight. For example, the DN600 butterfly valve has a disc weight of about 150 kg and an increase in opening and closing torque of up to 30% when installed vertically. This constant overload can significantly shorten the life of the worm gear drive mechanism.

Solid particles in the medium are more likely to be deposited in vertical pipes, creating a unique "stalactite" effect. Vertically mounted butterfly valves have up to 8 times the thickness of deposits at the seat than when installed horizontally, a difference that is particularly noticeable in non-full flow conditions.

Solution

When space constraints must be installed vertically, a butterfly valve with a special reinforced stem bearing should be selected and a torque amplified actuator should be configured. A nuclear power plant's cooling water system uses a vertically mounted butterfly valve designed with double row tapered roller bearings, which successfully extends the maintenance interval from 3 months to 2 years. At the same time, it is necessary to set up a settling branch pipe behind the valve and flush the sediment regularly.