Butterfly valves are marked with bidirectional sealing, can the reverse pressure difference also be used at full rated value?

Allowing reverse flow when opened does not mean that the forward and reverse pressure differentials and sealing performance are the same when closed. The customer provides two different directions of working conditions and checks the arrows and test range to avoid misunderstanding of "bidirectional sealing".

First, distinguish the direction of flow from the direction of pressure difference when closing

The open state allows fluid to pass through from any direction, but it does not automatically indicate that both sides have the same sealing ability after being closed. The force during closure is related to the arrangement of the valve seat, and corresponding information is required for the actual product. Cannot use smooth flow when opened as a reverse shutdown test.

Project description: Normal direction and possible reasons for reverse direction, such as changes in pressure at both ends or process switching. Reverse flow can be a short-term state or a long-term task. List the design conditions for different tasks separately to avoid suppliers choosing only in the normal direction.

Bidirectional sealing requires specification of conditions and scope

When requesting bidirectional shutdown, clarify the positive and negative pressure difference, temperature, medium, and allowable leakage. A structure that meets bidirectional requirements under specified test conditions does not necessarily have the same performance under any pressure difference. Check the valve body pressure rating and reverse sealing range separately.

The manufacturer's documents may provide priority directions or restrictions on different directions. Even if it is written in both directions, arrows and installation instructions should not be ignored. When files contradict each other, obtain a complete set of confirmation first, and do not solve the problem of physical use by deleting arrows or rewriting pages.

The actuator load may also vary with direction and operating conditions

The actual driving demand needs to be evaluated based on pressure difference, temperature, and action stage. When the reverse pressure difference changes, the original no-load output comparison cannot be retained. The matching of valve position, shut-off and load requires a complete set of criteria, and a larger actuator does not automatically expand the pressure bearing capacity of the valve seat.

Closing feedback and leakage inspection still need to be separated. When the feedback is in place but the sealing is not satisfactory, investigate the actual working conditions, direction, and structure, and do not immediately increase the endpoint force. For valves with specific shut-off designs, adjustments require manufacturer and project basis.

Delivery acceptance should cover real reverse tasks

This site's pneumatic soft seal butterfly valve can be used for corresponding selection consultation. This article does not assume that ordinary models have all bi-directional grades. The confirmation form specifies the required forward and reverse performance, and the physical object and report point to the same configuration. Submitting only one test document without specifying the direction cannot prove all the requirements.

On site operation shall verify the relevant actions and working conditions according to the approved procedures, without the need to temporarily create reverse large pressure differentials with hazardous media. If the process conditions cannot be safely tested, confirmation should be made based on design, manufacturing, and appropriate acceptance data. The article provides direction for data organization and does not approve on-site testing.

Reconfirm after replacing parts and changing running tasks

Valve seat, seal or actuator replacement may change the original set boundary. Maintain records to preserve the identity of parts, assembly, and retest results. The original model text cannot be used, assuming that all forward and reverse conditions remain unchanged after repair.

When adding reverse tasks to the system renovation, provide the working conditions to the supplier again. In the past, one-way use was normal, but it does not prove that the new operating conditions are also applicable. Writing the direction and pressure difference into the operating data can reduce disputes among all parties regarding the meaning of "two-way" after a malfunction.

Two way requirement confirmed in four items

Corresponding products and further reading

Bidirectionality is a technical description that requires conditions, not a reason to omit operating conditions. Separate confirmation of flow paths, pressure differentials, seals, and drives is necessary to ensure consistency between products, reports, and on-site tasks.

Can be combinedPneumatic soft seal butterfly valveData compilation for this working condition; See for similar structurespneumatic valveColumn. The specific configuration and delivery basis need to be confirmed separately.

Extended reading:The difference between soft sealed butterfly valves and hard sealed butterfly valves: temperature, medium, and maintenance boundary。

General technical basis:Example of installation conditions for Fisher butterfly valve in both forward and reverse directionsThe specific configuration and rated conditions of the finished product shall be subject to the information provided in this supply.