Control Valves – Repeat Actuator Diaphragm Bursts

Instrumentation engineering root cause analysis (RCA) of repeat failures of actuator diaphragm bursts in control valves.

Article Type:Root Cause Analysis (RCA)
Category:Instrumentation
Equipment Type:Control Valves
Author:S. Raghava Chari

Note: This root cause analysis (RCA) is from real-time scenarios that happened in industries during the tenure of two or three decades ago. These articles will help you to improve your troubleshooting skills and knowledge.

Actuator Diaphragm Bursts Problem

2 Nos. 4” 1500 # angle design valves Double Acting Actuator diaphragms burst on pressuring; vendors repeated improvement attempts failed.

Root Cause Analysis

Why non-lasting and across diaphragm air leaking double-acting diaphragms?

The Author answers are

  1. Too thin 4.5 mm just  thick diaphragms
  2. Too short rubber beyond bolt holes near OD and also near central opening.
  3. Hence, the long 80-mm valve stem travel stretched diaphragm tears near OD and ID bolt holes peripheries

Author Solution

The author’s below-listed improvements stopped diaphragms bursts forever:

  1. Diaphragms duplicating the original cut out of 12 mm thick used conveyor belt pieces with central opening lasted a month; but the across diaphragm very small leaks at start became unacceptable within 2 weeks
  2. The vexed author got diaphragms cut out of 25 mm new conveyor belts as in 2 with 25 mm OD increase and no central opening. Secured the diaphragm plate with 2-bolts 90o apart – total 8 and not the original 24 –
  3. Diaphragms bursts and across diaphragm leaks vanished forever 
Control Valves - Repeat Actuator Diaphragm Bursts

Benefits Realized

Diaphragm failures totally vanished. No seat leak at 300 bars bench test confirmed full valve travel.

Author: S. Raghava Chari

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