ANOTHER CORROSION PROBLEM SOLVED
Seawater Application. Backwash Isolation Valve in Duel Media Filter (DMF).
Nominal Size of the Valve DN 700
Operating Temperature 23 - 35 oC. Operating Pressure 5 Bars
Desalination Plant, Kingdom Of Saudi Arabia.
The body material of existing valve is “A216 WCB Carbon steel” with rubber lining. Rubber lining was deteriorated and detaches, causing the body of the valve to get in contact with the fluid. This causes the process of corrosion to initiate at high rate causing Valve Body leakage.
- Due to intense rate of leakage the pumps working to fulfill the required quantity have to overdo thereby increasing the power consumption of the plant.
- Valves were badly damaged hence refurbishing and acquiring new spares was an expensive option.
- Client requested to utilize the old actuators and gearbox with new valve. Various tests were to be conducted before giving any statement as it was not certain whether the old accessories were compatible with our valves. Incompatibility would cost client an expensive replacement, which was not an option.
- The continuous seawater on ground started affecting the building infrastructure of the areas.
- The leakage point was from the neck of the valve mostly, thus damaging the gearbox along with actuators. Couple of gearbox were so badly damaged that they were not been able to refurbish and had to replace them with the new once.
- The isolation for servicing or other job of the DMF filters was not possible due to internal leakage through valve.
The process of corrosion won’t stop at any given point as body material of the valve is carbon steel which has a poor resistance to seawater when in contact. Without a reliable solution, the plant risked process instability and potential future shutdown. Hence the proposed replacement had the following features listed to overcome the challenges:
- 1st Class quality of material and workmanship technique used to fabricate the valve, which is guaranteed by giving a warranty of 5 years.
- Hybrid Design, consisting both the strength and the property of thermoplastic i.e. no corrosion.
- The durability of the valve can be deduced when engineers who fabricated it, states that the “O-Ring” installed can last for more than 15 year.
- Even though due to some uncertainty if there is a leakage caused. It would not intensify as the body is non-metallic. Hence the risk of plant instability or unable to conduct routine operations can be minimized to zero.
- Fast Track Delivery was necessary as the total plant shutdown was due in 2 months. Before the shutdown the material had to be in plant. The proposed valve fabrication period is 6 weeks only, thus making it possible for replacement.
- The tests carried out for installing the existing gear box along with actuators on new valves was successful. Certain customized jobs were carried out such as:
- An adaptor was designed to install actuator directly with the valve in three cases as the gearbox were badly damaged.
- The Shaft head of the valve was redesigned to be installed in to the old gearbox.
- Supports for the gearbox and actuators were designed to carry their load.