Hi collegues,
Greetings,
I would like to inquire about the closure of valve 2 or 3 which is an intermediate valve on a transmission line, hammer effect from various aspects:
1- Is it essential to study this valve closure effect in hammer.
2- Can the closure of this valve sudden closure and if what is the case that will cause this?
3- Will the surge vessel contribute in the protection of the line after valve ?
4- Generally in water hammer simulation is valve closure modeled separately from pump failure or in combination?
Abdallah Magdy said:1- Is it essential to study this valve closure effect in hammer.
Yes, It is a vital topic to model valve closure. Different valve elements serve various purposes and are frequently used in steady-state or Extended Period hydraulic models. They can generally be categorized as flow control. For example, the GPV defines a curve of flow versus headloss, the FCV (Flow Control Valve) controls flow to a set point and the PRV (Pressure Reducing Valve) controls the downstream pressure to be below a set point. Modeling Reference - Valve Closure explains how various types of valves work and their typical application in HAMMER and in WaterGEM / WaterCAD. It also provides an example model file for demonstration purposes. A video demonstration is found at the bottom. I request you to please go through it.
Abdallah Magdy said:Can the closure of this valve sudden closure and if what is the case that will cause this?
Sudden changes like these create a transient pressure pulse that rapidly propagates away from the disturbance, in every possible direction, and throughout the entire pressurized system. If no other transient event is triggered by the pressure wavefronts, unsteady-flow conditions continue until the transient energy is completely damped and dissipated by friction. I did not understand the question completely but it will be great if you can elaborate it.
The following article talks about how a dynamically-operating valve such as an FCV can be converted to a TCV, which has a bit more flexibility and control over the relative closure: Converting a PRV PSV or FCV to a Throttle Control Valve (TCV) in HAMMER
Abdallah Magdy said:Will the surge vessel contribute in the protection of the line after valve ?
There are many different surge mitigation strategies and devices to help protect a pressurized system from the damaging effects of a hydraulic transient. HAMMER is able to model most devices and protection strategies and has tools to help you visualize and compare effectiveness. However, engineering judgment plays a critical role in determining which strategy, device or combination of devices to use and where to place them. HAMMER will not do this for you as there are many factors to consider including cost, space, maintenance, local requirements, and more. As the engineer, you must take these factors into consideration and use HAMMER to help you quickly test and compare effectiveness. The transient Protection Strategies article provides guidance on the application of typical surge protection equipment and strategies.
Abdallah Magdy said:Generally in water hammer simulation is valve closure modeled separately from pump failure or in combination?
For the transient simulation, the pump does not necessarily assume a check valve. Under the "Transient (Operational)" section of the pump properties, you can choose between a check valve or a control valve. When using the "shut down after time delay" transient pump type, you have 3 options to select to model a valve in the pump which could be a check valve or control valve, which needs to be defined pump transient properties as below.
Please go through the Modeling a Check valve or Control valve in a pump for transient analysis wiki article.
A few important links -
Basics of a Transient Analysis in HAMMER
Hammer TechNotes and FAQs
HAMMER Playlist (YouTube)
Please reply if the answer is not satisfactory. We are happy to help you.