When someone’s job is that of an offshore deepwater oil rigger, it is a given that their career is fraught with danger. This is why it is critical to have the very best safety equipment available and in use BEFORE the disaster happens. Here is a little bit about one of the most important safety mechanisms one can have on a deep shore rig, that being safety valves.
Safety valves are very literally the last line of protection one can have before the disaster happens on the rig. It goes, in order: sensor, logic solver, final element. The final element is what the professional term for subsea valves is. While some subsea valves are controlled pneumatically, most of them are controlled via an electrohydraulic configuration. As far as subsea valves go, there is a plethora of designs and styles which can be most useful in virtually any situation.
Safety valves are part of a Subsea Saftey System which automatically goes into effect the minute an emergency arises. Known as a “Safety Instrumented System”, the safety control system goes to work by identifying energy sources of any abnormal incident, thereby averting unnecessary accidents on or around the rig.
Here is a breakdown of some of the many different safety valves with a brief description:
Directional Control- These valves can divert the fluid between ports when there is an emergency need to control the flow. It is common practice to multiplex these types of valves in order to establish a system of sequencing the shutdowns.
Gate Valves- The diameter of the production bore ultimately determines the size of these types of valves. They are referred to as either double acting or spring actuated. To be labeled double acting, the valve must possess an actuator which is required to open or close said valve. To be labeled spring actuated, the valve must rely on the power of hydraulics to open or close the valve. The spring acts as an extra power source and lets the valve open or close more quickly than its double acting cousin.
Shear Rams- These are highly specialized valves. Their purpose is to cut and then to seal the production bore. They are considered to be one of the most critical safety valves in existence. There are whole system set-ups which include these types of valves which can be purchased from specialty companies such as PRT Offshore