Oil and Gas Wellhead Valves Meet Special Application Challenges

Slab Gate Valve
Courtesy Flowserve - Valbart

Industrial valves are manufactured in a huge array of configurations to accommodate the specialized needs of a broad range of industrial process applications. The oil and gas industry is but one segment of many throughout the industrial sphere that presents its own set of application specific criteria.

Oil and gas production, essentially pulling raw material from the earth, has unique valve performance challenges. Extreme pressure and abrasive or erosive material are common elements of oil and gas production at the wellhead. The valves also need to tolerate the range of outdoor temperatures at the production site. Safe and reliable operation throughout these and a range of other conditions are part of the design criteria for these valves. Here are some of the specific valve variants and configurations applied in the oil and gas industry at the production wellhead.

Rising Stem Ball Valve
Courtesy Flowserve - Valbart

• Slab Gate Valve - Provides metal to metal seal and employs parallel gate and seal with a preloaded means of assuring positive upstream and downstream seal. Full port design allows for pigging.
• Expanding Gate Valve - A parallel expanding gate seals positively against both seats, which are protected from the flow medium in the open and closed positions.
• Mud Gate Valve - Designed to provide positive closure under rigorous field conditions with abrasive media. 
• Adjustable Choke Valve - Designed to regulate production well flow and downstream pressure. Different trim configurations provide appropriate levels of control.
• Needle Adjustable Choke Valve - Utilizes different trim arrangement than other types to provide good flow management, abrasion resistance, erosion resistance, and reliable service over a long life with low maintenance requirements.
• Check Valve - Check valves of various types are utilized throughout practically all fluid flow operations, essentially anywhere that fluid is supposed to flow in only one direction. Oil and gas production presents some special conditions of abrasion, erosion, and pressure that call for special accommodation in design and materials of construction.

There are other specialty valves employed at or near the wellhead, but the key take away here is that oil and gas production generally cannot be accommodated by general purpose valves. Share your oil and gas production challenges with a valve specialist. The combination of your process and production field experience with their product expertise will produce effective solutions.

Electric Control Valve Actuators

CVQ Electric Valve Actuator
For quarter turn valves
Courtesy Rotork

Many process control valve installations present the option of selecting either electric or pneumatic actuators as part of the control component train. Pneumatic actuators have been in use for many years, but advances in electric motor design that delivered greater torque and more precise operation have brought electric valve actuators into a prominent market position.

Electric actuators are compact and comparatively self contained, requiring only cable connections and none of the additional devices sometimes needed for a pneumatic installation. There are some points of advantage to consider with electric actuators. Rotork introduced their CVA line of electric actuators almost ten years ago, making it something of a mature product now. Here are some advantageous points about the CVA actuators that likely apply generically as well.

• Setup is accomplished with a Bluetooth enabled device which provides quick calibration of open and closed positions, as well as establishment of valve setup parameters.
• A separately sealed electrical connection compartment keeps motor and mechanical compartment isolated from the environment while electrical connection section cover is removed.
• An on board datalogger records thrust and position data over time for use in asset management and service functions. Data can be downloaded by Bluetooth or transmitted by common protocol to another station.
• Change in setpoint produces a rapid and precise change in valve position with high resolution accuracy and repeatability.
• Actuator can be programmed to move to a preset condition in the event of a loss of electric power. The energy to achieve the failsafe position is stored in the actuator.
• Force balance positioning used in pneumatic valves, with spring force vs. air pressure, has resilience that can result in a change in position of the valve trim in response to a bump in system pressure. Resistance from the gear train on electric drives prevents this movement.
• Static friction of the valve packing and other parts increases the amount of force to intially get the valve moving toward a new position. The additional time required to build air pressure and force to overcome static friction results in delayed valve response, then overshoot of the new setpoint. A combination of a sensor system and the mechanical drive section of an electric actuator eliminates overshoot and delayed response.

Electric actuators can be had in quarter turn and linear versions, with torque ranges suitable for a broad range of process control applications. The datasheet below, from Rotork, provides useful illustrations of the actuator interior, along with additional detail about electric actuators. Share your process control valve requirements and challenges with product application specialists, combining your own process knowledge and experience with their product application expertise to develop the best solutions.

Electric Control Valve Actuators for Industrial Process Applications from CTi Controltech

Innovative Boiler Water Level Gauge Delivers High Visibility

The Simpliport boiler water level gauge provides the type of performance always wanted by operators. It is visible from great distance at angles up to 180 degrees. The brightly illuminated display clearly shows what portion of the boiler contains water and what portion contains steam.

The short video provides a good demonstration. More information is available from steam system specialists. Share your combustion and steam system requirements and challenges with experts, combining your own knowledge and experience with their product application expertise to develop effective solutions.

Clean Steam Trap Ball Valves

Cutaway view of sanitary ball valve on clean steam trap piping
Courtesy PBM Valve Solutions

The use of clean steam generally implies that there are substantial concerns regarding sanitary aspects of an application. Clean steam systems, from production through distribution and return, differ in many respects from systems where clean steam is not the medium.

A major consideration for sanitary applications is the practical reduction or outright elimination of dead areas in piping systems. Any section, regardless of size, that can trap liquid is considered a potential harbor of contamination.

PBM Valve Solutions addresses some challenges posed by the use of ball valves at trap locations in a clean steam system. The valve materials and design modifications make them well suited for the intended application and reduce the pipe and fitting requirements for the trap installation.

The common design for a ball valve allows some amount of fluid to be retained within the port area of the valve when it is closed. This is undesirable for a clean steam system where the steam may come in contact with manufactured product. There can also be a requirement in such a system to maintain a minimum temperature throughout the steam distribution system under all conditions, to assure sterility is maintained. The specialty clean steam trap valve has  purge holes that drain the port area to the valve outlet that leads to the steam trap. Other features of this specialty valve support the effective use of clean steam in sanitary processing.

The document below, from PBM Valve Solutions, provides more detail on the operating features of the clean steam trap ball valve. Share your steam system and fluid processing challenges with application specialists, combining your own process and facilities knowledge with their product application expertise to develop effective solutions.

Ball Valves for Use in Clean Steam Trap from CTi Controltech

Boiler Feedwater Deaerator

Spray type feedwater deaerator
Courtesy Williams and Davis Boilers

Boiler feedwater can require treatment in order to minimize corrosion and scaling which lead to steam system performance reduction or eventual failure and repair. There are various technologies, methods, and units of equipment which process boiler feedwater for differing challenges. One of those equipment items is a deaerator.

The purpose of a deaerator is to reduce the amount of dissolved oxygen and carbon dioxide in the feedwater. Both of these dissolved gases contribute to corrosion in the boiler and steam system. Oxygen will promote the formation of oxides with metal surfaces, commonly steel, found in most steam systems. Dissolved carbon dioxide in the feedwater will promote the formation of carbonic acid (H2CO3) which is also corrosive to metals.

Feedwater deaerators come in two basic forms. The tray type deaerator will generally have two sections, an upper domed section where feedwater is heated by system steam and dissolved gases liberated from the water, and a lower shell vessel that serves as a collecting reservoir for the degassed water. The spray type deaerator employs a single vessel or tank, with feedwater sprayed into the vessel and heated by system steam. The steam strips the dissolved gases from the feedwater, then maintains the stored feedwater at a temperature high enough to prevent gases from re-dissolving in the feedwater. Both tray and spray systems vent the removed gases.

Williams and Davis Boilers, in addition to manufacturing a broad line of steam boilers, also manufactures spray type deaerators in vertical and horizontal configurations, as well as other steam system ancillary equipment.

Share your steam system challenges with the combustion and steam experts at CTI-Controltech, combining your own process and facilities knowledge with their steam system expertise to develop effective solutions.