Thursday, October 31, 2013

Baby Food Giant Turns to RENCOR for Tough Valve

steam control valve
The second largest baby food producer in the US needed a tough control valve to cook baby food. The valve was to be installed in a clean area where it would be washed with high-pressure hot water and harsh detergents several times a day.

The application was to accurately control steam so that precise temperature control could be maintained to properly cook the baby food. Accuracy is critical because of food safety and product quality.

RENCOR chose a Samson all 316 stainless steel globe control valve, with 316 stainless steel actuator and 316 stainless steel positioner as the solution. Samson control valves are known for their accurate steam control, are available in all-stainless construction, and are well suited for these types of applications.

RENCOR delivered the valve and all components just two weeks after receipt of order.

Thursday, October 24, 2013

Defining Cavitation in Control Valves

cavitation in control valves
Formation of cavitation
Cavitation is the formation of vapor spaces (bubbles) in the control valve cavity resulting from a rapid change in pressure. When the bubbles move downstream and are exposed to a larger cross-sectional area, velocity decreases and pressure increases. The surrounding higher pressure causes the lower pressure bubble to implode which causes shockwaves. These shockwaves can cause metal fatigue and cause excessive wear on the internals of the valve. As the bubbles collapse, they make a discernible sound with accompanying vibration and the damage to a valve can happen quickly (weeks or months).

Cavitation is very destructive and may wear out the trim and body parts of the valve in short time. Using hard internal materials provide a little improvement, but the harder materials also cost more and their use must be justified.

How can you minimize cavitation in control valves? You can change the process conditions and reduce operating temperatures. This may lower the vapor pressure enough to stop cavitation. Reducing the differential pressure across the valve can relieve or lower cavitation. Locating a control valve in the lowest elevation of the piping system and keeping the control valve as close as possible to the pump are  also recommended practices.

Here is an excellent and thorough technical paper on cavitation in control valves courtesy of Samson Controls.

Thursday, October 17, 2013

Superior Design Check Valve Better Than Swing Check

Proquip Check Valve Design
Many engineers apply swing check valves because they are inexpensive and their use is pretty wide spread. Our experience tells us there are better alternatives. Here are the reasons RENCOR favors Velan-Proquip valves over conventional swing check valves.

Reduced Size – Weight – Cost: 

The inherent design of the double flapper check valves results in a significantly reduced weight as compared to the conventional full bodied check valve. As the valves increase in size the Velan-Proquip valve will be as little as one fifth the weight of the full bodied unit. This results in savings in initial cost, space, and pipe support element installation.

Tuesday, October 8, 2013

What Does "Prepared for Oxygen Service" Mean for Valves?

oxygen service for valves
Image courtesy of Wikipedia
Oxygen service preparation refers to a special cleaning process that removes all traces of oils from a valve to allow use in with oxygen (O2).  Oxygen is odorless and colorless, and exists in air at approximately 21% concentration. It is non-flammable, but supports vigorous combustion to any materials that are combustible. Allowing oils or greases to contact higher concentrations of oxygen can cause ignition and even explosive outcomes. Aside from the reactive concerns, O2 preparation is also used for applications where purity is needed.

Oxygen is used extensively in medical, deep-sea, metal cutting, welding, and metal hardening. The steel industry uses oxygen to increase capacity and efficiency in furnaces. A major use is in production of gasoline, methanol and ammonia where it is used as a synthesis gas.

Friday, October 4, 2013

What is a Butterfly Valve?

high performance butterfly valve
RENCOR actuated HPBV
A butterfly valve is used for stopping or controlling flow of liquids or materials through pipes. The "butterfly" refers to the round, flat disk that allows for flow through the valve. Butterfly valves are a member of the "quarter-turn" valve family, meaning fully open to fully closed in 90 degrees rotation. They are opened and closed via a lever, manual gear operator, pneumatic actuator, or electric actuator. Butterfly valves can be used for on-off service and some varieties are used as control valves. Butterfly valves are generally less expensive than other high flow valves, lighter in weight, and take up less piping length. Since the disk is always in the flow path, butterfly valves always have a pressure drop across the valve.

Tuesday, October 1, 2013

Fail-Freeze Ball Valve with Manual Override

fail freeze ball valve and positionerThis means that, on loss of signal, the valve positioning unit will freeze the valve in the last known position based upon the pneumatic signal at the time of failure. Normally, on losing the signal air, the valve would open or close fully depending on the pneumatic positioner's setting.

However, in some situations, it's important to keep the process running at some level until the batch or system can be shutdown and checked out. This is where fail-freeze comes in handy.

RENCOR recently designed and built an automated 2" ball valve package with a fail-freeze pneumatic positioner, regulator, and pilot valve combination that assured the valve would stay put when the 3-15 psi signal air was lost.

A manual override was included that allowed for manual control of the valve during the batch process and for a controlled shut down after the batch was complete.