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Everything You Need to Know: 316L Stainless Steel

Did you know that low carbon steel alloys have a carbon content from 0.01% up to 0.3%? these alloys are used to make different types of objects and metal components such as fasteners, bolts, medical tools, shafts, spindles, and more.

One of the most popular types of low carbon steel is the 316l stainless steel alloy. This metal contains up to 0.03% carbon and it can be very easy to work with. You should not confuse the 316l alloy with the plain 316 stainless steel because there are important differences between them. Keep reading to find out more!

316l Stainless Steel 101 – Everything You Need To Know

One of the main differences between 316l stainless steel and 316 stainless steel is that the former contains up to 0.03% carbon and the later contains up to 0.08% carbon. These differences give them various properties. Let’s learn more about 316l stainless steel alloy.

1. 316l Is More Suitable for High-Corrosion Use

The 316l stainless steel alloy is used in various applications because it’s great at avoiding weld corrosion. It can also withstand high temperatures and it has a high melting point at around 2,500 degrees Fahrenheit or about 1,370 degrees Celsius. Apart from carbon, this alloy also contains up to 2% manganese and up to 0.75% silicon.

2. 316l Is Used In Multiple Applications and Industries

Unlike other types of steels such as 304 and 306, the 316l stainless steel alloy can be found in various applications where high resistance to corrosion is necessary. For example, experts use it in the chemical and pharmaceutical industry for making surgical tools and medical implants.

This alloy can also be used for making textile tubing as well as equipment for the petroleum refining industry. 316l steel has high formability which means that it can be bent and cut in various ways without damaging it. As a result, it’s also used for ductworks, for making ozone generators or sewage water filters.

3. 316l Comes In Various Shapes

Thanks to the fact that this alloy is easy to work with and can’t be easily damaged, companies bend it in various shapes and forms. For example, 316l stainless steel comes as ribbons, wires, sheets, strips, and other shapes. Each industry manipulates this metal with great success to create various finished products.

4. Understanding the Differences Between 316l and 316 Stainless Steel

Although both of these steels are considered to be low carbon steel alloys, they are quite different. For example, the “L” stands for “low” in 316l stainless steel and signifies that this alloy has a very low carbon content. The 316l variant is also more resistant to weld decay in comparison with 316 and it can withstand higher temperatures. That’s why 316l is used often in marine and construction projects.

Take Your Steel Knowledge to The Next Level

The 316l stainless steel alloy is a staple in today’s metallurgy industry and it can be tailored to accommodate the needs of your business. Make sure that you contact us today to learn more about steel fabrication and how our supplies of 316l stainless steel can benefit your company!

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Everything You Need to Know About Valve Symbols

Valves are the unsung hero of almost all industrial and engineering applications. You can find valves in use in pipelines, oil and gas, food and beverage, biopharma, marine, and many other industries. 

No matter what the final industry is, each of them uses planning documents and diagrams to outline their system processes. 

Without knowing the valve symbols, you’ll be at a loss for understanding the system. 

Gate Valves 

A gate valve will open or cut off the flow of water through a pipe. They typically have a wheel handle that gets turned to operate the metal disk that blocks the flow. 

Its symbol looks like the outline of a bowtie with two straight lines crossing each other to form an “X”. Then two vertical lines connect the ends to create an enclosed shape. 


Globe Valves 

These valves are similar to the gate valve in how they regulate the flow of liquid. The main difference being the movable disk and stationary ring. 

To differentiate these valves from gate valves, there’s a solid circle placed over the center of the “X” shape. 

Ball Valves 

A ball valve increases the control you have over the flow of liquid. Unlike the previous two that are straight on and off, a ball valve can direct the flow to align with a port. 

The symbol is slightly different by making the solid center circle an outline instead. 

Plug Valve 

These valves control flow by using a linear motion to move a cylindrical or conically shaped plug inside of the body of the valve. To signify these valves, an outline of a diamond is used in the place of the circle.

 

Needle Valve 

A needle valve is a perfect solution for when you need precise control of a low flow rate. A needle-shaped plunger moves up and down within the valve to open and close a small port. 

To signify this precise valve on a diagram, the bowtie symbol is used with a downward pointing arrow in the center. 

Diaphragm Valves

These valves have multiple ports within the body of the valve. The system then uses air pressure to control the opening and closing of the different valves. 

Since these valves operate slightly differently from the previous valves we’ve discussed, it’s no surprise we see the first real variation in the symbol. 

Take the bowtie symbol we have established and draw a horizontal line through the center of it. Now erase the top half. What you’re left with is the symbol for a diaphragm valve.  

Butterfly Valves

These valves excel in tight locations. They have a spring-loaded handle that locks the valve into the open position. 

The symbol for these valves consists of two vertical parallel lines. Then a diagonal line extends from the top of the left line to the bottom of the right line. In the center is a solid circle. 

Know Your Valve Symbols

Knowing your valve symbols will make your life much easier when it comes time to decipher your pipe and system diagram.  While each of these symbols has several variables for their different types of valves, these main category symbols will help get a general understanding. 

Use our valve product selection guide to find the perfect part for your specific application.

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A Stainless Steel Comparison – Grade 316 vs. Grade 304

All steels have the same basic iron and carbon composition, but stainless steel also contains a healthy dose of
chromium—the alloy that gives stainless steel its famous corrosion resistance. Stainless steel stains less easily than
other iron-based metals, but it’s not literally “stainless”. Just like standard steel, stainless can get marked up by
fingerprints and grease, develop discoloration, and eventually rust. The difference is resilience. Stainless steel can
withstand much more time and abuse before showing signs of wear.

Stainless steel must contain at least 10.5 percent chromium. Depending on the grade, it may contain much higher
chromium levels, and additional alloying ingredients. There are multiple grades under the stainless steel umbrella, each
with slightly different alloy composition, and therefore slightly different physical characteristics. Stainless steel types
include Ferritic, Austenitic, Martensitic, Duplex, and Precipitation Hardening (PH). A quick primer on the definitions of
stainless steel types can be found here.

The two most common austenitic stainless steel grades are 304 and 316. The key difference between stainless steel
grades 304 and 316 is the addition of molybdenum, an alloy that drastically enhances corrosion resistance, especially for
more saline or chloride-exposed environments. Commonly found in marine applications, 316 stainless steel contains 2
to 3% molybdenum, while 304 has none.

(Excerpts and content above from Reliance Foundry. “304 Stainless Steel versus 316 Stainless Steel”)

For pressure vessel components – our G-Series® & Mark VIII® Valves and all O-SEAL & Mark VIII® Fittings – CPV
Manufacturing uses austenitic grade 316/L SS as our standard offering. The 316 stainless steel we procure for our
fittings is dual certified to both 316 and 316L Grade. This dual certification ensures that the carbon content is 0.03% or
lower and the material has outstanding weldability.

Here’s a quick breakdown on the chemical composition, differentiating the two grades of stainless steel:

(Source: Australian Stainless Steel Development Association. “316: The First Step Up“)

(Source: Australian Stainless Steel Development Association. “304: The Place to Start“)

A few more key differences between these 304SS and 316SS include:
316/L stainless steel:

  •  Superior corrosion resistance
  • Chlorine resistant
  • Molybdenum content provides greater resistance to chemical attack than 304/L.
    • Is required for the manufacture of certain pharmaceuticals in order to avoid excessive metallic
      contamination, usually from manufacturing equipment.
  •  Considerably more resistant to solutions of sulfuric acid, chlorides, bromides, iodides and fatty acids at high
    temperatures.
  • Common applications:
    •  Offshore, marine (especially with chlorides present) & washdown
    •  Chemical processing and storage equipment
    •  Refinery equipment
    •  Medical devices & pharmaceutical equipment
    •  Outdoor electrical enclosures
  •  UL Nema 4x rated & certified

304/L stainless steel (also known as 18-8 or 18/8):

  • Lowest Cost Corrosion Resistance Option
  • No limitations on fabrication
  • Resistant to oxidation
  • Common applications:
    • Auto moldings and trim
    • Wheel covers
    • Storage tanks
    • Kitchen equipment/appliances
    • Electrical enclosures
  • UL Nema 4x rated & certified

(Excerpts and content above from Nema Enclosures. “What’s the difference between 304 and 316 stainless steel?”)

CPV Manufacturing stocks all standard fittings in 316/L stainless steel because of its strength, enhanced corrosion
resistance and compatibility with various gases. Experience shows its superior functionality in a wide variety of critical
industrial applications and environmental conditions.

We can provide 304/L stainless components in certain applications if requested by the customer. However, 316/L is the
material of choice and is generally suitable for anywhere 304/L is used.

Please reach out to our Sales Team here for further information and quote requests. Our Engineering team can answer
any technical questions you may have as well!

Additional Sources used for this article:

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Extreme Temperatures

Valves Below Zero

The high temperature extremes that occur in some processes or operations and the tolerance of certain metals to such heat tend to earn a lot of attention and respect. It’s got to be scorching hot before 316 stainless steel will melt (2507°F – 2552°F in case you were wondering).

At the other end of the spectrum, cold temperatures can wreak havoc on valves and fittings, too. The elastomers that comprise soft goods such as O-rings and discs may become brittle under frigid temperatures. The resulting inflexibility compromises the valve’s ability to seal.

Low temperatures should not be confused with cryogenic temperatures. Cryogenic environments range from a high temperature of -238°F (-150°C) to a low of -460°F (-273°C), also known as absolute zero.

When we talk about low temperatures in this article, we refer to the range between 32°F (0°C) and the low end of the ambient temperature scale – temperatures like one might find in northern regions of North America, Siberia, the Arctic and Antarctic. We are not referring to cryogenic temperatures.

Operations such as some oil and gas refining processes may take place in climates where the cold is unavoidable. Temperatures not only reach below freezing, but they can remain there for weeks on end. Standard valve models are rated for use down to 32°F.

Often times machinery and equipment in such locations is unattended and in remote areas where damaged valves and equipment are harder to get to for repairs.

What to Look For When Choosing Low-Temperature Valves

Material Selection

Selection of trim materials that will withstand low temperatures is crucial for reducing the risk of cold-related valve failure and/or malfunction. Two factors that affect the material’s cold tolerance are resiliency and periods of dormancy.

Resiliency – the ability of an item to return to its original shape after being stretched is known as resiliency. Resiliency declines as the temperature decreases. Under these conditions the valve’s disc, made of elastic polymers (a/k/a elastomers), will become hard or brittle, reducing its ability to form a proper seal and allowing for leakage. These elastomers also shrink under decreasing temperatures, further compromising the integrity of the seal.

Dormancy – in cases where a valve is not operated for long periods of time, such as when the cycling is long, the O-ring or seal may be in contact with the body for days or weeks. Long-term contact such as this can cause the seal to stick to the metal surfaces, no doubt affecting the valve’s performance.

The chart shown below shows the O-Ring and stem seal materials available from CPV Manufacturing and their corresponding temperature range. The standard, Viton, extends as low as -15°F (-26°C). Ethylene propylene (EPDM) ranges as low as -70°F (-57°C).

Low-Temperature Seal Materials

O-Ring & Stem Seal Temperature Ratings
Buna-N (Nitrile NBR) -30°F to +250°F (-34°C to 121°C)
Viton® (Fluorocarbon) -15°F to +400°F (-26°C to 205°C)
EPDM (Ethylene Propylene) -70°F to +250°F (-57°C to 121°C)
Polyurethane -40°F to +180°F (-40°C to 82°C)

 

It’s not only the trim materials that are subject to compromise in cold temperatures. The metal body has to be able to withstand the cold as well. Cast iron and some carbon steel alloys are not suited for cold temperatures beyond a certain range.

Quality Testing

Depending on the manufacturer, additional testing may be done to ensure quality and safety. Valves should always be tested to ensure that they meet at least the minimum safety and quality standards. These tests will include endurance, seat leakage, and external leakage. Always refer to industry regulations for required standards.

Manufacturers offering valves encompassing a lower temperature range do so using the newest technologies in valve manufacturing. Very few manufacturers offer these cold-temperature options.

You can trust that valves and fittings produced by CPV Manufacturing, with optional seal materials approved for temperatures as low as -70°F, are the highest quality and have met or exceeded all safety and quality standards.

Supplier Reliability

Low-temperature valves and fittings are not available from all manufacturers. In order to simplify inventory and ordering, and to ensure that worldwide industry standards and regulations are met, companies may choose to stick with one source and possibly one specific material for all their valves or for a particular application. They may use the same valves across the board, regardless of location and temperature.

When low-temperature valves and fittings are needed, be sure to consider the reliability of the materials as well as the reliability and reputation of the manufacturer. You want to be able to get the valves and fittings that you need quickly. It’s equally important to have access to customer support.

Questions about CPV’s low-temperature or other valves? Contact us.

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Understanding Bolts

Importance of Using the Right Bolts

Getting to The Nuts and Bolts of It

Nuts and bolts might not be the first things that come to mind when we think about valve maintenance and repair, but they’re definitely worthy of their share of attention.

The nuts and bolts are what hold everything together. Fasteners serve one of two functions: either holding valve components in place or clamping two parts together.

Stretching

Bolts are meant to stretch a little. The stretching is what gives them their force or clamping ability.

As with anything that stretches, fasteners can be overstretched causing them to lose their elasticity or ability to stretch. Think of a spring that’s been stretched out too far. It doesn’t return to its original shape. The same is true of a bolt. A bolt has an elastic limit. It should be torqued to just under its elastic limit. It stretches a little as it’s tightened. If it’s stretched too far–to the point just before it breaks–it will never return to its original size and shape.

You may have guessed then, that a fastener that has been overstretched and can no longer do its job (clamp or hold things in place) needs to be replaced, otherwise failure may occur.

Another factor that may lead to the need for replacement of fasteners is that there could be corrosion, thus reducing their strength or elasticity.

When it’s time to replace them, any old bolt won’t do.

Choices in Fastener Material

Like the valves themselves, nuts and bolts come in many types of metals. Selection of bolting material is based on several aspects such as:

  • base material of the valve
  • pressure class of the valve
  • operating temperature
  • nature of the media
  • placement or location of the fastener
  • whether or not it will be in contact with the media Here are the major players:

Cast iron valves

Where cast iron valves are used, the pressure and temperature are typically mild to moderate. ASTM A307 grade A bolt material along with ASTM A563 for the nuts is usually sufficient.

Steel and alloy valves

Material with high strength, moderate tensile strength, and moderate elongation qualities are a good choice for steel and alloys. ASTM A193 for bolts and A194 for nuts are generally chosen.

Carbon steel valves

When at moderate temperatures, A193 grade B7 bolts, and A194 grade 2H nuts are common for carbon steel valves. For Cr/Mo valves, A193 grade B16 bolts and A194 grade 4 (or occasionally grade 2H) nuts are recommended. B16 bolts have a higher tensile strength and elongation minimum than those mentioned above.

Austenitic stainless steel valves

Stainless steel fasteners are usually used for austenitic steel valves. A193 grade B8 and B8M bolts and A194 grade 8 and 8M nuts are typical.

Risk of Environmental Stress Corrosion Cracking (SCC)

Before the final decision can be made on the best material for the nuts and bolts, there’s another variable to look at corrosion. In situations where the risk of corrosion is normal or moderate, the general guidelines don’t require modification. Where the valves are subject to harsher environments with exposure to corrosives, either internally or externally, the need for corrosion resistance will require adjustments to the standard materials.

Environmental stress corrosion cracking differs from general corrosion. General corrosion can be seen. SCC, on the other hand, can occur without warning and usually is not visible. Materials that protect against SCC may not stand up as well to general corrosion. Because general corrosion will be visible though, corroded nuts and bolts can be replaced well before failure occurs. For this reason, it is better to choose the material that will resist the invisible stress corrosion damage that can bring sudden valve failure.

SCC can be caused by chloride, hydrogen sulfide, caustic embrittlement, and liquid metal embrittlement. Let’s take a look at each.

Chloride stress corrosion cracking (CSCC)

Chlorides and other halogens can cause SCC of austenitic stainless steels such as 304 or 316. Where chloride is present alloy steel fasteners should be used. Marine environments are corrosive to these carbon steels, so coating the alloy steel with a metal like zinc or cadmium will reduce the susceptibility to general corrosion. These platings are useful for protecting carbon steel fasteners under moderate temperatures.

Liquid metal embrittlement (LME) and solid metal induced embrittlement (SMIE) Unfortunately, under high operating temperatures zinc or cadmium plating can lead to liquid metal embrittlement or solid metal induced embrittlement. LME is the brittle failure of a normally ductile metal when in contact with a thin film of liquid metal and stressed in tension. It can occur when zinc and cadmium, which have low melting points (489°F zinc and 370°F cadmium), are heated to near or above that point. When the temperature reaches the melting point, the thin layer of liquid metal over the ductile carbon steel becomes liquefied and can cause LME. SMIE is pretty much the same, occurring below the melting point. Avoid LME and SMIE by restricting the use of zinc or cadmium to lower temperatures.

Hydrogen sulfide stress cracking (HSSC)

Highly corrosive hydrogen sulfide causes stress cracking or brittle failure in most highly stressed hard steels. Softer alloy fasteners such as A193 grade B7M and A194 grade 2HM help to alleviate this. They’ve been heat-­‐treated to reduce their hardness and strength making them less susceptible to HSSC. The details for fastener requirements in refineries are laid out in NACE International specification MR0103.

Installation

Proper installation of nuts and bolts goes beyond the selection of the right materials. There is a correct way to install fasteners. Always pay careful attention to the following factors:

  • Tightening must be done using a crosswise pattern to ensure even compression of all surfaces forming a seal.
  • Employment of the correct torque is essential. Always look for information on the bolting torque before installation. CPV Manufacturing provides the information for our product torque values here: torque valves.
  • The current industry best practices are available in ASME’S PCC­‐1 ­‐ 2013, “Guidelines for Pressure Boundary Bolted Flange Joint Assembly,” which should be kept on hand wherever pressure-­containing bolted joint assembly takes place.

Fastener selection isn’t always complex or challenging, but it can be. Be sure to give the nuts and bolts the attention they require. It could be the difference between reliability and catastrophe.

We’re 100% committed to customer satisfaction. Contact us by email or visit our website if you have any questions about our products.

 

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National Aviation History Month: Mechanics of an Aircraft

The United States has a lot to be proud of, but the most prominent achievements the country has had is within the aviation industry. National Aviation Month celebrates the country’s accomplishments in aviation.

Read on to learn more about National Aviation Month and the advancements and mechanics of today’s aircrafts.

About National Aviation History Month

National Aviation History MonthNational Aviation Month celebrates America’s most important contributions and achievements in the development of aviation. Throughout November, museums, historians, and other organizations across the country will showcase some of the nation’s most notable aviation successes, from the Wright Brothers to the constantly advancing technologies placed in aircrafts today.

Evolution of Aircrafts

In the early 1900s, the Wright Brothers created and flew the first successful fixed-wing aircraft. Their aircraft started as a simple mechanism compared to today’s jets and planes, but the Wright Brothers succeeded in creating a piece of technology that changed the aviation industry forever. That technology was the three-axis control.

The three-axis control allowed the pilot the steer and helped the aircraft to maintain its place in the air. Today, three-axis control is still used in modern airplanes. However, today’s aircrafts are now equipped with advanced technologies to make the flying easier, safer, and more efficient.

Mechanics of Modern Aircrafts

National Aviation History MonthModern aircrafts have evolved into more technologically advanced devices. For example, their wings now include various enhancements to improve flight performance.

According to NASA, the wings of a plane are designed specifically to make air move faster across the top of the wing. The faster the air moves, the less pressure there is above the wing. The wings are also designed to make sure that there’s more air pressure below them.

The difference between air pressure above and below the wings creates a force that helps lifts the aircraft into the air.

On top of that, enhancements in the overall structure of the aircraft as well as advanced controls make it easier to change direction and position while flying. There are three different dimensions that can change the position and direction of the plane:

  • Roll shifts the aircraft left or right. To do this, ailerons, or a hinged device on each wing, are raised or lowered to control position.
  • Pitch is when the aircraft moves up or down. The pilot tunes the elevators on the tail to make it ascend or descend in the air. Lowering the elevators makes it drop and raising it brings the aircraft up.
  • Yaw is motion of an aircraft turning. To turn an aircraft, the rudder and the ailerons are moved to the side so a plane can turn left or right.

Science of Modern Aircrafts

Regardless of technologies and structure, physics still plays a big role in aviation. NASA also stated that an aircraft is affected by four forces during flight:

  • Lift is the aerodynamic force produced when the aircraft when flying. It’s essentially what keeps it in the air.
  • Weight is the gravitational force that attracts the airplane to the ground and keeps it balanced.
  • Drag is the force that resists movement when flying.
  • Thrust is the force generated by the engine to overcome drag and ensure that the aircraft moves through the air smoothly.

To learn more about the latest industry news, check out CPV Manufacturing’s blog.