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Control Valves - Flow Characteristics

Flow capacities vs. stem opening..

The relationship between control valve capacity and valve stem travel is known as

  • the Flow Characteristic of the Control Valve

Trim design of the valve affects how the control valve capacity changes as the valve moves through its complete travel. Because of the variation in trim design, many valves are not linear in nature. Valve trims are instead designed, or characterized, in order to meet the large variety of control application needs. Many control loops have inherent non linearity's, which may be possible to compensate selecting the control valve trim .

Inherent Control Valve Flow Characteristics

The most common characteristics are shown in the figure above. The percent of flow through the valve is plotted against valve stem position. The curves shown are typical of those available from valve manufacturers. These curves are based on constant pressure drop across the valve and are called inherent flow characteristics .

  • Linear - flow capacity increases linearly with valve travel.
  • Equal percentage - flow capacity increases exponentially with valve trim travel. Equal increments of valve travel produce equal percentage changes in the existing C v .
  • A modified parabolic characteristic is approximately midway between linear and equal-percentage characteristics. It provides fine throttling at low flow capacity and approximately linear characteristics at higher flow capacity.
  • Quick opening provides large changes in flow for very small changes in lift. It usually has too high a valve gain for use in modulating control. So it is limited to on-off service, such as sequential operation in either batch or semi-continuous processes.
  • Square Root

The majority of control applications are with valves with linear, equal-percentage, or modified-flow characteristics.

Installed Control Valve Flow Characteristics

When valves are installed with pumps, piping and fittings, and other process equipment, the pressure drop across the valve will vary as the plug moves through its travel.

When the actual flow in a system is plotted against valve opening, the curve is called the Installed Flow Characteristic .

In most applications, when the valve opens, and the resistance due to fluids flow decreases the pressure drop across the valve. This moves the inherent characteristic:

  • A linear inherent curve will in general resemble a quick opening characteristic
  • An equal percentage curve will in general resemble a linear curve

Related Topics

Control valve sizing, related documents, ball valves - flow coefficients cv, control valves - leakage classification, process controllers - p, pi & pid, steam control valves - calculate flow factor kv, straight through diaphragm valves - flow coefficients, valve authority, valve selection guide, valve type classifications, valves - specific services, valves - typical operating temperatures, weir diaphragm valves - flow coefficients and flow factors.

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Basics of Control Valve Positioners

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Positioner Guidelines

G uidelines are never a substitute for good engineering practices and experience but they are better than proceeding down a trial-and-error learning path.

Guidelines for all positioner types

Positioners can reduce control valve deadband caused by friction. Most control valves without positioners, even those using ‘low friction’ packing material, may demonstrate a 5% deadband. Deadband greater than 1% can produce loop controllability problems. Use of a positioner can reduce deadband caused by friction to less than 1%.

Positioners can reduce the effects of frictional stick/slip. Control valves with significant stick/slip have poor performance as witnessed by a limit cycle graph (see CE, Oct. ’99 ). Limit cycle occurs when a valve first sticks and then jerks (slips) to a new position. Frequently the stick/slip action causes process variables to overshoot the setpoint. Control action reverses the signal to the control valve and the stick/slip action is repeated in the opposite direction. A positioner’s stem feedback can reduce stick/slip effects and maintain the process variable closer to the setpoint.

Split ranged control elements normally require positioners. Processes requiring extended flow rangeability may use two control valves. The first valve operates over the first half of the range. When the first valve is nearly 100% open, the control action begins to open the second valve. This is called control valve split ranging. When split ranging is performed on the pneumatic signal to the valve actuators, positioners on each valve are used to achieve full valve travel over the reduced input range. Most applications need a predictable overlap region in the middle of the signal to avoid a zone of no control. Positioners provide accuracy to ensure the correct overlap exists.

Positioners can be used to increase seating force and improve shutoff. A positioner will drive the output pressure to either zero or full supply pressure whenever the valve reaches a physical travel stop. An air-to-close actuator can use the full supply pressure to provide greater valve seat loading. Completely removing the air signal from air-to-open actuators allows the full force of the spring to load the valve seat.

Double acting actuators must have a positioner. All double acting piston actuators must have a positioner because the pressure on both sides of the piston must be precisely controlled. This can only be accomplished with the stem feedback in a positioner.

Positioners with feedback cams can be used to linearize control valve and process characteristics. Care should be used when applying cam linearization, generally cam linearization works only for slow (i.e., temperature) reacting process loops.

Two-stage pneumatic analog positioners have superior performance over single-stage pneumatic analog positioners. Positioners using a nozzle flapper and relay are called two-stage pneumatic analog positioners, and positioners using a spool valve are single stage pneumatic analog positioners. Single stage positioners offer the advantage of being very simple in mechanical design, but will not provide the performance of two-stage positioners. The nozzle flapper in two-stage positioners provides very high gain for accuracy, and the relay ensures high airflow for fast response. Fast response is especially important for fast processes such a liquid flow and pressure.

Controller tuning can be modified to stabilize a ‘nervous’ fast process with a positioner. Older guidelines stated that control valves in fast processes should not have positioners because the loops become too nervous and hard to control. That was true of pneumatic controllers because of their limited adjustment range.. Today’s microprocessor controllers provide broad tuning adjustment ranges. The controller gain can be set much lower than historical guidelines to stabilize fast processes and controller integral (reset) can remain fast to match the fast process.

Guidelines for digital positioners Intelligent digital positioners can extend capabilities and benefits of traditional analog positioners. Using digital communications, such as HART and FOUNDATION Fieldbus, digital positioners provide the features listed above, but can also provide the following additional benefits.

Calibration can be performed automatically and remotely. Digital positioners can perform the same zero and span calibration in a few minutes. A task that can take a few hours with non-digital positioners.

Characterization is provided on the output signal. The output signal can be characterized to match the system to achieve a linear process with constant gain. Digital positioner’s characterization benefit, over cam linearization described above, is the linearization performed on the output signal, not the feedback from the valve stem.

Digital noise filters can be applied. Filters should be applied carefully, but where appropriate a digital filter time constant can be applied to minimize the effects of excessive process noise. Users should remember filters add to process response times. Applying a filter will likely require retuning the control loop.

Positioners can generate alarms to the operator interface. Users can assign positioner-based alarms such as valve travel deviation from the input signal, travel beyond a certain point, and others. These alarms can be displayed on operator graphics.

Maintenance related data could be provided. Digital positioners can track valve reversal and total stem travel data that can be correlated with time and actual maintenance events to improve predictive maintenance forecasting.

Valve stroke speeds can be slowed. Applications where hydraulic ‘hammering’ might occur can use a digital positioner to slow the valve stroke.

Valve travel limits can be applied. Applications where a valve should never reach full close can have travel limits applied in digital positioners.

Installed valve performance testing can be automated. Digital positioners communicate well with control valve performance software. Following a pre-defined test, data curves and calculated results can be compared with previous tests to help determine if a control valve requires maintenance. Being able to compare control valve performance can save time and money during planned outages by focusing maintenance activities on the control valves needing maintenance.

Digital positioners are less susceptible to vibration influences. The solid state electronics in digital positioners provides a device with few moving parts and helps maintain positioner performance in high vibration installations.

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Stem Valves

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Stem valves change the flow path when the stem is either depressed or released. Offered in both Normally-Open and Normally-Closed as 2-Way, 3-Way, 4-Way and 5-Way configurations. #10-32, 1/8" NPT, 1/4" NPT, 1/16" NPT and #3-56 ports available.

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Linear Actuators

The 3 Types of Control Valve Trim

What is control valve trim.

High Pressure Control Valve trim consists of three basic items: the stem, ball, and seat.

These are the operative parts that control the flow of liquid and gas through a valve. They are also the parts most exposed to process elements, and therefore most vulnerable to wear over time.

What Types of Valve Trim Are There?

There are three primary types of control valve trim:

  • Snap Trim (also referred to as Quick-Opening trim)
  • Nominal Trim (also referred to as Linear trim)
  • Equal Percentage Trim

Below, we'll outline the specific operation and typical applications for each control valve type.  

Types of Valve Trims

What is a Valve's Flow Characteristic?

A valve trim’s flow characteristic is the relationship between the percentage of flow and the percentage of valve stem travel between 0% and 100%.

1. Snap Valve Trim

Snap Valve Trim opens quickly and is used for on/off service.

Primary applications include liquid dump, pressure relief, and metering. We also offer zirconia seats for erosive applications.

2. Nominal Valve Trim

Nominal valve trim is used for throttling liquids, liquid level control, and in applications where water hammering has been an issue.

3. Equal Percentage Valve Trim

Equal percentage valve trim is used to control pressure or flow of gases and vapors in throttling applications.

Valve trim for abrasive conditions

In oil and gas applications with highly abrasive conditions, control valves take a real beating.

Sand, salt, and other abrasive elements wear away the internal trim, packing, and body as it moves through the valve. Sources of valve abrasion include  flowback , natural sand in the formation, and saltwater.

Wear and abrasion resistance is critical to optimal performance of oil and gas control valves. The premature wear abrasion causes to standard trim in control valves can cost you thousands in repairs and replacement valves, not to mention downtime. Therefore, choosing the right type of valve trim for your environment is key.

Kimray offers two High Pressure Control Valve trim materials designed to perform well in erosive conditions. These materials are harder than our standard trim and don’t wash out as fast.

Carbide Valve Trim

Carbide is a hard metal we recommend using for valve trim during flowback. In an ASTM G65 test of material loss, Carbide trim performed 2.5x better than standard D2 Steel trim.  

Zirconia Valve Trim

Kimray’s wear-resistant Zirconia Trim is designed specifically for highly abrasive oil and gas applications. Zirconia offers a combination of abrasion and corrosion resistance not found in steels, alloys, or many forms of other ceramics and carbides.

Stellite vs. tungsten carbide vs. zirconia

Zirconia is a robust, hard ceramic material. It outperforms metal trim materials in abrasion resistance. This is an ideal solution for high-sand areas like North Texas, Australia, India, and China.

Zirconia is superior to Stellite and other metals for two reasons:

  • It is a harder material than metal
  • Because it is a ceramic and not metal, it is inert to corrosive material

Valve Trim Material Chart

In an ASTM G65 Sand Abrasion Test of material loss, Zirconia outperformed 316 Stainless Steel and Stellite.  

ASTM G65 Test of Material Loss

The chart above shows the results of this test. It measures material loss based in cubic millimeters (mm3).

Kimray’s Magnesia Stabilized Zirconia valve trim performed 10 times better than Stellite Alloy and nearly 90 times better than 316 Stainless Steel. Kimray Tungsten Carbide also performed better than other metals.

Do You Operate Under Extreme Conditions?

Valve trim performance can be affected by more than just valve abrasion. Extremely high temperatures compromise metals like Stellite. Zirconia Trim is an ideal solution for operation in extreme temperatures.

This trim is designed to perform at temperatures ranging from -200°C to 850°C. Stellite, meanwhile, is only tested for temperatures between 315°C– 600°C. And because Zirconia is not a metal, it’s not subject to NACE.

Zirconia Applications

  • Erosive/Abrasive Conditions
  • Coal Seam Gas

Valve Trim Choices Are Easy with Zirconia

Kimray’s Zirconia Trim combats valve abrasion more effectively than any choice on the market. That keeps your valves up and running, and your well site reaching its peak performance.

Zirconia Trim is available now in Kimray High Pressure Control Valves. For more information on Zirconia Trim, you can download our brochure.

THE WRONG VALVE TRIM: A use case 

Recently a producer in the Woodford Shale contacted us with a problem. 

They had been using Kimray  High Pressure Control Valves  for years, but had begun to burn through a lot of trim sets in the valves, replacing them more often than expected. We began asking questions.

Q: What have you been ordering? A: High Pressure Control Valve packages for all new construction

Q: What type of trim are you requesting on these valves? A: 5/8" equal percentage trim

Q: What are the temperatures and flow rates of your wells? A: Conditions differ depending on the well

This was a problem we were prepared for.

Conditions are rarely the same well to well in the various locations and applications where Kimray customers operate. Because of this, we offer different types of valve trim designed to handle different temperatures, pressures, flow rates, and process fluids.

In this case, the equal percentage trim this customer was using was designed primarily for gas applications, where precise throttling is ideal. 

Their new wells, however, were flowing liquid, and bringing a lot of sand to the surface along with it. Because they were using equal percentage trim, the valve was consistently open, subjecting the trim to the abrasive, sandy flow path. This was the central reason for the premature wear.

We advised the customer that carbide snap trim for these valves would be a better option. This would give them a harder ball and seat, and the snap trim opens and closes quickly, so it would be exposed to the abrasive flow less often and therefore last longer.

We also helped the customer resize their valves accordingly to the appropriate flow rates of the wells. Because our trim can be field converted, they didn’t have to order new valves, just outfit their existing ones with the new, better suited trim.

Step-By-Step Guide to replace Valve Trim

Need to update the trim in your existing valves to handle changing conditions?  Follow our step-by-step video on replacing valve trim . 

To speak with an expert about finding the trim set that best fit your flow conditions, contact your local Kimray store or authorized distributor .

Breck Swigart, Director of Product Management

  • High Pressure Control Valves
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About On/Off Valves

Snap-shut threaded on/off valves.

For applications that require intermittent operation, such as spraying and washing, push or pull the lever on these valves to start flow. They spring closed when the lever is released.

Zinc valves are good for low-pressure applications. Use them as a control valve for tools such as blow guns and tire-changing machines.

Brass valves are stronger and less brittle than zinc valves for use in higher-pressure applications.

Push - lever valves are commonly used in car wash systems. However, you can’t use them as blow guns. Those with a Viton® fluoroelastomer rubber seal stand up to long-term use with harsh solutions, such as wheel and tire cleaners. Valves with a TFE plastic seat are more durable than those with a Viton® fluoroelastomer rubber seat. For even more durability, choose those with a thick spring — their spring is stronger and lasts longer than standard springs. You can install valves with a mounting stem and nut in a fixed position. Valves with offset ports come with a wand bracket to attach an upholstery cleaning wand, so they’re best for floor and upholstery cleaning equipment. Connect the bracket to the top of the offset ports.

Replace worn components on 30° elbow valves with a repair kit (sold separately).

Flow coefficient (Cv) is the amount of water (in gallons per minute) at 60° F that will flow through a fully open valve with a difference of 1 psi between the inlet and the outlet.

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Flow Characteristics

The Flow Characteristic of a Control Valve is the Relationship between the Control Valve Capacity and valve stem travel.

Inherent Characteristics represents this relationship with constant pressure drop across the valve.

Installed Characteristics represents the same relationship but with varying pressure drop due to losses in the pipeline and any equipment installed in series.

Equal Percentage

Equal Percentage is considered to be the most common characteristic used in process control. The inherent characteristic of a equal percentage plug allows for flow capacity to increase exponentially with valve stroke. i.e. equal increments in valve stroke result in equal percentage change in the existing Cv. When Installed, an equal percentage plug will tend to behave similarly to a Linear Characteristic valve in Inherent conditions.

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The Linear characteristic creates equal changes in Cv per unit of valve stroke, when the pressure drop is constant. Linear plugs are frequently used in systems where the differential pressure through the valve corresponds to the major part of the total differential pressure of the system. When installed, and due to the changes in pressure drop across the valve, a Linear trim will tend to behave similarly to Quick-Open trim.

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Quick-open plugs are used in on-off services and are designed to create large increments of flow rate, even from small opening percentages.

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Control Valves

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Control valves are mechanical devices used to regulate and control the flow of fluids, such as gases, liquids, or steam, through a pipe or other conduit. They are used in a variety of industries, including oil and gas, chemical processing, power generation, and water treatment.

Table of content: 1. What Are Control Valves? 2. How Do Control Valves Work? 3. Control Valve Characteristics 4. Types of Valves 5. Sizing of Control Valves 6. Parts of Control Valves 7. Control Valves Applications 8. Selection of Valves 9. Control Valve Troubleshooting Guidelines 10. Valve P&ID Symbols 11. Control Valves P&ID Arrangement 12. Typical Control Valve Datasheet 13. Types of Valve Actuators

What Are Control Valves?

Control valves are elements used in process control loops to adjust process variables such as flow, liquid levels, pressure, temperature etc. Control valves maintain the desired operating conditions such as flow rate, level, temperature and pressure required for the efficient operation of the process plant.

Control valves essentially consist of a valve and an actuator, more valve control elements may also be present in certain cases. Control valves work by opening or closing to regulate the flow of fluid through a pipe. They are typically controlled by an actuator that responds to a signal from a controller, such as a flow meter, pressure sensor, or temperature sensor.

These valves achieve the desired controlling effect essentially by throttling the flow.

control valves

How Do Control Valves Work?

The control valve contains two major components. One is the valve body that actually controls the flow of fluid. Actuator is another major part that moves valve body either manually or by using electric, pneumatic or a hydraulic signal.

The control valve opens and closes to regulate the flow of fluid through a pipe. Actuator receives signal from a controller such as flow meter, pressure sensor or temperature sensor and controls the valve body according to received signal from a controller. This process continues until the process variable reaches desired set point or comes within the desired operating range.

Check how different types of control valves work in the below given posts.

  • How temperature control valve works?
  • How level control valve works?
  • How flow control valve works?
  • How pressure control valve works?
  • How control valve actuators works?

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Control Valve Characteristics

The relationship between the control valve opening (also known as ‘valve travel’) and the flow through valve is known as the flow characteristic of that valve. An inherent flow characteristic is the relation between valve opening and flow under constant pressure conditions.

The gain of a valve is defined as the change in flow per unit % change in the valve opening.

stem travel valve

  • The linear flow characteristic has a constant slope, meaning that valves of this type have constant gain through complete range of flows. These valves are often used for liquid level control and certain flow control operations requiring constant gain.
  • Equal percentage valves are known by that name because whenever the valve opening is changed, the percentage change in flow is equal to percentage change in the valve opening. This means the change in flow proportional to the flow just before the incremental valve opening is performed. This can also observed in the following figure. This type of valves is commonly used for pressure control applications. They can be considered for applications where high variations in pressure drop are expected.
  • Quick opening type of valves does not have a specific mathematical definition. These valves give a large increment in flow for relatively smaller valve opening, as can be observed in the following figure. These valves usually find use for on-off service applications.
  • Modified parabolic valves lie somewhere between the linear valves and equal percentage valves. As can be observed in the following figure, they can be used for throttling at low flow levels and have almost linear characteristics at higher flows.

Types of Valves

Valves can be broadly categorized based on the type of stem movement – linear or rotary type.

Globe valve

Globe valves are most commonly used liner stem motion type control valves. The flow control for this type of valves is achieved by motion of a plug as shown in the following figure. The shape and type of the plus also determines the valve flow characteristics.

Globe control valve

Gate valves use linear type of stem motion for opening and closing of valve. These valves use discs as closure member, as can be seen in the following figure. The faces of this disc can be either parallel or the disc can be wedge shaped.

Butterfly Valve

Butterfly valves are known for their compact size and low initial costs, which is primarily due to the small wafer and body size of these valves and the simplicity of this design. This valve belongs to the rotary stem motion type of valves.

Butterfly control valve

These valves use a spherical shaped closure member with a cylindrical bore through the member for passage of flow. This spherical closure member has to be rotated by 90 degrees to bring the valve from fully closed position to fully open position. This type gets the name from the shape of the closure member. If the diameter of the cylindrical bore is same as that of the connecting pipe, the valve is known as full bore valve. If this diameter is less than that of the connecting pipe, the valve is known venturi style valve. These valves rotary stem motion.

Click the button and check the given guide for details on types of control valves . Also study the use of different type of valves as control valves based on application as well as services and caution where not to use it.

Types of control valves

Sizing of Control Valves

The orifices of control valves can be adjusted to control the flow through them. Control valve sizing and selection is based on a combination of theory and empirical data. The capacity, characteristic, rangeability and recovery are four important elements for selection of a control valve . C v is known as flow coefficient or orifice coefficient of a valve. This coefficient C v is related to the flow and pressure conditions by the following basic liquid equation.

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The required C v for a valve can thus be calculated based on flow and pressure conditions. This C v should then be matched to that of the available valves and a suitable valve should be selected so that the required C v falls between 70% to 90% of the selected valves C v capability. The possibility of maximum and minimum process flows has also to be taken into consideration while selecting the valve.

Many flow cases may often fall outside the range of the basic liquid equation mentioned above for C v calculation. For these cases a modified liquid equation for C v calculation is given as,

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The basic equation mentioned above for liquids is given below in the modified form for gases.

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The capacity of a control valve is represented as,

C d = C v / d 2 (d being the diameter of the valve)

Valve characteristic is the relation between valve opening (valve travel) and flow through the valve.

Rangeability of valve can be defined as the ratio of maximum to minimum flow over which good control can be achieved by using the valve.

Recovery is refers to the pressure recovery from the low pressure at vena contracta to the valve outlet. Pressure recovery is high for well streamlined valves.

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Control valve sizing calculation is crucial for maintaining efficient and reliable industrial processes. By following the proper sizing process and selecting the appropriate valve type, engineers and operators can ensure the optimal performance of their industrial processes. This post contains a sample control valve sizing calculation which demonstrates steps to be followed when solving control valve sizing problem for flow control.

Parts of Control Valves

Control valves are typically composed of several key components that work together to control the flow of fluid in a system. Check the given post for detailed study on different parts of control valves.

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Control Valves Applications

In the Process industry whether it is oil and gas, refinery, petrochemical, chemicals, specialty chemicals, pharmaceutical, power etc., to control the process or process related utilities some control elements is required. Control valves play a crucial role in maintaining desired process conditions such as pressure, temperature, flow rate, and level in process industries. Check detailed post on control valve applications.

Selection of Valves

Different structures of different types of valves make them suitable for a wide range of applications. For each application some types of valves are more suitable compared to others. Check this post that lists some criteria for selection of valves that are most suitable for a given application or service.

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Control Valve Troubleshooting Guidelines

Valve p&id symbols.

Study here various commonly used valve P&ID symbols ( Piping and Instrumentation Diagram symbols) for manual valves such as gate valve , ball valve , plug valve, butterfly valve , 3 way valve, globe valve , check valve etc.

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Control Valves P&ID Arrangement

Take a quick look at typical P&ID arrangement for control valves along with basic elements used in designing and operating control valves.

Typical Control Valve Datasheet

In order to be able to order the best control valve suited for the application, the user has to provide the valve manufacturer with all the necessary information to select and design a suitable control valve.

A typical control valve datasheet captures important parameters for its design and selection - like operating conditions, design conditions, line size, valve type, actuator type etc. This information help engineers and professionals make informed decisions.

stem travel valve

Types of Valve Actuators

Control valve actuators are devices that are used to control the opening and closing of control valves in various industrial processes. These actuators are responsible for converting the control signal into mechanical motion, which then positions the valve accordingly. Check different types of valve actuators in this post.

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How Temperature Control Valves Work

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Control valve assembly and actuator P&ID symbols

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API Standards for Pressure Relieving Systems

Table of content:1. API-520 Part I2. API 520 Part II3. API-5214. API-5265. API-5276. API-5767. API-2000

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Rising Stem Valve vs. Rotary Valve

Selecting a valve style.

Figure 1: Control valve cost comparison

Potential for Cavitation

Figure 3: Behavior of liquid pressure inside a control valve

Inherent Flow Characteristic

Figure 5. Ideal inherent flow characteristics

Installed Characteristics and Gain

Figure 7: Comparison of the installed gain of two different valves in the same system

A lesson for me is that I need to involve you earlier in the program.

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Calculate Control Valve Stem Position

An electronic  loop controller  outputs  a signal of 8.55 ma to a direct-responding control valve (where 4 ma is shut and 20 ma is wide open)., how far open should the control  valve be at this mv signal level.

Calculate Control Valve Stem Position

We are solving this problem using standard 4-20mA conversion Formula. Click here for formula

To solve for percentage of stem travel (x) at 8.55 milliamps of signal current (y), we may use the linear equation developed previously to predict  current in milliamps (y) from signal value in percent (x):

Valve Position Find

Therefore, we should expect the valve to be 28.4% open at an applied MV signal of 8.55 milliamps.

We can also solve the problem using direct formula. Click here for formula

Also Read: Instrumentation Formulas

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How To Fix a Leaky Street Valve on Your Water Line

Time: 10 minutes

Complexity: Beginner

Cost: $0 - $20

Repack a Stem Seal on a Valve

If you're dealing with a leaky street-side valve at your water meter, you don't have to pay the utility to come out and shut off the water so you can fix it. You can repack the stem with the water on.

You will get some water spray once you loosen the packing nut, however. So before starting, be sure to move anything you care about away from the meter area. It would be a shame to have to deal with water damage  after such an easy fix.

Clear the valve

Most old valves have rust and mineral deposits in the receiving groove. That crud can jam the gate and damage the valve.

Gently close the valve first. Don't force it shut; you don't want to cause more damage. Then open the cold faucet at your laundry tub.

Next, open the street-side valve slightly. The rush of water will flush out the crud. Shut off the laundry faucet, then the street-side valve (in that order).

Wind on special packing rope

Buy Teflon packing rope at any hardware store or home center. With the valve in the off position, loosen the packing nut and slide it toward the handle. Then repack the stem .

Wrap one wind of stem packing rope around the stem. Tighten the packing nut and open the valve. If it still leaks , back off the packing nut and add a few more winds of packing rope.

And there you have it, a quick and easy fix for a leaky street valve. You can solve this problem in no time!

How To Fix A Leaky Street Valve On Your Water Line Gettyimages 654085128

What we know about CrowdStrike’s update fail that’s causing global outages and travel chaos

Person looking at monitors with overlaid Crowdstrike and Microsoft Windows logos (Image Credits: Bryce Durbin / TechCrunch)

A faulty software update issued by security giant CrowdStrike has resulted in a massive overnight outage that’s affected Windows computers around the world , disrupting businesses, airports, train stations, banks, broadcasters and the healthcare sector.

CrowdStrike said the outage was not caused by a cyberattack, but was the result of a “defect” in a software update for its flagship security product, Falcon Sensor. The defect caused any Windows computers that Falcon is installed on to crash without fully loading.

“The issue has been identified, isolated and a fix has been deployed,” said CrowdStrike in a statement on Friday . Some businesses and organizations are beginning to recover, but many expect the outages to drag on into the weekend or next week given the complexity of the fix. CrowdStrike CEO George Kurtz told NBC News that it may take “some time for some systems that just automatically won’t recover.” In a later tweet , Kurtz apologized for the disruption.

Here’s everything you need to know about the outages.

What happened?

Late Thursday into Friday, reports began to emerge of IT problems wherein Windows computers were getting stuck with the infamous “blue screen of death” — a bright blue error screen with a message that displays when Windows encounters a critical failure, crashes or cannot load.

The outages were first noticed in Australia early on Friday, and reports quickly came in from the rest of Asia and Europe as the regions began their day, as well as the United States.

Within a short time, CrowdStrike confirmed that a software update for Falcon had malfunctioned and was causing Windows computers that had the software installed to crash. Falcon lets CrowdStrike remotely analyze and check for malicious threats and malware on installed computers.

At around the same time, Microsoft reported a significant outage at one of its most used Azure cloud regions covering much of the central United States. A spokesperson for Microsoft told TechCrunch that its outage was unrelated to CrowdStrike’s incident .

Around Friday noon (Eastern time), Microsoft CEO Satya Nadella posted on X saying the company is aware of the CrowdStrike botched update and is “working closely with CrowdStrike and across the industry to provide customers technical guidance and support to safely bring their systems back online.”

What is CrowdStrike and what does Falcon Sensor do?

CrowdStrike, founded in 2011, has quickly grown into a cybersecurity giant. Today the company provides software and services to 29,000 corporate customers, including around half of Fortune 500 companies, 43 out of 50 U.S. states and eight out of the top 10 tech firms, according to its website .

The company’s cybersecurity software, Falcon, is used by enterprises to manage security on millions of computers around the world. These businesses include large corporations, hospitals, transportation hubs and government departments. Most consumer devices do not run Falcon and are unaffected by this outage.

One of the company’s biggest recent claims to fame was when it caught a group of Russian government hackers breaking into the Democratic National Committee ahead of the 2016 U.S. presidential election. CrowdStrike is also known for using memorable animal-themed names for the hacking groups it tracks based on their nationality, such as: Fancy Bear , believed to be part of Russia’s General Staff Main Intelligence Directorate, or GRU; Cozy Bear , believed to be part of Russia’s Foreign Intelligence Service, or SVR; Gothic Panda , believed to be a Chinese government group; and Charming Kitten , believed to be an Iranian state-backed group. The company even makes action figures to represent these groups, which it sells as swag .

CrowdStrike is so big it’s one of the sponsors of the Mercedes F1 team , and this year even aired a Super Bowl ad — a first for a cybersecurity company. 

Who are the outages affecting?

Practically anyone who during their everyday life interacts with a computer system running software from CrowdStrike is affected, even if the computer isn’t theirs. 

These devices include the cash registers at grocery stores, departure boards at airports and train stations, school computers, your work-issued laptops and desktops, airport check-in systems, airlines’ own ticketing and scheduling platforms, healthcare networks and many more. Because CrowdStrike’s software is so ubiquitous, the outages are causing chaos around the world in a variety of ways. A single affected Windows computer in a fleet of systems could be enough to disrupt the network. 

TechCrunch reporters around the world are seeing and experiencing outages, including at points of travel, doctors’ offices and online. Early on Friday, the Federal Aviation Administration put in effect a ground stop, effectively grounding flights across the United States, citing the disruption. It looks like so far the national Amtrak rail network is functioning as normal. 

What is the U.S. government doing so far?

Given that the problem stems from a company, there isn’t much that the U.S. federal government can do. According to a pool report, President Biden was briefed on the CrowdStrike outage, and “his team is in touch with CrowdStrike and impacted entities.” That’s in large part because the federal government is a customer of CrowdStrike and also affected.

Several federal agencies are affected by the incident, including the Department of Education , and Social Security Administration, which said Friday that it closed its offices as a result of the outage.

The pool report said Biden’s team is “engaged across the interagency to get sector by sector updates throughout the day and is standing by to provide assistance as needed.” 

In a separate tweet, Homeland Security said it was working with its U.S. cybersecurity agency CISA, CrowdStrike and Microsoft — as well as its federal, state, local and critical infrastructure partners — to “fully assess and address system outages.”

There will no doubt be questions for CrowdStrike (and to some extent Microsoft, whose unrelated outage also caused disruption overnight for its customers) from government and congressional investigators. 

For now, the immediate focus will be on the recovery of affected systems.

How do affected customers fix their Windows computers?

The major problem here is that CrowdStrike’s Falcon Sensor software malfunctioned, causing Windows machines to crash, and there’s no easy way to fix that. 

So far, CrowdStrike has issued a patch, and it has also detailed a workaround that could help affected systems function normally until it has a permanent solution. One option is for users to “reboot the [affected computer] to give it an opportunity to download the reverted channel file,” referring to the fixed file.

In a message to users , CrowdStrike detailed a few steps customers can take, one of which requires physical access to an affected system to remove the defective file. CrowdStrike says users should boot the computer into Safe Mode or Windows Recovery Environment, navigate to the CrowdStrike directory, and delete the faulty file “C-00000291*.sys.”

The wider problem with having to fix the file manually could be a major headache for companies and organizations with large numbers of computers, or Windows-powered servers in datacenters or locations that might be in another region, or an entirely different country.

CISA warns that malicious actors are ‘taking advantage’ of the outage

In a statement on Friday, CISA attributed the outages to the faulty CrowdStrike update and that the issue was not due to a cyberattack. CISA said that it was “working closely with CrowdStrike and federal, state, local, tribal and territorial partners, as well as critical infrastructure and international partners to assess impacts and support remediation efforts.”

CISA did note, however, that it has “observed threat actors taking advantage of this incident for phishing and other malicious activity.” The cybersecurity agency did not provide more specifics, but warned organizations to stay vigilant.

Malicious actors can and will exploit confusion and chaos to carry out cyberattacks on their own. Rachel Tobac, a social engineering expert and founder of cybersecurity firm SocialProof Security, said in a series of posts on X to “verify people are who they say they are before taking sensitive actions.”

“Criminals will attempt to use this IT outage to pretend to be IT to you or you to IT to steal access, passwords, codes, etc.,” Tobac said.

What do we know about misinformation so far?

It’s easy to understand why some might have thought that this outage was a cyberattack. Sudden outages, blue screens at airports, office computers filled with error messages, and chaos and confusion. As you might expect, a fair amount of misinformation is already flying around , even as social media sites incorrectly flag trending topics like “cyberattack.”

Remember to check official sources of news and information, and if something seems too good to be true, it might just well be.

TechCrunch will keep this report updated throughout the day.

TechCrunch’s Ram Iyer contributed reporting.

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IMAGES

  1. Sliding stem valve travel demonstration

    stem travel valve

  2. Sliding-stem Valves

    stem travel valve

  3. Learn about valve stem packing and Fugitive emissions testing

    stem travel valve

  4. Sliding-stem Valves

    stem travel valve

  5. Sliding-stem Valves

    stem travel valve

  6. Sliding-stem Valves

    stem travel valve

VIDEO

  1. Adjusting Valves on a Four-Stroke Motorcycle Engine With Rocker Arms

  2. Caterpillar 303 CR Travel valve leaks part 2

  3. WELDING VALVE LINE TRANSMITTER STEAM DRUM

  4. Steam engine with sleeve piston valve reversing gear

  5. Ferrea Titanium & Stainless Steel Hollow Stem Valves

  6. The Tesla Valve

COMMENTS

  1. Control Valves

    The relationship between control valve capacity and valve stem travel is known as. the Flow Characteristic of the Control Valve; Trim design of the valve affects how the control valve capacity changes as the valve moves through its complete travel. Because of the variation in trim design, many valves are not linear in nature.

  2. Valve Positioners

    Total valve stem travel (like an odometer in an automobile) Additionally, the microprocessor embedded within an electronic valve positioner is capable of performing self-tests, self-calibrations, and other routine procedures traditionally performed by instrument technicians on mechanical valve positioners. Having access to such measurements as ...

  3. What is Travel Stop in Control Valve?

    A travel stop in the control valve is used as a mechanical limiter for stem travel. In fact, these travel stops are used to limit the stem travel at certain % travel whether limited to travel in the up direction or down direction. This restriction usually comes because of the capacity limitation in the downstream of the control valve.

  4. Control Valve Characterization

    "Linear" valve trim exhibits a fairly proportional relationship between valve stem travel and flow capacity (\(C_v\)), while "equal percentage" trim is decidedly nonlinear. A control valve with "linear" trim will exhibit consistent responsiveness only with a constant pressure drop, while "equal percentage" trim is designed to ...

  5. PDF Fisher ET, EAT, and ETR Sliding Stem Control Valves

    Fisher™ ET, EAT, and ETR Sliding-Stem Control Valves Fisher ET, EAT, and ETR general-purpose control valves (figures 2, 3, and 4) are used for throttling or on-off ... properly-sized valve, a standard-travel, Cavitrol III, one-stage cage (figure 9) and a long-travel, Cavitrol III, two-stage cage are available in the NPS 1 through NPS 8 ET ...

  6. Difference between Quick Opening, Linear & Equal Percentage Valves

    A quick opening valve plug produces a large increase in flow for a small initial change in stem travel. Near maximum flow is reached at a relatively low percentage of maximum stem lift. Quick opening plugs are normally utilized in two position "On-Off" applications but may be used in some linear valve applications.

  7. Basics of Control Valve Positioners ~ Learning Instrumentation And

    If no travel is fed back to the positioner, positioner output will continue to change until stem travel is confirmed. The plot of positioner output/LOAD versus % valve travel shows that the hysteresis present is very small compared to the one without a valve positioner. Typically valve hysteresis with positioners is 5% of valve stroke.

  8. Sliding-stem Valves

    A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of sliding-stem valve body designs are shown here: Most sliding-stem control valves are direct acting, which means the valve opens up wider as the stem is drawn out of the body.Conversely, a direct-acting valve shuts off (closes) when the stem is pushed into the body.

  9. Control Valve Trim Characteristics

    Control valve trim is manufactured in a variety of different "characteristics" to provide the desired installed behavior. The two most common inherent characteristics are linear and equal percentage. "Linear" valve trim exhibits a fairly proportional relationship between valve stem travel and flow capacity (Cv), while "equal ...

  10. Positioner Guidelines

    Digital positioners can track valve reversal and total stem travel data that can be correlated with time and actual maintenance events to improve predictive maintenance forecasting. Valve stroke speeds can be slowed. Applications where hydraulic 'hammering' might occur can use a digital positioner to slow the valve stroke.

  11. Stem Valves

    Clippard offers a wide range of pneumatic and mechanical valve actuators that work with all Clippard stem valves. The GV series valves offer the same characteristics of its original line with flow 10 times more than the MAV series and 2.5 times the flow of the MJV series. These 2-Way and 3-Way valves are offered in 1/4" NPT and G1/4 ports ...

  12. The 3 Types of Control Valve Trim

    A valve trim's flow characteristic is the relationship between the percentage of flow and the percentage of valve stem travel between 0% and 100%. 1. Snap Valve Trim. Snap Valve Trim opens quickly and is used for on/off service. Primary applications include liquid dump, pressure relief, and metering.

  13. Stem Movement

    Correction elements. W. Bolton, in Instrumentation and Control Systems, 2004 Example. A valve has a stem movement at full travel of 30 mm and has a linear plug which has a minimum flow rate of 0 and a maximum flow rate of 20 m 3 /s. What will be the flow rate when the stem movement is 15 mm? The percentage change in the stem position from the zero setting is (15/30) × 100 = 50%.

  14. PDF Sliding-Stem Valve Product Guide

    the valve plug resulting in an upward stem force that must be overcome by the actuator. Yoke, stem adaptor, travel scale, and spacers required to accomodate ISO 5210 mounted electric actuators. Piston actuator Sizes 25-130 up to 111kN (25,000 lbf) Max thrust Spring-return piston actuator Sizes 10 to 28 354 kN (79,000 lbf) Max thrust

  15. Stem Valves

    Fast-ActingPanel-Mount Threaded On/Off Valves. Open and close these valves with the flip of the toggle switch. Commonly used for equipment testing and gas sampling, they have threads and a hex nut below the handle for installation in instrument panels. 316stainlesssteel valves are more corrosion resistant than brass valves.

  16. Guide to Selecting Control Valves

    The pressure drop for a quick-opening two-way valve should be 10 to 20 percent of the piping-system pressure differential, leaving the other 80 to 90 percent for the load and piping connections. Figure 5 shows the relationship of flow vs. stem travel for a quick-opening valve. To achieve 90-percent flow, the stem must open only 20 percent.

  17. Flow Characteristics

    The Flow Characteristic of a Control Valve is the Relationship between the Control Valve Capacity and valve stem travel. Inherent Characteristics represents this relationship with constant pressure drop across the valve. Installed Characteristics represents the same relationship but with varying pressure drop due to losses in the pipeline and ...

  18. Control Valves

    The relationship between the control valve opening (also known as 'valve travel') and the flow through valve is known as the flow characteristic of that valve. ... If this diameter is less than that of the connecting pipe, the valve is known venturi style valve. These valves rotary stem motion. Click the button and check the given guide for ...

  19. Control Valve Sizing

    Typical valve problems such as stem friction, hysteresis, and calibration error, therefore, become amplified when the valve is over-sized because any amount of imprecision in stem positioning becomes a greater percentage of the valve's useful travel range than if the valve were properly sized and able to use its full range of motion.

  20. Globe Valves Selection Guide: Types, Features, Applications

    Since the seat is horizontal, the disk and stem travel at right angles to the pipe axis. The stem passes through the bonnet which is attached to a large opening at the top of the valve body. The symmetrical form simplifies manufacturing, installation, and repair. Globe valve body types. Image Credit: Valve Handbook

  21. PDF Proper Valve Stem Sealing Best Pract ces

    s.Measuring valve stem seal performanceValve stem seals. must accomplish two contradictory goals. First, they must seal the valve stem completely and reduce—and ideally eliminate—. ny fugiti ve emissions from the process. Second, they must accomplish this feat while allowing the valve stem to move freely and conti nue sealing, even as t.

  22. Rising Stem Valve vs. Rotary Valve

    Rising Stem Valve vs. Rotary Valve. The growing interest in rotary-action control valves resulted in a perceived battle between globe valves and the various styles of rotary valves. In a few industries and applications there is a clear winner. For example, globe valves are really not suitable for handling pulp stock in pulp and paper mills.

  23. Calculate Control Valve Stem Position

    Click here for formula. To solve for percentage of stem travel (x) at 8.55 milliamps of signal current (y), we may use the linear equation developed previously to predict current in milliamps (y) from signal value in percent (x): Therefore, we should expect the valve to be 28.4% open at an applied MV signal of 8.55 milliamps.

  24. Prier® 18" Style H Diamond Series Model P-164 Replacement Stem

    Prier H style Diamond series stem, 18" P-164 20 7/8" Overall Length

  25. How To Fix a Leaky Street Valve on Your Water Line

    Wrap one wind of stem packing rope around the stem. Tighten the packing nut and open the valve. If it still leaks , back off the packing nut and add a few more winds of packing rope.

  26. Prier® 4" Model C-434/534 Replacement Stem at Menards®

    Stem Assembly for 4" C-434/534

  27. Rotary-stem Valves

    An important advantage of rotary control valves over sliding-stem designs such as the globe valve and diaphragm valve is a virtually obstructionless path for fluid when the valve is wide-open. Ball valves. In the ball valve design, a spherical ball with a passageway cut through the center rotates to allow fluid more or less access to the ...

  28. Prier® 12" Model C-634 Replacement Stem at Menards®

    Stem Assembly for 12" new style C-634

  29. What we know about CrowdStrike's update fail that's causing global

    Given that the problem stems from a company, there isn't much that the U.S. federal government can do. According to a pool report, President Biden was briefed on the CrowdStrike outage, and ...