What is Cracking Pressure? (2023)

Last updated on June 4, 2019

Why check valve cracking pressure is such a critical specification

COP series compression bymale NPT check valves

What is check valve cracking pressure?Cracking pressure is the minimum upstream pressure required to open a check valve enough to allow detectable flow. Detectable flow is when the check valve allows a small but steady flow of liquid or gas to pass through the valve body and out through its outlet port.

A check valve’s cracking pressure is a technical specification and is usually provided as psi or psig (pounds per square inch or pounds per square inch gauge) or bar (the metric equivalent of psi and psig) or both.

A more precise way to describe check valve cracking pressure is to say that it is a measure of the pressure differential between the valve’s inlet and outlet ports when flow is first detected.

An inexact but informative way to test cracking pressureA simple air pressure test is an easy way to estimate the cracking pressure of a spring loaded check valve. It involves attaching a pressurized air line with a control valve and a pressure gauge to the inlet side of the check valve. The check valve is then placed in a container filled with water. The pressure of the air coming into the check valve can be gradually increased using the control valve.

G series subminiaturepressure gauge

The cracking pressure of the valve will be about the same as the pressure gauge measurement when there is detectable flow through the check valve. Detectable flow will be the first small but steady stream of bubbles to come out through the outlet port of the check valve.

This is obviously a very rough-and-ready approach and cracking pressure quality control testing rigs are much more rigorous and carefully designed.

One thing a simple air pressure test clearly demonstrates is what it means to say a check valve’s cracking pressure has been reached because there is detectable flow.

On a related point, this is also useful for understanding where the phrases “bubble tight seal” and “its shutoff is bubble tight” come from.

What is a bubble tight seal or bubble tight shutoff?To describe a check valve seal as bubble tight is to describe the sealing ability of a valve. If a closed check valve is air pressure tested for backflow, any leaking around the valve seals will causes bubbling up through water similar to the case above. A bubble tight seal produces no bubbles.

The key takeaway from this is to realize that there is a significant difference between a check valve’s flow rate at detectable flow and its flow rate when it is fully open. This is an important difference to be aware of when “sizing” a check valve for a specific application.

Modular Check Valves

We've taken spring-loaded check valves to a whole new level. Mix and match imperial and metric connections. Watch the video.

Size the check valve for the applicationChoosing the right check valve size for an application helps prevent premature check valve wear and failure. It also helps ensure the check valve and the application perform as expected.

(Video) How to Differentiate Between Cracking and Resealing Pressure in Your Fluid System

Sizing check valves is different from sizing many other types of flow control and shutoff valves. The best operating results are usually when a check valve has been sized for the application and not for the pipe or tubing size.

In a majority of check valve installations, normal operating conditions will produce a fairly steady flow. For this situation, a check valve will usually be considered properly sized when this flow keeps the valve between about 80% open and fully open.

Sizing check valves becomes more complex when an application has a range of normal operating flow rates. In this case, the best check valve size choice will probably be when, at the lowest operating flow rate, the check valve opens up between about 80% open and fully open.

Determining which is the right check valve and especially choosing its size might be a little tricky. It will probably involve getting and testing samples in real operating conditions. The good news is that spring loaded or spring assist check valves are designed with a wide range of very specific cracking pressures.

Learn more about estimating valve flow and valve sizing at Valve Flow and Sizing from IEEE GlobalSpec Engineering360.

Need product samples?Fill out the form on this page and a member of our team will get in touch with you to find the right product samples for your unique application needs.

ISM Product Sample Boxes

CVIS series modularcheck valves

A review of check valve fundamentalsCheck valves allow liquid or gas to flow in one direction while preventing flow in the reverse direction. Flow in the reverse direction is called backflow or upstream flow.

Because check valves provide automatic flow control while using relatively simple and durable designs, they are widely used in all sorts of applications.

Cracking pressure is a key specificationCracking pressure comes up whenever you talk about check valves because it is such an important check valve specification.

What is reseal pressure and how is reseal pressure related to cracking pressure?Reseal, re-seal or resealing pressure is the backflow pressure required to close a check valve tightly enough so that there is no longer any detectable flow. It is also described as the measure of backflow pressure when the check valve closes bubble tight.

Spring loaded (spring assist) check valves reseal with the help of the force of the spring. This means the lower the cracking pressure, the higher the reseal pressure needed for a bubble tight seal.

CVNMCB series nylon check valve adapters

What does this mean practically (two cases)?

Spring pressure alone provides a bubble tight sealSpring loaded check valves that have a cracking pressure higher than about 3 psig (0.21 bar) to 5 psig (0.34 bar) will usually close or reseal bubble tight because of the force of the spring alone.

In these cases, if a check valve’s rated reseal pressure specification is provided, it will usually be lower than its cracking pressure.

Spring pressure plus back pressure provide a bubble tight sealSpring loaded check valves that have a cracking pressure lower than about 3 psig (0.21 bar) to 5 psig (0.34 bar) will usually not return to a bubble tight seal with just the force provided by the spring. They usually need a little additional back pressure from the system in order to form a bubble tight seal.

(Video) Pressure Relief Valve Cracking Pressure Example

These low cracking pressure check valves will have reseal pressures that are higher than their cracking pressure, sometimes even significantly higher.

Other factors that may affect a check valve’s reseal pressure

  • The design of the check valve
  • The speed of back pressure buildup
  • The pressure and temperature of the environment surrounding the check valve
  • The pressure and temperature of the air, gas or liquid moving through the valve

What is back pressure?Back pressure is when there is upstream flow pressure in the system. In other words, the pressure at the check valve outlet port is higher than the inlet port. Check valves without springs require backflow and the resulting backflow pressure in order to close. This includes both free floating elastomer diaphragm check valve designs and springless (no spring) ball, poppet, cartridge and piston check valve designs.

Our Vacuum Pressure Unit Conversions Chart is a handy reference to compare and convert between the most commonly used vacuum and pressure units of measure.

Factors that affect cracking pressure:

  • Check valve design
  • Condition of the valve
  • Orientation of the valve
  • Contamination in the pressurized air, gas or fluid passing through the valve

Check valve designs matter

A more detailed look at diaphragm check valves and check valves with rigid sealing elements (ball, poppet, cartridge, piston and so on).

Plastic diaphragm check valves

Diaphragm check valves

  • Floating elastomer disc or diaphragm
  • Reseals with minimal backflow pressure
  • Generally, they do not provide bubble tight seals
  • Probably not a good choice for thick or viscous fluids
  • A low-pressure check valve for low-pressure applications
  • Opens with minimal downstream flow or pressure differential

Free floating elastomer discs or diaphragms do not provide a positive seal even though they require very low backflow pressure to close. This can lead to some leakage around the seal, especially in low flow applications.

Learn more about diaphragm check valves in our blog post How Do Diaphragm Check Valves Work?

What is a positive seal?A positive seal, also called a leak tight or bubble tight seal, is exactly that. For a check valve this means that when the check valve closes, it also reseals so that no backflow leaks past the sealing surfaces. As I mentioned earlier, some very low cracking pressure spring loaded check valves may require back pressure in addition to the spring pressure to create a positive, bubble tight seal.

Check valves that use springless or spring loaded rigid sealing elements

NVRT series miniatureplastic in-line relief valves

Many types of springless (no spring or floating) and spring loaded check valves use a rigid internal part that moves to either allow downstream flow or prevent backflow. This rigid internal part is usually called the sealing element.

The shape of the check valve sealing element is generally used to describe its type. Ball, poppet, cartridge or piston for example:

  • Poppet check valves tend to have higher flow rates
  • Ball check valves are relatively simple and cheap to make
  • Piston and cartridge check valves provide especially good positive seals

In general, the interior design of a valve’s parts and sealing mechanism determines its cracking pressure, how well it reseals, its flow efficiency and its maximum flow rate.

Important cracking pressure considerations

(Video) Check Valve Basics

Spring loaded vs springless (no spring) check valves

Springless check valves

  • Very low cracking pressure
  • Very little downstream flow pressure opens springless check valves
  • Backflow and backflow pressure alone close springless check valves

Springless (no spring) check valves provide a near zero pressure differential to allow free flow. Springless check valves also require sufficient backflow to close and cannot provide a positive seal in most low pressure and low flow applications.

Spring loaded check valves

  • Positive seal
  • More resistant to leaking

Spring loaded check valves provide positive seals when they close and are more resistant to leaking than springless (no spring) check valves.

Check valve orientation matters

Proper installation is importantBecause check valves are one-way valves, they need to be installed in the correct flow direction or orientation in order to work properly.

The inlet port or inlet valve connection is the upstream side of the valve. The outlet port is on the downstream side of the valve. Because check valves must be installed in the direction of flow, they usually have the direction of flow marked on the valve bodies. This marking is either a check valve symbol or an arrow that indicates flow direction.

What if there are no markings on a check valve to indicate flow direction?For some customized check valve components, flow direction may not be marked on the check valve body. In this situation there are two ways to know the correct flow direction when installing the check valve:

  • The manufacturer or part design and customization service provides documentation indicating flow direction. This is pretty straight forward when there is a clearly observable difference between the connection types at the inlet and the outlet ports.
  • A simple air pressure test can determine which connection is the check valve inlet port.

Horizontal, vertical flow up or vertical flow downGravity can play an important role in check valve function and affect its cracking pressure. This is true for both springless and spring loaded designs.

The specific gravity or density of the liquid in an application determines how much a pipe or tube full the liquid weighs.

Horizontal installationCheck valves in horizontal lines are the most common type of check valve installation. In this case the only important thing to remember is to orient the check valve correctly for the direction of flow.

Vertical installation - flow direction upWhen a spring loaded check valve is installed vertically, with the flow direction up, the weight of the liquid above the valve increases the amount of force required to open the valve. This type of installation increases the check valve’s cracking pressure.

A springless check valve mounted in the same way will have a cracking pressure determined by the weight of the liquid above it.

Vertical installation - flow direction downIf the valve flow direction is down, the weight of media pushes against the valve spring. This means the valve’s cracking pressure needs to be selected so that it is high enough to neutralize the weight of the liquid in the pipe or tube above the valve. Generally, springless (no spring) check valves will not work properly when they are installed vertically with downward flow.

Learn more about check valve flow orientation at A 360° Look at Check Valve Flow Orientation from Triangle Fluid Controls.

Why it matters what chemicals are passing through a check valveCheck valve designs frequently include more than one material option. This includes material options for all the check valve’s internal components too. There will probably be material choices to be made for the check valve body, the sealing element (diaphragm, ball, piston, poppet, cartridge and so on), the elastomer seal or seals and the spring metal.

One example of how chemical exposure can cause problems is the case of plastics and elastomers. Chemicals can potentially cause these materials to swell or the sealing surfaces to become sticky. To avoid this, evaluate what chemicals will be passing through the check valve. Use chemical compatibility guides to make the best material choices.

Get a better insight into material chemical compatibility and get a copy of our chemical compatibility chart.

What are wetted surfaces?The wetted surfaces or wetted parts of a valve are the internal surfaces and components that will be exposed to gases or liquids passing through the valve. When selecting a check valve for an application, all the component materials used in the valve should be evaluated for their compatibility with chemicals they will be in contact with.

Learn more about the meaning of wetted parts at Wetted Parts of pressure sensors – definition and overview from WIKA.

Why the weight and density of fluids passing through a check valve matterLiquids passing through an application have mass or weight. The mass of the liquid in a system is a function of its volume and its density. A heavy liquid will have a relatively higher mass per volume of fluid than a lighter liquid.

The mass of the liquid in an application affects how rapidly a check valve will be able to respond to pressure changes to either open or to reseal. In general, a dense liquid with a low flow volume will tend to take longer both to fully open and to reseal.

Viscosity of fluids passing through the valveA viscous or thick liquid provides resistance to the movement of check valve sealing elements like the free-floating elastomer disc, ball, poppet, cartridge or piston. In low-flow systems, viscosity can affect both the cracking pressure of a check valve and its ability to reseal when there is backflow. A simple way to think about this to the difference between honey and alcohol on a cold day.

(Video) What are the Cracking Pressures for the SVC/SHC Springless Sanitary Check Valve?

Some final tips about selecting check valvesUse a material chemical compatibility guide to be sure the check valve component materials are compatible with the media passing through it.

A large number of miniature and compact small-bore check valves use elastomer seals. In general, the temperature rating of a particular elastomer seal material is usually what limits a check valve’s operating temperature range.

Get the ISM Chemical Compatibility Chart.

Check valves are frequently used in series. Using two check valves in series can reduce the amount of reseal pressure required for bubble tight sealing.

Installing filtration upstream of a check valve to improve its performance. Filters capture particles and debris that can interfere with check valve sealing surfaces and resealing mechanisms. Keep in mind that switching out components as well as system repair and maintenance may introduce dirt, chips, scale or other contaminants into the system.

Learn more about the importance of protecting valves with filters in our blog post In-line Filters for Miniature Flow Control Component Protection.

Some related posts

Checking Out Check Valves – An Introduction

Plastic Diaphragm Check Valves – Check ValvesPart II

Spring Loaded Check Valves – Check Valves Part III

How Do Diaphragm Check Valves Work?

Any problems figuring out if a particular check valve type is the right solution for your system requirements? Help us by telling others what you learned.

Have more questions about how miniature check valves work? If so, send me an email - steven.williams@industrialspec.com. You can also ask questions using the comments section below

What is Cracking Pressure? (10)

About the authorWhat is Cracking Pressure? (11)Steven C. Williams, BS, is the technical writer and an inbound marketing specialist at Industrial Specialties Manufacturing (ISM), an ISO 9001-2015 supplier of miniature pneumatic, vacuum and fluid circuitry components to OEM's and distributors all over the world. He writes on technical topics related to miniature pneumatic and fluidic components as well as topics of general interest at ISM.

Diaphragm Check ValvesSpring Loaded Check Valves Duckbill Check ValvesPlastic Push-In Check ValvesBall Check ValvesPiston Check ValvesPoppet Check ValvesModular Check Valves

Are you developing a design for or maintaining a low-pressure (less than 125 psi, 8.6 bar) small-bore air, gas or fluid system? Then ISM has the valve for it. Get a catalog and find out more about all the different types of stainless steel valves we offer.

What is Cracking Pressure? (12)

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What is Cracking Pressure? (13)

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(Video) Relief Valve Basics

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What does crack pressure mean? ›

What is Cracking Pressure? Often measured in pounds per square inch (PSI), cracking pressure is the difference in pressure between the valve's inlet and outlet ports. It's the pressure differential required to “crack” open the valve (the point at which there is a sudden rise in flow).

What is cracking pressure and full flow pressure? ›

The pressure at which a relief valve first opens to allow fluid to flow through is known as cracking pressure. When the valve is bypassing its full rated flow, it is in a state of full-flow pressure.

How is cracking pressure measured? ›

An inexact but informative way to test cracking pressureA simple air pressure test is an easy way to estimate the cracking pressure of a spring loaded check valve. It involves attaching a pressurized air line with a control valve and a pressure gauge to the inlet side of the check valve.

How do you calculate the pressure of a cracking valve? ›

Given the maximum pump flow and the relief valve set pressure, the maximum system pressure can be determined as follows: Maximum system pressure = Relief valve set pressure + Relief valve overpressure.

What is air brake crack pressure? ›

Crack pressure is the air pressure value required at the input from the foot valve before the relay valve will send air pressure to the brakes controlled by that valve.

What is full flow pressure? ›

Full-Flow Pressure - The pressure at which a valve is wide open and passes its full flow. Operating Pressure - The pressure at which a system is normally operated. Pilot Pressure - Auxiliary pressure used to actuate or control a component.

How much pressure is needed to open a check valve? ›

The minimum upstream pressure required to operate the valve is called the cracking pressure, generally between 1 and 5 psi. Check valves are designed specifically with this number in mind. The degree of opening on a check valve is determined by the flow rate.

Which causes more than 90% of hydraulic system failure? ›

Air and water contamination are the leading causes of hydraulic failure, accounting for 80 to 90% of hydraulic failures. Faulty pumps, system breaches or temperature issues often cause both types of contamination.

What is a PRV valve used for? ›

The purpose of a pressure relief valve is to control or limit surges of pressure within pipelines, acting as protection for the system, and defending against instrument or equipment failure. They are usually present in clean water industries.

Is high pressure needed for cracking? ›

Introduction. Cracking is the name given to breaking up large hydrocarbon molecules into smaller and more useful bits. This is achieved by using high pressures and temperatures without a catalyst, or lower temperatures and pressures in the presence of a catalyst.

Does check valve increase pressure? ›

Check valves do not reduce pressure, they actually help maintain it. In the setup you describe, it might work. However you will DEFINITELY need another check valve on the outlet of the tank to prevent the high pressure flow from backwashing in through the bottom, since there is no shuttoff/float valve there.

What is blowdown in safety valve? ›

Blowdown is the difference between set pressure and reseating pressure of a safety valve expressed as a percentage of set pressure. Typical blowdown values as defined in codes and standards are -7% and -10%, ranging from -4% to -20% depending on the code and service (steam, gas or liquid).

How do you calculate backpressure? ›

This force is the source of backpressure, which can be calculated by dividing the force by the area of exertion. The resistance force of a mechanical brake can be added to the backpressure by installation of one in the system. Ram force must overcome the total resistance presented by backpressure and the brake.

How do you calculate relief valve capacity? ›

The Relief Pressure is generally determined by the equipment being protected, and is calculated as Relief Pressure = Set Pressure + Overpressure.

How do you calculate back pressure on a PSV? ›

For example, assume MAWP = 100 psig, accumulation = 10% or 10 psi, and set pressure = 90 psig, then allowable overpressure = (MAWP + accumulation – set pressure) / set pressure = 22% of set pressure. Built-up backpressure could be acceptable up to 22%.

Why does my semi trailer bounce when I brake? ›

The most common causes are incorrect or malfunctioning relay valves. Quick-release valves also can have characteristics that upset pressure balance. Other causes include air leaks, air system contamination, a front-axle-limiting valve and excessive use of the trolley valve.

How do I adjust the air pressure in my brakes? ›

How to Adjust a Manual Slack Adjuster for your CDL Air Brakes

How long should air brakes take to build pressure? ›

Air pressure build-up from 85 psi to 100 psi should take 45 seconds or less. While driving, observe the air pressure gauge during build-up to ensure proper air system operation. braking, pull over at a safe place and perform the 2 minute / 5 psi leakage test.

Can you have pressure without flow? ›

Without flow, there is no pressure. In a positive displacement pump, such as a plunger pump, the rating in pounds per square inch, or PSI, outlines how much resistance the pump is designed to withstand.

What is the difference between flow and pressure? ›

What is the difference between Pressure and Flow? Pressure is the force acting per unit area; it is a scalar point property of fluids. Flow is the rate at which fluid passes through a gives surface and flow is caused by the difference in pressure within a fluid.

What is normal hydraulic pressure? ›

The accepted international standard for maximum working pressure in the high pressure hydraulic tools industry is 700 Bar (10,000 PSI) and the majority of the products offered by Hi-Force are in line with this standard.

What is the difference between check valve and backflow preventer? ›

Check valves use a hinged plug that allows water to pass through the pipeline but blocks it from coming back. Backflow preventers, on the other hand, apply an increased amount of pressure on a pipe to ensure the water can only flow one way.

What is API standard for valves? ›

API 6D is the primary standard for valves used in pipeline service, including gate, plug, ball and check valves. Occasionally refinery and petrochemical purchasers will reference the more stringent testing requirements of 6D although the valve may have built under API 600, 602, 608 or 609 design criteria.

Can you have too many check valves? ›

Several problems can arise from having multiple check valves in the system. The more check valves in a system, the more friction loss. A larger pump may even be needed to compensate for the additional friction loss. Multiple check valves can possibly cause contamination of the water.

What causes hydraulics to lose pressure? ›

If your hydraulic pump is losing pressure, it's likely due to one of two things: a leak in the system, or a problem with the pump itself. To check for leaks, you'll need to take apart the system and look for any signs of damage. If the pump itself is causing the loss of pressure, you can try replacing it.

How do you get air out of hydraulic system? ›

For dissolved air, you can remove it by raising the temperature of the fluid until the air is released. This should only be done if absolutely necessary as hydraulic oil will normally tend to be at least 10% dissolved air.

What causes hydraulics to run slow? ›

The most common causes of poor hydraulic performance are particulate contamination, water contamination, clogged filters, high fluid temperature and incorrect hydraulic fluids.

What is the difference between PSV and PRV? ›

While the term PRV is sometimes used interchangeably with PSV, there is a difference between the two. A PRV opens gradually in relation to the pressure, while a PSV is opened suddenly once the pressure hits a certain level in order to avoid over pressurization and a potential process safety incident.

What are the three types of relief valves? ›

The three basic types of pressure-relief valves are conventional spring loaded, balanced spring loaded, and the pilot operated.

How many types of PRV are there? ›

There are three types of pressure reducing valves.

What is the effect of pressure on cracking? ›

At the temperatures investigated, the effect of pressure on oil cracking and product generation is small. Rates of early hydrocarbon gas generation (350 and 380 °C, 72 h) decrease with increasing pressure by 9−15% in the 90−210 bar range and by 7% for gas generation (400 °C, 72 h) in the 90−345 bar range.

What are two types of cracking? ›

Various methods can be used for cracking, eg catalytic cracking and steam cracking: Catalytic cracking uses a temperature of approximately 550°C and a catalyst known as a zeolite which contains aluminium oxide and silicon oxide. Steam cracking uses a higher temperature of over 800°C and no catalyst.

What are the conditions of cracking? ›

Thermal cracking uses harsh conditions like high temperature and high pressure. It breaks the alkanes into a high percentage of alkenes and comparatively few alkanes. Thermal cracking is done at about 1,000 degrees Celcius and 70 atm pressure.

What are the 5 types of check valves? ›

Most common types of Check valves are swing, lift (piston and ball), butterfly, stop and tilting-disk.

Where should a check valve be installed? ›

Check valve can be installed in horizontal or vertical piping runs, with the flow running upward. Mounting for vertical installations is critical.

Does check valve reduce water flow? ›

Check valves also known as "one-way" valves are autonomously operated unidirectional valves that allow fluid to flow in a singular direction, thus reducing or preventing backflow.

Why do boilers have 2 safety valves? ›

Safety Valve: Each boiler shall be equipped with two safety valves for relieving the steam pressure. The diameter of the valve shall not be less than 19 mm.

Why boiler safety valve lift is D 4? ›

Area of valve bore = area of escape i.e the valve circumference X lift; Neglecting area taken by the valve prongs. To give greater lift than D/4, is unnecessary, this gives the full equivalent area. Excessive lift results in shock or hammering thus the fatigue will take place.

What is the maximum set pressure for safety valve? ›

The safety valves shall be reset at a pressure at least 2.5% below, but not more than 5% below the safety valve set pressure. The 5% limit is increased to 10% for valves having a body seat bore less than 32 mm and/or having a set pressure of 2 bar gauge or less.

Why do you need back pressure? ›

Stop Saying Car Exhausts Need Back Pressure - YouTube

What is called as back pressure? ›

Simply put, back pressure is pressure that is held back. “Back” in this context means against the natural flow of fluid or gas. In oil and gas applications it refers to upstream pressure that is held, or maintained, in a variety of production vessels to provide the right conditions for separation and processing.

Is back pressure and exit pressure the same? ›

Generally P2 is also called exit pressure, PExit but if it is controllable it is called PB. So the two are different. Pressure drop is caused by agents inside whereas back pressure is controlled by you from outside.

What is minimum relief valve capacity? ›

The safety relief valve inlet must not be smaller than NPS 3/4 nor larger than NPS 4-1/2. The minimum relieving capacity of safety or safety relief valves must equal or exceed the maximum output of the boiler.

What is relief capacity? ›

Capacity Relief means relief from making 100% of the monthly payments owing by Seller and its Affiliates under the satellite contracts, between Seller and its Affiliates on the one hand and Buyer and its Affiliates on the other (it being understood and agreed that Buyer and its Affiliates are currently providing 50% ...

Why is fire overpressure 21% for relief valve sizing? ›

Because in case of a fire, the engulfed vessel is assumed "destroyed". Therefore, by increasing the PSV overpressure by another 10% of the normal 10% overpressure (i.e. 1.1*1.1 = 1.21), this will help reduce the size of the PSV by using the design pressure margin "a little bit more".

What is relieving temperature of PSV? ›

6) showed an initial high relieving point (A) of 26,100 kg/hr when the PSV pops open, but an associated temperature of 291°C (559°F) was significantly higher than the bubble point of the steady-state top-tray boiling liquid at relieving condition.

What is overpressure PSV? ›

An overpressure event refers to any condition which would cause pressure in a vessel or system to increase beyond the specified design pressure or maximum allowable working pressure (MAWP). The primary purpose of a pressure Relief Valve is protection of life and property by venting fluid from an overpressurized vessel.

How much pressure does it take to open a check valve? ›

The minimum upstream pressure required to operate the valve is called the cracking pressure, generally between 1 and 5 psi. Check valves are designed specifically with this number in mind.

What is crack open? ›

(informal) To open (a bottle, can, etc. of drink, especially alcoholic drink), especially in order to celebrate; also extended to other packaged items. Let's crack open a few beers and get the party started.

What is a low pressure check valve? ›

Low pressure check valves are check valves used for low pressure applications. It include spring check valve, swing check valve, and wafer check valve. It allow fluids to flow in one direction only and prevent back-flow of fluids.

What is back pressure check valve? ›

A back pressure valve is a type of control valve that holds pressure on production vessels such as separators, treaters, and free water knockouts and releases upstream pressure when a designated set point is reached.

What are the 5 types of check valves? ›

Most common types of Check valves are swing, lift (piston and ball), butterfly, stop and tilting-disk.

Why are there 2 valves on a backflow preventer? ›

These backflow preventers are specifically designed to prevent reverse flow in fire sprinkler systems, using two check valves assembled in a series to prevent water from backing up into the supply line. This redundancy ensures that one check valve will continue to protect the city water supply even if the other fails.

Will a check valve increase pressure? ›

Check valves do not reduce pressure, they actually help maintain it. In the setup you describe, it might work. However you will DEFINITELY need another check valve on the outlet of the tank to prevent the high pressure flow from backwashing in through the bottom, since there is no shuttoff/float valve there.

What's the meaning of crack down? ›

to start dealing with bad or illegal behaviour in a more severe way: The library is cracking down on people who lose their books. Preventing and impeding. avert. avoid.

What is another word for cracked open? ›

What is another word for crack open?
cleavesplit open
tear asunderchop up
lay opencut up
slice up
16 more rows

What is the synonym of cracked? ›

unhinged, unsound, wacko. (also whacko), wacky.

How do check valves work? ›

How Do Check Valves Work? | Spec. Sense - YouTube

Why is a low cracking pressure so important in a check valve used for air or vacuum? ›

Low cracking pressure check valves have many incredible features that make them perfect for the aerospace industry. They create an air-tight seal for fuel or air that ensures no leakage from the valve. It is adaptable to most fluids and gases used in the aerospace industry.

What is swing check valve? ›

What is a swing check valve? A swing check valve is mounted with a disc that swings on a hinge or shaft. The disc swings off the seat to allow forward flow and when the flow is stopped, the disc swings back onto the seat to block reverse flow.

What is the difference between check valve and backflow preventer? ›

Check valves use a hinged plug that allows water to pass through the pipeline but blocks it from coming back. Backflow preventers, on the other hand, apply an increased amount of pressure on a pipe to ensure the water can only flow one way.

What is called as back pressure? ›

Simply put, back pressure is pressure that is held back. “Back” in this context means against the natural flow of fluid or gas. In oil and gas applications it refers to upstream pressure that is held, or maintained, in a variety of production vessels to provide the right conditions for separation and processing.

Where are back pressure valves used? ›

A Back pressure valve or regulator is often used in:
  • recirculating loops.
  • chemical reactors.
  • fuel cell testing.
  • flow control.
  • vacuum control.


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Introduction: My name is Terrell Hackett, I am a gleaming, brainy, courageous, helpful, healthy, cooperative, graceful person who loves writing and wants to share my knowledge and understanding with you.