How to make a check valve for the compressor

Air check valve for the compressor with his own hands

Т.к. The topic about the compressor has grown as much as 3 records, I have decided to create the record touching on all aspects of assemblage of the home-made compressor on the basis of a head ZIL-130. From idea to implementation. This item will be updated periodically.Build/buy ready made is up to each individual. Similar compressor in capacity and liters I found from 15 thousand. Direct drive (the life of a small). After deliberation, began assembling his.

1) Receiver (compressed air reservoir), the bigger the better. fast wear and tear piston) to inflate the tires and an occasional piece-by-piece paint 50.100 liters is enough. A large air tank will allow to get more stable result.2) Motor (electric) to drive the compressor head (recommended with a reserve of 20-40%, in order to avoid possible problems of non-starting under load). (As a rule, there are asynchronous motors with condensers) 3) Safety grid (so that the hands do not wind up on the belt) 4) drive belt (usually wedge, in the case of a hellish overload will slip and not kill the motor) 5) check valve (is required to start the compressor under load, the principle of operation: in the receiver to let in from the receiver does not let out) 6) Air tube into the receiver (usually copper or aluminum).7) Compressor head (as a rule, are placed under the cooling air, in our case the cooling water / antifreeze, with prolonged operation is desirable), it depends on the performance of the system as a whole.8) pressure switch. the heart of the compressor, in this box is the pressure switch, usually set to: 8 atmospheres turns off the motor, reducing the pressure to 4-6 atmospheres starts the motor and so on around.Also in this unit is a pressure regulator with two gauges. its task is to set the desired user pressure for a particular tool, such as a spray gun. Now about manometers, usually there are two, one that indicates the pressure in the receiver, the second shows the air flow to the tool. regulator on the outlet has a connection fitting: either a Rapid or a bypass. There is also an option herringbone).This assembly has a small but very important detail. pressure relief valve (in common parlance a fart).Necessary in case of PRESSOSTAT failure.9) Drain valve. function to free the receiver from condensate (and it will be in any case).

Now let’s solve the following unobvious thing: for what such a long pipe from head to receiver is done?Needed to make compressor easier to start. The principle of operation of this unit is simple: the air from the compressor head goes through the line through the check valve into the receiver. Compressor has stopped. check valve has blocked air in receiver, air is standing in tube. 9) Compressor valves are not so tight and let air out little by little and thus pressure in the pipe decreases. It takes a few moments for the motor to start working and these few moments are provided by the tube and the check valve.

Second, to reduce condensate at the compressor outlet, it is recommended to do the air inlet further from the outlet.

So, after understanding the design of the compressor and clarifying some aspects, it was decided to design, which is not difficult to repeat.

1) Receiver. domestic propane tank 40-50 liters.( Before welding perform degassing, I am not responsible for your rash actions.) In the receiver body welded: a piece of water pipe fitting under the 1/2″ reverse pressure valve, a piece of water pipe fitting under the condensate drain valve, a nut M12 under the emergency pressure valve, (formerly it was a valve under the 1/4 thread, cut with a die under M12). Air output is carried out through the neck of the cylinder. 3/4″, screwed into the cylinder (in the cylinder thread 3/4 to (tapered), screwed into easily.

To ensure the correct operation of the compressor equipment used various technical devices, among which you can highlight the check valve for the compressor. Without this part, it is almost impossible to imagine the work of equipment intended for air compression.

Valves for the compressor. what are they

Air compressor is a unit, the principle of operation of which is based on compression and supply of air to pneumatic equipment at the required pressure. Such units are indispensable element both in the household and in industry, being an autonomously operating technical unit or being included into more complex electrical appliances (such as climatic or refrigeration equipment). The basic scheme of any compressor includes a working chamber and valve system. And as these devices, as well as any other mechanisms, can break, it is necessary to know how they are constructed, what valves are, how to choose them or make them yourself. About all this. in the material below.

Valves on the compressor with their own hands

Т.к. topic about the compressor has grown as much as 3 records, I decided to create a record affecting all aspects of assembling a homemade compressor on the basis of the head ZIL-130. From idea to realization. This record will be periodically updated.To assemble / buy ready made a personal matter. Similar compressor in capacity and liters I found from 15 thousand. Direct drive (small capacity). After thinking about it, started assembling my.

1) receiver (storage of compressed air), the more. the better (for the direct drive a large receiver. fast wear and tear piston) for tire inflation and a rare piece-by-piece painting 50.100 liters is more than enough. A big air reservoir will give you a more stable result.2) Motor (electric) for compressor head drive (it is recommended to have 20-40% reserve, in order to avoid possible problems with non-starting under load). (As a rule, motors are asynchronous with capacitors) 3) Safety grid (so that the hands on the belt does not wind up) 4) drive belt (usually wedge, in the case of a hellish overload will slip and not kill the motor) 5) check valve (required to start the compressor under load, the principle of operation: in the receiver to let in from the receiver do not let out) 6) Air tube into the receiver (usually copper or aluminum).7) Compressor head (usually placed under the cooling air, in our case, cooling water / antifreeze, with prolonged operation is desirable), it depends on the performance of the system as a whole.8) Pressostat. heart of the compressor, in the box is the pressure switch, usually regulated to: 8 atm switching off the motor, reducing the pressure to 4-6 atm starts the motor and so on around.Also in this node is a pressure regulator with two gauges. its task is to set the desired user pressure for a particular tool, such as a spray gun. Now about the pressure gauges, usually there are two, one shows the pressure in the receiver, the second shows the air flow to the tool. Regulator on the outlet has a connection fitting: either Rapid or bypass. There is also a variant herringbone).This unit has a small but very important detail. pressure relief valve (in common parlance fart).Needed in case of a pressure switch failure.9) drain valve. the function to release the receiver from the condensate (and it will be in any case).

Now let’s understand the following non-obvious thing: why such a long line from the head to the receiver is made?It is necessary for easier start of the compressor. The principle of operation of this unit is simple. the air from the compressor head passes through the line through the check valve into the receiver. Compressor stopped. check valve locked air in receiver, air stays in tube. The compressor valves are not so tight and let the air out little by little, thus the pressure in the tube drops. The motor needs a few moments to get to work, and these few moments provides a tube and check valve.

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Second, to reduce condensate at the compressor outlet, it is recommended to install air inlet farther from the outlet.

So, after we understood the compressor design and clarified some aspects, we decided to create a design, which is not difficult to repeat.

1) Receiver. domestic propane tank 40-50 liters.( Before welding to produce decontamination, I am not responsible for your ill-considered actions.) In the receiver body there are: a piece of water pipe fitting for 1/2″ back pressure valve, a piece of water pipe fitting for condensate drain valve, M12 nut for overpressure valve, (earlier it was 1/4″ thread valve, I cut it under M12 with a pipe cutter). The air is exhausted through the cylinder neck. a 3/4″ nozzle screwed into the cylinder (the cylinder thread is 3/4″ (tapered), screwed in without any problems).

This model compressor uses plate valves, which wear out during operation and must be replaced. The valves in the compressor are structurally located between the cylinder and head. Wear is a result of the alternating loads that occur during the start-up and exhaust cycle.

At startup, air entering through the air filter into the headspace presses the inlet plate valve against the cylinder, thus opening the two elongated holes in the head, with the other half of the cylinder also pressed by the exhaust valve, preventing air from escaping the air line. During the exhaust stroke, the valve is pressed against the cylinder head, preventing air from escaping and allowing air to be forced from the cylinder into the receiver through the exhaust holes in the cylinder head. In the process of shifting from the cylinder to the head and vice versa, the front and back edges of the valve wear out, which subsequently leads to air leakage. The stress on the exhaust valve is considerably greater as it is re-routed from the cylinder head to the cylinder in a pressurized condition. Because of this, the exhaust valve is the one that wears first and is often the only valve that needs to be replaced.

To replace the leaf valves, it is necessary to:

  • Let the compressor run for about three minutes to warm up (necessary to facilitate the loosening of the screws)
  • De-energize the compressor
  • Remove the four screws that hold the cylinder head to the cylinder one after the other
  • Note the position of the metal gasket and pull it out together with the valves
  • To wipe the mating surfaces of the head and the cylinder, as well as the metal gasket, with a soft rag soaked in kerosene
  • Place the inlet valve in a notch on the cylinder
  • Apply a thin film of grease to the underside of the gasket and reinstall it in its place and press the gasket all the way around the cylinder
  • Lubricate the tips of the new valve and install it in the recess in the cylinder head. The grease is only needed to temporarily stick the valve to the notch, otherwise it will fall out during installation
  • Press the head against the cylinder and screw in the screws, pulling them crosswise one after the other

How To Test A Check Valve (One-way Valve) On An Air Compressor

In conditions of tire fitting shop, at intensive work, inspection of valves of the compressor should be made at least once in two years or at appearance of extraneous noises similar to sharp pops during air pumping in the air tank.

In order to ensure the correct operation of compressor units, used today almost everywhere, use a number of additional technical devices, one of which is a check valve for the compressor. Such a valve, which today is completed by the majority of compressor units, also protects them from premature failure and provides soft start.

Part selection tips

When choosing a check valve for a compressor, you should know the size of the threads cut on the cylinder outlet. Threads can be different on each model. The easiest way is to take the defective part with you and choose a similar one in the store.

If it is necessary to change a check valve, for example, for a more reliable model, it is necessary to get acquainted with the technical characteristics of the new part. Some are not designed to work with high-pressure compressors. The maximum pressure at which the return valve can work is usually marked on the package.

Also it is necessary to take into account temperature characteristics of the given node. If the air after compression is heated to high temperatures, it is not worth buying a plastic unit. Prefer a metal check valve, which is installed inside the air duct.

Advice! A good choice is the collapsible brass check valve. If it fails, you can always find spare parts to repair it.

Safety valve

Relief valve (another name. safety valve) serves for emergency pressure relief and is the final device to protect pneumatic equipment connected to the compressor from damage.

Attention! It is not advisable to run the compressor without a safety valve.

To the varieties of non-return valve specialists also include:

Despite minor design differences their operating principle is identical to that of the safety relief valve.

Safety relief valve principle

In compressor equipment which is not intended for operation under industrial conditions, spring safety valves are installed. When such a compressor is operating in normal mode, it is closed (see “The compressor is closed”). diagram). A graduated spring balances out the air pressure on the valve head and prevents the shut-off mechanism from opening. If a sudden increase in pressure over the set pressure level decreases, the contact force applied to the nozzle and the valve starts to open. This action relieves excess air and allows the shutoff mechanism to return to its original position.

Important! If the relief valve does not return for a long time, shutdown compressor and eliminate cause of the unauthorized pressure increase

Relief valve

The by-pass (or overflow) valve maintains the pressure of the fluid at a predetermined level. For this purpose, through the available branch, a constant, not single or periodic, as in the safety valve, removal of excessive amounts of the working environment (compressed air, gas, liquid) is carried out, which ensures the stability of pressure in the system. Such valves are used, for example, in turbochargers installed in automobile engines.

Relief valve

The unloading valve ensures that the compressed air remaining in the manifold between the piston unit and the return valve is bled off when the compressor is stopped. At the same time the pressure at the compressor outlet is reduced to atmospheric pressure. In general, the presence of a relief valve makes it possible:

  • to relieve pressure in the pipeline when the compressor is switched off;
  • to set the compressor to zero capacity when there is no flow of the working medium;
  • Facilitate restarting of both the compressor and the connected pneumatic equipment.

In addition, the unloading valve is used when it is not possible to disconnect the mechanical drive of the connected pneumatic equipment. It is installed at the compressor outlet before the return valve.

So, the more productive and powerful the compressor equipment, the more complex the valve system. The simplest check valve for use in a domestic low-pressure compressor can be made by your own. But in order for the installation to work correctly, it is recommended to buy a factory part.

I made and adjusted the air pressure switch for the compressor myself: find out how

Russian market offers a variety of tools for potential customers. Analyzing market condition, experts note some growth of pneumatic tools popularity.

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However, surpassing basic parameters (power, reliability, durability) of traditional types of electric tools, pneumatic tools require source of compressed air.

Such source is an air compressor, the purchase of which for one-time work is not economically feasible. That is why, widely used by professionals, pneumatic tools are rarely used in the home.

It is this device which regulates the air pressure in the compressor

Structurally, the air compressor is a device that can be manufactured by a person with some knowledge and skills of carrying out plumbing and electrical works in the home. The critical component is the air pressure switch (pressostat), which can be installed and adjusted independently. Besides, it is possible to remove the simplest malfunctions of the pressostat by yourself.

Pressure switch: function and principle of operation

Pressostat is a device (actuator), which turns on or off the electric motor of compressor. It is mounted on the reservoir (receiver) and connected to its check valve and compressor head.

Pressostat ensures automatic operation of the whole product. It is used to maintain the required air pressure in the air reservoir.

The principle of operation of such a relay is the use of a normally closed contact in the electric circuit to control the electric motor. The electric supply circuit closes or opens depending on the air pressure in the pneumatic system. This causes the motor to start at insufficient air pressure or to cut off the power supply when the maximum air pressure is reached.

As the operating mechanism of the pressostat, springs of varying stiffness are used, responding differently to changes in the amount of air pressure in the receiver. The actuator is actuated by the spring force due to the compressed air pressure in the air reservoir. This causes the motor power supply contact to close or open.

Accessories

In general, the pressostat kit includes (maximum configuration):

Safety valve an important part of the pressostat

Each of these devices has a specific function:

  • The relief valve opens when the motor stops and relieves the pressure from the pneumatic circuit. The next time the electric motor is switched on and accelerates, the check valve closes, thus facilitating the start of the entire device from the off state.
  • A thermal motor protection relay limits the intensity of the current in the windings. A special regulating element is used to set the permissible current intensity, exceeding which will lead to the electric motor shutdown.
  • A mechanical switch enables automatic operation of the product (AUTO position) and enables forced shutdown of the motor (OFF position).
  • A safety valve is triggered if compressor‘s pressostat fails and produces an emergency release of compressed air from air reservoir, preventing increase of pressure over admissible value.

wiring diagram

Existing air pressure switches for 220 V compressor are used in various schemes of connection of load.

  • If using a single-phase motor use a pressostat with two contact groups, designed to work in a network of 220 V.
  • If a three-phase motor is used, a relay with an operating voltage of 380 V and three contact groups must be used.

WARNING! It is not recommended to use a single-phase air pressure switch (220 V) for connecting a three-phase motor.

The pressostat is connected to the electrical circuit of the compressor using special contactors (connectors) built into its housing.

Connection Flanges

Connect the pressostat to the receiver using a standard 1/4 in. female threaded flange. Many pressure switches are equipped with a 4-way flange that allows up to three additional devices, for example, to be connected if necessary:

If no auxiliary device is required, the flanges are closed by special plugs.

IMPORTANT: Threaded holes on flanges are 3/8″ or 1/2″. The auxiliary devices must also have the appropriate threads.

Receiver, relay all assembled, great compressor

Installing

Compressor pressure switch mounted directly on the compressor tank (1/4″ threaded center flange). If necessary, additional devices are installed through loose flanges. If additional devices are not necessary, threaded holes of flanges are closed with special plugs.

Control circuit for turning compressor motor on and off is connected to contacts of pressure switch.

CAUTION! If the load current exceeds the current rating of the relay contacts, a mains contactor (magnetic contactor) must be used.

Setting

The commercially available pressostats do not need to be adjusted. At operation of the compressor, however, there can be situations in which it is necessary to change the thresholds of its actuator. Adjustment procedure:

  • Determine the variation range of compressed air pressure.
  • Disconnect the appliance from the electricity supply.
  • Remove the upper cover of the pressostat.
  • Set the required relay thresholds using the two special spring-loaded adjusting screws located under the cover. Check the value of the set values with a manometer.
  • To set the upper threshold, at which the motor is switched off, turn the adjusting screw marked with the symbol P. To change the actuator threshold, turn the screw in the direction of the arrow corresponding to the symbols and
  • Set the lower pressure switch threshold, at which the motor will start automatically, by turning the second adjusting screw marked 5P towards the symbol and
  • Replace the top cover of the air pressure switch.

Pressostat with your own hands

Having taken up the task of making an air compressor themselves, some amateur craftsmen may also dare to make a pressure switch with their own hands.

Making your own equipment is interesting, practical and very economical

In the Internet you can find variants of such devices, for example, made of the thermal relay from the fridge or made with parts from CDs and plastic bottles.

However, it should be noted that their design is no comparison with the design of commercially available pressostat for the compressor.

In addition, the use of a home-made device, in the case of a sudden failure, can lead to an emergency situation with unpredictable consequences for others.

TIP: Considering that the air pressure switch is one of the most critical units of the compressor, it is better to install even in a self-made compressor an industrial pressure switch.

make, check, valve, compressor

Relay failure and troubleshooting

There are several typical problems inherent in pressostats. In most cases the relay is simply replaced with a new one, but there are also such failures that can be repaired with your own hands. Among them are most often met:

  • Leakage of air through the pressostat when the compressor stops.The reason of malfunction is the contamination of the receiver check valve.For elimination of malfunction it is necessary to drain the compressed air from the reservoir, remove the valve plug and clean the valve seat and the sealing ring.
  • When the compressor operates, compressed air leaks through the pressure switch.This is caused by a broken start-up valve.Remedy by replacing the starter valve gasket.
  • Compressor starts to cut in frequently.This is due to vibration of the compressor and shifting of the adjusting screws. It is necessary to check pressure switch on and off thresholds and adjust them according to the instructions in Adjustment section.
  • The compressor does not start.In this case there could be several causes, but one of them is burning of the contact group of the pressure switch. Burning of contacts occurs owing to electrospark erosion arising at opening of contact group.
  • by replacing the pressostat;
  • Clean the contact surfaces (prolongs the life of the device by 2 to 3 months)
  • Having replaced the contact group with a new one (not all modifications are available on the market);
  • Repairing the contact group with your own hands (replacement of contacts in the terminals).

Repair of the contact group with their own hands

Having begun repair it is necessary to pit the air from the receiver, to disconnect the compressor and to dismantle the pressostat. Repair work should be carried out in the following order:

  • Remove protective shroud.
  • Disconnect the wires to the contact group.
  • Using a flathead screwdriver, remove the contact group and the terminal block. It is necessary to remember the position of the return spring, which can shoot out when dismantling the contact group.Pull out the terminals from their holder and bore out the burned out contacts.
  • Take a piece of copper wire 10 mm long and insert it into a drilled hole. The diameter of the wire should ensure a snug fit in this hole.
  • Crimp the wire on both sides so as to ensure that it is securely fastened in the hole.
  • If necessary, repeat the same procedure with the remaining terminals.
  • Reassemble the contact group by performing the necessary operations in reverse order.
  • Put the contact group back in place and close the pressostat with the cover.
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INFRASTRUCTURE: when the service representative comes to repair the compressor, if the pressostat is defective, he will insist that it be replaced. He will not clean and change details of contact group, as execution of such works will cost more to the consumer, than purchase and installation of new.

Design and principle of operation

The checker design includes the following elements (see. figure. below):

  • The valve (6), which covers the inlet opening and is equipped with guide ribs to prevent skewing;
  • the rubber ring (5) installed in the upper part of the valve (6);
  • a spring (4) that presses a rubber ring to the inlet port and is dressed on the lugs on the plug (1) and valve (6);
  • the plug, which is sealed with a cardboard gasket (2) and allows disassembly of the assembly for cleaning and repair.

The returner, except the inlet connection, has a side outlet, through which it is connected to the receiver, and 1 thin outlet for connection of the pressostat.

The check valve works according to the following principle. When the compressor is turned on, air passes through the cylinder suction valve, enters the compression chamber, then exits through the exhaust valve and enters the inlet fitting of the return (7). When a certain pressure is reached, the valve (6) together with the rubber ring rises and compresses the spring (4). It opens the air passage. the air flows in the housing cavity (3) and then to the outlet connection connected to the air receiver. When the unit is turned off, the valve (6) is pressurized by the spring and air pressure from the air reservoir and returns to its original position to close off the inlet port.

Check valve

A check valve is a device that allows compressed air to pass in one direction only. Structurally it is assembled (ref. fig.) in the metal housing (pos. 3), inside which are placed:

  • Inner plug (pos. 6), blocking the inlet opening;
  • A spring (pos.4), pressing the rubber ring (pos.5) to the plug seat;
  • Inlet fitting (pos.7);
  • plug (pos.1) with cardboard gasket (pos.2) (plug allows disassembling check valve for repair or maintenance).

Note! The check valve has a branch for connection to the air receiver and a small branch for connection to the pressostat.

how it works

The check valve works in the following way. Passing through the exhaust valve of the piston cylinder, the compressed air enters the check valve through the inlet connection (pos.7). On reaching a certain pressure, the air lifts the inner plug (pos.6) and through the cavity in the housing (pos.3) flows into the accumulation reservoir of the air receiver. When the compressor is turned off, the spring (pos.4) Returns the inner plug into the receiver, cutting off the flow of air from the receiver back to the piston cylinder.

Varieties

In the domestic market, it is possible to encounter compressors with reciprocators made of three different materials: aluminum, plastic and brass. This aluminum part differs from its counterparts with high reliability and durability. It is built into the air duct between the piston cylinder and the air receiver and is able to operate at high temperatures (up to 200°C). Whereas plastic check valves are used on low-priced models that operate at low fluid temperatures, plastic check valves are used on low-priced models that operate at low fluid temperatures. As for valves made of brass, they are widely used. These reversing teeth are sufficiently reliable and maintain their operating characteristics perfectly in cases where the temperature during compression does not exceed 140°C.

Suggestions for selection

If the compressor check valve is out of order it is not difficult to replace it with the similar one. But before to buy a new valve it is necessary to pay special attention to the thread diameter which is cut on the branches of its case. After all, the connecting dimensions of the check valve, the compressor and the receiver may differ from each other.

Advice! Going to buy a new check valve for the compressor, do not forget to take with itself a damaged part. This will make the procedure of selecting a new unit much easier.

make, check, valve, compressor

The technical characteristics and operating conditions of the compressor must also be taken into account. There are valves that are not designed for use with high-pressure compressor equipment. Besides, when the working medium heats up to high temperature while compressing, it is not reasonable to use plastic returners. it is better to buy a node in a metal case that is installed inside the air pipe connecting the compressor and receiver. It will not be superfluous and purchase a collapsible design. it will allow in the future to buy the appropriate repair kit and fix the defect of the returner itself, replacing the failed parts with purchased spare parts.

Making a check valve with your own hands

In cases where buying a new check valve to replace a failed one is not possible, you can make it with your own hands from improvised materials. To do this you will need:

  • tee with internal thread;
  • spring;
  • 2 sockets with an external thread, the diameter corresponding to the internal thread of the tee;
  • a ball, the diameter of which is larger than the size of the inner hole in the socket;
  • metal plug with an external thread that matches the internal thread of the tee.

The valve is assembled in the following sequence: first the socket is screwed into one of the tee branches, then the ball is inserted into the tee from the other side, and then the plug is screwed in, pressing the ball with the spring.

There are some practical tips for the manufacture of a backsplash.

  • The ball is best taken from an old computer mouse. it has a rubberized surface that will fit tighter to the edges of the hole.
  • You can also use an ordinary piece of pipe with a suitable diameter as a housing. True, in this case it is necessary to drill a side hole, weld another tap and thread all the ends.
  • The spring must press the ball with a certain force and under no circumstances must be loose.

Basic varieties

The examined receiver valve can be classified by quite a large number of features, but the main thing is the design features of the mechanism. The following designs are distinguished:

  • Angular.
  • Straight type.
  • Ball valves.
  • Spring-loaded.
  • Attached by a flange.
  • Casement.
  • Installed by using soldering technology.
  • Fitted for flanging.

Classification is performed by the type of material used in the manufacture. Most often the valve is made of metal with high corrosion resistance, but there are other executions.

The locking element is also characterized by different design features. According to this feature the following versions are distinguished:

Ball-type versions are rather popular. This is due to their practicality and high reliability in application.

In addition, on sale there are versions, in which the control of the locking element is represented by an electromagnetic element, rather than a spring. They are more precise in operation, but cost much more.