Self Acting Controls and Systems

So far THINKTANK has participated in 12 projects about self-operated regulators.

What is a self-acting control valve?

A self-acting control valve is also known as a self-operated pressure regulator, which doesn’t need any auxiliary power to drive the valve, the self-acting control valve through the medium energy to operate the valve itself, that’s why it is called self-acting or self-operated. A self-operated control valve can realize the adjustment of temperature, pressure, differential pressure, flow rate, and other parameters. It has the characteristics of simple structure, low price, reliable action, and so on. It is suitable for occasions where flow rate changes are small, adjustment accuracy is not high, or instrument air/power supply is difficult. 

Self-operated temperature regulators

What are self-acting temperature control valves?

Self-acting temperature control valves also known of self-operated temperature regulator, it doesn’t need any external power sources to regulate the temperature of process streams, tanks, and various systems. THINKTANK’s self-operated temperature regulators are often used for boiler temperature adjustment. It can maintain a linear functional relationship between temperature and valve opening.

How does a self-acting temperature control valve work?

self acting temperature regulator
Figure 1. Components of a typical self-acting temperature control system
  1. Valve
  2. Piston
  3. Capillary tube
  4. Sensor
  5. Pressure gauge
  6. Temperature overload device
  7. Adjustment knob

The working priciple of self-acting temperature control valve is:

As long as sensor 4 (figure 1)is inserted into the pipeline to be temperature adjusted, the change in the temperature of the medium can be felt, thereby controlling the opening of the valve. Because the temperature-sensitive fluid is fill in sensor 4, then responds to capillary tube 3. 

If medium temperature rising up, the temperature-sensitive fluid in the sensor is heated and will expand capillary to close the valve. If medium cooled, the temperature-sensitive fluid in the sensor is contacted then makes the valve open. 

In figure 1, using a temperature overload device and adjustment knob could change the volume of sensor 4 filled with the sensitive liquid to set the regulating valve at an appropriate prescribed temperature value. After the temperature in the sensor changes, the sensitive liquid volume changes, and this change is transmitted to the piston by force through the capillary tube 3, then the piston actuator 2 acts on the valve stem. When the temperature is heated, it will close the control valve. If the temperature is cooled, it will open the control valve by the spring force.

The temperature overload device sometimes also includes pressure gauge 5, and we can read the temperature data for temperature-sensitive liquid. 

self acting temperature regulator thinktank

(Above picture resource from Spirax Sarco)

Specification of self-acting temperature control valves

* Size: DN15 to DN200
* Pressure Rating: PN16 to PN25, Class 150LB
* Trim Type: Single-seated, double-seated, cage-guided, three ways
* Applicable Medium: Hot water, Cooling water, Steam, Hot oil and etc.,
* Applicable Temperature: -20℃~350℃
* Overrun is typically 30°C to 50°C above the set temperature, according to the control type
* Control Temperature Range: 0~70℃/50~120℃/100~170℃/150~220℃/200~270℃
* Environment Temperature: -40℃~+80℃
* Adjustment Accuracy: ±5%
* Capillary Tube: 3.5 to 4.5m, or the length which the customer required.
* Balance Component: Bellows, Spring

Dimensions

structure self actuated temperature control valve (1)

Size

H1

D1

D

D2

L

d

G

H2

n-Φ

DN32

555

135

32

100

180

25

1-1/4″

180

4-Φ18

DN40

570

145

40

110

200

25

1-1/4″

180

4-Φ18

DN50

610

160

50

125

230

25

1-1/4″

280

4-Φ18

DN65

635

180

65

145

290

25

1-1/4″

280

4-Φ18

DN80

680

195

80

160

310

25

1-1/4″

280

8-Φ18

DN100

720

215

100

180

350

25

1-1/4″

280

8-Φ18

DN125

760

245

125

210

395

25

1-1/4″

380

8-Φ18

DN150

800

280

150

240

470

25

1-1/4″

380

8-Φ23

DN200

950

335

200

300

550

25

1-1/4″

480

12-Φ22

DN250

985

405

250

355

640

25

1-1/4″

480

12-Φ22

installation manual of self acting temperature control valves
Figure 2. Typical Installation

Typical installation method of self-acting temperature regulator

  • Body Part

Step 1: Make sure the valve body is installed at the inlet of the primary heat medium with a horizontal position, and the valve stem upwards to ensure that the self-actuating actuator is positioning vertically. 

Step 2: At the inlet of the self-acting temperature control valve, it needs to install a strainer, and the required filter mesh corresponds with the medium.

Step 3: It should be installed on/off valve inlet and outlet of the self-acting temperature control valve. And install globe valve of bypass pipeline. 

Please refer to figure 2 for installation layout, and kindly noted that the optimum working range of the inlet stream is around 3.0 to 7.0 bar. Any information just feel free to contact us representative marketing at cncontrolvalve.com 

  • Sensor Part

The sensor is inserted around the outlet of the heat exchanger or outlet pipe of water. Be careful of the valve stem and capillary tube during installation.  Drilling a hole in the pipeline to insert the sensor,  then welding without any leakage from this connect part. 

  • Actuator Part

THINKTANK supply the complete self-acting temperature control valve before shipment, so the actuator has already assembly on the valve body, all you need to do is tighten the nuts between the sensor and temperature overload device. 

Learn the typical application of self-acting temperature control valve

typical application of self acting temperature control valve
Control the outlet temeperature of hot water of heat exchanger

The hot water or steam enters the heat exchanger, and the sensor of self-acting temperature control valve to sense the temperature of the outlet of the heat exchanger, if a temperature-sensitive fluid is heated, it will expand to the closing valve. If it is cooled, it will contract to open the valve.

Ask For Quote

As a responsible valve company, we have participated in many self-regulating valve projects. We believe that our rich experience and reasonable prices can help you open up the market.

Before you send RFQ, Please kindly share the following data if possible, in order to work out the best price for you.

 1. Medium Flow Rate(Q) (T/H)
2. Inlet Pressure P1 (Mpa)
3. Outlet Pressure P2 (Mpa)
4. Medium Name
5. Temperature of Medium (
)
6. Other Requirement

Self-operated pressure regulators

What are self-acting pressure control valves?

Self acting pressure control valves used to keep the adjustable set-point pressure within certain range in tanks or processes. It doesn’t request any auxiliary energy to operate valves but by the medium energy itself.

Since the self-acting pressure control valves do not need air supply or electric power to operate, so it’s kind of the most cost-effective pressure control valves to achieve a simple process of pressure control. 

What are the different types of pressure control valves?

Nowadays, there are two types of self-operated pressure regulators, direct-acting self-operated pressure regulators, and pilot-operated pressure regulators.

Many people may don’t familiar with the last 1960s, there is a lever and weight type direct-acting self-operated pressure regulator(figure 5), and its inherent flow characteristics you can refer to in figure 6. 

direct loaded self acting pressure control valve1
Figure 5
direct loaded self acting pressure control valve
Figure 6

This lever and weight type direct-acting self-operated pressure control valve are barely not used for modern industry, but still wort at some old equipment.

The principle diagram figure 7. of direct-acting pressure control valve with lever and weight

working principle direct acting pressure control valve
Figure 7
  1. Diaphragm of Main Valve
  2. Lever
  3. Weight/Hammer
  4. Plug

According to the action type, there are inlet/upstream pressure control type and outlet/downstream pressure control type self-acting pressure regulating valve. 

When controlling the downstream pressure of the self-acting control valve (figure 7 b), the signal is taken over the control line to the downstream of the valve pipeline and maintains the set pressure downstream constantly. This magnitude of set pressure depends on the weight of the heavy hammer, on the other hand, if the weight of the heavy hammer is changed, the set pressure value will be changed correspond. 

The control line passes the downstream pressure on the diaphragm 1 of the main valve is increased, the valve plug moves downward and the passage of flow area becomes smaller.  When the torque exerted by downstream pressure on lever 2 is equal to the torque exerted by the heavy hammer on the lever, it is in a balanced state then the valve remains to open.

When controlling the upstream pressure of the self-acting control valve (figure 7 a), the signal is taken over the control line to the upstream of the valve pipeline and maintains the set pressure upstream constantly. The control line passes the upstream pressure on the diaphragm 1 of the main valve is increased, the valve plug moves downward and the passage of flow area becomes larger, then the inlet pressure corresponds decreases, it will make the lever and weight 3 force plug moves upward, the passage of flow area becomes smaller until the upstream pressure meets the set pressure. 

What is the working principle of pilot pressure control valve? and How does a pilot operated pressure regulator work?

pilot operated pressure regulator
Figure 8
  1. Needle valve
  2. Diaphragm of main valve
  3. Pilot diaphragm
  4. Orifice plate
  5. Nozzle
  6. Pilot diaphragm subassembly
  7. Pilot set spring
  8. Filter
  9. Plug

If the pilot self-operated pressure control valve is used for controlling downstream pressure(Figure 8 b) when the downstream pressure rises, the pressure acting under the main valve diaphragm 2 is greater than upper chamber pressure, and plug 9 moves upward to reduce the flow passage area, in this way, the downstream pressure correspond decreased. Meanwhile, the pressure acting on the pilot diaphragm 3 increases, when the force acting on the diaphragm 3 is greater than the force of the pilot set spring 7, the pilot diaphragm subassembly 6 moves to the right, and the orifice plate 4 approaches the nozzle 5. The output pressure of the pilot decreases, and the pressure on the main valve diaphragm 2 decreases accordingly, the plug 9 continues to move upwards, the flow passage area continues to decrease, and the pressure of the medium to be adjusted continues to decrease until balanced with the spring force is set by the pilot.

Conversely, when the downstream pressure decreases, the pressure acting on the pilot diaphragm 3 decreases, when this pressure is less than the force of the pilot set spring, the pilot diaphragm subassembly 6 moves to the left, and the orifice plate 4 leaves nozzele5, the output pressure of the pilot increases, the valve plug 9 is opened, and the downstream pressure rises to meet set pressure value. Needle valve 1 is used to adjust the magnification, and filter 8 can filter out particles in the medium to prevent the nozzle from being blocked and losing its function.

What is the pilot-operated self-acting pressure control valve?

A pilot-operated self-operated pressure control valve also known as a nitrogen regulating valve, this valve does not require auxiliary energy, uses the energy of the process medium (gas) as power. The pilot valve amplifies the feedback signal and then through the actuator, drives the movement of the main valve plug to the opening valve. 

As a general rule, the control accuracy of the direct-acting self-operated pressure control valve is not high. A pilot valve design is mainly to increase the control accuracy. The control accuracy can be twice as high as the general direct operation pressure regulating valve, and the adjustment of differential pressure ratio is large (such as 0.8MPa upstream, 0.001MPa downstream), Especially suitable for micro pressure gas control. THINKTANK’s gas regulators serve for many projects of gas sealing system and safety protection system of the storage tank. Such as nitrogen sealing of storage tanks. 

normal close self acting pressure regulator
normal open self acting pressure regulator

Typical installation of pilot self-acting control valve

typical installation of pilot self acting control valve
Pilot pressure regulator control system installation diagram
  1. On/off valve
  2. Pressure gauge
  3. Filter
  4. Pilot pressure regulator
  5. Storage tank
  6. Pressure gauge

Operation

(1) Open the on/off valve inlet of the pilot pressure regulator, so that the medium slowly flows into the valve body.

(2) Unscrew the pilot protective cover and loosen the pilot adjusting screw.

(3) Adjust the mainspring of the pilot to make the downstream pressure reach the set value.

(4) Fix the pilot adjusting screw, install the protective cover, and the pilot pressure regulator can start to work.

(5) If stops working, close the on/off valve before the regulator. 

What is the direct-acting self Operated Pressure Control Valve?

The direct-acting balanced self-operated pressure control valve is the controlled inlet/outlet pressure that directly acts under the diaphragm and is balanced with the spring above or below the diaphragm. The preload of the spring can be adjusted to change the control pressure.

Based on the difference of any working condition, the direct-acting ZZY series self-operated pressure regulator can be classified into 3 types according to its inside part: ZZYP (single-seat self-operated pressure regulator); ZZYM (cage type self-operated pressure regulator); ZZYN (double seat self-operated pressure regulator), customers can also choose the type by the local actual working condition(differential pressure, temperature, medium state) or leakage requirement.
There are 3 different bonnet types according to the working condition: standard (normal condition), long neck type(big range for pressure adjusting), heat radiation type(temperature 350~550°C). The ZZY series Self-operated pressure regulator applies with the quick opening flow characteristic, which is quickly acted and highly accurate adjusted (error≤10%), so it can be widely used in many fields like petroleum, chemical, electricity, metallurgy, food, textile, machinery, and civilian building and so on to reduce/release or stabilize the pressure of the gas, steam, and liquid and so on.

self acting pressure regulator

 ZZY(Diaphragm type, Downstream Pressure Setting)

1. Body     2. Gasket     3. Seat     4. Plug     5. Grand    6. Double Stud      7. Bolts     8. Bonnet     9. Bolts     10. Yoke     11. Adjusting Plate     12. Travel Gasket     13. Inside Spring     14.
Outside Spring     15. Packing     16. Thrust Needle Bearings     17. Gasket     18. Nuts     19. Spring Seat     20. Actuator

SPECIFICATIONS
Valve Body

  • Plug Type Single-Seated(ZZYP), Cage Type(ZZYM), Double-Seated(ZZYN)
  • Action Type Control Upstream Pressure(B Type) and Control Downstream Pressure(K Type)
  • Nominal Diameter DN15mm ~ 300mm(1/2’’ ~ 12’’)
  • Flow Characteristic Quick Open
  • Adjusting Accuracy ±3 ~ 10%
  • Working Temperature ≤350
  • Pressure Reduction Rate Max. 10, Min. 1.25
  • Nominal Pressure PN1.6MPa, 4.0MPa, 6.3MPa, 10.0MPa, Class 150, 300, 600.
  • Connection Type Flanged Ends, Welded Ends, and Threaded Ends.
  • Body & Bonnet Material WCB, WC9, CF8, CF8M
  • Actuator Type Diaphragm, Piston/Cylinder, Bellows
  • Packing PTFE, Flexible Graphite

 Trim Material

trim material

Packing Material

packing material

Plug Material

plug material

Soft Seat/RPTFE Plug

STL Sealing Plug

Rated Kv Value · Rated Travel · Adjusting Pressure Range

Nominal Diameter
DN(mm)
20253240506580100125150200250300
Rated KvSingle-Seated 71120304875120190300480760  
Cage-Guided71120304875120190300480760  
Double-Seated  2233538313220933052883612101925
Rated Travel(mm)81014202540506070    
Adjusting Pressure Range
( kPa)
15~50, 40~80, 60~100, 80~140, 120~180, 160~220,
200~260,  240~300,  280~350,  330~400, 380~450,  430~500,
480~560,  540~620,  600~700,  680~800,  780~900,  880~1000,  950~1100,
1080~1250,  1230~1400,  1380~1550,  1530~1800,  1780~2000,  1980~2300,  2280~2500

Main Parameters & Specification For Micro-Flow, Single-Seated

Nominal Diameter
DN(mm)
20、 25
Seat Prot dg(mm)678101215
Rated Kv0.010.020.0480.060.080.120.20.320.50.81.82.84.4
Rated Travel(mm)5

Flow Characteristic

flow characteristic

Different Design and Construction Type

different self acting pressure control valves1

1. Control downstream pressure, when an outlet pressure is rising then the valve shutoff

2. Control downstream
pressure, when an outlet
pressure is rising then the valve shutoff

3. Use metal bellows to balance inlet and outlet pressure, then control the downstream pressure.

4. Use metal bellow to seal and balance inlet and outlet pressure, then control downstream pressure.

different self acting pressure control valves2

5.  Control upstream pressure, when inlet pressure is rising then valve open. 

6. Control downstream pressure in steam application.

 

7. Metal bellows as an actuator and control upstream pressure.

 

different self acting pressure control valves3

8. Construction of cage type and control downstream pressure.

9. Construction of double-seated, and use piston/cylinder type actuator to control upstream pressure.

10. Construction for blocking low noise.

Installation

installation of self acting pressure control valves

 1. Filter     2. Self-operated pressure regulator     3. Control line     4. Condenser

Self-operated differential flow control valves

What is a self-operated differential pressure regulator?

ZZC, ZZV self-operated differential (micro) pressure regulator is not needed to require external energy, and differential (micro) pressure can be adjusted in sections, ranging from 50mm.w.c to 0.1MPa. It has a wide range of uses and can be used in industrial combustion furnace systems to control the ratio of two materials, such as gas and air, to achieve ideal combustion. Used in the sealing oil system of hydrogen-cooled generator sets to control the differential pressure between the sealing oil and hydrogen to ensure reliable sealing. When the low-pressure end of the differential pressure regulator is open to the atmosphere, it is named the micro pressure regulator.

working principle of self acting differential pressure control valve
differential pressure regulators
pressure regulators 4 41 removebg preview

Rated Kv Value · Rated Travel · Adjusting Pressure Range

Nominal Diameter
DN(mm)
20253240506580100125150200250300
Rated KvSingle-Seated71120304875120190     
Double-Seat  2233538313220933052883612101925
Rated Travel(mm)6810152030405060
Adjusting Pressure Range
kPa
0.3~2 0.5~4.5 1~8 5~15 6.5~20 10~30 15~40 35~80

Main Parameters & Specification For Micro-Flow, Single-Seated

Nominal Diameter
DN(mm)
20、 25
Seat Prot dg(mm)678101215
Rated Kv0.010.020.0480.060.080.120.20.320.50.81.82.84.4
Rated Travel(mm)5

What's the advantage and disadvantage for different types of self-operated pressure regulator?

Direct-actingPilot-Operated
Bellows Operated Diaphragm Operated 
Small CapacityLarge CapacityLarge Capacity
CompactRelatively LargeCompact For Capacity
Low CostRobustExtremely Accurate
Steady LoadSteady LoadVarying Loads
Coarse ControlCoarse ControlFind Control

Ask For Quote

As a responsible valve company, we have participated in many self-regulating valve projects. We believe that our rich experience and reasonable prices can help you open up the market.

Before you send RFQ, Please kindly share the following data if possible, in order to work out the best price for you.

 1. Medium Flow Rate(Q) (T/H)
2. Inlet Pressure P1 (Mpa)
3. Outlet Pressure P2 (Mpa)
4. Medium Name
5. Temperature of Medium (
)
6. Other Requirement

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