Valve with pressure lightened plug are used as final elements in automatic and remote control systems. They are designed for the flow control of liquids and gases in chemical industry, heat engineering, power industry, metallurgy, shipbuilding etc. Valves can be supplied with or without drive mechanism.  37/38  type pneumatic diaphragm spring actuators are their standard drive mechanisms.



The valve mounted with 37/38 type actuator is composed of the following main parts:

1-body , 2-bonnet , 3-plug, 4-seat, 5-bottom plug , 6- plug stem, 7-packing box , 8-actuator yoke,

9-10 cases, 11-diaphragm , 12-actuator stem, 13-adjusting screw , 14-spring , 15-spring cage ,

16- actuator packing box .


Body ( 1 )

Double ported, moulded.

Nominal diameters ND: 20,25,32,40,50,65,80,100,150,250,300 .

Nominal pressure PN: 10,16,25,40,63,100,160 .



Flangle with raised face therefore or groove RTJ acc. To ANSI B16.5-1986-for welded ends with

PN 160 . In case of coagulation of flowing liquid or liberation of crystals which can immobilise the valve plug, the steel body may be fitted with heating jacket made of piping elements of pressed sheets connected by means of welding. The body with heating jacket is applied for valves DN 20...40, 150...200 with nominal pressure 1,6.....10 Mpa and folr valves DN 50...100

Nominal pressure 1,6....10 Mpa.  Steam , water or oil with working temperature 200 C is a heating medium.  These bodies have the folowing connections for attachment to heating medium pipelines:

DN 15 P  1,6 Mpa acc. To PN-H74731: 1978: DN 20.....80

DN 25 P  1,6 Mpa acc. To PN-H74731: 1978: DN 100.....200




Sayfa 2


Bonnet ( 2 )

Made of the same materials as the body is available in four variaties:

----standard – for agent temperature   -20......260 C

----finned AB – for agent temperature 260.....650 C

----extension EB – for agent temperature  -180......-20 C

----belows DM – for agent temperature up to 300 C for valves with diameters ND 20...100 and nominal pressur 1,6 – 2,5 Mpa and for valves with ND 150 and nominal pressure 1,6 Mpa.

Bellows bonnets are used for toxic, explosiv and flammable agents. Valves with bellows bonnet are irreversible what means that the change of valve action from “air – to close “

İnto “ air to open “  is possible through the change of 37 type actuator for the 38 type actuator.


Plug ( 3 ) and seat ( 4 )

Made of stainless steel or nitriding steel ( option ).

In case of fluid with abrasive features being used iti is possible to stellite the raying faces of plugs and seats within the entire range of valve diameters  DN 20...300 or their whole profiles for valves DN 20....100 or to apply plasma nitriding.


Subject to the characteristic required the following types of plugs are made:

***equal percentage contoured,

***quick – opening disk for on – off action,

***linear contured


Additionally for the nominal pressure range  1...10 Mpa, ND 50...300 working temperature

 -180..... +180 C there are being produced euqual percentage contured  No 122 and quick – opening disk No 162 plugs with soft seat inserts of PTFE for full seat capacity providing the entire tightness of valve in “ closed” position. Valves with plugs with soft insert are irreversible.



Sayfa 3


Finned AB

Extension EB

Belows DM


Table 1. plug types and valve marking

Plug type and characteristic               plug symbol                             air to  close     open

Equal procentage contoured

Quick-opening disk

Linear conteured


Plugs are being made for full seat capacity and reduced up to 40% of rated capacity-acc to table 2


Table 2 : applications of plugs

Seat capacity

Plug symbol  : full                      reduced 0,4



Sayfa 4


Bottom plug ( 5 )

İs made of the same material variaties as the body- except its basic function of closing the bottom side of the valve and guiding the plug-it can be used for easy removing of impurities gathering during the operation without the necessity of dismounting the bonnet and the actuator.


Plug steam ( 6 )

Made of acidproff steel provides rigid connection the plug with the actuator stem.


Packing box ( 7 )  made as rings of the following materials;

PTFE woven, PTFE , V rings graphite woven , expanded graphite rings.

The choice of the packing kind depends on the medium kind, temperature and working pressure.


Table 3  : kinds and types of packing box.

Allowable pressure

PTFE braided


Actuator yoke ( 8 ) made of gray cast iron.


Cases ( 9,10 ) made of pressed steel create a pressure chamber.


Diaphragm ( 11 ) made of neoprene with a spacer.


Stem ( 12 ) is made of stainless toughened steel


Adjusting screw ( 13 ) is used for initial spring tension.


Spring ( 14 ) is made of constructional spring steel


Spring case ( 15 ) is made of gray cast iron ( only for 38 type actuator )

Actuator packing box ( 16 ) is made of carbon steel ( only for 38 type actuator )



Operation Principle : 

Under air pressure the actuator diaphragm presses the diaphragm plate and overcoming the resistance of the spring couses linear displacement of the actuator stem and connected with it the valve stem. This displacement of valve stem attached to the plug causes the change of the seat flow area owing to that volumetric rate of flow changes in realtion to the plug position.

Full rated plug stroke is being reached at the change of air pressure within the limits corresponding to the normal pneumatic signal 20....100 kpa or raised signal 40...20 kpa.

Valves are reversible that means that their construction enables the change of valve action

“air to close” into “ air to open “ through turning of the body and plug by 180 C around the pipeline axis without the necessity of changing the actuator type and application of additional parts of valves with tight plugs and bellows bonnets are irreversible.


Technical data:
charakteristic of flow :   equal percentage, linear, quick- opening.


Hysteresis :

Without positioner :  4% of nominal stroke range.

With positioner : 1% of nominal stroke range


Basic error:

Without positioner : +- 4% of nominal stroke range.

With positioner :   +- 1,5% of nominal stroke range


Dead bond :

Without positioner : 2% of input signal variation range.

With positioner :   0,5% of input signal variation range


Pneumatic setting signal:

Normal :  20.......100 kpa

Raised : 40......200 kpa


Maximum supply pressure : 240 kpa

Medium temperature range :  -180......650 C

Nominal pressure range NP : 10.....160

Nominal diameters range ND  : 20.......300

Tightness of closed valve : below  0,5% kvs ( class VI acc. To IEC 534/4 for hard seats )

                                               Bubble type ( class VI IEC 534/4 for tight plugs )