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
type pneumatic diaphragm spring actuators are their standard drive
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
Bonnet ( 2 )
Made of the same materials as the body is available in four
----standard for agent temperature
----finned AB for agent temperature 260.....650 C
----extension EB for agent temperature
----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
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,
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.
Table 1. plug types and valve marking
Plug type and characteristic
air to close
Equal procentage contoured
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
Plug symbol :
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
The choice of the packing kind depends on the medium kind,
temperature and working pressure.
Table 3 : kinds
and types of packing box.
Actuator yoke ( 8 ) made of gray cast iron.
Cases ( 9,10 ) made of pressed steel create a pressure
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
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.
charakteristic of flow : equal percentage, linear, quick- opening.
Without positioner : 4%
of nominal stroke range.
With positioner : 1% of nominal stroke range
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
Raised : 40......200 kpa
Maximum supply pressure : 240 kpa
Medium temperature range :
Nominal pressure range NP : 10.....160
Nominal diameters range ND
Tightness of closed valve : below 0,5% kvs ( class VI acc. To IEC 534/4 for hard seats )
Bubble type ( class VI acc.to IEC 534/4 for tight plugs )