8
GENERAL VALVE COMPANY
GENERAL VALVE COMPANY
GENERAL
VALVE
COMPANY
General Valve Company began as a valve
reconditioning shop in 1929. Today, we
are the worlds leading manufacturer of
high-integrity, positive shutoff Double
Block & Bleed valves which serve the
following markets: pipeline, liquid bulk
terminals, aviation fueling, refining, oil/
gas production, and custody transfer for
the petroleum and oil and gas industries.
Introduced in 1941, General Twin Seal
valves, were the first to meet the rigid
requirements of Double Block & Bleed
service - more than 60 years ago. In the
years since, subtle yet significant design
refinements have been made to improve
the valves performance. Superior design
innovations, pride in manufacturing
workmanship, and the selection of the
best materials, support General Valves
commitment to excellence and complete
customer satisfaction.
The Twin Seal replaces this antiquated
two-valve system with just one double-
seated bubble-tight valve. The upstream
and downstream seal provide the same
function as the two block valves. The body
(serving as a spool piece) bleed verifies
seal integrity.
Seal abrasion is inherent in the design of
most ball and gate valves. In most
instances, the seats are ground or wedged
against metal every time the valve cycles.
Any foreign material lodged between the
seats and ball or gate will score the seating
surfaces. Once the seating segment is
scored, product loss and contamination
results. The Twin Seal avoids abrasion
by having both independant slips totally
retracted from the body bore during
cycling.
Twin Seals totally retracted slipdesign eliminates wear, minimizes leakage risk,
reduces maintenance, and saves money.
Marine Loading
Tank Farm
The age-old Double Block & Bleed
system (as shown above) required the
use of two valves and a spool piece.
A bleed valve was used to drain the spool
and verify seal integrity.
The Evolutionof DoubleBlock & BleedContinues . . .
Scored seating segments
Tw
in S
eal
General ValveGTS 8000TM
Still the Best Valve, Best Value
Upper Stem Made from pressure vesselapproved 17-4 PH SS material
Internal Thrust BearingsInternal thrust bearings for smooth operation and long cycle life
Indicator Shaft & FlagProvides positive indication
Self-Purging Lower Plate Drain CavityFlushes lower plate cavity with each valve cycle
Packing GlandMade from NACE compliant17-4 PH SS material
Fyre BoxTM
Tapered design assures fire safe integrity
Fyre RingTM
Metal-to-metal design assures fire safe integrity
Bleed AccessAll bleed holes located in bodysimplifies field maintenance
Seal Material Test CouponDesign assures slip seal material and bond integrity
Jack-Screw HolesSimplifies field maintenance
Worm Gear SetSelf- locking non-back driving worm gear set
Fyre PackTM
Live-loaded packing assures firesafe integrity
GENERAL
VALVE
COMPANY
Valve Dimensional Table
(1) Face-to-face per API 6D(1A) 24" Face-to-face not per API 6D(2) All throat taps and body taps are 1/2" NPT (3) 2-4" have 1/2" NPT, 6-8" have 3/4" NPT, 10" and above have 1" NPT
*Size of tapped holes per each flangeNotes:
F
Typical Worm Gear Operated Valve
468
10121624
46
234
23
2
8104810681088110811281168124
82048206
840284038404
86028503
8602
273/4311/2393/4
425364
723/4
2836
251/4263/4373/4
313/4313/4
313/4
161/2181/4
2324
301/238
411/2
161/2211/4
151/2161/4191/2
1919
19
61/48
93/41113
161/4211/2
61/473/4
441/451/461/2
53/453/4
53/4
9101/2111/2
131416
36 1A
12157/8
111/21417
141/215
141/2
911
131/21619
231/232
10121/2
61/281/4103/4
81/291/2
81/2
51/29
121/215172228
51/49
51/451/4
6
44
4
165255405518790
13403830
174312
131165287
250271
250
(4) 5/8-11UNC
(4) 3/4-10UNC
(4) 3/4-10UNC
(4) 7/8- 9UNC
(4) 7/8- 9UNC
(8) 1.00-8UNC
(4) 1.25-8UNC
--
--
--
--
--
--
--
--
10101414202020
1014
101014
1414
14
AN
SI 1
50
Size Model A B C G H *D Weight Oper.501G501G625G625G751G1261G1261G
501G625G
501G501G625G
625G625G
625G
13/413/4
33
31/255
13/43
13/413/4
3
33
3
300
600
1500
J543
14322420357840006600
24000
5741769
197401585
900
Max O
verall
Heigh
t (in)
Centerl
ine of
Valve
to
Cent
erline
of Hand
wheel
(in)
Centerl
ine of
Valve
to
Low
est Poi
nt (in)
Handw
heel Di
amete
r (in)
Face-to
-Face
(in) (1)
Valve
Flange
O.D.
(in)
Minimu
m Clea
rance
Req'd f
or
Botto
m Slip
Replac
ement
(in)
Numb
er & Siz
e of Ta
pped
Hole
s Each
Flange
Weigh
t (lbs)
Worm
Offset
Flow C
oeffici
ent (C v
)
A
C
FG H(3)
(2)(2)
(2)
J
D
B
Dim
ensional Table
Typical Worm Gear Operated Valve
GTS
1
2
3
4
How theTwin SealTM works
A big advantage of Twin Seals design is
that it permits in-line servicing. By
simply removing the valve bonnet or lower
plate (after the line is depressurized and
drained), all models may be repaired from
top or bottom without removing the valve
from the line.
Full Open PositionGuide pin is shown atits full open positionwith the upper andlower stems turned 90o
so that the roller is dis-placed from the rollertracks.
Neutral PositionGuide pin is shown inthe corner of the L-slot.The roller is moving in-wardly out of the rollertrack and into the uppers tem recess therebylocking the s temsrotationally together.Meanwhile, the upperand lower stems arefully engaged.
Seated PositionGuide pin is shown atits highest point in theL-slot. The roller residesin the lower stem and is
at its lowest point of travel within the rollertrack. The upper and lower stems are fully ex-tended.
TM
Simple, in-line fieldmaintenance keepscosts down
The internal design is very simple.
Seals (A) are permanently bonded
into the slips (B) which are
mounted on a central plug. In the
open position the slip seals are
completely out of the flow.
Turning the operator handwheel
clockwise rotates the plug assembly
90o to block flow. During rotation,
clearance is maintained between the
seal and the valve body, allowing
free movement and avoiding
abrasion.
When the operator is turned further
clockwise, the tapered plug begins to
lower, forcing the slips against the
body initiating the verifiable seal.
Because the seals never drag, the
valve requires less torque to cycle.
In the closed position, the slip seals
are expanded, compressing the slip
seals until metal-to-metal seating is
effected. Because it is mechanical,
the Twin Seal doesnt rely on line
pressure differential to help make its
seal. It even seals in vacuum service.
B A
GENERAL
VALVE
COMPANY
Ble
eds
Syst
em
s
Pressure Relief SystemsTo satisfy the requirements of API 6D, a pressure relief device must be provided on all double block and bleed valves in liquid service. When
the General Twin Seal valve is seated and completely filled with liquid, any slight variation in temperature due to the suns rays or ambient
thermal fluctuations will cause drastic changes in body cavity pressure resulting from thermal expansion.
Valves filled with fuel oil in a laboratory setting have exhibited a 75 PSI increase in pressure with a temperature rise of only 10F. While
results may vary under actual service conditions (depending on media, pressure vessel rigidity, and presence of entrained gas), it is known
that dangerously high pressures will build up in liquid filled, positive shutoff valves. The General Twin Seal in liquid service must always be
installed with a pressure relief device.
A Manual Body Bleed Valve is included onthis General Twin Seal. This bleed valveinstalled in the body cavity is only openedafter the Twin Seal is closed. Seal effective-ness can be immediately evaluated. Thisbleed valve must be closed before the TwinSeal is reopened.
The Safety Block/DTR functions exactly asthe basic Safety Bleed. However, all workingcomponents are housed in a virtuallyindestructible compact carbon steel mani-fold. The benefits of this incident controlequipment are: fire safety, complete compo-nent access for maintenance purposes, allsocket welded joints, heavy wall pipe andtotal incident control.
Manual Bleed (MBBV) Safety Block/DTR
The differential thermal relief system is ar-ranged as shown. The integral relief valve,mounted in the upper relief/vent manifold,routes excess pressure to the upstream throatof the valve. The standard relief valve is setto open at 25 PSI above upstream pressure.This system functions only when the valve isclosed. A manual body bleed, also integrallymounted in the upper relief/vent manifold,is opened only to vent and verify sealintegrity. An isolation valve installed in theupstream throat tap is also included in thissystem. It must be left open to permit therelief system to relieve pressure upstream.
Safety Bleed/DTR
Actuation
All models can be adapted to accept electric or pneumatic actuators.
Actuators can be set to operate valves at various speeds. Do not exceed
144 RPM without consulting factory.
Low torque requirements.
Twin Seal models incorporate a non-backdriving worm gear set.
GTSTM
General Valve Company is proud to be the only double block and bleed valvemanufacturer to develop and produce in house its own slip seal materials.Proper seal selection includes a myriad of considerations such as media, pressure class, valve type, differential pressure, low temperature, high tem-perature, seal type, etc. To that end we present our selection of slip seal materials and a brief list of considerations:
General Valve Company has a slip exchange program that encourages environmental sensitivity. Pre-owned slips may be returned to the factory forrecycling credits. Consult your General Valve Representative for details.
Standard Materials of ConstructionBodyBonnet/Lower PlatePlug
StemSlipsPacking GlandFyre RingTM
Fyre PackTM
FastenersO-Rings & Slip Seals
Cast Carbon Steel ASTM A216-WCC, Body Bore Chrome PlatedCarbon Steel ASTM A36 PlateCast Ductile Iron ASTM A395 Grade 60-40-18, Manganese PhosphateBase Coating, P92 Intermediate Coat with Fluoropolymer Top CoatASTM 17-4 PH SS, NACE Compliant Cast Ductile Iron ASTM A536 65-45-12, Manganese Phosphate CoatedASTM 17-4 PH SS, NACE Compliant GraphiteGraphite with ASTM A693 17-7 Live Loaded SS CapASTM A193-B7Viton
Other materials available upon request. Material Test Reports (MTR's) are available on all pressure vessel components. ISO 9001 License API 6D Monogrammable API 6FA Fire Safe Certified CE Mark/PED Certified
General Twin Seal Trim Selection
VV9VFRVGFVGLTVGL9
VitonViton 90 DuroFiber reinforced VitonViton GFViton GFLTViton 90 Duro GFLT
Our standard material since 1958Standard HIPOptional HIPViton w/enhanced chem. resistanceLow temp Viton GFHIP low temp Viton GF
303730423033304330443059
Fluoro Elastomers Slip Seal MaterialsFor more infoask for GVMPS
HH9LHH5
NitrileNitrile 90 DuroLow temp nitrileModified nitrile
Our original standard materialHIP nitrileLow temp nitrileReformulate Gasoline seal material
3048304930503053
Nitrile Elastomers Slip Seal Materials
CEUHSRZLAFLGVXT
EpichlorohydrinEthylenepropyleneFlurosiliconeRezilonAFLASVTR 6279Teflon
Good low temp materialAmmonia but not hydrocarbonGood high and low tempHIP RFGAmines, exp. decomp., steam, 600 FUltra chemical resistantGood for just about anything
3054305730323034304530473041
Specialty Slip Seal Materials
GENERAL
VALVE
COMPANY
Tw
in S
eal
Main Office and Manufacturing Plant:800 Koomey Road, Brookshire, Texas 77423
Tel: (281) 934-6013 Toll-free: (800) 926-2288Fax: (281) 934-6058 Toll-free Fax: (800) 765-2266http://www.general-valve.com
GENERAL VALVE'S modern Corporate Headquartersand manufacturing complex cover 250,000 square feet on 53 acresin Brookshire (Houston), Texas.
2004 GENERAL VALVE Bulletin 1000 All specifications and materials are subject to change without notice.
GENERAL TWIN SEAL, GVM, REZILON, VFR, GVX, BEST VALVE BEST VALUE, WHEN LEAKS MATTER, SEAT AND RESEAT,
HGO, GOSP, SAFETY BLEED, SAFETY BLOCK AND SAFETY CHECK are registered trademarks of General Valve
Company. VITON and TEFLON are registered trademarks of DuPont Dow Elastomers, L.L.C. Printed in the USA
6D-0075
a PCC Flow Technologies Company
QSR Certificate No. - 027Scope: Design, Development,Manufacture and Servicingof API Spec6D Plug Valves
