Surge Relief

7/29/2019 Surge Relief

1/12

Mokveld

surge relief valves


2/12


3/12

As in other Mokveld products the

design of the Mokveld self acting surgerelief valve is based on the axial flowconcept.Axial flow describes the in-linesymmetrical flow path between thevalve inner body and outer body beforethe flow reaches the trim zone.The axial flow concept, used fordecades by Mokveld in their design forshut off, control and check valves, hasproven to be so advantageous that itcould easily be incorporated in thedesign of a surge relief valve.

In order to develop reliable devices,

designs have to be based on simplicity.This has been achieved in the design ofthe Mokveld self acting surge reliefvalve.Mokveld valves typically make use ofthis philosophy by implementing aminimum of components in theirdesign of surge relief valves. This isextremely advantageous, impactingdirectly and positively both onreliability and maintenance. Relatedcosts are also correspondingly lower.

A pressure surge is generated in a

pipeline system when there is a changein the rate of flow in the system. Thesurge pressure can be dangerouslyhigh if the change is too rapid.Surge pressures, moving along thepipe line with the speed of sound, varyin their magnitude.The Mokveld surge relief valve,because of its axial flow and thus stableopening behaviour, its pilot design andconsequently high effective capacity,allows the valve to fully protect thepiping systems against dangerous andcostly surge pressure damages.

Mokveld pilot operated surge relief valvesa concept that works

1


4/12

high available capacity

Because of the high effective valvecapacity, a result of the linear responseof the pilot valve, sizes are smallercompared to those of competitors.Extreme oversizing is not required.

quick response time

The proportional pilot design is of ahigh capacity, allowing fast response ofhe surge relief valve.

ow tolerance of set pressure

As a result of the pilot design theoverpressure can be limited to 1% ofhe set pressure.

no external energy; no nitrogen

consumption

The use of the pilot type designeliminates the nitrogen back-upncluding temperature compensationdevices.

simple installation layout

Because of the absence of a nitrogensystem, the main reason for skidmounting is eliminated.

high performance

Pilot and surge valve design are basedon simplicity. All components are fieldproven to provide maximum reliabilityto protect your system.

stable operation

Because of the cage trim, the openingbehaviour remains stable andpredictable at each differentialpressure.

anti-cavitation trims available

Optional trim types are availableeliminating cavitation and vibration todownstream piping.

The Mokveld surge relief valve is

engineered to quickly measureunabated surge pressures, then to openfast to relief and close, withoutslamming, into seating.The operation of the surge relief valveis simple, since only the liquid pressureis used to open and close the valve.The pressure of the liquid is directlyconnected to the right chamber as wellas ported via the pilot to the leftchamber of the internal cylinder of thevalve.In normal situations, the valve is seated(forced to close) because of a resulting

force generated through the largereffective area of the left chamber.

If the upstream pipeline pressureexceeds the set-point pressure of thepilot, (i.e. adjustable at the pilot) thepilot will change position and willconnect the low downstream pressureto the left chamber of the internal valvecylinder. The resulting force will movethe internal plunger and consequentlythe valve piston to open and relievingwill start via the seat zone, allowingupstream pipeline pressure to drop.

Once the pilots set-point has beenreached, the valve will openproportionally on higher pressures,controlling the inlet pressure with anaccuracy of 1%.

The closing cycle is vice versa butdampened to avoid slamming.

the surge relief valvethat offers more

principle ofoperation

2


5/12

3


6/12

sizing

The Mokveld axial-flow surge reliefvalve is equipped with a trim cage.A wide selection of trims is availablencluding multi-stage anti-cavitationstyles.Please advise the Mokveld designengineers on flow conditions forcalculation of the most suitable valvesize and trim.These trims are based on well-provendesigns which have been widely usedn Mokveld control valves.The design of the trim will counteract

unbalanced forces. Opening behaviours therefore stable.

pilot assembly

The pilot is a Mokveld designed reliable3-way, 2 position type. Special attentionhas been given to low hysteresis andhis is obtained by using friction free

metal bellows instead of O-rings.

The use of bellows will furthermore

eliminate failures as a result of debris inthe fluid.The pilot unit is directly bolted on topof the valve, to maintain full integrity ofthe pilot system with the valve.

valve maintenance

Due to the absence of nitrogen,possible valve failure because of rubbertube splits, non possibility of springfailure etc., the need for any specificattention and maintenance duringnormal operation is eliminated.

As there is a minimum of moving parts,employment of PTFE seals and theinstallation of friction-free bellows inthe pilot, the risk of valve failure isminimized.Please note also that the pilot is noteasily affected by dirt. However whenused in high sand loaded media orused in crude fluids containing wax,

a seal pot can be installed between the

pressure intake and the pilot sensor.All this leads to an expected timebetween inspection or maintenance ofat least five (5) years. Mokveld advisestesting of the valve/pilot operation to bedone at regular intervals, using thetesting connection on the valve.

response time

Although time responses vary in eachapplication, the surge relief valvealways responds rapidly and verysmoothly. Typical response times of

Mokveld surge relief valves aremilliseconds to full capacity.The valve closes in direct response tothe pressure decay at valve inlet.Closing times are adjustable between3 and 40 seconds.

sizing and maintenance

4


7/12

Mokveld Valves is manufacturer of:

control valvesshut-off valvessurge relief valveschoke valvescheck valvesactuators and control systems

Separate brochures are available uponrequest.

other Mokveld products

5

flowline shut-off valvesgas production plant,

N/E Netherlands(by courtesy of NAM)

anti-surge control valve 12" ANSI 600,compressor station Russia


8/12

6

adjustable choke valves 71/16

API 10,000 with inconel cladding,gas production field UAE

adjustable choke valves 8 ANSI 900 lbswith pneumatic actuators,gas production offshore Malaysia

surge control valves 20" and 24"ANSI 300 lbs,gas compression facility New Mexico



9/12

pressure control valves 20 ANSI 600 lbs and safety slam shut valves16 ANSI 600 lbs, M & R station Germany

flow control valves, underground gasstorage field Germany


7

safety shut-off valve 16 ANSI 600,underground storage field Germany

inline production chokes 10 ANSI 1500,

FPSO Norway


10/12

8

flow pressure control valves and safety shut-offvalves, M & R station Germany


8

shut-off valves and non-slam check valves6 ANSI 900 lbs, water injection manifoldof a crude oil production field, North Africa


11/12


12/12

Mokveld ValvesMokveld Valves bv P.O. Box 227

2800 AE Gouda Holland

Nijverheidsstraat 67

telephone (31) 182 597500

facsimile (31) 182 517977

[email protected]

www.mokveld.com

Mokveld offices in: Houston, United States of America

Wesel, Germany

Swindon, United Kingdom

Dubai, United Arab Emirates

Sumy, Ukraine

Beijing, the Peoples Republic of China

Kuala Lumpur, MalaysiaStavanger, Norway

0303 Technical information and illustrations included are subject to changes without notice.

Documents

Surge Relief