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8 comments
Participant

Join Date: Dec 2011
Posts: 1

Installation of Gate Valves

12/24/2011 5:13 AM

Why can't larger size gate valves be operated in any position, say 45/60/90/180 degrees?

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Engineering Fields - Piping Design Engineering - Retired Piper

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#1

Re: Installation of Gate Valves

12/24/2011 7:33 AM

This sounds like a question from a student. Is that correct, are you a student?

If so you need to ask your instructor.

If you are not a student then you need to ask for the same information as the instructor should have given to the student.

What is meant by "Large Size" valve?

Under what condition (in a horizontal run) should you not install a Gate Valve with the stem vertically down?

Under what condition (in a horizontal run) should you not install a Gate Valve with the stem vertically up?

What in meant by and what is required in order to install a Gate Valve (or any other Valve) in an odd degree position (vertical run or horizontal run)?

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Anonymous Poster #1
#2
In reply to #1

Re: Installation of Gate Valves

12/24/2011 7:45 AM

Please better analyse question only.

Generally valves could be installed in any orientations except for check valves, certain orientations would hamper the function of the valves.

- For gate valves - for smaller sizes the impact will not be much where as when sizes goes larger and larger ( 10" onwards ) the effective operation of the valve would be easier and operable for its proper functions only in stem vertical / flow horizontal installed position .

- When the stem horizontal and flow vertical or stem and flow horizontal the disc of the gate valve rests at the guide rib and rubbing takes place there by the positioning of the disc for its operation would be difficult and due to the clearance between body guide rib face to face and disc guide slot inner end to end the disc seats at the undesirable position sometime resulting in valve leakage and increased torques.

- Pl refer API-598, indicates " Valves shall be tested with the stem in the vertical up-right position.

- Pl refer API-600, covers whenever the valve installation requires different positions it has to be indicated in customer purchase order and only through special fit achieved between guiding surfaces of disc and body has to be achieved through improved machining operations viz., grinding. Even then we cannot guarantee for the minimum torque and function of the valve when it orients from vertically installed positions.

Many a customers have been expecting valve producers to supply gate valves of all sizes ( ½" - 42" as covered in BS:1414 ) to get operated effectively when installed in different orientations for its functions.

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#3

Re: Installation of Gate Valves

12/24/2011 11:46 AM

AP1 has answered correctly, although at length. The short answer is that pressure assist and gravity assist will make the valve easier to operate and will make it seat properly when installed per manufacturer specification (generally horizontally, stem up).

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Guru
Engineering Fields - Mechanical Engineering -

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#4
In reply to #3

Re: Installation of Gate Valves

12/24/2011 1:14 PM

Gravity will make it easier to move the valve in one direction only, it will hinder operation in the opposite direction.

To explain AP1's answer further, the bottom line on large valves is the guides that hold the gate in place would be damaged if the valve were not vertical.

If your valve is only operated once or twice, it might last awhile, but damage will occur every time it is operated because it is not designed to work at an angle.

If you are required to place your large valve at an angle you might find one or have one made to work at that angle.

Drew K

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#5
In reply to #4

Re: Installation of Gate Valves

12/24/2011 2:45 PM

Gravity will make it easier to move the valve in one direction only, it will hinder operation in the opposite direction.

Correct. And as I also said, pressure will assist in the other direction.

I use these valves quite frequently in water systems. Based on the OP's question, brevity trumps technical explanation in this case.

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Anonymous Poster #2
#6
In reply to #5

Re: Installation of Gate Valves

12/24/2011 8:25 PM

Not sure how pressure will help a gate valve open, usually pressure is normal to the direction of travel of a gate valve.

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#8
In reply to #6

Re: Installation of Gate Valves

12/26/2011 9:04 AM

The most simple calculation for the thrust needed to move a gate valve are: One part to overcome pressure differential, another to overcome the frictions (mainly packing friction), the stem and gate weight, and finally what is called "stem rejection load" which is due to the fact that when closing the valve we must introduce a portion of stem in a pressurized fluid (force needed equals pressure times the cross section of the stem). When opening the valve, the pressure assist to "reject" the valve stem.

Kind regards

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#7

Re: Installation of Gate Valves

12/24/2011 11:38 PM

When the gate is closed (not leaking) the pressure is normal. When it is opening it is being pushed (in the opening direction) by the pressure in the fluid.

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Anonymous Poster (2); Drew K (1); Kwetz (1); PennPiper (1); Wal (1); WJMFIRE (2)

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