Piston valve - Revision history

Technician1002: Added Supah as an example

2010-12-18T01:22:06Z

Added Supah as an example

← Older revision		Revision as of 20:22, 17 December 2010
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	These valves are often used on [[over/under]]s, as the flow is already turned around 90<sup>o</sup>.		These valves are often used on [[over/under]]s, as the flow is already turned around 90<sup>o</sup>.

			A commercially manufactured valve for spudding is the Supah Valve.

	=== Use ===		=== Use ===

Technician1002: Added Mauler as an example.

2010-12-18T01:20:52Z

Added Mauler as an example.

← Older revision		Revision as of 20:20, 17 December 2010
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	These valves are often used on [[coaxial]]s and [[over/under]]s. In an over/under, the valve is built in a "T" fitting. The barrel is put co-axially through one end, the pilot and piston are put in the opposite one, and a chamber is connected to the perpendicular opening with a 90° elbow.		These valves are often used on [[coaxial]]s and [[over/under]]s. In an over/under, the valve is built in a "T" fitting. The barrel is put co-axially through one end, the pilot and piston are put in the opposite one, and a chamber is connected to the perpendicular opening with a 90° elbow.

			A commercially manufactured valve for spudding is the Mauler Valve.

	=== Use ===		=== Use ===

Technician1002: Formatting

2010-12-13T18:23:20Z

Formatting

← Older revision		Revision as of 13:23, 13 December 2010
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	Here is a drawing showing the force of the pressure on the o ring to provide a tight seal.		Here is a drawing showing the force of the pressure on the o ring to provide a tight seal.
	[[Image:123_floatingpneumatic1.jpg]]		[[Image:123_floatingpneumatic1.jpg]]

	Source: RL Hudson O-Ring Design & Materials Guide. Used with permission.		Source: RL Hudson O-Ring Design & Materials Guide. Used with permission.

	[[category:valves]]		[[category:valves]]

Technician1002: /* Common traits */

2010-12-13T18:20:59Z

Common traits

← Older revision		Revision as of 13:20, 13 December 2010
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	#The performance of these valves can be calculated with the [[GGDT]].		#The performance of these valves can be calculated with the [[GGDT]].
	#If your valve [[honking\|honks]], it is probably a good idea to invest in a better pilot valve, though this is more of a problem with barrel-sealing valves.		#If your valve [[honking\|honks]], it is probably a good idea to invest in a better pilot valve, though this is more of a problem with barrel-sealing valves. Narrow ratio barrel sealers tend to be immune to honking due to the low pressure at which they crack open. A larger pilot volume on a narrow ratio barrel sealer can reduce pilot pressure rise from the piston moving into the plot space causing compression. With less compression, the valve will not re-close early due to the rapid drop in chamber pressure. This eliminates honking.
	#In both cases, provided there is a good deal of space around the barrel, the full flow potential of the valve is realized when the piston has moved back 1/4th of the barrel's inside diameter (I.D./4). The derivation of this formula is as follows:		#In both cases, provided there is a good deal of space around the barrel, the full flow potential of the valve is realized when the piston has moved back 1/4th of the barrel's inside diameter (I.D./4). The derivation of this formula is as follows:

Technician1002: /* 1:1 Ratio or QDV */ Fixed dead link to QDV page

2010-05-13T19:24:28Z

1:1 Ratio or QDV: Fixed dead link to QDV page

← Older revision		Revision as of 14:24, 13 May 2010
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	The quick dump valve has the piston OD the same size as the seat. It requires an external force to start it opening. It has no pilot pressure to hold it against a seat so it is often built with o rings on a piston. The valve cylinder can be built out of a pipe with ports cut in the side.		The quick dump valve has the piston OD the same size as the seat. It requires an external force to start it opening. It has no pilot pressure to hold it against a seat so it is often built with o rings on a piston. The valve cylinder can be built out of a pipe with ports cut in the side.

			*[http://www.spudfiles.com/spud_wiki/index.php?title=Quick_Dump_Valve The Quick Dump Valve, by Technician1002.] Wiki page on the QDV

	A video on the theory of the QDV cannon is here.		A video on the theory of the QDV cannon is here.

Technician1002: /* 1:1 Ratio or QDV */ Removed dead link to QDV page.

2010-05-10T06:34:57Z

1:1 Ratio or QDV: Removed dead link to QDV page.

← Older revision		Revision as of 01:34, 10 May 2010
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	=== 1:1 Ratio or QDV ===		=== 1:1 Ratio or QDV ===
	~~A new page dedicated to the QDV is here;~~
	~~[http://www.spudfiles.com/spud_wiki/index.php/Quick_Dump_Valve Quick Dump Valve Piston]~~

	If the ratio of the piston diameter is reduced to the diameter of the valve seat in a spool valve, then the valve won't open even when the pilot area is not under pressure. If the chamber is pressurized and no pressure is in the pilot area, the valve has the least back pressure of any of the piston valves and therefore the fastest opening when the valve is unseated by force. Even though the pilot area may half in volume as the piston moves into this space, the pressure rise from 1 atm to 2 atm is still less than the chamber force on the newly exposed face of the piston, so this piston will open fast regardless of the vent size or speed. This last category of piston valve is known as a Quick Dump Valve. To operate this valve in an air cannon, consideration must be made to mechanically move the piston and when the piston moves, the force will avalanche quickly as the piston face becomes exposed to the chamber pressure. For mechanical trigger the use a rope pull or a rod with a "sliding" piston are options to a spring or air start. The loose piston on a rope or rod provides speed as the core can accelerate freely when triggered. Decoupling the triggering mechanism from the piston prevents the trigger from adding to the moving mass of the piston. These valves are not subject to honking, but may "bounce" back closed after the shot by the pressure built up in the pilot area and bumper recoil after the chamber pressure is gone.		If the ratio of the piston diameter is reduced to the diameter of the valve seat in a spool valve, then the valve won't open even when the pilot area is not under pressure. If the chamber is pressurized and no pressure is in the pilot area, the valve has the least back pressure of any of the piston valves and therefore the fastest opening when the valve is unseated by force. Even though the pilot area may half in volume as the piston moves into this space, the pressure rise from 1 atm to 2 atm is still less than the chamber force on the newly exposed face of the piston, so this piston will open fast regardless of the vent size or speed. This last category of piston valve is known as a Quick Dump Valve. To operate this valve in an air cannon, consideration must be made to mechanically move the piston and when the piston moves, the force will avalanche quickly as the piston face becomes exposed to the chamber pressure. For mechanical trigger the use a rope pull or a rod with a "sliding" piston are options to a spring or air start. The loose piston on a rope or rod provides speed as the core can accelerate freely when triggered. Decoupling the triggering mechanism from the piston prevents the trigger from adding to the moving mass of the piston. These valves are not subject to honking, but may "bounce" back closed after the shot by the pressure built up in the pilot area and bumper recoil after the chamber pressure is gone.

MrCrowley at 06:38, 20 August 2009

2009-08-20T06:38:56Z

← Older revision		Revision as of 01:38, 20 August 2009
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	Floating piston rings fit loose in the grooves. The o ring is sized to be slightly larger than the cylinder diameter it slides inside.		Floating piston rings fit loose in the grooves. The o ring is sized to be slightly larger than the cylinder diameter it slides inside.
			This photo is of a 1 inch quick dump valve piston.
			[[Image:Piston_rings.jpg]]

	~~[[Image:Piston_rings.jpg\|frame\|This photo is of a 1 inch quick dump valve piston.]]~~
	Here is a drawing showing the force of the pressure on the o ring to provide a tight seal.		Here is a drawing showing the force of the pressure on the o ring to provide a tight seal.
			[[Image:123_floatingpneumatic1.jpg]]
	[[Image:123_floatingpneumatic1.jpg~~\|frame\|Here is a drawing showing the force of the pressure on the o ring to provide a tight seal~~]]
	Source: RL Hudson O-Ring Design & Materials Guide. Used with permission.		Source: RL Hudson O-Ring Design & Materials Guide. Used with permission.

	[[category:valves]]		[[category:valves]]

MrCrowley at 06:36, 20 August 2009

2009-08-20T06:36:48Z

← Older revision		Revision as of 01:36, 20 August 2009
Line 125:		Line 125:
	Floating piston rings fit loose in the grooves. The o ring is sized to be slightly larger than the cylinder diameter it slides inside.		Floating piston rings fit loose in the grooves. The o ring is sized to be slightly larger than the cylinder diameter it slides inside.

	[[Image:Piston_rings.jpg\|This photo is of a 1 inch quick dump valve piston.]]		[[Image:Piston_rings.jpg\|frame\|This photo is of a 1 inch quick dump valve piston.]]
	Here is a drawing showing the force of the pressure on the o ring to provide a tight seal.		Here is a drawing showing the force of the pressure on the o ring to provide a tight seal.

MrCrowley at 06:36, 20 August 2009

2009-08-20T06:36:12Z

← Older revision		Revision as of 01:36, 20 August 2009
Line 124:		Line 124:

	Floating piston rings fit loose in the grooves. The o ring is sized to be slightly larger than the cylinder diameter it slides inside.		Floating piston rings fit loose in the grooves. The o ring is sized to be slightly larger than the cylinder diameter it slides inside.
	~~This photo is of a 1 inch quick dump valve piston.~~

	~~[[Image:Piston_rings.jpg]]~~

			[[Image:Piston_rings.jpg\|This photo is of a 1 inch quick dump valve piston.]]
	Here is a drawing showing the force of the pressure on the o ring to provide a tight seal.		Here is a drawing showing the force of the pressure on the o ring to provide a tight seal.

	~~[[Image:123_floatingpneumatic1.jpg]]~~
	[[Image:123_floatingpneumatic1.jpg\|frame\|Here is a drawing showing the force of the pressure on the o ring to provide a tight seal]]		[[Image:123_floatingpneumatic1.jpg\|frame\|Here is a drawing showing the force of the pressure on the o ring to provide a tight seal]]
	Source: RL Hudson O-Ring Design & Materials Guide. Used with permission.		Source: RL Hudson O-Ring Design & Materials Guide. Used with permission.

	[[category:valves]]		[[category:valves]]

MrCrowley at 06:34, 20 August 2009

2009-08-20T06:34:24Z

← Older revision		Revision as of 01:34, 20 August 2009
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	[[Image:123_floatingpneumatic1.jpg]]		[[Image:123_floatingpneumatic1.jpg]]
			[[Image:123_floatingpneumatic1.jpg\|frame\|Here is a drawing showing the force of the pressure on the o ring to provide a tight seal]]
	Source: RL Hudson O-Ring Design & Materials Guide. Used with permission.		Source: RL Hudson O-Ring Design & Materials Guide. Used with permission.

	[[category:valves]]		[[category:valves]]