JPS63210472A - Seal device for fire prevention safe butterfly valve - Google Patents

Abstract

PURPOSE:To seal with high precision at the normal time and prevent leakage at a fire with the metal sealing by jointly using a metallic seal and a nonmetallic seal in the said device preventing the spread of a fire on a ship or the like. CONSTITUTION:A circular recess 7 is formed on a retainer 5 fixed to the valve box 1 of a butterfly valve, and the inner periphery side of the retainer 5 is formed into a circular tongue piece 10 which is brought into contact with a valve body 11 and performs the metal sealing with the resiliency by elastic deformation. A circular nonmetallic seal packing 12, the base section 13 of which is pinched and fixed by a valve box 1 and the retainer 5 and the tip section 14 soft-seals the valve body 11, is stored in the circular recess 7. The seal packing 12 is pressed inward by a spring fit ring 18. Accordingly, both the circular tongue piece 10 and the nonmetallic seal packing 12 are pressed to the valve body 11 when the valve is closed, thus the sealing is performed with high precision by the seal packing 12 at the normal time, and the sealing is maintained by the circular tongue piece 10 at a fire.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is mainly applicable to ship fires, cargo oil, LPG, LPG, etc.
This invention relates to a fire safety butterfly valve that prevents the spread of fire by blocking the outflow of flammable fluids such as NG.

(Prior technology) In Japan, which is dependent on foreign countries for petroleum, LPG, LNG, etc. are transported by sea from oil-producing areas by tankers or by special carriers, but fires often occur in tankers, causing damage to the cargo. In addition to losses, the damage caused by the tanker itself was rendered inoperable, reaching an enormous amount of money.

Furthermore, LPG, LNG, etc. carry the risk of low-temperature brittle fracture of the ship's hull and explosion and fire due to leakage, so various safety measures are being taken.

Generally speaking, the oil tank of a tanker is subdivided into vertical and horizontal bulkheads to maintain stability and the correct arrangement of cargo oil, and to allow for the separation of different types of oil. There are many piping systems including oil pipes, unloading oil pipes, gas suction pipes, etc., and all cargo handling is carried out through the oil pipes installed on the deck and in the oil tank.The cargo is transported by a land pump or by a land pump by connecting a hose to the ship's intake port. Loading is done by driving the ship's cargo oil pump.

Each oil tank is equipped with fire extinguishing equipment using seawater, steam, foam, carbon dioxide, or flue gas, and various pumps are equipped with various fire extinguishing equipment, such as electrical contacts, short circuits, or grounding to prevent sparks. Safety measures are adopted.

The sealing gasket supported by the retainer of the butterfly valve for cryogenic liquefied gas is generally made of non-metallic materials, especially fluorine-based resin, in order to withstand a wide temperature range from the ultra-low temperature of LNG to liquefied gas at room temperature. Because it has a large coefficient of expansion, it contracts well at extremely low temperatures, and it tightly adheres to the valve body to maintain a complete seal, so it is often used in LNG valves in particular.

However, even though the seal packing has such excellent properties, it has a weak point of low heat resistance.

That is, when a fire occurs and the valve becomes hot, the fluororesin sealing gasket softens and melts due to the high heat, or burns out, causing the LNG inside the pipe to leak and the fire to continue for a long time.

There is a valve device described in Japanese Patent Publication No. 45-32861 as a prior art technology that ensures valve sealing even in the event of a fire.
A relatively low temperature fusible material (e.g. white alloy) is placed in the cavity of the valve housing.
In the event of a fire, this member melts and the repulsive force of the spring causes the fixing ring to advance toward the valve body. Low-temperature soluble materials (for example, white alloy) must be filled, making the configuration and assembly complicated, and measures to ensure the sealing of this spring and the valve housing have not been taken into account, and gasoline It cannot be used for combustible fluids such as LPG, LNG, etc., which have high vapor pressure 1 and may leak from even the slightest gap.

Another prior art is a metal touch type valve seat for a butterfly valve described in Japanese Utility Model Publication No. 51-24565.
The seal gasket always touches metal and is not flexible, making it difficult to contact the entire surface, resulting in poor sealing performance (particularly with low-temperature fluids, there is no way to stop leakage, and as above, it cannot be used for LPG, LNG, etc.) Utility Model Publication 51- as other prior art
Publication No. 39230 discloses a butterfly valve in which a seat ring, which is a metal tube pre-curved into an elliptical shape, is loosely held in an annular groove as a sealing material, and the seal is deformed from an ellipse to a perfect circle when the valve is closed on the hour. However, it is almost impossible to deform into a perfect circle, and when the sealing pressure is high, the metal tube is partially deformed, making it impractical, and gasoline leaks even if there is a small gap. , LPG, and LNG are completely unreliable.

Measures to solve the problem) Regarding soft touch by seal, API (American Petroleum Institute Standards) also adopts strict standards for soft seals using Teflon, which do not allow leakage. However, since an ideal seal cannot be expected for metal touch,
It stipulates that leakage tolerance is left to consultation between the valve manufacturer and the user, and the current situation is that deterioration in accuracy is inevitable. Therefore, there are concerns about adopting Metal Touch alone for LNG and LPG.

In view of the above, the present invention uses a Teflon gasket, which normally has excellent sealing properties even at ultra-low temperatures, and further uses a spring ring to seal LNG.

In addition to accurately blocking leakage of LPG, etc., a ring-shaped metal tongue piece is always in contact with the valve body when the valve is closed to maintain a seal, although the accuracy is slightly lower than the former, and these two systems of seals maintain normal operating conditions. In this case, the ultra-low temperature fluid is kept almost completely shut off. The Teflon packing is brought into contact with the valve body at an appropriate location depending on the size of the valve body.

The Teflon gasket is one example, and it goes without saying that other non-metallic seal gaskets can also be used.

In the event of a fire, even if a portion of the Teflon gasket melts, the metal tongue pieces will maintain the seal by the repulsive force of elastic deformation, and although the seal will be a single system, it will be effective for fire prevention, and the present invention By installing these two systems of seals, gases such as LNG and LPG can be safely shut off.

(Operation and Effect) In the present invention, the metal annular tongue piece at the lower end of the inner side of the recess formed on the inner circumferential surface of the retainer fixed to the valve body is constantly in contact with the valve body due to the repulsive force caused by elastic deformation, and further, the base is clamped and fixed between the valve box and retainer, and the tip of the Teflon gasket is constantly in contact with the valve body due to the contraction force of the spring ring.
This contact is almost perfect due to the flexibility of Teflon.

In this way, in the present invention, which employs two types of contact means: metal touch, which is slightly less accurate, and Teflon touch, which is more precise, in the event of a fire, the Teflon gasket will be exposed to metal tongue pieces even if only one part melts. maintains a seal and helps with fire protection.

(Example) 1 is a valve box formed in an annular shape, and both piping flanges 2 (
(one is omitted and not shown) and is clamped by a bolt 3.

The valve body has an annular notch 4, and a stainless steel retainer 5 is fixed to the notch 4 with bolts 6. The retainer has a recess 7 formed on the inner circumferential side, and the recess 7 is formed in the center. It is divided into upper and lower parts by a protruding partition piece 8, and the lower end of the lower four parts 9 becomes an annular tongue piece 10, and a stainless steel valve body 11
The metal seal is maintained by constant contact with the repulsive force caused by elastic deformation. The base 13 of the Teflon seal packing 12 is clamped and fixed to the valve box 1 and the retainer 5, the bent part is supported by the partition piece 8, and the tip of the partition piece 8 is attached with a slight gap 22 maintained, The two protrusions 15 and 16 are the valve body 11.
Contact seal. As mentioned above, the Teflon seal packing 12 is supported by the partition piece 8 protruding from the recess 7 and bent while maintaining its shape, and aluminum alloy spring rings 18 are fitted into the outer periphery of the bent portion 17 and the tip 14, respectively. The Teflon seal packing 12 is constantly compressed inward to maintain the seal. A metal O-ring 19 is fitted between the valve box 1 and the retainer 5 to keep the gap sealed when the Teflon packing melts and disappears in the event of a fire. Of course, the mounting of the valve box 1 is not limited to the flange, but may be welded or other suitable methods.

In addition, when the valve box is held between the flanges, the annular notch 4 as shown in FIG.
Instead of fixing the retainer 5 to the valve body, the valve body itself may be made slightly smaller, the notch may be omitted, and the retainer may be directly fixed to one end of the valve body with a bolt.

In the fire protection safety butterfly valve having the above configuration, normally the Teflon seal packing 12 seals LNG, LPG, etc. with high precision, and the metal tongue piece 1
0 contact, sealing is performed although the accuracy is slightly lower, and the seal is almost perfect with two systems.

In the event of a fire, the Teflon gasket should be
Even if the sealing property is lost due to melting of the part, the metal tongue piece 1
0 and metal O-ring 19 still maintain a seal,
LNG.

Prevent LPG leaks and protect plants from major disasters.

FIG. 2 shows another embodiment in which the annular notch 4 provided at one end of the valve body 1 is fitted with a bolt 6 or formed on the inner peripheral side between the retainer 5 and the valve body 1. An annular tongue piece 10 is formed at the inner lower end of the annular recess 7 to maintain an annular space 20 and perform a metal seal using repulsive force due to elastic deformation. The base 13 of the Teflon seal packing is clamped and fixed to the valve box 1 and the retainer 5, and one protrusion 21 at the tip contacts the valve body 11 for sealing. This Teflon seal is constantly compressed inward from the outer periphery by a spring ring 18 to maintain a perfect soft seal. Therefore, in the event of a fire, the metal tongue remains as in the case of the first embodiment to maintain the seal and help prevent leakage of LNG and LPG.

As described above, the present invention uses a non-metallic seal packing such as Teflon and two types of seals, such as metal, in one valve box, thereby contributing to fire prevention with a compact device, and is highly effective.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of different embodiments of the present invention.

Claims (1)

[Claims] A valve box of a butterfly valve, in which a retainer fixed to one end of the valve box and an inner lower end of an annular recess formed on the inner peripheral side of the retainer come into contact with the valve body, and a repulsive force caused by elastic deformation creates a metal seal. The valve comprises: an annular non-metallic seal packing whose base part is clamped and fixed to the valve body and retainer and whose tip part soft-seals the valve body; and a spring ring which presses the seal packing inward. A fire prevention and safety butterfly valve sealing device in which both the annular tongue piece for metal sealing and the nonmetallic seal packing are pressed against the valve body when closed.