Valve material and valve standards-(5)-packing material

Packing /Filler material:
On the valve, the packing is used to fill the space of the valve cover packing chamber to prevent the medium from leaking through the valve stem and the bonnet packing chamber.

Requirements for packing.

• 1. Good corrosion resistance, the filler must be able to withstand the corrosion of the medium in contact with the medium.
• 2. Good airtightness, the packing will not leak under the action of the medium and working temperature.
• 3. The friction coefficient is small to reduce the friction torque between the valve stem and the packing.

Types of filler:

1. Soft filler: it is a string woven from plant matter, that is hemp, flax, cotton, jute, etc., or mineral, that is, asbestos fiber, or asbestos fiber with metal wire inside and graphite powder coated on the outside. Pressed molding fillers, and flexible graphite filler materials developed in recent years.
Vegetable packing is often used for low pressure valves below 100°C; mineral packing can be used for valves with 450-500°C. In recent years, the temperature of structural media using rubber O-rings as fillers is generally limited to below 60°C.
The packing on the high temperature and high pressure valve is also made of pure asbestos and flake graphite powder.

2. Hard filler: that is, filler made of metal or metal mixed with asbestos and graphite and filler formed by pressing and sintering of PTFE, metal filler is used less.

Selection of filling material:
The choice of packing should be based on the medium, temperature and pressure. The commonly used materials are as follows:

• 1. Oil-impregnated asbestos rope, can be selected according to Table 5-2
• 2. Rubber asbestos rope, can be selected according to 5-3
• 3. Graphite asbestos rope: The asbestos rope is coated with graphite powder, the usable temperature is above 450°C, and the pressure can reach 16MPA, which is generally suitable for high-pressure steam. Lately, it gradually adopts the compressed herringbone type packing, which is placed in a single circle and has good sealing performance.
• 4. Polytetrafluoroethylene: This is a kind of filler that is currently widely used. Especially suitable for corrosive media, but the temperature should not exceed 200°C. Generally, it is made by pressing or rod car.

Fig.5-2:

Material	Grade name	shape	size(dia or square)	Max Pressure kgf/cm2	max temp/ °C	application
Oil-impregnated asbestos rope	YS450	F	3,4,5,6,8,10,13,16,19,22,25	60	450	water, steam,air,petroleum products
		Y	5,6,8,10,13,16,19,22,25
		N	3,5,6,8,10,13,16,19,22,25
	YS350	F,Y,N	3,5,6,8,10,13,16,19,22,25	45	350
	YS250	F,Y,N	3,5,6,8,10,13,16,19,22,25	45	250

Note: The shape code F means square, through the heart or one or more layers of weaving; Y means round, with a twisted core in the middle and one or more layers of weaving on the outside; N means twisted.

Fig.5-3:

Material	Grade name	size(dia or square)	Max Pressure kgf/cm2	max temp/ °C	application
Rubber, asbestos, packing	XS450	3,4,5,6,8,10,13,16,19,22,25,28	60	450	steam,petroleum products
	XS350		45	350
	XS250		45	250

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

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