Operation and Maintenance Manual of Gate Valves

2.4 Main Components and Material

NAME	MATERIAL
Body /Bonnet	WCB、LCB、WC6、WC9、CF3、CF3M CF8、CF8M
Gate	WCB、LCB、WC6、WC9、CF3、CF3M CF8、CF8M
Seat	A105、 LF2、F11、F22、F304（304L）、F316（316L）
Stem	F304（304L）、F316（316L）、2Cr13，1Cr13
Packing	Braided graphite & Flexible graphite & PTFE etc
Bolt/Nut	35/25、35CrMoA/45
Gasket	304（316）+Graphite /304（316）+Gasket
SeatRing/Disc/Sealing	13Cr、18Cr-8Ni、18Cr-8Ni-Mo、PP、PTFE、STL etc

 

3.  Storage & Maintenance & Installation & Operation

3.1 Storage & Maintenance

3.1.1 Valves should be stored in the indoor condition. The cavity ends should be covered by plug.

3.1.2 Periodic inspection and clearance is required for long time stored valves, especially for sealing surface cleaning. No damage is allowed. Oil coating is requested to avoid rust for machining surface.

3.1.3 Concerning the valve storage more than 18 months, tests are required before valve installation and record the result.

3.1.4 Valves should be periodically inspected and maintained after installation. Main points are as the below:

1）Sealing surface

2）Stem and Stem nut

3）Packing

4）Internal surface cleaning of Body and Bonnet.

3.2 Installation

3.2.1 Recheck the valve markings (Type, DN, Rating, Material) which complies with markings requested by pipeline system.

3.2.2 Complete cleaning of cavity and sealing surface is requested before valve installation.

3.2.3 Ensure the bolts are tight before installation.

3.2.4 Ensure the packing is tight before installation. However, it should not disturb stem movement.

3.2.5 Valve location should be convenient for inspection and operation. Horizontal to pipeline is preferred. Keep hand wheel up and stem vertical.

3.2.6 For shut-off valve, it is not suitable to be installed in high pressure working condition. Stem should be avoided to be damaged.

3.2.7 For Socket welding valve, attentions are requested during valve connection as the following:

1）Welder should be certified.

2）Welding process parameter must be in conformance to relative welding material quality certificate.

3）Filler material of welding line, the chemical and mechanical performance together with anti-corrosion should be similar to body parent material.

3.2.8 Valve installation should avoid high pressure from attachments or pipes.

3.2.9 After installation, valves should be open during pipeline pressure test.

3.2.10 Support Point：if the pipe is strong enough to support valve weight and operation torque, the support point is not requested. Otherwise it is needed.

3.2.11 Lifting：Hand wheel lifting is not allowed for valves.

3.3 Operation and Usage

3.3.1 Gate valves should be completely open or closed during usage to avoid seat sealing ring and disc surface caused by high speed medium. They can’t be sued for flow regulation.

3.3.2 Hand wheel should be used to replace other instruments to open or close valves

3.3.3 During the allowed service temperature, instantaneous pressure should be lower than rated pressure according to ASME B16.34

3.3.4 No damage or strike is allowed during valve transportation, installation and operation.

3.3.5 Measure instrument to check the unstable flow is requested to control and get rid of the decomposition factor to avoid valve damage and leakage.

3.3.6 Cold condensation will influence valve performance, and measure instruments should be used to reduce flow temperature or replace the valve.

3.3.7 For self-inflammable fluid, use appropriate measuring instruments to guarantee ambient and working pressure do not exceed its auto-ignition point (especially notice sunshine or external fire).

3.3.8 In case of dangerous fluid, such as explosive, inflammable, toxic, oxidation products, it is prohibited to replace packing under pressure. Anyhow, in emergency case, it is not recommended to replace packing under pressure (although the valve has such a function).

3.3.9 Make sure the fluid is not dirty, which affects valve performance, not including hard solids, otherwise appropriate measuring instruments should be used to remove the dirt and hard solids, or replace it with other type of valve.

3.3.10 Applicable working temperature

Material	Temperature	Material	Temperature
WCB	-29～425℃	WC6	-29～538℃
LCB	-46～343℃	WC9	--29～570℃
CF3（CF3M）	-196～454℃	CF8（CF8M）	-196～454℃

3.3.11 Make sure material of valve body is suitable for use in corrosion resistant and rust preventing fluid environment.

3.3.12 During service period, check for sealing performance as per the table below:

Inspection point	Leak
Connection  between  valve  body  and  valve bonnet	Zero
Packing seal	Zero
Valve body seat	As per technical specification

3.3.13 Regularly check for the wear of seating fare, packing aging and damage.

3.3.14 After repair, re-assemble and adjust the valve, then test tightness performance and make records.

4.  Possible problems, causes and remedial measures

Problem description	Possible cause	Remedial measures
Leak at packing	Insufficiently compressed packing	Re-tighten packing nut
	Inadequate quantity of packing	Add more packing
	Damaged packing  due to long-time service or improper protection	Replace packing
Leak on valve seating face	Dirty seating face	Remove dirt
	Worn seating face	Repair it or replace seat ring or valve plate
	Damaged seating face due to hard solids	Remove hard solids in the fluid, replace seat ring or valve plate, or replace with other type of valve
Leak at connection between valve body and valve bonnet	Bolts are not properly fastened	Uniformly fasten bolts
	Damaged bonnet sealing face of  valve body and valve flange	Repair it
	Damaged or broken gasket	Replace gasket
Difficult rotation of hand wheel or valve plate can’t be opened or closed.	Too tightly fastened packing	Appropriately loosen packing nut
	Deformation or bending of sealing gland	Adjust sealing gland
	Damaged valve stem nut	Correct thread and remove the dirty
	Worn or broken valve stem nut thread	Replace valve stem nut
	Bent valve stem	Replace valve stem
	Dirty guide surface of valve plate or valve body	Remove dirt on guide surface

Note: Service person should have relevant knowledge and experience with valves Water sealing gate valve

The bonnet packing is water sealing structure, it will be separated from the air while the water pressure reaches to 0.6~1.0MP to guarantee good air sealing performance.

5.Warranty:

After the valve is put into use, the warranty period of valve is 12 months, but does not exceed 18 months after delivery date. During warranty period, the manufacturer will provide repair service or spare parts free of charge for the damage due to material, workmanship or damage provided that operation is correct.