06. June 2016 · Comments Off · Categories: Uncategorized

Why cryogenic ball valves prone to pull stuck motionless phenomenon, how should it be solved?

A: The low temperature ball valve(cryogenic ball valve) installed at room temperature, work at low temperatures large temperature range. If the design, improper installation, it is prone to heat stress or strain. At the same time, the ball valve is in the normal operating portion, circulation portion is low. To reduce cold damage, stem often do very long, it is easy to be deformed and stuck. Cryogenic ball valves(low temperature ball valves) are often rotated at room temperature flexibility at low temperatures is very tight, and even open. Valve stuck at low temperatures the main reasons are:
1)The installation, low temperature ball valve(cryogenic ball valve) and pipeline configuration unreasonable generate prestressing; or poor pipe cold compensation, at a low temperature ball valve(cryogenic ball valve) position change; or lack valve stent deformation at low temperature; or ball fixed properly, cold box at a low temperature deformation The influence of concentricity with the valve stem.
2)In the design, because of the different stem and the low temperature ball valve(cryogenic ball valve) sleeve material, the linear expansion coefficient is different. Usually the stem stainless steel, linear expansion coefficient of 1.73 × 10-6 ℃ -1; brass sleeve, linear expansion coefficient of 19.9 × 10-6 ℃ -1, i.e., greater than the contraction brass stainless steel, low temperatures may the threaded bite. Especially when using fine thread, threaded a temperature range of large and small thread gap, the phenomenon is more prone to bite.
3)In the operation, due to the low temperature heating is not complete at the ball, or valve packing at the water, causing freeze, or at room temperature, the valve is closed tight at low temperatures, making threaded chewed like.
To prevent hypothermia valve stuck phenomenon, the design should be broad trapezoidal screw threads; there should be a firm stand in the valve at the installation to prevent the valve with the stem pipe displacement and bending. Ball and low temperature cold box can be elastically fixed connection to prevent deformation of the stem and the body different heart; during the cold bare, to check and adjust the cryogenic valve installation in the cold state, when it was found jammed valve cooling When the phenomenon, adjustable valve mounting flange on the cylinder housing, so that the switch easily.
In operation, before the start of the heating should be complete, close the low temperature ball valve (cryogenic ball valve) when the principle of not leak, do not use excessive force.

Should you want to know more about butterfly valve from Reliable China valve manufacturer, please visit www.reliavalve.com or email us via sales@reliavalve.com.

25. August 2015 · Comments Off · Categories: Uncategorized

First, the expanding metal seated ball valve working principle.
Expansion ball valve open wedge block and dovetail principle. Expansion bidirectional ball metal seated ball valve to break the traditional structure of the whole ball spin, ball valve cut into three parts: the wedge block and two ball crowns. It works by opening and closing the ball valve during rotation of the two dovetail groove ball cap gather the valve ball and seat cover from the sealing surface, so that the rotation of the process to avoid the friction between the seal faces, greatly improving the valve life; when the rotary valve in place, re-use wedge-shaped block two balls into the seats crown cover a seal. This kind of ball valves for high temperature, high-pressure conditions, safe and reliable.

Second, expanding metal seated ball can namely relief structure.
Three piece ball valve when the valve is open style dovetail gather the ball through the ball and seat to find things out, cavity pressure relief safety, after spinning ball to an open or closed system, so that the process of sealing between the opening and closing never touching, friction-free seal, easy operation. Greatly extending the life of the valve allows.

Third, the expanding metal seated ball valve ball motion sealing surface wear comparison
Three piece ball valve opening and closing movement of ball valve fixed ring is positioned to ensure that two piece ball valve in the seat center position, the ball valve to achieve expansion of the seal structure reduced wear. To solve the traditional float up and down shift, pressing the upper and lower valve acne, could easily lead to uneven wear and leakage sealing surface opacity disease.

Expanding metal seated ball valve for low temperature conditions, the use of long-necked design makes packing away from the media, to avoid packing failure. Extended this structure and operation of institutions have essential differences.

Should you want to know more about ball valve, such as trunnion ball valve from Reliable China valve manufacturer, please visit www.reliavalve.com or email us via sales@reliavalve.com.

02. January 2015 · Comments Off · Categories: Uncategorized

4.Ordering Information
4.1 The inquiry and order should include or indicate the following:
4.1.1 A description of the casting by pattern number or drawing (dimensional tolerances shall be included on the casting drawing),
4.1.2 Grade of steel(such as cast steel trunnion mounted ball valves), opinions in the specification.
4.1.2 Wether the castings are to produced using the investment casting process, and
4.1.5 The supplementary requirements desired including the standards of acceptance.

5. Heat Treatment
5.1 All castings shall receive a heat treatment proper to their design and chemical composition.
5.2 Castings shall be furnished in the annealed, or normilized or normilized and tempered condition unless supplementary requirement S15 is specified.
5.3 Heat treatment shall be performed after casting have been allowed to cool before the tranformation range.

6. Temperature Cool
6.1 Furnace temperatures for heat treating shall be affectively controlled by pyrometer.

7. Chemical Composition
7.1 The steel shall be in accordance with the requirements as to chemical composition prescribled in table 1.

8. Tensile Requirement
Steel used in casting shall be in accordance with the requirements as to tensile properties prescribled in table 2.

9. Quality’
9.1 Surface of the casting (such as cast steel gate valves ) shall be examined visually and shall be free of adhering sand, scale, cracks and hot tears.
9.2 When the additional inspection is desired, supplementary requirements S4, S5 and S10 may be ordered.
9.3 The casting shall not be peened, plugged, or impregnated to stop leaks.

10. Repair by Welding
10.1 Repair by welding10.1 Repairs shall be made using procedures and welders qualified under A488/A488M.
10.2 Weld repairs shall be inspected to the same quality standards that are used to inspect the castings. When castings are produced with supplementary requirement S4 specified, weld repair shall be inspected by magnetic particle examination to the same standards that are used to inspect the casting. When casting are produced with the S5 specified, weld repairs on casting that have leaked on hydrostatic test, or on castings in which any cavity prepared for welding is greater than approximately 10 square in shall be radiographed to the same standards that are used to inspect the castings.
10.3 Castings containing any repair weld that exceed 20% of the wall thickness or 1 square in, whichever is smaller or that exceeds approximately 10 square in area, or that was made to correct hydrostatic test defects, shall be stressed relieved or heat treatment after the welding. This mandatory stress relief or heat treatment shall be in accordance with the procedure qualification used.

03. October 2014 · Comments Off · Categories: Uncategorized

Flange face finish

The ASME B16.5 code requires that the flange face (raised face and flat face) has a specific roughness to ensure that this surface be compatible with the gasket and provide a high quality seal.
A serrated finish, either concentric or spiral, is required with 30 to 55 grooves per inch and a resultant roughness between 125 and 500 micro inches. This allows for various grades of surface finish to be made available by flange manufactures (and valve manufacturer) for the gasket contact surface of metal flanges.
The picture on the right shows a serrated finish on a Raised Face.

Cast steel globe valves

The most used Surfaces
Stock Finish
The most widely used of any flange surface finish, because practically, is suitable for all ordinary service conditions. Under compression, the soft face from a gasket will embed into this finish, which helps create a seal, and a high level of friction is generated between the mating surfaces.
The finish for these flanges is generated by a 1.6 mm radius round-nosed tool at a feed rate of 0.8 mm per revolution up to 12 inch. For sizes 14 inch and larger, the finish is made with 3.2 mm round-nosed tool at a feed of 1.2 mm per revolution.
Spiral Serrated (commonly used for valves, such as ball valves)
This is also a continuous or phonographic spiral groove, but it differs from the stock finish in that the groove typically is generated using a 90-deg tool which creates a “V” geometry with 45° angled serration.
Concentric Serrated
As the name suggests, this finish is comprised of concentric grooves. A 90° tool is used and the serrations are spaced evenly across the face.
Smooth Finish
This finish shows no visually apparent tool markings. These finishes are typically utilized for gaskets with metal facings such as double jacketed, flat steel and corrugated metal. The smooth surfaces mate to create a seal and depend on the flatness of the opposing faces to effect a seal. This is typically achieved by having the gasket contact surface formed by a continuous (sometimes called phonographic) spiral groove generated by a 0.8 mm radius round-nosed tool at a feed rate of 0.3 mm per revolution with a depth of 0.05 mm. This will result in a roughness between Ra 3.2 and 6.3 micrometers (125 – 250 micro inch).

API 6D valves

SMOOTH FINISH
Is it suitable for spiral gasket and non metallic gasket?
For what kind of application is this type?
The above questions are often asked. I try to answer.
Smooth finish flanges are more common for low pressure and/or large diameter pipelines and primarily intended for use with solid metal or spiral wound gaskets.
Smooth finishes are usually found on machinery or flanged joints other than pipe flanges. When working with a smooth finish, it is important to consider using a thinner gasket to lessen the effects of creep and cold flow. It should be noted, however, that both a thinner gasket and the smooth finish, in and of themselves, require a higher compressive force (i.e. bolt torque) to achieve the seal.
You may have probably seen this comment:
Machining of gasket faces of flanges (end flanges of valves, such as gate valves) to a smooth finish of Ra = 3.2 – 6.3 micrometer
(= 125 – 250 microinches AARH)
AARH stands for Arithmetic Average Roughness Height. It is used to measure the roughness (rather smoothness) of surfaces. 125 AARH means 125 micro inches will be the average height of the ups and downs of the surface.
63 AARH is specified for Ring Type Joints.
125-250 AARH (it is called smooth finish) is specified for Spiral Wound Gaskets.
250-500 AARH (it is called stock finish) is specified for soft gaskets such as NON Asbestos, Graphite sheets, Elastomers etc. If we use smooth finish for soft gaskets enough “biting effect” will not occur and hence the joint may develop leak.
Sometimes AARH is referred also as Ra which stands for Roughness Average and means the same.

07. July 2014 · Comments Off · Categories: Uncategorized

The failure may arise during the usage of swing check valves. Generally, more failure arises if there are more valve parts. The main reason of flow backwards for check valves are mainly damage of check valve parts, damage of seal surface, dirt on seat surface.

Some solutions for solving the above problems:

  1. Periodic cleaning to make the seat surface clean
  2. Correct installation or assembly, no distortion between body and bonnet
  3. Correct selection of seal material
  4.  Periodically examine and repair, and replace the rubber seal material
  5. Assemble strainer or filter before the check valve if there is much the impurity

check valves

By Kevin Tsai for Relia Valve-Professional, China  valve & China gate  valve supplier.

14. March 2014 · Comments Off · Categories: Uncategorized

Valve Packing of Live Loading

The “live loading” of valve packing has been the topic of many articles and papers over the past few years. While highly recommended by some, others claim it has no value. The truth is both statements can be correct-it all depends on the individual application.

The problem is determining if a valve is a candidate for live loading. In most cases this can be decided by answering a few questions:

 

  • Is it a packed valve?
  • Does the valve cycle frequently?
  • Is it motor operated?
  • Is the valve difficult to get at?
  • Is the valve subject to high temperatures and pressures?
  • Is the valve in a critical application?
  • Does the valve have a history of packing leaks?
  • Does the valve have to be monitored under EPA regulations?

If the answer to the first question and any of the others is “yes,” there is a good possibility the valve is a candidate for live loading.

Many different packing materials can and have been live loaded, but since the graphite-based materials are the most commonly used in live-load applications, the data referred to is based on these materials.

Live Loading
In its simplest form, live loading is the application of a spring load to the gland follower of a packed valve. A Belleville spring between the gland follower and its fastening studs and nuts provides an effective way to establish and maintain a controlled amount of stress in the packing set. The amount of the packing stress in a live-loaded system can be controlled by the size of the Belleville spring used and how far it is compressed or deflected. In a live-loaded packing system, the follower will continue to push against the packing even when packing volume is lost (by friction, extrusion, consolidation, etc.) The spring load will be slightly reduced as the springs expand, but this reduction in load will be much less than the load that is lost if the packing set was not live loaded. This remaining load allows the packing stress to remain at a level above the minimum sealing stress and enables the packing to remain leak free. There are many reasons why packed valves leak.

The most common problems are listed here, though some cannot be overcome by live loading alone:

  • Wrong packing material for the application.
  • Bent, scored, or pitted valve stems. No amount of spring load can overcome the damage these can cause to a packing set.
  • Improper packing installation. This may be the single biggest reason repacked valves leak. Graphite-based materials are not as forgiving as asbestos. These materials must be installed properly. This includes initially consolidating the packing by cycling the valve and retorqueing. This may take from as few as three to five times, to as many as 15 to 20. Installation procedures can vary from one packing manufacturer to another. Follow the manufacturer’s procedures, whether the repacking is being done in house or by an outside contractor. The benefits of live loading are greatest when the packing has been installed properly.

Infrequent Use
A valve that is not used often, like an isolation valve, tends to leak when it has opened or closed after remaining unused for an extended period of time. What has happened is that the packing has consolidated over time, and the initial compressive load is reduced. Also, when the valve is actuated, additional compressive load is lost. If this reduction in packing stress falls below the minimum seal pressure, the valve will leak. Valves that fall into this category are not typically live loaded, but the addition of a single set of springs has been beneficial.

Frequent or High Cycles
When a valve is cycled, the packing around the stem wears. As the packing is lost, the stress on the packing is reduced. If left unchecked, the valve will eventually leak, which becomes very apparent on highly cycled valves, typically control and motor-operated valves. The normal method of overcoming this is frequent retightening of the gland follower bolts. Live loading can alleviate this stress reduction and eliminate the need for constant retightening.

High Temperatures, Pressures and Critical Applications
When valves work at high temperatures and pressures, they are usually in a critical application. Keeping these valves from leaking can be a difficult job. They are subjected to additional factors that make it harder to keep the proper stress on the packing set.

High temperatures can cause the gland follower bolts to creep or relax, which will reduce the stress on the packing set. High pressures usually mean higher packing loads, which can be difficult to maintain. Critical application usually means a need for a higher standard of safety. Live loading can be used to help eliminate these problems.

Maintenance Headaches
Valves that have been chronic leakers and valves that are inaccessible also are good candidates for live loading. Live-loaded valves require less packing maintenance, and the controlled load on the packing set may just help those chronic leakers.

EPA Monitoring
The Clean Air Act has made everyone take a closer look at packing leaks. If a valve has to be monitored, it must not only meet the EPA standard leak rate, but must be able to maintain that leak rate. Also, it must be able to do this without being adjusted. Controlled load on the packing set is essential in attaining this. Live loading may be the most cost-effective way to meet the EPA’s standards.

Almost all of the major valve manufacturers, valve rebuilders, packing manufacturers, and packing distributors now have live-loading programs. Some are more complex then others, but all of them work basically the same way: Belleville springs are used to maintain the load on the packing set.

By Kevin, from China gate valve manufacturer- professional for cast steel gate valves, forged steel gate valves, trunnion mounted ball valves etc.

19. February 2014 · Comments Off · Categories: Uncategorized

China valve price in 2014 keeps the same level as in 2013

Good news to the clients! China valve price keeps the same level as in 2013 as the price of valve raw material keeps still.

The labour cost rises in 2014, however, due to the firece competition in valve industry, China valve suppliers do not change the price to a higher level. Zhejiang Relia Valve Co., Ltd. also keep the price still.

Welcome to contact Relia Valve for your valve request.

P1050134

 

 

By Kevin, for Relia Valve, professional China gate valve manufacturer