Ningbo Valve Factory » Valve Knowledges

End Connection of valve

nvf-admin — Tue, 18 Feb 2014 08:46:26 +0000

a) multi-threaded end-turn valves, check valves and ball valves with female tapered threads are the ANSI used with pipes up to 2 1/2 “or 3″.

b) welding valves range for the direct connection of multi-turn brass valves, check valves and ball valves up to 3 “copper tubing. should be careful not to overheat and damage the valves during welding.

c) The flanged end connections are the most common design used for the installation of iron multi-turn valves 2 “and larger.

d) Wafer and lug body styles are used with dampers and valves height / double door verification for quick and easy installation between two flanges. e) the slotted end ball, butterfly and check valves allow the size of the quickest installation of 2 “and larger.

Check Valve (Backflow Prevention) Design Detail Circuit Balancing Valve Design Detail

nvf-admin — Wed, 13 Nov 2013 08:58:48 +0000

check valves (Backflow Prevention)
a) Swing-type check offer the least pressure drop and offer simple automatic closure; when fluid flow stops, gravity and flow reversal closes valve. Many bronze valves offer a Y-pattern body with an angle seat for improved performance. Resilient seating preferred for tighter shutoff.
b) Lift checks come in in-line or globe-style body patterns. Both cause greater pressure drop than the swing type, with the horizontal pattern similar in restriction to globe valves. Some styles are spring-actuated for immediate closure when flow stops. The in-line spring-actuated lift check also is referred to as the “silent check”because the spring closes the valve before gravity and fluid reversal can slam the valve closed. Resilient seating recommended.
c) Double-door checks have twin discs on a spring-loaded center shaft. These valves have better flow than lift checks and most often use a wafer body for low cost and easy installation. Resilient seating recommended.

Circuit Balancing Valves
a) A Balancing Valve is used to regulate and measure the rate of flow of water. The valve can positively isolate the flow and be set at an intermediate position to maintain the design flow rate. Pressure tapping points on either side of the seat provide the means for flow measurement. Most Balancing Valves are globe style and incorpora

Quarter-Turn Valve Design Detail

nvf-admin — Fri, 01 Nov 2013 15:09:31 +0000

　a) ball valves 　　　Positive Features – Recommendations 　　　1) Bubble-tight shut-off from resilient (TFE) seats 　　　2) Quick 90° open/close, not torque-dependent for seating 　　　3) Straight-through unobstructed flow, bidirectional 　　　4) Minimal pressure drop if full-port selected 　　　5) Can be throttled (Application dependent) 　　　6) Easier to automate than multi-turn valves 　　　7) More compact than multi-turn valves 　　　8) Offers high cycle life 　　　Disadvantages 　　　1) Temperature range limited by seat material 　　　Body Styles 　　　1) One-piece has no potential body leak path, but requires use of reduced port ball; thus, significant pressure drop. Not repairable. 　　　2) Two-piece end entry is most common in building services. Best price value. Available full- or standard-port balls. Not recommended to be repaired. 　　　3) Three-piece is more costly, but is easier to disassemble and offers in-line repairability. Available in full- or standard-port balls. 　　　4) Top entry is preferred in some industrial applications where access for repair is required without removing body from the line. More costly than two-piece style. 　　　Port Size 　　　1) Full-Port ball valves provide pressure drop equal to equivalent length of pipe, and even slightly better than gate valves. 　　　2) Standard (conventional) port balls are up to one pipe size smaller than nominal pipe size, but still have significantly better flow than globe valves. 　　　3) Reduced port ball valves have more than one pipe size flow restriction and are not recommended in building services piping, but rather for process piping in hazardous material transfer. b) butterfly valves – Resilient Seated Positive Features – Recommendations 1) Bubble-tight shut-off from resilient seats 2) Quick 90° open/close, easier to automate than multi-turn valves 3) Very cost-effective compared to alternate valve choices 4) Broad range of throttling capabilities 5) Nearly full flow, less pressure drop than globe valves 6) Broad selection of trim materials to match different fluid conditions 7) More compact than multi-turn valves 8) Offers high cycle life Disadvantages 1) Not for use with steam 2) Gear operators needed larger than 6” to aid in operation and protect against operating too quickly and causing destructive line shock. Body Styles 1) Wafer-style held in place between two pipe flanges. Easy to install but cannot be used as isolation valve. 2) Lug-style is a wafer body but has tapped lugs matching up to bolt circle of Class 125/150 flanges. Easily installed with cap screws from either side. Lug-style designs from some manufacturers permit dropping the pipe from one side and the valve will hold full pressure when needed. (Dead end service) 3) Grooved butterfly valves direct connect to pipe using iron pipe size couplings. Grooved valves are easiest to install. 4) Flanged butterfly valves face to face dimension conforms to ANSI Standard B16.10 and

Multi-Turn Valve Design Detail (1)

nvf-admin — Fri, 01 Nov 2013 15:05:46 +0000

a) gate valves

Positive Features – Recommendations
1) Good choice for on-off service
2) Full flow-low pressure drop
3) Bidirectional

Disadvantages
1) Not for throttling; use fully opened or fully closed
2) Metal-to-metal seating means not best choice for frequent operation. Bubble-tight seating should not be expected with metal-to-metal design.
3) Difficult to automate.

Wedge and Seat Designs
1) Solid wedge best choice for all building services. Modern foundry and machining controls enable the solid wedge to give good performance in a broad range of services.
2) Metal solid wedge seating against metal seat in body is the most common in building service piping. Rubber-coated solid wedge (resilient wedge) has become popular in fire protection and municipal cold water service. The resilient wedge design offers bubble-tight seating, but is limited to 160°F water service.

Stem Designs
1) Rising stem-inside screw is the most common and preferred design for bronze multi-turn valves. In the fully open “back seated” position*, the stem threads are protected from the circulation of flow media. Because the stem rises as the valve is opened, clearance must be provided and stem orientation should
protect it from external damage. The stem position indicates to the observer if the valve is opened or closed.
*Repacking while valve is pressurized is not recommended.
2) Non-rising-inside screw stems are used in bronze and iron gate valves. While they are more compact than rising stem valves, the stem threads are always exposed to flowing media, allowing for possible erosion/corrosion. Open/close indication is not provided with this design.
3) Rising stem-outside screw and yoke is preferred in iron multi-turn valves. threads are external to the valve, protecting them from flow media and enabling lubrication. Care should be taken for clearance as the stem rises so that threads are not damaged. The stem position provides indication that valve is opened or closed.

Body-Bonnet Connection
1) Union bonnet is recommended as the best choice for building services piping for bronze multi-turn valves, although not all styles offer this design. The union bonnet offers strength and ease of assembly-disassembly.
2) Threaded-in bonnet is common in lighter-duty services and smaller sizes of bronze multi-turn valves.
3) Bolted body-bonnet connection is the principal design used in iron multi-turn valves. This gasketed joint is strong and easy to assemble/disassemble.

b) Globe/Angle-globe valves

Positive Features – Recommendations
1) Recommended for throttling applications
2) Positive bubble-tight shutoff when equipped with resilient seating
3) Good for frequent operation

Disadvantages
1) Significant pressure drop due to flow path
2) More costly than alternate valves

Disc and Seat Designs
1) Resilient (soft) seat discs are preferred over metalto-metal except where temperatures, very close throttling or abrasive flow make metal alloy seating a better choice. TFE is the best resilient disc material for most services, although rubber’s softness gives good performance in cold water.
2) Plug-type disc/seat, often with harder metal alloys, is best for very close throttling, when media temperature is beyond the range of TFE (500°F) or when abrasive flow is involved. Iron globe valves most commonly use semi-plug bronze disc/seat design.
3) Automatic steam stop-check angle-globe valves are best on medium-pressure steam service where the sliding action of the semi-plug disc assembly permits the valve to serve as a shut-off valve, a throttling valve and a check valve.

Posted by Ningbo Valve Factory – China valve manufacturer & Supplier.

Butterfly Valve Technical Information

nvf-admin — Tue, 29 Oct 2013 02:32:08 +0000

Installation Guide

This butterfly valve is bi-directional and may be installed in either direction.
Install this valve between any ANSI Class 125 or 150 flange. Cast iron, bronze, plastic or steel flanges may be used. No flange gaskets are required.
The stem can be installed in any position, but if a choice of stem positions exists, good practice dictates that the valve be installed with the stem horizontal. This will minimize liner wear by distributing stem and disc weight evenly.
Valves should be installed with the disc in the closed or almost closed position. This will prevent damage to the disc sealing edge.
Before any flange bolts are tightened, valves should be centered within the flanges and then carefully opened to assure free, unobstructed disc movement. Disc interference may result when valves are installed in pipelines having smaller than normal inside diameters, such as heavy wall pipe, plastic lined pipe, or as cast flanges. Suitable corrective measures must be taken to remove these obstructions, such as taper boring the pipe or installing a spacer.
After proper operation has been verified, tighten all bolts using the crossover method. Recommended tightening torques pattern is listed below.

Flange Size	Recommended Min. Bolt Torque	Flange Size	Recommended Min. Bolt Torque
2 – 4″	20 – 30 ft. lbs.	18 – 20″	150 – 210 ft. lbs.
6 – 8″	33 – 50 ft. lbs.	24 – 30″	215 – 300 ft. lbs.
10″	53 – 75 ft. lbs.	36″	300 – 375 ft. lbs.
12″	80 – 110 ft. lbs.	42 – 48″	350 – 425 ft. lbs.
14- 16″	140 – 200 ft. lbs.

Interference may also occur when butterfly valves are bolted directly to the outlet flange of a swing check, silent check, or reducing flange. check valve and butterfly valve combinations are very popular; normally a short spool piece is required between the valves.