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How to Choose the Best Rapid Prototyping Method

How to Choose the Best Rapid Prototyping Method

As new products are designed, including ...

Monitoring Valve Health via the Internet

Monitoring Valve Health via the Internet

Most valve end users are already using s...

Valves in Oxygen Service

Valves in Oxygen Service

In his presentation at VMA’s 2017 ...

Thermal Spray Coating

Thermal Spray Coating

Q: What are the pros and cons of us...

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Industry Headlines

Crane Co. Reports Second Quarter Results

Tuesday, 25 July 2017  |  Chris Guy

Crane Co. reported second quarter 2017 earnings of $1.14 per diluted share, compared to $1.15 per share in the second quarter of 2016. Excluding Specia...

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The Actuation Selection Process

The Actuation Selection Process

Tuesday, 25 July 2017  |  Carlos Gamero

A common misconception in our industry is that actuating a valve is as simple as putting the most cost-efficient actuator on top of your valve of choi...

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Industry Headlines

Crane Co. Reports Second Quarter Results

-1 DAYS AGO

Crane Co. reported second quarter 2017 earnings of $1.14 per diluted share, compared to $1.15 per share in the second quarter of 2016. Excluding Special Items, second quarter 2017 earnings per diluted share were $1.17, compared to $1.21 per share in the second quarter of 2016.

Second quarter 2017 sale...

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Badger Alloys Joins VMA as Associate Member

7 DAYS AGO

This week the Valve Manufacturers Association (VMA) welcomes Badger Alloys as an official associate supplier member. This is VMA’s fourth new member in 2017.

Located in the heart of Milwaukee and founded in 1966, Badger Alloys offers single source capabilities for custom castings. The company pou...

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U.S. Chemical Production Moved Higher in June

20 MINS AGO

According to the American Chemistry Council (ACC), the U.S. Chemical Production Regional Index (U.S. CPRI) edged higher by 0.3% in June, following a 0.3% gain in May, and a 0.4% decline in April, as measured on a three-month moving average (3MMA) basis. During June, output grew in all regions except t...

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U.S. Fuel Ethanol Production Continues to Grow in 2017

1 DAY AGO

Through the first six months of 2017, U.S. weekly ethanol production averaged 1.02 million barrels per day (b/d), an increase of 5% over the same period in 2016. On a weekly basis, U.S. ethanol production set a record of 1.06 million b/d in the week of January 27, 2017, and it has averaged near or a...

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IHS Market PMI Index Reached Four-Month High in July

3 HOURS AGO

July data revealed a further acceleration in business activity growth across the U.S. private sector. At 54.2, up from 53.9 in June, the seasonally adjusted IHS Markit Flash U.S. Composite PMI Output Index signaled the strongest rate of expansion since January.

The pickup in business activity growth ...

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IMF Lowers 2017 Growth Forecast for U.S.

1 DAY AGO

The growth forecast in the United States has been revised down from 2.3% to 2.1% in 2017 and from 2.5% to 2.1% in 2018, according to the IMF’s World Economic Outlook. While the markdown in the 2017 forecast reflects in part the weak growth outturn in the first quarter of the year, the major fa...

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Preventive Maintenance and Repair for Sleeved Plug Valves

Preventive maintenance and repair for valves is an important part of keeping operations running smoothly and efficiently. For the sleeved plug valve (SPV), such maintenance is minimal—simply requiring an occasional adjustment to prevent both external and internal leakage in certain applications. The repair process for SPVs can be more extensive—inspection of parts and use of proper replacement parts are vital for ensuring a safe, successful overhaul. Additionally, root cause failure diagnosis is a critical part of this process. This is because the damage detected is the best indicator of the type of change to the valve or modification to the process that, if made, will extend the useful life of the valve.

 


PREVENTIVE MAINTENANCE

If the SPV is operated on a regular basis for standard applications and no leaks are present, preventive maintenance is unnecessary. SPVs should be cycled, however, at least once every three months to minimize the need for maintenance and to ensure proper valve operation. The only potential maintenance needed for this valve is a simple plug adjustment in response to inline or top seal leakage. A plug adjustment is performed by simply tightening the adjustment screws located in the valve cover or bonnet. The adjustment procedure involves tightening each of the screws a quarter turn, cycling the valve two to three times, then checking to see if the leak has been eliminated. This procedure can be performed continuously until the leak is eliminated or the adjustment screws bottom out. If the screws bottom out before the leak is eliminated, the valve will need to be repaired or replaced.

For atypical applications, such as low temperature (below the freezing point), a plug adjustment should be made after the valve is installed and has reached operating temperature. This is recommended because cold temperatures can affect the sealing properties of the sleeve, which could increase the risk of leaks. To combat this risk, valve users should adjust the valve plug to ensure the correct amount of compression is applied to the sleeve to achieve a proper seal. Similarly, for high-cycle applications (i.e., cycling once per minute), a monthly minimal plug adjustment is recommended to compensate for wear on the sleeve.


REPAIR

If a valve experiences leakage that cannot be adjusted out, it will need to be repaired or replaced (with a required cost analysis). Before a repair occurs, the valve must be disassembled and completely decontaminated according to plant requirements, as well as applicable hazardous materials-handling regulations to ensure repair personnel safety.

When repairing an SPV, the sleeve and all stem/cover seals must be replaced. It also is highly recommended that repair parts be factory, original equipment manufacturer parts to ensure continued integrity of the valve’s sealing properties.

Once the valve is disassembled, the body, plug and cover need to be inspected closely. Any defects on sealing surfaces will require replacement of that component. It is important to pay particular attention to the plug taper and stem, the body internal areas and the seal surface of the valve cover. Scratches or nicks on these surfaces could result in a leak path. All other machined surfaces should be inspected for signs of wear, scratches, burrs, corrosion or other damage. Mechanical or corrosive damage indicates the damaged part should be replaced.


FAILURE DIAGNOSIS

Failure diagnosis is a critical step in the rebuild process. Any damage detected can indicate the need for changes to processes or equipment. More specifically, problems associated with cavitations, high velocities, high-pressure drops, throttling and solids/slurries can be identified and corrected based on the specific signs of damage.

Damage from cavitation usually is detected on the downstream portions of the metal body. To remedy problems, replace the valve with a low-pressure drop/high-flow capacity valve or alter the process to reduce the pressure drop.

A high-velocity flow can damage the sealing surfaces and cause erosive damage to the plug, as well as dramatic wear damage to the sleeve. To ­minimize this, a full port plug valve should be used to allow more flow and reduce the velocity.

Tearing or ripping of the sleeve can indicate high-pressure drop across a valve. To combat this, a full port valve or installing other devices in the piping systems (i.e., orifice plate) to absorb the impact of the high pressure drop is recommended.

If a standard sleeved plug valve is used for a throttling application, the sleeve is exposed to the flowing media, which can result in damage. In such throttling applications, a cage control design should be used because the cage will protect the sleeve from direct impingement of the flow media.

Solids or slurries can cause abrasive or erosive damage on the body or body flow passage. This can indicate the wrong valve is in use. To solve this issue, a full port plug valve or another suitable alternative is recommended to limit flow restrictions.

The condition of the sleeve of a failed valve is usually the best indicator of what is occurring in the valve itself. If it appears the sleeve has cold flowed into the waterway, the application temperature should be reviewed, and a different sleeve with higher temperature capabilities might be used. If the sleeve has apparent erosion from aggressive media such as a slurry, a harder sleeve material could be used.

In sum, in normal applications, preventive maintenance for a sleeved plug valve is unnecessary unless a leak is detected. If used in the right applications and cycled regularly, SPVs require no periodic adjustments, lubrication or recalibration. For atypical applications, such as low temperature or high cycle, minimal plug adjustments may be necessary to protect against leakage. To minimize future repairs and downtime, the repair and failure diagnosis process is important in determining whether or not adjustments or improvements should be made to the application process, whether changes to equipment are called for, or both.


Rob Enneking is sleeved plug valve business ­manager – Americas, CRANE ChemPharma Flow Solutions, Xomox. Reach him at This email address is being protected from spambots. You need JavaScript enabled to view it..

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