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Last updateFri, 23 Sep 2016 2pm

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An Alternative Basics Education: Valve Ed Comes to You!

An Alternative Basics Education: Valve Ed Comes to You!

For the first time in the seven-year his...

Give Your Flow Meter a Happy Home

Give Your Flow Meter a Happy Home

Increased emphasis on the need to improv...

What’s in Store for the Construction Market?

What’s in Store for the Construction Market?

As was the case with many of the present...

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Pentair Valves & Controls Hosts Customer Appreciation Training Event

2 DAYS AGO
Pentair Valves & Controls Hosts Customer Appreciation Training Event

More than 200 representatives from Houston’s refinery, chemical and petrochemical industries joined Pentair Valves & Controls on Sept. 15 at its Pasadena, TX facility for a customer appreciation BBQ and training event . The presented seminars are a part of Valves & Controls’ Pentai...

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Mueller Water Products Recognized for Best Smart Water Solution

3 DAYS AGO

Mueller Water Products, Inc. received the 2016 Best Smart Water Solution award at the third annual Smart Water Summit in Palm Beach Gardens, FL. Mueller Water Products, who won this award for the second time, was recognized for smart technology solutions offered through its Mueller Co., Mueller System...

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Senate Overwhelmingly Passes Water Resources Development Act

2 DAYS AGO

The U.S. Senate recently passed the Water Resources Development Act (WRDA) of 2016 with a broad bipartisan vote of 95 to 3. This legislation not only authorizes critical U.S. Army Corps of Engineers projects that drive investment in navigation, flood management, and ecosystem restoration, it provides ...

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Alaska Railroad Prepares First U.S. Shipments of LNG

2 DAYS AGO

The Alaska Railroad (ARRC) will demonstrate its ability to safely transport liquefied natural gas (LNG) in intermodal LNG ISO containers from southcentral to interior Alaska during a month-long operational performance project in early fall 2016.

ARRC is the first railroad in the country to obtain permi...

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Manufacturing Growth Eases Again in September

1 DAY AGO

At 51.4 in September, the seasonally adjusted Markit Flash U.S. Manufacturing Purchasing Managers’ Index (PMI) was down from 52.0 in August and pointed to the weakest improvement in overall business conditions since June. The latest PMI reading marked seven years of continuous growth across the ...

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Leading Economic Indicators Down Slightly in August

2 DAYS AGO

The Conference Board Leading Economic Index (LEI) for the U.S. declined 0.2% in August to 124.1, following a 0.5% increase in July, and a 0.2% increase in June.

“While the U.S. LEI declined in August, its trend still points to moderate economic growth in the months ahead,” said Ataman Ozy...

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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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