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Valve Basics Training Helps Fill Industry Skills Gap

Valve Basics Training Helps Fill Industry Skills Gap

One of the most keenly felt needs in tod...

An End-User’s Perspective on Valve Selection and Risk

An End-User’s Perspective on Valve Selection and Risk

I am not a valve expert, although I ofte...

New Test Stamp and More Updates on Pressure Vessel Codes

New Test Stamp and More Updates on Pressure Vessel Codes

A new test organization program and stam...

The Role of Valves in HAZOP Studies

The Role of Valves in HAZOP Studies

Process hazard analysis (PHA) is require...

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Lee Howard Named President of Rotork Controls

1 DAY AGO
Lee Howard Named President of Rotork Controls

Lee Howard has been named president of Rotork Controls , overseeing both the U.S. and Canada. He replaces the recently retired Bob Arnold, a former VMA chairman, who served as president of Rotork Controls since 1988.

Lee was born in Wales and is a native of the UK. He previously served as managing dire...

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Val-Matic Names Mark Troyanowski VP of Sales & Marketing

1 DAY AGO
Val-Matic Names Mark Troyanowski VP of Sales & Marketing

Val-Matic Valve & Manufacturing Corp. has appointed Mark T. Troyanowski as vice president of sales and marketing. Mr. Troyanowski joined Val-Matic earlier this year and previously worked in various sales management roles at other manufacturing companies.

Over his career, he has participated in seve...

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Chemical Activity Barometer Suggests Accelerated Business Activity

-1 DAYS AGO

The Chemical Activity Barometer (CAB) expanded 0.4% in August following an upward revision for July. This marks the barometer’s sixth consecutive monthly gain. Accounting for adjustments, the CAB is up 3.2% over this time last year, the strongest year over year growth since January 2015. All d...

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Innovation Could Lead to Significant Cuts in Chemical Manufacturing Energy Use

-1 DAYS AGO

Scientists from ExxonMobil and Georgia Tech have developed a new technology that could significantly reduce the amount of energy and emissions associated with manufacturing plastics. If brought to industrial scale, this breakthrough could reduce industry’s global annual carbon dioxide emissions ...

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Manufacturing Output Up, Firms Signal Softer Expansion in New Work

1 HOUR AGO

U.S. goods producers saw a further upturn in overall business conditions during August, though the rate of improvement was softer than seen in July. While output continued to rise markedly, total new work rose at a slower pace and employment expanded at the weakest rate in four months. Meanwhile, co...

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Leading Economic Indicators Gained Ground in July

4 DAYS AGO

The Conference Board Leading Economic Index (LEI) for the U.S. increased 0.4% in July to 124.3, following a 0.3% increase in June, and a 0.2% decline in May.

“The U.S. LEI picked up again in July, suggesting moderate economic growth should continue through the end of 2016,” said Ataman Ozyi...

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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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