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Last updateThu, 26 Apr 2018 2pm

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The VMA Knowledge Forum, Part One: Technology at the Forefront

The VMA Knowledge Forum, Part One: Technology at the Forefront

The first VMA Valve Industry Knowledge F...

Air Valves in Piping Systems

Air Valves in Piping Systems

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Are Valves from Low-Cost Countries Getting Better?

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Managing the Generation Gap: Much Ado About Nothing?

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Industry Headlines

Chemical Activity Trends Suggest Growth into Early 2019

Wednesday, 25 April 2018  |  Chris Guy

The American Chemistry Council's Chemical Activity Barometer slipped 0.1% in April to 121.6% on a three-month moving average (3MMA) basis. This follow...

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Industry Headlines

Val-Matic Names Andrew Brudniak Project Manager

1 DAY AGO
Val-Matic Names Andrew Brudniak Project Manager

After four years with Val-Matic Valve & Mfg. Corp. , Andrew Brudniak was recently promoted to project manager, after having recently held the position of sales engineer for the northeast territory.

Brudniak also has passed the exam for the Project Management Professional (PMP) certification offered...

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Weir Group Plans to Sell Flow Control Division

5 DAYS AGO

The Weir Group’s board of directors will initiate a process to sell the Flow Control division. This process will focus on maximizing value for shareholders, with all options to be considered and no fixed timetable. Proceeds will be used to further reduce leverage and to fund future investment in...

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Chemical Activity Trends Suggest Growth into Early 2019

19 HOURS AGO

The American Chemistry Council's Chemical Activity Barometer slipped 0.1% in April to 121.6% on a three-month moving average (3MMA) basis. This follows six consecutive monthly gains and a dip from the barometer’s highest point since modeling began. The barometer remains up 3.8% on a 3MMA compa...

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Formosa Selects Louisiana for $9.4B Petrochemical Project

22 HOURS AGO

Formosa Petrochemical Corp. has selected St. James Parish in Louisiana for a $9.4 billion chemical manufacturing complex and has purchased a 2,400-acre site along the west bank of the Mississippi River.

Located just downriver from the Sunshine Bridge, the complex would be built in two phases and prod...

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40% of Small Manufacturers Likely to Add Staff this Year

22 HOURS AGO

Xometry released the findings of its quarterly Small Manufacturing Index, showing that 40% of small manufacturers surveyed are likely to hire more employees this year as business confidence has risen from a year ago. Additionally, 28% of those surveyed stated they have hired more employees since Q1 20...

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IHS Markit U.S. Manufacturing Index Rose in April

1 DAY AGO

Manufacturers reported the greatest improvement in overall business conditions since September 2014 in April. This was highlighted by the seasonally adjusted IHS Markit Flash U.S. Manufacturing Purchasing Managers’ Index (PMI) rising from 55.6 in March to 56.5.

Stronger growth in new orders drov...

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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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