February 2022

Valves, Pumps and Turbomachinery

Achieve greater reliability with a redesigned instrument manifold

Across industries, ranging from chemical upstream oil and gas to food and beverage applications, the manifold has proven to be a solid and hard-working instrument that receives little attention until it stops performing as designed.

Haschke, B., Emerson

Across industries, ranging from chemical upstream oil and gas to food and beverage applications, the manifold has proven to be a solid and hard-working instrument that receives little attention until it stops performing as designed. The ability to equalize or shut off pressure is an essential part of the efficiency required to operate a plant. However, the traditional manifold design has remained the same, with reliability issues tied to viscous applications that contain abrasive materials or grit, which can impact the operation of the manifold (FIG. 1).

FIG. 1. Instrument manifolds provide isolation, venting and equalization for various types of pressure measurement applications.

Improving an existing design requires a deep understanding of what that piece of equipment does and why it is important. Manifolds are put in place to efficiently and safely isolate the pressure sensor so maintenance can be performed. Systems and processes that deal with abrasive or dangerous materials require that the manifolds operate reliably and minimize liability.

The elements of the manifold’s standard design that cause the primary reliability issue are those that can cause or allow process fluid to reach and damage the transmitter. When process fluid damages the manifold, even before it reaches the transmitter, it can distort the accuracy of the readings, which can significantly impact the process in the facility.

A pressure-lock design

It is easier to securely position the manifold with a two-piece stem design and a non-rotating valve tip (FIG. 2) than with a standard manifold. Creating a more secure seat and providing closure with minimal wear ensures equipment lasts longer and is not affected by process fluid. In challenging processes—where sand and grit in the flow can cause unexpected pressure changes or damage to the pressure sensor—an operator may need to quickly close a valve manually. Doing so with a two-piece design will make it easier to turn the handle, saving time as well as reducing the risk of injury to the operator gripping the handle. An added benefit is that a manually closable manifold creates a mechanical barrier, keeping process fluid where it should be.

FIG. 2. Unlike standard manifold needle valves, enhanced manifolds with a two-piece stem design offer simplified operation, enhanced reliability and increased operating safety.

Consider, too, that an instrument manifold designed with a wider bore channel makes clogging less likely, as small sedimentary material or viscous fluids can more easily flow through the manifold. This makes it more suitable for applications that can have sand, grit or even sludge in the process flow, such as found in fracking, mining, or paper and pulp industries.

The manifold at work

In a plant environment where dozens of manifolds may be operating at one time, it is up to the process engineer to control valves in a pressure measurement application by way of manifolds. The easier the manifold is to use, the more efficient the process engineer can be, and the lower the risk of process upsets from delayed valve opening or closing. Reducing the risk of process fluid leaks using better-designed equipment (FIG. 3) ensures the safety and longevity of the equipment.

FIG. 3. Enhanced manifolds enable compatibility with a variety of pressure instrumentation.

Opening and closing a valve manually is not necessarily a daily occurrence in a plant, especially when pressure can be read digitally; however, having a user-friendly device is preferred when it does need to be done. Being able to stop the process fluid to conduct routine scheduled transmitter maintenance is one instance when manual operations are required.

Applications with particularly challenging material flow may benefit from the wider bore channel. For example, hot tar, maple syrup or even peanut butter can all quickly build up and clog a manifold, making it harder to get correct measurements. In extreme cases, if the buildup becomes too great, it can cause a blowout or manifold failure. This can mean that pressure behind the manifold becomes too great because the material cannot flow through at the appropriate speed, plugging the line and causing pressure to build. Avoiding these dangers is a benefit of the wider bore channel.

Manifolds in the field

An example of utilizing a pressure-lock design is found in chemical plants with reactions that can quickly spike in pressure. These processes are monitored closely because fast reactions or potentially valuable or hazardous processes must not, under any circumstances, be allowed to leak into the ambient environment. Therefore, a valve must be sealed tightly after maintenance—a manifold that is easier to manipulate ensures the valve is sealed more securely.

In oil field applications, it is imperative that manifolds operate correctly, ensuring that operators can read pressure spikes from a well. A missed, delayed or inaccurate reading can mean that abrasive process fluids can reach the sensor, thereby damaging it. Undetected spikes both in chemical and oil field applications spell safety concerns with potentially catastrophic consequences.

If a manifold requires special tools or is difficult to operate, it makes the process more difficult and can lead to repetitive strain injuries for the operator who must continually adjust the manifold. Especially in the field, out in the elements and where actions sometimes must be made quickly, avoiding injury and keeping operators safe are important considerations when sourcing a manifold.

The evidence is clear

A better-designed manifold can help processes run more smoothly and make the life of the operator easier. The two-piece stem design with a non-rotating valve tip makes operations run more smoothly, while the adjustable packing nut simplifies maintenance and allows for easier open and close operations. The added benefit of having the stem and bonnet threads isolated from the process fluid minimizes the potential for corrosion.

Meeting industry requirements and providing a better device, especially for highly corrosive, gritty or sludge-like materials in the process flow, ensures greater efficiency, reliability and longevity for equipment that requires manifolds. HP

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