Basics of a Great Feed System

Accessories; How to select, install and maintain common accessories

Introduction

Who am I? Danny Smith, Business Development Manager,

Maltz Sales Company.

What experience do I bring to the lecture? I have spent the last 25 years selling, installing,

troubleshooting and repairing pumps, instruments and accessories for the fluid handling markets.

The Objective:

It is the aim of this class to offer basic understanding of common accessories used in chemical feed or chemical transfer systems.

Included in this presentation will be a hands on portion of the class where we will disassemble and reassemble some of these components.

We will conclude with a demonstration of the products in use in a sample system.

Questions

What are some of the common accessories seen used in a chemical feed or chemical transfer application?

What are some of the issues that you see when you use these devices?

What is your least favorite accessory that you use and why?

Typical Installation Drawing

CPVC vs PVC

Temperature: PVC is rated to 140ºF, CPVC is rated 200ºF

Chemical Resistance: Similar, although CPVC tends to be slightly better in some applications.

Physical Attributes: CPVC is slightly more flexible and significantly less prone to fracture.

Cost: CPVC is noticeably more expensive

Proper Solvents

When using PVC or CPVC with strong caustics such as Sodium Hydroxide or Potassium Hydroxide and with Sodium Hypochlorite it is strongly recommended that you use a glue that specifically states on the label “industrial duty, high-strength, chemical-resistant solvent cement for use with CPVC or PVC piping systems carrying acids, bases, salts, and sodium hypochlorite."

LPE vs Teflon Tubing

Temperature: LPE, 140ºF; Teflon, >210ºF

Chemical Resistance: LPE is limited, not good often with strong oxidizers, strong acids; Teflon has exceptional resistance nearly across the board.

Physical Attributes: LPE is more flexible and can come in many colors, typically opaque or black; Teflon is typical more translucent and far stiffer.

Cost: Teflon is far more expensive

Rigid Pipe vs Tubing

Rigid pipe typically is more expensive to install, however, it is far more forgiving than tubing when talking about abrasion, accidental damage and adding other accessories. Tubing is far faster to replace and often far cheaper to install.

Rigid Pipe will typically last longer than LPE but not as long as Teflon Tubing.

Safety Note

If you chose to hard pipe your sodium hypochlorite system it is highly recommended that you use a vented ball valve.

The vent hole should be directed back towards the pump or tank (Upstream) when the valve is closed.

Adapter Fittings - Tubing to Pipe

Adapter fittings come in a wide assortment of styles, materials and sizes. The range in costs from very inexpensive to very expensive.

Most frequently I recommend using glued fittings vs threaded fittings. The glued fittings leak far less often. The two drawbacks to glued fittings are they must be cut out and thrown away if there is an issue and they typically are far more expensive.

When using threaded fittings machined fittings are much less prone to leaking and often are easier to seal.

Adapter Fittings - Tubing to Pipe (continued)

When using the lower cost fittings the more preferred material is PVDF. (Kynar)

The molded, plastic fittings often have three materials of construction; The body is polypro, polyethylene or PVDF, the grommets are often BUNA, EPDM or VITON and the grab rings are either plastic or metal.

Make sure that you always try to eliminate as many connections as possible.

Calibration Columns

Key Features

Most common material of construction are Clear PVC or Glass

They can come with loose tops for easy cleaning or sealed tops (glued) for venting purposes.

They come in various sizes and shapes.

They are intended for verification purposes and should be treated as such because accuracies can vary with installation

Before you start

The following items make testing and verifying your pump easier: Stopwatch, graph paper, pencil and straight edge.

Make sure that you have everything you need to isolate the calibration column from the day tank.

Make sure that you have a way to safely fill the calibration column.

Testing

Step 1: Fill the calibration column slowly, either by opening a valve from the day tank or from the top, depending on how the column is plumbed. Fill as precisely to the top calibration line as possible and close valves to the day tank.

Step 2: Utilizing the stopwatch run the pump for thirty seconds and note how far the chemical has been drawn down.

Step 3: Repeat at least twice for best accuracy. (Average the three results)

Benefits

The calibration column is a great diagnostic tool. Some common issues that the column can diagnose include worn check valves, inaccurate dosing or clogged lines.

The calibration column allows for a better understanding of each unique application.

Pressure Relief Valves

Pressure Relief Basics

We are strictly talking about pressure relief valves for Chemical Feed

We will talk about several different types; two port or three port, fixed or adjustable and threaded vs socket vs flanged

We will review how to service the valves as well.

PRV’s

According to Griffco Valve, “diaphragm pressure relief valves operate when the pressure in the chemical system exceeds the preset pressure of the valve. The diaphragm is held against the valve seat by an internal spring. When the preset pressure is exceeded the diaphragm is forced up and the chemical flows out the relief port, back to the chemical tank or to the suction side of the pump.”

The number one reason for installing pressure relief valves is operator safety.

Installation Arrangements

Different types of PRV’s

Flanged, union, socket, threaded Provide for a wide variety of installation

arrangements Allow easy maintenance or replacement

Three Port (90º angled) or two port (180º or 90º) Benefits of a three port include tighter space for

piping Benefits of a two port allow the system to plumbed

in a more convenient way for service.

Fixed or adjustable

Where to install

It is often recommended that you install the PRV as close to the pump as possible.

The PRV must be installed before any Tees, ball valves or other fittings that could divert or alter the flow.

PRVs should be installed anywhere that pressure can be trapped or accumulate. (Areas such as piping arrangements that allow for multiple pumps to flow into one system)

Physical Characteristics

Materials of construction for the body include: PVC, CPVC, PVDF, Stainless Steel

Diaphragm materials include: Teflon, Viton and EPDM

Temperature ranges vary with materials of construction

Pressure ranges vary as well, typical is 5 – 150 with a factory preset of 50 PSI

Testing and adjusting

You must use a pressure gauge in the system for accurate testing.

Pressurize your system to desired system pressure, checking the pressure gauge. If the pressure exceeds factory setting and valve is relieving remove cap and slowly adjust the screw until valve stops relieving. For many manufactures each complete revolution is approximately 8 – 10 PSI.

Some tips

When installing a PRV it is beneficial to use a portion of clear PVC to tell when the valve is relieving.

Make sure that you have installed a place where you can clean the chemical from the piping in the case of the system relieving.

If you glue the valve in place make sure that you can remove the top to do your yearly maintenance.

Never install a shut off valve in the relief line

Back Pressure Valves

According to Sigmamotor, “diaphragm back pressure valves are used to enhance the performance of chemical feed pumps and systems by providing a constant discharge head pressure. These valves also function as an anti-siphon valve.

The diaphragm is held against the seat by the internal spring. Back pressure is adjustable from 10 - 150 psi via the adjustment screw. When the inlet pressure exceeds the preset pressure the diaphragm lifts off the seat and the chemical flows to the injection point. After each discharge stroke of the pump, as the pressure drops, the diaphragm reseats itself.

Installation

Generally, the back pressure valve can be installed anywhere in the discharge line, provided there is some downstream pressure at the dosage point. If there is no downstream pressure the back pressure valve should be installed at the dosage point to prevent siphoning and drainage of the chemical line.

All valves are factory set at the pressure specified when ordering. Field adjustment is possible with the adjustment screw, (approx. 8 psi/revolution with a 150 psi spring).

Options

Air release valve (pictured)

Gauge port

Physical Characteristics

Materials of construction for the body include: PVC, CPVC, PVDF, Stainless Steel

Diaphragm materials include: Teflon, Viton and EPDM

Temperature ranges vary with materials of construction

Pressure ranges vary as well, typical is 5 – 150 with a factory preset of 50 PSI

Options include ARV ports, pressure gauge port…

Pressure Gauges and Gauge Isolators

Pressure Gauge and Gauge Isolator Video

Pulsation Dampener

There are three major types found in the metering pump market: Automatic, Adjustable and Chargeable

They come in a wide variety of materials

They are sized for specific output volumes from the metering pump.

Technical info

“In order to accelerate the fluid to maximum velocity, each piston stroke must overcome the inertia of the columns of fluid in the suction and discharge pipe work.  At the end of each stroke, this inertia must again be overcome to bring the fluid columns to rest.  This cycle of alternate acceleration and deceleration is the primary cause of fluid pulsations or pressure spikes.”

These spikes are very similar to water hammer

Hard pulsation can damage chemical feed system piping, fittings and equipment

How they work

Dampeners found in our industry are sealed pressure vessels with the process chemical on one side of a bladder and a gas on the on the other side. (Often either air or nitrogen)

The gas side is charged to within 7 psi of the system operating pressure

The liquid side is designed to handle a very specific volume.

The chamber stores up pressure and acts much like a DC rectifier, chopping off and smoothing the flow.

Peristaltic Pulsation Dampener

Metering Pump Pulsation Dampener

Installation

It is important to install the Dampeners as close to the pump as possible, preferably within 10 pipe diameters from the pump. It should be mounted after the pressure relief valve.

A true union ball valve placed before the dampener will allow for maintenance of the unit without shutting the system down.

There must be at least 5-10 psi back pressure downstream of the dampener.

Utilizing a downstream pressure gauge set the pressure in the chamber between 2 – 7 psi below the operating pressure.

Installation continued…

Once system pressure is in contact with the bladder/bellows, the air charge will be compressed to the system pressure and the dampener gauge will read the system pressure, not the initial charge pressure.

Once working pressure is achieved, adjustment may be necessary. Gradually increase or decrease the air charge in the dampener by bleeding or filling through the self-relieving pressure regulator. Allow the system to respond to each adjustment (this may take a minute or two) before making further adjustments.

Injection Checks & Corporation Stops

Installation Diagram

Transfer Pump Accessories

Priming Chambers

Vacuum Breakers

Pressure Gauges

Vacuum Breakers

In Conclusion

Why do we use various pump accessories? Safety first Longevity of the equipment and the system as a

whole Repeatability and accuracy Efficiency More consistent dosing by making the flow closer to

a centrifugal output. Help in troubleshooting