FAQ’s - May, 2006

Elimination of R2 PTFE diaphragm

Engineered Valves (EV) has been offering two grades of PTFE diaphragms since late 09/97, R2 and TM. The R2 was the original PTFE diaphragm material that you have known for many years and the only plastic diaphragm material we had offered until the introduction of the TM diaphragm.

The TM diaphragm is a modified PTFE material originally developed for the hygienic valves used in critical process protocols associated with the Pharmaceutical and Bioprocessing industries. The TM diaphragm is a more amorphous compound which translates into increased flex life and better mechanical properties.

The TM diaphragm is considered a direct replacement for the R2 diaphragm. The TM diaphragm for the Industrial market carries different part numbers than those used in hygienic Pure-Flo diaphragm valves. The difference is that the hygienic diaphragms have more rigid QA requirements and material certifications, and special packaging requirements.

Can I use plastic diaphragms on valves originally manufactured using elastomer diaphragm or vice versa?

No, because the design of the plastic diaphragm requires the use of a floating tube nut to ensure downward closing force is absorbed by the backing cushion and evenly distributed across the closing surface.

What is your standard painting system?

Dia-Flo diaphragm valves and Cam-Line ball valves that are made of cast/ductile iron bodies are painted with dispersion resin modified medium oil alkyd fast dry primer generally in accordance with Federal Spec #TT-P-1757. Also painted are the Dia-Flo actuators and metallic bonnets and hand wheels, machined surfaces or stainless steel. Solid plastic valves are not painted.

Quarter turn valves that are actuated are supplied with enamel coated brackets and cadmium plated fasteners. Non-ITT actuators are coated with the manufacturer’s standard finish.

For corrosive environment, available is the white epoxy coating and PVDF. For additional information, contact your nearest distributor.

What is the significance of 0% and 100% ∆P when selecting an actuator for diaphragm valves?

The 0% ∆P relates to applications in which a valve is being closed against a maintained pressure on either side of weir. The 100% ∆P is when the valve is closed; the pressure on one side of weir reduces to zero or atmospheric.

Can I use water pressure instead of air on Dia-Flo actuators?

The Dia-Flo actuators were originally designed for operating in plant air supply pressure. The actuator assembly is comprised of covers that are made from die cast aluminum, Buna-N diaphragm, cast iron diaphragm plates, carbon steel springs and steel fasteners. The metallic parts will corrode when exposed to untreated water or moisture.

Therefore, if pressurized air is not available, potable water may be substituted but parts subject to corrosion must be protected. The atmospheric white epoxy option will afford some degree of protection as we coat actuator internal surfaces prior to assembly. Additionally, the air motor cover fasteners are upgraded to stainless steel giving additional degree of corrosion protection.

Does ITT Engineered Valves still offer the angle body diaphragm valves?

No. This product has been discontinued due to low demand coupled with high cost of manufacturing in low volume business beginning January 2005. The body figure numbers affected were 2611, 2621, 2622, 2623 & 2624.

What are your other discontinued diaphragm valve products?

Other products that were discontinued along with the angle bodies mentioned above are 3 straightway body configurations, namely, figures 2832 (cast iron straightway glass lined flanged ends), 2801 (cast iron straightway screwed ends) and 2803 (stainless steel straightway screwed ends).

How do you calculate the forces in closing and opening diaphragm valves with Dia-Flo actuators?

Selecting the appropriate Dia-Flo actuator was made simpler using the table format rather than by calculation. The tables are grouped by diaphragm material and operating mode. The operating mode is classified as 1) air-to-open, spring-to-close (AO/SC), 2) air-to-close, spring-to-open (AC/SO), and 3) air-to-close, air-to-open (double acting); and grouped according to system condition, such as, 0% and 100% pressure drop. Look on page 32 in our DV-01 for definition of these terms.

The Dia-Flo actuator selection guide was based on many years of lab testing. The results were field verified and refined through the years from customer’s feedback thus ensuring optimum shut off valves.

Raised faced versus flat faced flanges on steel valves

Through the years, we have offered both flat faced and raised faced flanges on all bodies made of carbon steel, stainless steel and other highly corrosion resistant steels.

In order to stay competitive, we were forced to offer the raised faced only as our standard offering. However, we can still offer the flat faced flanges by machining off the raised face, but the end-to-end dimension will no longer be in accordance with MSS-SP-88.

Queries on nuclear safety related (NSR) products

All questions relating to nuclear safety related products are handled through our Nuclear Sales department. These include activities such quote request, order follow-up, drawing requests and technical questions. Technical questions that can not be resolved over the phone or requiring further review will be taken up with our engineering department for resolution and guidance.

Can we use Advantage Actuators on Dia-Flo bodies?

Advantage actuators can now be used on Dia-Flo bodies with certain restrictions, as follows. 

1. Solid plastic bodies can be fitted with advantage actuators including accessories such as the SP 2.0 & SP 3.0 switch packs and selected Westlock limit switches that are also standard offerings in Pure-Flo. The bonnet material is made of PAS in the most common valve sizes.  
2. Lined and un-lined Dia-Flo bodies can take advantage of the Advantage Actuator including accessories. Use catalog DFAA-04 for sizing charts. Bonnet for 2” and smaller must be stainless steel.

Do you perform production tests on Dia-Flo diaphragm valves prior to shipment?

We test Dia-Flo diaphragm valves 100% prior to being released for shipment. The tests include hydrostatic and seat leakage, following the guidelines as set forth in MSS-SP-88 standard. The seat test is an operational test at no flow condition to ensure that the assembly is operating as designed.

Valves supplied with positioners are calibrated, thus, requiring little or no adjustment at all during installation.

Valves supplied with electric actuators are cycled and end-of-travel limit switches set to ensure that the actuator will not overtravel. If furnished, torque switches are factory set by the actuator manufacturer using torques values provided by ITT.

We warrant the complete valve assembly including the actuator and accessories. If actuation is performed by a third party, our limitation of liability will be restricted to the valve only.

FAQ's - 2002

Can I order an actuator only?

No, all Dia-Flo actuators must be ordered with bonnet/actuator assembly. This applies to diaphragm valves but not quarter-turn valves.

How do I get material certs for my valves?

The preferred method of obtaining material certs. on valve components is to make the request at the time of order placement. Generally certs are readily available on all steel components. Other materials including gray and ductile iron typically require special requests from our suppliers. If the request for material certs is made after the valve has been shipped to the customer, a full description of the component part and a full listing of all characters appearing on the outside of the part, including numbers and single letters must be forwarded to the customer service representative at ITT. This information provides the path in identifying the material of the part, the supplier, and other details leading to a material certification document. Many material certification documents for steel components are on file in the Quality Assurance retrieval system and can be forwarded quickly. However if the original material supplier must be contacted for the document, additional time will be required.

How do I know what elastomer diaphragm material my customer has?

Diaphragm material on an existing valve may be determined by examining the tabs on the diaphragm. Tabs are molded protrusions on the outer rim of the diaphragm that extend out from the bolted joint. The valve size and material grade will appear on the tabs, either on two small tabs or one large tab depending on the diaphragm. If the customer is unable to provide this information, than the media flowing through the valve must be known so a diaphragm selction can be made.

How do I price a valve with epoxy or PVDF coating?

In order to price an epoxy or PVDF coated valve, the following adders must be considered:

1. Body Only Coating 
2. Body and Bonnet Coating (Complete Manual Valves) 
3. Body, Bonnet & Air Motor Coating (Complete Actuated Valves)

If I change from an elastomer to an PTFE diaphragm, what parts do I need?

In order to convert to a weir diaphragm valve from an elastomer diaphragm to a PTFE diaphragm, the following parts are required: 

1. Compressor 
2. Compressor pin 
3. Tube nut 
4. Diaphragm kit to convert from a PTFE to elastomer diaphragm, a new compressor and compressor pin are required. The tube nut is no longer required.

My diaphragm valve won't close - or shutoff, how do I adjust the actuator?

First, double-check the process data for accuracy. Then verify the actuator sizing using the appropriate table in the catalog. If spring-to-close unit, insure that the proper spring is selected, or if double acting, insure that the air supply pressure at the actuator chamber is equal to that listed on the table. The valve may not close or open fully if air pressure is too low. Check the adjustment of the travel stop, if so equipped. All reverse acting Dia-Flo actuators size #25 and larger come with a travel stop as standard.

Should the yellow indicator be taken off during the autoclave cycle?

No, if you are using the newer PPS cap that is amber in color. Yes, if the cap is made of PSU which is tinted a light gray color.

Typically how many cycles can you expect to get from a diaphragm - assuming water or air as the media?

Under benign condition, the weir diaphragms may last for 20,000 cycles.Cycle life of valve diaphragms will vary widely from plant-to-plant due to field variables and differing operating conditions and PM schedules.

What do I need to know in order to determine what the spring number(s) are for the reverse acting Dia-Flo actuators?

The information required to determine the correct spring or spring set is as follows: 

1. Maximum line pressure and differential pressure (to determine the size of spring required to close the valve). Note that zero (0) differential pressure is worst case. 
2. Available air pressure (to assure the spring can be released to open the valve). Consult the actuator sizing chart in the Dia-Flo catalog to determine the spring requirements.

What does Cv factor mean?

The definition of Cv factor is the number of U.S. gallons of water per minute that will pass through a valve with a pressure drop of one psi at 60°F. This is represented by the expression; Cv is equal to flow capacity in gpm times the square root of the ratio of the specific gravity and pressure drop in psi.

What is the shelf life of my diaphragm?

Diaphragm shelf life varies depending on the material grade. When stored in a covered, ventilated and dry location with temperatures maintained between 40°F to 120°F, maximum recommended shelf life from date of manufacture is as follows:

What is the standard diaphragm material?

There are NO standard diaphragms. Each application must be considered separately. To determine the appropriate diaphragm material the following must be known:

1. Media 
2. Max. temperature 
3. Concentration by weight of the media

What is the test procedure for diaphragm valves?

The Dia-Flo diaphragm valves are tested to the requirements of MSS-SP-88 Standard Practice for Diaphragm Valves.

What is the typical information required for sizing and evaluating whether or not a diaphragm valve can be used as a control valve?

Complete process data must be given using ISA form S20.50, Rev. 1.

What limits the pressure rating of a diaphragm valve?

The diaphragm for the lined and unlined valves, and the combination of diaphragm & body material for the solid plastic bodies.

Why are there different temperature ratings for the same material diaphragm in the Dia-Flo catalog (Weir vs. Straightway)?

The diaphragm, being a non-metallic material, is the weakest component in the diaphragm valve. The diaphragm's physical properties will degrade with increasing temperature. The straightway diaphragm must go through a much larger deflection than the weir diaphragm. Therefore, its tolerance on higher temperatures is lower.

Why can't I just change from an elastomer diaphragm to a PTFE diaphragm without changing the compressor?

The method of attachment is different between the elastomer and PTFE diaphragm. A floating tube nut is used on PTFE diaphragm so that the downward force of the stem is transferred to the compressor, bypassing the floating tube nut and thus preventing over-compression.

Why do I need an adjustable travel stop for certain actuated valves with rubber lined bodies?

Adjustable travel stops are required on 3100 and 3300 series actuators on rubber lined valves. The adjustable travel stop is required to prevent damage to the valve liner and/or diaphragm during operation due to excessive closing thrust.

Why do you need to know the spring number(s) for the reverse acting Dia-Flo actuators?

All 3200 series (reverse acting) air motors are air to open, spring to close. A spring or set of springs are required to close the valve. In order to provide the correct air motor, spring number(s) must be supplied.