Thermal mass devices operate on the principle that a flowing gas cools a heated body. There are two type of thermal mass flow technology:

• Constant Temperature Anemometers (CTA) heat the reference sensor to a fixed temperature and use the process sensor to monitor the flow temperature. Mass flow is determined based on the amount of electrical current used to maintain a constant temperature differential between the two sensors. The advantage of CTA meters is that the flow signal remains the same at all mass flow rates.

• Constant Power Anemometers (CPA) heat the reference sensor with constant fixed current and use the process sensor to monitor the flow temperature. Mass flow is determined based on the temperature difference between the reference sensor and the process sensor. The disadvantage of CPA meters is that the flow signal decreases with increasing mass flow rate.

The file provides instructions for building a Zero Flow calibration chamber and using the chamber to confirm that a flow meter is still within 3% of its original calibration.

Download zero flow calibration file

Enclosure heads are configured based on the initial order and are not intended to be rotated. Contact Kurz Customer Support for information about rotating the enclosure head.

ORDERS All orders are received subject to acceptance by KURZ INSTRUMENTS, INC. at the factory in Monterey, CA, U.S.A., herein referred to as COMPANY, and may be accepted only on Company’s printed acknowledgement form. Purchase orders for Company products and services must be made out to the Company and must be received in writing at Monterey, CA before performance is completed unless otherwise approved by the company.

 

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TERMS The terms of sale shown in the published price list shall apply from the date of shipment by the Company. If the Company in its judgment at any time deems that by reason of the financial condition of the Buyer or otherwise the continuance of production or shipment on the terms specified herein is not justified, the Company may require full or partial payment in advance. Certain orders may, in the judgment of the Company, because of their nature or the delivery involved, require progress payments. Pro rate payments shall become due as shipments are made. Terms are cash net 10 days. Amounts past due are subject to a service charge of 1.5% per month (or fraction thereof). Should the Buyer be in default of the terms stated above, the Company shall add to the Buyer’s account, all reasonable costs, including attorneys’ fees, filing fees and any other fees or expenses deemed reasonable by the Company in collecting the amounts due.

 

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DELIVERY Shipping dates given by the Company are approximate and are based on prompt receipt of all necessary information regarding the order. The Company will use its best efforts to meet the ARO date provided the Buyer supplies all necessary information and data promptly, but cannot be held responsible for causes beyond its reasonable control. The Company shall in no event be responsible for loss of profits, damages incurred by the buyer to its customers or other consequential damages resulting from Company’s failure to deliver within the time specified herein. In the event of any delay requested by the Buyer or any delay caused by lack of shipping instructions, the Company will store all items ordered at the Buyer’s risk and expense, and will invoice the Buyer for the full contract price of the apparatus on or after the date on which the same is ready for delivery. If manufacture is delayed by the Buyer, payment shall be made based on the percent of completion and the contract price.

 

SHIPPING COSTS AND INSURANCE Shipments are f.o.b. factory, Monterey, CA, freight and insurance prepaid and added, or freight collect unless otherwise requested and agreed to by the Company. If insurance is being provided by the Buyer a formal statement of Buyer responsibility must accompany purchase order. Customer is responsible for notification in writing to the Company within 72 hours of any loss or damage of the shipment if the shipment was made f.o.b. destination. In the absence of specific instructions, the Company will select the carrier.

 

CHANGES The Buyer may from time to time, but only with the written consent of the Company, make any change in the order. In the event of any such change, the Buyer shall pay to the Company the reasonable costs and other expenses (including engineering expenses and all commitments to its suppliers and sub-contractors incurred by the Company prior to receipt of notice of such change for all work rendered unnecessary by such change or incurred by the Company thereafter for all work required to effect such change. In either case, an amount determined by the Company in its discretion by applying to the amount such costs and other expenses and the Company’s usual rate of profit for similar work. In the event of any such change, the Company shall further be entitled to revise its price and delivery schedules to reflect such change.

 

CANCELLATION In the event of cancellation, the Buyer shall be liable for the payment of reasonable cancellation charges, which shall not exceed the unit retail list price of the items cancelled and shall include among other things expenses already incurred by the Company, actual liabilities against Commitments incident to the order involved, and properly allowable indirect charges as well as a reasonable profit. No delivery delay requested by Buyer on an order placed under this Agreement shall be effective unless covered by an amendment to the order that provides for the payment of any agreed upon costs the delay imposes on the Company and that is accepted on the Company’s printed acknowledgement form. Standard products only once delivered may be returned to the Company’s discretion and upon approval from the Company in Monterey, CA, at a minimum charge for restocking of 20% of list price. Return shipping charges are at Buyer’s expense. If the Buyer makes an assignment for the benefit of creditors, if a voluntary or involuntary petition or other action in bankruptcy or for reorganization or under any other insolvency law shall be filed by or against the Buyer, if the Buyer shall admit inability to pay its debts, if trustee, receiver or liquidator is appointed for any part of the assets of the Buyer, or if the Buyer fails to make payments to the Company in accordance with the terms hereof, the Company may at its option cancel all undelivered parts of any order by written notice to the Buyer at no expenses to the Company.

 

ACCEPTANCE — PRODUCT Unless otherwise agreed to by the Company, the criterion for acceptance of the Company’s products including options shall be the successful operation of the product and options using the Company’s standard test procedures applicable to the product and options involved. All acceptance tests shall be run by Company personnel at the Company’s factory, unless otherwise allowed for and agreed to by the Company.

 

LIMITED WARRANTY— Liability for Repair and Replacement Only   

Kurz products are warranted to be free from defects in material and workmanship from date of shipment from the Kurz manufacturing facility for 3 years for all B-Series products and 1 year for all other products. The Kurz obligation is limited to repairing, or at its option replacing, products and components that are verified and proven to be defective, at the manufacturing facility in Monterey, CA. Kurz warranty is limited to coverage of product specified and supplied by Kurz Instruments Incorporated.

Kurz extends this warranty only upon proper use and/or installation of the product in the application for which it was intended and does not cover products that have been modified without the Company’s approval, that have been subjected to unusual physical or electrical stress, or upon which the original identification marks have been removed or altered.

Kurz is not liable for installation charges, expenses of Buyer repairs or replacement, damages from delay or loss of use, or any indirect or consequential damages of any kind.
The customer is responsible for selecting the correct material of construction based on the material’s suitability for the intended use of the Kurz equipment.

Transportation charges to the Kurz manufacturing facility for materials shipped for warranty repair are paid by the shipper. Kurz will return repaired or replaced warranty products prepaid. No products will be accepted for warranty repair without prior authorization (RMA) from Kurz Instruments. No repaired products will be shipped from Kurz Instruments without prior authorization.

 

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DOCUMENTATION AND TRAINING In no event shall orders be accepted where payment is contingent on provision of documentation, unless agreed to in advance. Documentation is generic in nature, no guarantee is made that the documentation conforms to the equipment produced as built. As built documentation entails an additional charge. The Company will supply reasonable written documentation including operator instructions. Factory and on-site training in use and operation of the Company’s products may be made available at Buyer’s expense, subject to acceptance by the Company.

 

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EXCUSABLE CESSATION OF PERFORMANCE FOR NON-PAYMENT Whenever Buyer fails to meet the payment requirements set forth in this condition, manufacturer may cease performance and delivery and accelerate payment of any and all unpaid charges, such cessation of performance shall not be construed to be a breach of any contract or agreement and manufacturer will resume production as soon as reasonably possible upon receipt of payment of all balances due.

 

NUCLEAR QUALIFICATION Equipment sold by Kurz Instruments, Inc. is not intended for use in connection with any nuclear facility or activity unless covered by a specific quotation where the conditions of such usage will be detailed. If equipment is used in a nuclear facility or activity without a supporting quotation, Kurz disclaims all liability for any damage injury or contamination, and the buyer shall indemnify and hold Kurz, its officers, agents, employees, successors, assigns and customers, whether direct or indirect, harmless from and against any and all losses, damages or expenses of whatever form or nature (including attorney’s fees and other costs of defending any action) which they, or any of them, may sustain or incur, whether as a result of breach of contract, warranty, tort (including negligence), strict liability or other theories in law, by reason of such uses.

Thermal mass flow meters are designed to measure the dry gas flow in pipes, ducts, vents, stacks, and flares in industrial and commercial processes. Industries include petroleum & petrochemicals, pulp & paper mills, wastewater, nuclear, landfills, semiconductors, and cement. The environments and applications include coal power generation, incinerators, continuous emissions monitoring systems, bulk powder drying, combustion air, recirculation air, and boilers.

Until the commercialization of the Kurz wet gas flow metering line (WGF), the answer to this question was no. All thermal flow meters prior to this advent are affected by liquid water which robs heat from the heated sensor and results in erroneous flow errors. Only the Kurz WGF successfully operates in a condensing gas environment.

 

Thermal flow meters are intrinsically mass flow measurement devices. Pressure merely affects the empty space between gas molecules, and changing pressure doesn’t change the mass, only the space between the molecules, so it does not generally impact the thermal instrument.

Kurz thermal mass flow meters are temperature compensated to account for changing temperatures in the gas stream. Without temperature compensation, a thermal flow meter is affected by changing temperatures because temperature affects the heat transfer properties of a gas.

The thermal properties of a gas determine how fast or slow heat is pulled away from the heat source. Calibrating the heated sensor to a specific gas or gas composition allows a thermal sensor to accurately determine the flow rate. Operating a thermal meter outside its calibrated range can result in uncertain measurements.

If used correctly a Kurz flow meter does not need to be recalibrated. The sensing element should be periodically inspected (based on the process environment) to be free and clean of debris, as buildup can affect calibration. Once the sensor is cleaned, the meter will be back in calibration.

 

Kurz Instruments Thermal Flow Meter Calibration Policy

After sale meter calibration is not required provided the meter has been operated within its design specification and the sensors are clean, free from corrosion, erosion, or other physical damage.

 

The sensor and electronics do not drift when used within these limits.
However, verification of the meters calibration is sometimes desired by the end user. Some popular calibration verification options are zero flow air testing, insitu-field calibrations, and laboratory flow tests. All of these calibration options are available from Kurz Instruments or third-party service providers.

 

Download calibration policy

A laboratory calibration uses the same gas for calibration as where the meter will be installed.

A laboratory calibration is performed by characterizing the instrument’s response to the flow of a specific gas of choice.

A correlation calibration begins by characterizing the instrument’s response to flowing air and then using a proprietary algorithm, the air response data is adjusted to the specific gas of choice.

A laboratory calibration is more accurate than a correlation calibration, but a correlation calibration is more economical than a laboratory calibration.

There is no maintenance required other than periodically checking the sensor for particulate buildup. The process environment determines the maintenance schedule. Noncorrosive, particulate-free flows require less frequent checking than flows that have particulates or corrosive gases.

There are 2-wire and 4-wire modules (or meters) that connect to a controller. The looped-powered, 2-wire module uses a single pair of wires to power both the 4-20mA signal and module via the controller’s 24v power supply. The self-powered 4-20 mA loop for a 4-wire module is externally powered and configured to power the 4-20 mA loop too. This self-powered 4-20 mA configuration will source the current or drive the current to a load sensing resistor in the controller.

The meter itself is not loop-powered however the 4-20 mA output signals can be wired as a loop powered signal (see below). The meter is a 4 wire device requiring auxiliary power (many watts) beyond the 4-20 mA current loop capability to operate the meter. The auxiliary power can be 24 VDC or 85-265 VAC.

The Kurz thermal mass flow instrument supports either self-powered or loop-powered circuits with a simple field wiring arrangement. The meters 4-20 mA output signal circuit can be powered either by the meter or by the customer’s control system.

If the signal circuit is powered by the meter then it would be considered a “self-powered” signal loop.

If the signal circuit is powered by the customer’s control system then it would be considered a loop-powered signal loop.

Thermal flow meters are designed to measure the mass of gas flows in pipes, ducts, vents, and stacks for dry or wet gas processes. All thermal flow meters indicate velocities referenced to a set of standard conditions. Kurz Instruments standard conditions are defined as 25°C at 101.325 kPa.

• Standard (or Mass) Velocity is the velocity that a mass of gas would be moving if the temperature and pressure were at standard conditions. Standard Velocity is in units of standard feet per minute (SFPM) or standard meters per second (SMPS).

Standard Velocity: Vs = ρ • v / ρ s

Where: ρ = actual gas density
v = actual gas velocity
ρs = standard gas density

• Sometimes it is necessary to derive actual velocity from standard velocity. Actual Velocity is the velocity a “particle of dust” would be traveling if it were in a gas stream. When using actual velocity you will not know the mass or rather how many dust particles are moving in the gas stream. Actual Velocity is in units of feet per minute (FPM) or meters per second (m/s).

Actual Velocity: Va=Vs• (Ps/Pa)•(Ta/Ts)

Where: Va= actual gas velocity
Vs = standard gas velocity
Pa = actual pressure in absolute units
Ps = standard pressure in absolute units
Ta = actual temperature in absolute units (degrees Kelvin or Rankin)
Ts = standard temperature in absolute units (degrees Kelvin or Rankin)