Cleaning Plant Facilities Using aLow-Pressure Composite Water Flow
Cleaner（Cavitation Cleaning）
1. Introduction

Summer 2018
No.35

Cleaning had been performed on-site simply by blowing
air into water pipes. Due to clogging since the machine

A low-pressure composite water flow cleaner physicallywas installed, the product molding cycle of the mold had

removes sludge that has adhered to the inside surface ofincreased from the initial 113 seconds to 123 seconds orwater pipes by using water and air. The cleaninglonger. For the analysis, pre-cleaning and post-cleaning

process does not use any high-pressure water, chemicals,conditions were compared as follows: ⑴ Parts wereor chemical reactions. Previously, such removal required

produced at the mold’s passing water flow rate and at

dismantling, liquid-chemical management, and liquid

the initial condition of 113 seconds. ⑵ After the mold’s

disposal, all of which are costly. Thanks to the cleaner’s

temperature stabilized, the temperature was measured

system, the sludge removal does not involve any

using a thermograph. ⑶ The mold’s temperaturedismantling or chemicals, thus achieving low-cost, eco-distribution and defects of molded products before

friendly cleaning.

cleaning were compared with those after cleaning.
【Discussion】

2. Cleaning method

The overall flow rate was improved as shown in
Table1. Before cleaning, two surface sink marks

A hose with a pressure resistance of at least 0.8 MPa isdeveloped as shown by circles in Figure1. Whenconnected to the“IN”and“OUT”ports of the

manufacturing parts, a molding cycle of 123 seconds

equipment to be cleaned. Water is fed at 0.4 MPa into

was required. However, after cleaning, the temperature

the hose, while being mixed with fine air bubbles which

distribution of the mold improved, the surface sinkserve as centers for cavitation. In addition, the direction

marks disappeared, and the defects were resolved.

of water flow is rapidly reversed to create shock waves,

Also, the overall temperature was lower. However, thewhich make the fine air bubbles swell and contract,temperature of some areas increased due to changes incausing cavitation. Also, the air bubbles act as dampers,

the resin flux. Therefore, the molding cycle should bethus helping to control the cavitation force. Therefore,

made longer than the initial cycle. Through thecleaning can be executed without damaging theextension, the temperature of such areas was lowered.

equipment to be cleaned.

As a result, we showed that parts could be produced
without problems at a molding cycle of 115 seconds,

3. ‌Cleaning effects of resin
molding-die water pipes

which is just 2 seconds longer than the initial condition.
【Results】

The molding cycle was shortened by 8 seconds. We

This section introduces the case of a customer. The

found that regular cleaning of the mold eliminatedcustomer uses an 850T-class molding machine to moldperforation troubles and achieved stable production.

panel parts, and the mold which we cleaned had beenAlso, unlike chemicals, the cleaning process is not

manufactured 7 years ago and then used for production.

associated with melting, and thus frequent cleaning

5

C u s t o m e r S o l u t i o n s 《C o n t r i b u t i o n 》

equipment, and rotatory blowing machinery. With

does not damage the mold.

these findings, the machine is expected to be used also
in the PET bottle industry. Regarding other uses, themachine is used for cleaning the water pipes ofcastings including aluminum die castings. Althoughutilization in plants is limited, we have received
positive customer feedback. Relative to the effects ofchemical cleaning at 100%, the cleaning effect of themachine is 80%. Sometimes, chemical cleaning causes
problems for production lines such as chemicals
remaining in the lines when production restarts.
Figure1

Table1‌Pre-cleaning
temperature distribution of the moldand defective areas

However, with our cleaning machine, no troubles have‌
Numerical
comparison of pre-cleaning and postcleaning conditions

tube-type heat exchangers（on the side of the shell）,

been reported. In addition, when cleaning shell- andonly the surface can be cleaned even though aEndpoint
Overall flow rate
（0.2MPa）
Circuit 1

Pre-cleaning

Post-cleaning

59.6L/min

74.6L/min

1.1L/min4.2L/minCircuit 2

8.1L/min10.3L/mintubes. Such characteristics have been positively

Circuit 3

3.2L/min5.3L/minCircuit 45.4L/min

7.0L/minevaluated. Since this machine enables plate-type heat

Circuit 5

10.8L/min

12.5L/min

Sub-circuit 1

16.9L/min

19.5L/minhave received positive feedback such as about thelower cost of exchanging packings.

14.1L/min

15.8L/min123seconds

115seconds

Defective molding（At initial condition）

Surface sink marks
developed.

No defectcleaning machine can also clean the space between

exchangers to be cleaned without dismantling, weSummer 2018

Sub-circuit 2
Molding cycle

hyperbaric cleaning method is used. However, our5. Effects of plant facility cleaning

4. Sales of the cleaning machine5-1）‌Effects for a shell- and tube-type heat

Although we have limited results regarding sales for

We cleaned a horizontal-type shell- and tube-type heatplants, we have a number of successful sales for theexchanger shown in Figure2. Before cleaning, a reddish-resin-molding industry, and particularly with automobilebrown deposit covered the side of the shell as shown inparts manufacturers. The cleaning machine is applicable

Figure3. The deposit was such that the red deposit

to water pipes, not only cast pipes but also those under

could be removed by scratching with a finger. The

the molding machine’s hopper and in the chiller’s heatcleaning machine’s“IN”and“OUT”were connected toexchanger. Therefore, the machine can be used forthe handholes and cleaning was conducted without

various purposes. Recently, the cleaning machine

removing the“IN”and“OUT.”During cleaning, a large

reduced the cleaning time from approximately 3 days toamount of deposit precipitated in the tank as shown in

24 hours at a PET bottle factory, where previously itFigure4. This precipitate rapidly clogged the filters as

was necessary to dismantle pre-form molding dies andshown in Figure5. A considerable amount of deposit

the take-out devices’water pipes in order to clean

could be removed. In addition, when we confirmed thefacilities.

post-cleaning conditions of the connection outlets, weIn addition, we found that the cleaning machine canfound that deposit had been thoroughly removed as

be used for cleaning the water pipes of sintering

shown in Figure6, since these areas were exposed tomachines for pre-formed screw parts in manufacturing

powerful flows.

exchanger（horizontal-type）

6No.35

Cleaning Plant Facilities Using a Low-Pressure Composite Water Flow Cleaner（Cavitation Cleaning）

5-3）Effects‌for a large plate-type heat exchanger
As Figure9 shows, the cleaning machine was connected
to a large plate-type heat exchanger with a plate numberof 410 and a heat transfer area of 391.7m2 without
dismantling. Then, we conducted cleaning for 50 hours
Figure2 ‌Shape of heat exchanger

Figure3 Pre-cleaning conditionon the cooling-water side and for 70 hours on thecirculating-water side.
The results are shown in Table2. The flow rate of
circulating water was sped up by approximately 45%
and the heat exchange amount was increased byapproximately 75%. Since the plates were not dismantled,
the packing did not need to be exchanged. Customers
appreciate such benefits.

Figure4 During-cleaning condition

Figure5Filter condition
Cooling water（IN）
Cooling water（Out）

Summer 2018

Cleaning
water tank

Figure9
Figure6 Post-cleaning condition

5-2）‌Effects for a large shell- and tube-type
heat exchanger

No.35

Before cleaning, as shown in Figure7, the spacesbetween tubes were clogged with oxide. However, aftercleaning, as shown in Figure8, the clogging was

Table2

Low-pressurecomposite waterflow cleaner

Schematic drawing of the connection‌
Numerical
comparison of pre- and post-cleaning
conditions for a large plate-type heat exchanger
Heat
Cooling water
Circulating water Circulating Heatwater exchange transmission
temperature（℃） temperature（℃） amount amount rateＫｃａｌ/
IN OUT Disparity IN OUT Disparity ｍ３/ｈｒ Ｋｃａｌ/ｈｒ㎡・ｈ・℃

Pre７ ３５．
３ ６．
６ ４７．
０ ４２．
３ ４．
７
cleaning ２８．
Post- ２７．
５ ３６．
０ ８．
５ ４５．
５ ３９．
８ ５．
７
cleaning

１５０ ７０５０００ １４３
２１６ １２３１２００ ２９０

removed. The oxide covering the tube surface was notcompletely removed. However, when the heat exchange
conditions during operation were measured, we foundthat the cleaning was effective.

5-4）‌In-line cleaning of a small plate-type heatexchanger for spa facilities
Although the conditions are different from those ofplants, plate-type heat exchangers are also used at spa
facilities, which sometimes suffer clogged water pipes.
When this happens, they have to dismantle and clean
the heat exchangers. Accordingly, we used an in-line
cleaning machine（which is less effective than an offline machine）to clean a small plate-type heat exchanger.

Figure7 Pre-cleaning condition

Figure8 Post-cleaning condition

During the cleaning, we opened the plates andconfirmed the conditions. The cleaning machine wasconnected to the heat exchanger and the plates werewashed for 2 hours as shown in Figure10.
Before cleaning, the entire plates were covered withdeposit as shown in Figure11. However, after the7C u s t o m e r S o l u t i o n s 《C o n t r i b u t i o n 》

cleaning, approximately 80% of the plate surface could
be seen, as shown in Figure12. Thus, the cleaning

6. Conclusion（Expansion to plants）

restored the heat-exchange amount and resolved theUntil now, plate-type heat exchangers and shell- andpressure loss, returning the equipment to normal

tube-type heat exchangers（on the side of the shell）

operation.

have been cleaned with chemicals or high-pressure

Connection of cleaning machine
Spa’swater
storagetankwater or had to be replaced since such areas could not

Plate-type
heatexchanger

be dismantled. We have started developing a large
cleaning machine（NR-2000）together with VALQUA
Warm
water

DrainagechannelAlso, when cleaning plant facilities, the channel areas
are expected to be large. Therefore, the effects of
bubbling through a two-layer fluid and turbulence

Bathtub

Figure10LTD., which we expect will overcome such problems.

Connection of cleaning machine

effects, which develop from switching the flow
direction, can exert powerful cleaning rather thanwith cavitation, which occurs during cast cleaning.
Therefore, we need to continue studying physicalphenomena regarding cleaning effects.

Summer 2018

Figure11 Pre-cleaning condition

Figure12 Post-cleaning condition

No.35

Masaru Kitagawa
Blue Engineering, LTD.

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